Preface
In November 2006, the 35th Japan-US Joint Meeting of UJNR (U.S.-Japan Cooperative Program in Natural
Resource) Aquaculture Panel was held in National Research Institute of Aquaculture in Minami-ise, Mie
Prefecture. Through the long history of UJNR, Aquaculture Panel has contributed to development ofaquaculture researches of both countries by means of various cooperative activities, i.e. the exchange ofscientists, the exchange of literatures and promoting joint research projects. It is understood that the
Aquaculture Panel is one of the most active UJNR panels by both countries. Further positive action is
expected to the UJNR Aquaculture Panel for a solution of the varied problems presenting in aquaculture ofboth countries.
The present special issue of Bulletin of Fisheries Research Agency is the proceedings of the 35th UJNR
Aquaculture Panel Symposium “Building Sustainable Food Supplies through Aquaculture, Wild Stock
Enhancement, and Habitat Management” which is held in accordance with the 6th UJNR five-year plan.
Development of aquaculture in harmony with the environmental conservation of coastal and freshwater
ecosystems is extremely important for stable supplies of aquatic products, and the issue has been globally acommon theme. It is my great pleasure that the present UJNR proceedings containing high quality papersof the selected American and Japanese aquaculture scientists will help integrating aquaculture and fisheries
technologies to optimize value from coastal resources, zoning for aquaculture, use of biotechnology inaquaculture and effects on natural population, and improvement of public perception.
Finally I would like to express my sincere gratitude to the colleagues involved in the UJNR Aquaculture
Panel for their efforts to prepare and organize the symposium. I also would like to deeply thank the editorial
board members for publishing the proceedings.

Hiroshi Nakano
Chair of UJNR Aquaculture Panel
Director General
National Research Institute of Aquaculture
Fisheries Research Agency

The 35th Scientific Symposium of the UJNR Aquaculture Panel
Building Sustainable Food Supplies through Aquaculture, Wild Stock Enhancement,
and Habitat Management
National Fisheries Research Institute of Aquaculture, Mie
November 13th-14th, 2006
Key note of the symposium
The role of aquaculture in stabilizing food supplies has been globally important, while production basedon capture fisheries has become depressed due to the decline of wild resources. Since the sustainable use ofresources in the exclusive economic zone (EEZ) was made an obligation by the United Nations Convention
on the Law of the Sea, aquaculture technology R&D aimed to maintain sustainable production while
preserving coastal environments and ecosystems have become the common issues to the US and Japan.
The UJNR Aquaculture Panel has discussed various science and technologies as follows: 1) algae andfilter feeders aquaculture, 2) crustacean aquaculture and pathology, 3) ecosystems and carrying capacityof aquaculture grounds, and 4) finfish aquaculture in accordance with the 6th 5-years Plan (2002-2006).
During the last year of the plan, how to achieve sustainable fisheries production and food supplies throughaquaculture and stock enhancement was explored among aquaculture scientists as well as socio-economists
and member of governmental sectors, while summarizing discussions covering previously developed
aquaculture technologies.
In the present symposium, the following issues were discussed in order to promote the futuresustainability of the fisheries community and fisheries industry by means of aquaculture and stockenhancement.
1. Aquaculture technologies harmonized with coastal ecosystems to realize sustainable production
2. Sustainable stock enhancement technologies harmonized with the ecosystem
3. Environmental conservation and mitigation technologies for sustainable use of aquaculture grounds
4. Sociological and economic measures for sustainable development and use of coastal resources
Key Categories: Integrating aquaculture and fisheries technologies to optimize value from coastal
resources, zoning for aquaculture, use of biotechnology in aquaculture and effects on natural population,
improvement of public perception

Program
Monday, November 13th, 2006

Registration

12:30-14:00

NRIA tour for guests・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 13:00-14:00
Opening remarks (Yasuji Sakai, Japan Panel Chair)・・・・・・・・・・・・・・・・ 14:00-14:10
Aim of the symposium (Kazumasa Ikuta)・ ・・・・・・・・・・・・・・・・・・・ 14:10-14:15
Keynote presentation (Moderators: Kunihiko Fukusho & Conrad Mahnken)
			・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 14:15-15:00
An Overview of the US/Japan UJNR Aquaculture Panel: Past, Present and Future
James P. McVey
Break・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 15:00-15:20
Session Ⅰ. Aquaculture technologies harmonized with coastal ecosystems to realize
sustainable production (Moderators: Cheng-Sheg Lee & Takao Yoshimatsu)
1. Recent Progress in Closed Recirculation Seed Production System for Environmental
Preservation in Japan・・・・・・・・・・・・・・・・・・・・・・・・・ 15:20-15:45
		

Yoshihisa Yamamoto

2. Utilization of Waste Porphyra Products as Eco-friendly Feed Ingredients・・ 15:45-16:10
		

Tsuyoshi Sugita

3. The Relationship between Growth of Cultured Red Sea Bream (Pagrus major)and Method of Farming・・・・・・・・・・・・・・・・・・・・・・・・16:10-16:45
		Takashi Uede

4. Manila Clam and Pacific Oyster Culture in Isahaya Bay- For the
Sustainable Production in Stressful Environment-・ ・・・・・・・・・・・16:35-17:00
		Junya Higano

Tuesday, November 14th, 2006

Registration

8:30- 9:30

Keynote presentation (Moderators: Charles E. Helsley & Satoru Toda)
Recent Attempt towards Environmental Restoration of Enclosed Coastal Seas:		

Ago Bay Restoration Project Based on the New Concept of Sato-Umi

			・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 9:30-10:15
		Osamu Matsuda

Break ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 10:15-10:35
Session Ⅱ. Environmental conservation and mitigation technologies for sustainable use of
aquaculture grounds (Moderators: Thomas A. Flagg & Hisashi Yokoyama)
1. The Role of Aquaculture in Integrated Coastal Management・ ・・・・・・ 10:35-11:00
		Charles E. Helsley

2. New Technology for Developing Biologically Productive Shallow Area in Ago Bay
			・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 11:00-11:25
		Hideki Kokubu

3. Stable Isotope Analyses of the Trophic Structure of Macrobenthos on an
Artificial Tidal Flat Developed Using Sediments Dredged from Pearl-oyster Farms
in Ago Bay・ ・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 11:25-11:50
		Yuka Ishihi

Announcements・ ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 11:50-12:00
Lunch ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 12:00-13:00
Session Ⅲ. Conservation of biodiversities and ecosystems for sustainable use of aquatic
resources (Moderators: William Fairgrieve & Hiroyuki Sudo)
1. Introduced Species and Aquaculture・ ・・・・・・・・・・・・・・・・・ 13:00-13:25
		Cheng-Sheng Lee

2. Countermeasures against Alien Fish (Largemouth Bass and Bluegill) in Lake Biwa
			・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 13:25-13:50
		Atsuhiko Ide

3. Conservation Aquaculture Approaches for Hatchery Reform・ ・・・・・・ 13:50-14:15
		Thomas A. Flagg

4. Environmental Standards for Marine Aquaculture in the United States; Minimizing
Negative Interactions of Escaped Farm Fish and Natural Populations・ ・・ 14:15-14:40
		Conrad Mahnken

Break・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 14:40-15:00
Session Ⅳ. Sociological and economic measures for sustainable development and use ofcoastal resources (Moderators: Kazumasa Ikuta & James J. Sullivan)
1. Accounting for Economic Risk and Uncertainty in Offshore Aquaculture:
A Case Study of Korean Rock Bream Production・ ・・・・・・・・・・・ 15:00-15:25
		Douglas Lipton

2. Economic Evaluation of Various Roles and Functions of Propagation and Aquaculture			・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 15:25-15:50
		Yasuji Tamaki

3. Risk and Risk Management for Feed and Seed for Carnivorous Marine Fish
Aquaculture・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 15:50-16:15
		Michael B. Rust

4. Ecological Risk Assessment of Marine Fish Aquaculture in the Coastal Zone
			・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 16:15-16:40
		William Fairgrieve

5. The Measures for Sustainable Marine Aquaculture in Japan・・・・・・・・ 16:40-17:05
		Ikuo Takeda

General discussion (Moderators: Panel members)・ ・・・・・・・・・・・・・・・ 17:05-17:30
Closing remarks (Robert Iwamoto, U.S.A. Panel Chair)・・・・・・・・・・・・・・ 17:30-17:40

1

An Overview of the US/Japan Natural Resource's Panel on Aquaculture:
Past, Present and Future.
James P. McVey＊
Background: The United States Japan Cooperative Program in Natural Resources (UJNR)
was initiated by a proposal made during the Third Cabinet-Level Meeting of the Joint UnitedStates-Japan Committee on Trade and Economic Affairs in January 1964. An aquaculture panel
was formed in 1969 and was charged with exploring and developing bilateral cooperation.

Inaddition to the aquaculture panel, their were other programs on desalination of seawater, toxic
microorganisms, air pollution, energy, forage crops, national/park management, mycoplasmosis,
wind and seismic effects, protein resources, forestry and several joint panels in marine research,development and utilization.
The First Joint Meeting of the U.S.-Japan

These early meetings established the general

Cooperative Program in Natural Resource's Panelformat for conduct of the UJNR technicalon Aquaculture was held in Tokyo, Japan, on

exchange that we have followed throughout the

October 18-19 and 29, 1971

35 year history of the program. Meetings are

Dr. Atsushi Furukawa and Mr. William N.

alternated between the two countries on an annual

Shaw, were elected co-chairmen for the Meetingbasis with a two day symposium and then a field

and were accompanied by Robert Hiatt, Roberttrip for the delegations to view the research

Wildman Harvey Willoughby, A. Crosby Longwell,facilities and observe the industry. During thisJohn Glude and Cornelius Mock on the US sidetime there is adequate opportunity for individual

and Yoshio Hasegawa, Yukimasa Kuwatani,scientists to talk with one another regarding topics

Shunzo Suto, Hiroshi Kan-no, Tomoo Hayashi andof mutual interest and to identify joint research

Masaru Fujiya on the Japan side. This meeting

projects. These projects can be supported in a

included presentations by both sides and a week

formal way under the UJNR structure or arranged

long field trip to see aquaculture site in Japan. The

between cooperating institutions, both Federal andJapan presentations were on marine cultivation

academic.

in Hokkaido, seaweed mariculture, freshwater
culture, shellfish culture, finfish culture in Japan.

Since that time 35 years ago there have been

The US presentations were on Penaeid shrimp

annual meetings alternating between our twolarval culture, Sea Grant research, mollusc culture

countries on a broad range of topics:in S. Atlantic, Gulf and Pacific NW, genetics of･ 71 Overview papers of Japan and US

American oyster, and freshwater fish culture.

･ 72/73 Pathology and Nutrition

A second meeting of the Aquaculture Panel･ 74 Pathology

was held in the United States in Washington, DC･ 75 Nutrition

and Seattle, Washington in 1972. Dr. Furukawa･ 76 General Discussion FAO meetingand William Shaw remained the Chairs and they･ 77 Marine Algae

identified Nutrition and Pathology as issue of･ 78 Marine Fishmutual concerns and scientific exchanges were･ 79 Freshwater and Marine overviews

planed on these topics.

･ 80 Crustaceans

2009 年 8 月 10 日受理（Received. August 10. 2009）＊
US Panel Emeritus Chair, National Sea Grant College Program Office of Oceanic and Atmospheric Research, NOAA 1315, East-West Highway,
SSMC-3, Rm# 11838 Silver Spring, MD 20910-3282, USA

2James P. McVey･ 81 Molluscan Aquaculturethat served to focus world attention on the issue･ 82 Salmon Enhancementof aquaculture and set the course of research for･ 83 Reproduction, maturation and seed production

the next decade. The UJNR met as part of the･ 84 Environmental Quality

FAO meeting and I had the honor of attending･ 85 Innovative Advances Bio/Engineeringthat meeting as a young scientist just starting his･ 86 Marine farming and Enhancementcareer.

･ 87 Genetics

During the next five year period the UJNR

･ 88 Marine Ranching

symposiums tended to focus on culture of･ 89 Reproductive Physiology

different phyla and species, i.e. marine fish, algae,･ 90 Disease

crustaceans, mollusks, salmon. These discussions･ 91 Nutrition

allowed us to look at the life histories of these･ 92 Environmental Management

groups as well as the technical and husbandry･ 93 Interactions of Cultured and Natural Species

aspects of their culture.

･ 94 Biological Control of Salmon and Advanced
Tech

During the next ten year period we continued
to discuss the basic disciplines underlying the･ 95 Water Effluent & Quality, Fish and Shrimp

industry needs and we saw the appearance of･ 96 Biodiversity and Aquaculture

marine biotechnology as applied to aquaculture.

･ 97 Nutrition and Technology Development

This advanced technology used for diagnosis･ 98 Goals and Strategies for Breedingof pathogenic organisms, control of endocrine･ 99 Spawning and Maturation

processes for reproduction, and genetic･ 00 Pathogenic Organisms/Stock Enhancement

manipulation of marine species has been an･ 01 Ecology of Aqua species/stock enhancement

important part of our technical exchange. It was･ 02 Aquaculture and Stock Enhancement Algae/

during this period that serious questions about

Filter feeders

environmental issues related to aquaculture･ 03 Pathology of Crustaceans

started to be asked and the 1984 meeting focused･ 04 Ecosystem Carrying Capacity/Sustainable

on this topic.

Development･ 05 Aquaculture Stock Enhancement

Starting in 1992 we held a series of meetings
related to environmental issues:

These topics were identified in a series of five･ 92 Environmental Management

year plans and we have just completed the sixth･ 93 Interactions of Cultured and Natural Species

five year plan with this, the 35th meeting of the･ 94 Biological Control of Salmon and Advanced

UJNR Aquaculture Panel. Studying the flow ofTechtopics over time there are trends that follow the･ 95 Water Effluent & Quality, Fish and Shrimp

development of the industry in both Japan and the･ 96 Biodiversity and Aquaculture

US.
During the first five years of our cooperation

These meetings helped define the key issues

there was an emphasis on understanding the issues

relative to environmental concerns about

in each country and formulating a plan for the best

aquaculture. These issues were being discussed

areas of cooperation. The first two meetings wereby scientists around the world and by the media

spent on providing overviews of national researchand the press. It was during this time period that

activities and identifying two research topics:

the rise of Non Government Organizations (NGO's)

nutrition and pathology, that were important toconcerned about environmental matters turned

both parties. These themes were discussed in thetheir attention to aquaculture issues. The UJNR

next two meetings and then, in 1976, Japan hosted

Aquaculture Panel helped to bring science to these

the strategic United Nations Food and Agriculture

issues and I believe helped both countries to define

Organization (FAO) meeting on world aquaculture

the research needed to provide solutions. It is3very important to have the view of more than one

date.

country when looking at broad issues as individual･ Aquaculture is being integrated into the newcountries have different public views of any

paradigm of ecosystem-based management fordevelopmental technology. This will become more
apparent during the discussion that comes later inthis paper.

seafood supplies in several countries.
･ Creation of UJNR websites in both countries thatare updated periodically to provide information

From 1997 to 2003 we see the topics turningon the science and accomplishments of UJNR

back towards the disciplinary subjects ofgenetics, pathology, nutrition, endocrinology andThis list of accomplishments does not take into

biotechnology. This time period corresponded toaccount the increased cultural understanding

a leveling off of aquaculture production in both

between our two countries, the formulation ofcountries as well as a sharp decline in wild fisherylong term friendships between scientists, theproduction. Increased imports were needed in both

broadening of understanding of world issues, theJapan and the US to meet public demand. Supply

establishment of career lines or focus for youngof seafood shifted to more imports than domestic

scientists.

production and the economics associated withseafood changed accordingly. Prices fell.
The most recent meetings, 2004 and 2005, as

Status of Marine Aquaculture in the US andJapan:

well as this meeting entitled "Building Sustainable

It is important to put this flow of research

Food Supplies through Aquaculture, Wild Stockand discussion into context with the status of

Enhancement and Habitat Management", arethe aquaculture industry in our two countries.

adjusting to the shift of world opinion about the

Attached are graphs showing the growth ofneed to manage coastal resources in a moreproduction of marine aquaculture in our respective

holistic manner. Many are attempting to movecountries during 1970 to the present. I have nottowards ecosystem-based management or

included freshwater aquaculture statistics in orderintegrated coastal management and away fromto simplify the analysis and reflect the primary

single species management for seafood and living

focus of US/Japan cooperation.

resources. In 2005 Japan and the US participated

In 1970 Japan had marine aquaculture

in a meeting with China, Korea, Viet Nam, Canada

production of approximately 550,000 tons comparedand representatives from Chile, European Union,

to the US production of about 130,000 metric tons

Taiwan and Malaysia to discuss the role of(Figure 1)(FAO statistics 2006). Japan had a fairly

aquaculture in ecosystem based management. This

broad range of species that they were producing

will be discussed later in this paper.

including mollusks, finfish, crustaceans and algae
while the US production was mainly in mollusks.

Significant Accomplishments:

Over the course of the 70's decade Japan's･ Approximately 530 oral presentations at

production increased dramatically to nearly 900,000

Symposia evenly distributed between bothtons while US production of mollusks actuallycountries as determined through 32 publisheddeclined to about 100,000 metric tons. This decline

Proceedings.

was probably due to loss of habitat and increases･ Thousands of scientists and students attending
symposia and meetings.

in disease in molluscan stocks.
In the 1980's Japan's marine aquaculture･ Exchanges of scientists, students and scientificproduction increased to nearly 1,300,000 tons

information between Federal, Provincial, andand US production rose slightly back to pre-1970

academic institutions.

A perusal of UJNR

levels of about 130,000 (Figure 2). The rise of

documents indicates that the US sent a minimum

US production corresponds to increased shellfishof 104 scientists to Japan and Japan sent 327

production resulting from improvements inscientists to the US during our cooperation tohatchery supply of commercial mollusks and the4James P. McVey

initiation of coastal shrimp and salmon farms insome states.

During the last four years of the statistics
available from FAO, Japan has again declined

During the 1990's (Figure 3) both the Japanslightly in its marine aquaculture production while

and US marine aquaculture production leveled

the US, for the first time, has moved up fromout at the levels realized at the end of the 1980's.

130,000 metric tons of production to over 200,000

There appeared to be a slight decline in Japan's

metric tons in 2004(Figures 4 and Table 1). During

production by the end of the decade and the US

this time period the value of marine aquaculture

remained essentially level around 130,000 metricproduction in Japan was a little under $4 billion

tons.

while the US production moved from $94 million

Fig. 1. 1970’s Marine Aquaculture Production.
Fig.1.

Fig. 2. 1980’s Marine Aquaculture Production.

Fig.2.

5

Fig. 3. 1990’s Marine Aquaculture Production.
to $191 million or a doubling over the four year
Fig.3.
period (Figures
5 and Table 2). This increase

profound effect on both countries production andfor the US appears to be a result in a dramatic

represent my personal opinions, help set theincrease in mollucan production as well as thestage for this years UJNR symposium.

value of seafood.

These observations, which

initiation of a marine finfish industry.
UJNR 2006 Symposium Topic: Building
Significance of FAO statistics:

Sustainable Food Supplies through Aquaculture,･ Marine Aquaculture is a significant part ofWild Stock Enhancement and Habitat

Japan's seafood supply and economic well being
but has not expanded in last decade.

Management
This topic implies a holistic look at seafood･ Marine Aquaculture is a very small part of US

production that includes aquaculture, fisheries,

seafood supply and is just starting to expand.

habitats and the coastal communities that depend･ The ten fold difference in production and value

upon these resources. We have a range ofin marine aquaculture between the US andpresentations from both US and Japanese scientists

Japan may be attributed to differences in publicthat will examine these issues and hopefully add toperceptions and traditions, regulatory and policy

our understanding of these critical relationships.

structures, and timing relative to environmental
issues among other factors.

This years UJNR meeting will build upona multi-lateral meeting held with several key･ Possible factors influencing the stagnation ofcountries, mentioned earlier, that was attended

Japanese marine aquaculture production andby UJNR leadership last year in Hawaii entitled:

the prolonged low production of US may be:

The Role of Aquaculture in Ecosystem Basedresponse to competition from cheap seafood

Management, This meeting came up with several

imports making the economics of aquaculture

products that add to this overall discussion, these

difficult, competition over limited space andare:resources in coastal zones, and concern over･ Guiding Principles for Marine Aquaculture

environmental impacts,･ Coastal Managers' Considerations for･ The shift from self sufficiency in seafoods
to importation of cheap seafoods has had a

Aquaculture and Integrated Coastal
Management

6James P. McVey･ Requirements for Models used in Managing
Coastal Aquaculture

production in our respective countries as well as
recent meetings and discussions on this year's･ Country Scenarios for Ecosystem Based Coastal
Aquaculture

topic I would like to offer several questions thatmight guide some of our discussions:

We expect the publication of these products➣How do developed countries develop their own

in book form in the next year and they can beaquaculture industry in the face of cheaper

added to the publication of the Proceedings of thismeeting as we continue to look at aquaculture incoastal environments.

imports?
➣How does large scale aquaculture integratewith fisheries and coastal communities in the
coastal zone of developed countries?

Questions for the Future:➣How do environmental concerns limit

Looking at the past 35 years of the Unitedaquaculture development?

States and Japan Aquaculture Panel activities➣What regulatory and financial changes need toin combination with the analysis of aquaculture

be made to develop the aquaculture industry

Table 1. 2000-2004 Marine Aquaculture Production.
Fig. 4. 2000-2004 Marine Aquaculture Production.

Fig.4.

11/13/06

FAO Fisheries Global Information System

7

Table 2. 2000-2004 Marine Aquaculture Value.

Fig. 5. 2000-2004 Marine Aquaculture Value.

Fig.5.

sector while protecting the environment?
➣What11/13/06
is the future of offshore technologies?

FAO Fisheries Global Information System➣What predictive models and monitoring

In closing, I would like to reflect on some
additional FAO information that deals with thetechniques will be necessary for situating andneeds of the future:

managing aquaculture in coastal areas･ In 2006, FAO's "The State of World Aquaculture"➣What genetic guidelines will be necessary forreported that world aquaculture is n o w

safe-guarding natural fishery stocks relative tocontributing 45.5 million tons (43%) of fish supply.

aquaculture

The world will need 40 million tons more by➣How can we capture and recycle marine

2030 based on present per capita consumption.

proteins and obtain alternative proteins andCatches in the wild have leveled off and theoils from both land and ocean for aquaculture

only hope for meeting future demand is throughdiets

farming. Imports of seafood by developed➣What diagnostic tools and disease treatments
are appropriate for sustainable aquaculture

nations have reached 33 million tons valued at$62 billion.

8James P. McVey

These statistics show how far we have comeand how far we have have to go! Aquaculture
production is now nearly equal to wild fisheries
production and the combination of the two equal
our seafood supply. The loss of habitat, declining
water quality in our coastal areas, the declining
fisheries around the world, the limited amount ofmarine protein available for aquaculture feeds, thelimited amount of space available for aquaculture
in nearshore environments, presents greatchallenges to future production.
Working together the US and Japan have madegreat strides in providing aquaculture scienceand technology for developing world aquaculture.
Technologies developed through our joint efforts
are being used throughout the world and havehelped lead to the increased production recorded
in FAO statistics.
I anticipate that our cooperation will continue
for a long time to come and the professional
relationships and friendships that have evolved
over the past 35 years will form the base of futureendeavors.

9

Recent Attempt towards Environmental Restoration of Enclosed Coastal Seas:
Ago Bay Restoration Project Based on the New Concept of Sato-Umi
Osamu MATSUDA＊
Abstract

Since the present status of the enclosed seas along the coast of Japan is moreor less "damaged" or "deteriorated" mainly due to prolonged impact of human activities,
environmental restoration followed by rehabilitation of the natural ecosystem is one of themost important subjects to be tackled from the view point of both environmental conservationand living resource management. Ago Bay is one of the deteriorated areas especially from theviewpoint of aquaculture grounds in Japan. Although the bay is known to be a world-famous
cradle of pearl culture, conditions of the bay in terms of sediment quality, dissolved oxygen andharmful algal blooms have deteriorated during the long history of pearl culture. The ongoing"Environmental Restoration Project on Enclosed Coastal Seas" in Ago Bay mainly deals withrestoration of deteriorated tidal flats and seagrass beds and also development of environmental
forecasting technology based on environmental monitoring and modeling. Since the project
conducted under the collaboration program of the Japan Science and Technology Agency
with industries, academies and public services includes not only scientific and technologicalstudies but also components of environmental education, environmental management and wider
cooperation with varieties of stakeholders, it can be a model of environmental restoration andmanagement of enclosed coastal seas. The outline of the project as well as its present status
and future perspective is introduced with particular emphasis on the new concept of SatoUmi, which in Japanese means coastal sea under the harmonization of sustainable wise usewith conservation of appropriate natural environment and habitat conditions. An automatic
monitoring system to monitor water quality has been established and real time observation
data are open to the public through the Internet. Varieties of restoration methods for damaged
shallow environments and habitats with the use of environment friendly technology based on
the concept of Sato-Umi is being developed and applied in this project.
Key words: environmental restoration, environmental monitoring, enclosed coastal sea, Ago
Bay, pearl culture, Sato-Umi
conservation and living resource management.
Introduction

Among 88 officially designated enclosed coastal
seas in Japan, Ago Bay is one of the deteriorated

Since the present status of the enclosed seas

areas especially from the viewpoint ofalong the coast of Japan is more or less "damaged"

environmental quality and aquaculture grounds.

or "deteriorated" mainly due to prolonged impact

Although the bay is known to be a world-famousof human activities, environmental restoration

cradle of pearl culture, environmental conditions infollowed by rehabilitation of the natural ecosystem

the bay in terms of sediment quality, dissolved

is one of the most important subjects to be tackled

oxygen in bottom water and occurrence of harmful

from the viewpoint of both environmental

algal blooms have deteriorated during the long2009 年 8 月 10 日受理（Received. August 10. 2009）＊
Professor Emeritus, Hiroshima University; Core Research Laboratory, Ago Bay Restoration Project 3098-9 Kawamukai, Ugata, Shima, Mie 5170501 Japan
Email: matsuda036@go3.enjoy.ne.jp

10Osamu MATSUDA

history of pearl culture spanning more than 100
years. Ago Bay is located in Ise-Shima National

Outlined framework of thePark, Mie prefecture, the central part of Japan andenvironmental restoration project

the enclosed topography of the bay surrounded by

The bay is a typical enclosed coastal sea,

deeply indented rias-type coastline protects theconnected to the Pacific Ocean with a very narrowintrusion of ocean waves from the sea andand shallow entrance (Figure 1). The environmental

provides an adequate place for pearl culture.

quality of the bay, in particular of the sediments

The "Environmental Restoration Project on

quality, has deteriorated in conjunction with the

Enclosed Coastal Seas" conducted in Ago Bay

continuation of pearl culture and development ofduring 2003-2007 under the collaboration program

the coastal area. Therefore, in the project, attemptsof the Japan Science and Technology Agency (JST)are being made to improve the natural self-with industries, academies and public services

purification capability in the shallow areas of themainly deals with restoration of deteriorated tidal

bay by constructing functional tidal flat andflats and seagrass beds and also the development

seagrass beds that contribute to the enhancementof environmental forecasting technology based onof both the biological diversity and biological

the real time environmental monitoring andproductivity of Sato-Umi. At the same time,modeling. The central organization forsustainable aquaculture system is also developed

implementation of this project is the Mie Industry

to build a new ecosystem based management ofand Enterprise Support Center (MIESC) and thepearl culture. The project consists of following two

Mie Prefecture Science and Technology Promotion

themes.

Center (MPSTPC) has full administration

Theme 1. Integrated restoration of coastal

responsibilities. Since the project includes not only

environment and ecosystem to establish a regional

scientific and technological studies but alsomodel of Sato-Umi. In Ago Bay, deteriorated

includes components of environmental education,

sediments with COD values higher than 30 mg/g

environmental management and wider cooperation

dry sediment have been dredged up as anwith varieties of stakeholders, it can be a model ofadministrative measure for environmental

environmental restoration and management of

improvement. In order to make use of the dredged

small scale enclosed coastal seas.

sediments rich in organic matter accumulated at

This paper outlines the project as well as thethe bottom of the bay, technology for dewatering

present status and future perspective withdredged sediment was developed and the treatedparticular emphasis on the new concept of Sato-sediments were applied as raw material toUmi, which in Japanese means coastal sea underconstruct functionally improved artificial tidal flat

the harmonization of sustainable wise use withand seagrass beds. The function of tidal flats andconservation of appropriate natural environment

seagrass beds were quantitatively evaluated fromand habitat condition. In this project, varieties ofthe viewpoint of material cycling, self-purification,

restoration methods for damaged shallow

biological diversity and biological productivity inenvironments and habitats with the use oforder to establish a reliable method forenvironment friendly technology based on theconstructing functional tidal flats and seagrassconcept of Sato-Umi are developed and applied.

beds. In addition to the development of technology

Compared with deteriorated coastal environments,

to make the best use of dredged sediments,

Sato-Umi is able to provide higher biologicalpractical methods for environment friendly pearl

diversity for habitat and higher biologicalculture were also developed.

productivity for living resources. These

Theme II. Development of an automaticcharacteristics of Sato-Umi are also suitable sites

environmental monitoring system andfor demonstrating multi-functional roles of fisheries.

environmental forecasting technology. An
automatic monitoring system to monitor water
quality has been established in Ago Bay and the

11

ay

Fig. 1. Location of Ago Bay and its outline showing the enclosed topography and rias-type coastline.
real time observation data are open to the public

muddy dredged sediment which contains richthrough the Internet. An ecosystem model is alsoorganic matter but has always been treated as

being developed. By combining these two tools,

useless material in Ago Bay.

construction of a system that can forecast

We set up the six experimental tidal flats inenvironmental changes in water quality is being

which the mixing ratio of dredged sediment with

developed.

original sandy sediment in the area was changed
stepwise (Figure 3). Sediment quality and benthic
New technology forspecies on experimental tidal flats have beendeveloping biologically active tidal flats

monitored for three years. The following results

Sediment eutrophication and the frequent

were obtained from the field study: 1) The number

occurrence of oxygen-deficient water at the bottomof benthic species in the experimental tidal flats

layer has caused the destruction of the benthic

constructed by muddy dredged sediment increased

ecosystem and hence a decrease in biologicalafter six months (Figure 4), and 2) The suitable

activity in recent years. As a result of multi-

range of sediment quality on tidal flats forspectrum aerial picture analyses, it was found thatmacrobenthic species was found to be 3-10 mg/g

approximately 70% of the tidal flat and shallow

dry sediment for COD and 15-35% for mud content

areas had been decreased by land reclamation andratio (i.e. silt and clay content ratio). These results

other artificial environmental transformation along

indicate that macrobenthic species decreased not

the coast of Ago Bay (Figure 2). Therefore, one of

only when organic matter and mud content was

the major causes of environmental deterioration is

too high but also when organic matter and mud

considered to be reduction of shallow coastal areas,

content was too low in the sediments. Accordingly,

including tidal flats and seagrass beds that

artificial tidal flat material mixed with muddy

originally provided shallow areas with natural

dredged sediment rich in organic matter andpurification capability. In this context, the present

natural tidal flat sediments provides better

Ago Bay Restoration Project aims to enhance theconditions for the habitat of the benthic species

natural purification capability and to recoverthan a conventional construction method of a tidal

better material circulation around the shallow

flat that uses clean sand.

areas. New technology has been developed forconstructing functional artificial tidal flats using

12

Osamu MATSUDA

Old tidal flat area

Fig. 2. An aerialFig.2.photograph in which transformation of shallow coastal areas toreclaimed land (shaded area) are shown.

大規模干潟

浚渫土50%

浚渫土30%

浚渫土30%

Fig. 3. Sketch of the experimental site and scenes of construction at Tategamiura
where new technology for tidal flats and Zostera beds were developed.

Fig. 4. Schematic display on the effects of tidal flat enrichment by dredged sediment inwhich species numbers and the biomass of macrobenthos increased.

13bases for seagrass beds that were prepared mainly
Technology development forfrom dredged sediments treated with a coagulant

dewatering dredged sediments and its application(Aquarefine: ARP), then mixed with different

In Ago Bay area, dredged sediments have so far

hardeners to be used as a bed for eelgrass (Zostera

been placed in confined disposal sites but recently,

marina Linnè) germination. Hardeners used in thisacquisition of disposal sites is becoming difficult

study were Gypsander, polyvinyl alcohol (PVA).

and the cost of land development is rising.

Eelgrass germination and propagation were closely

Therefore, emphasis is shifting toward utilizing

observed for almost six months. Data show highthese materials for beneficial application in thegermination rates in the samples treated withmarine environment. One of the main obstacles tohardeners compared with the ones without

treat dredged sediment is its extremely high water

treatment. For original sandy sediments that were

content. In order to overcome this problem,

used as control samples, low germination rate wastreatment by appropriate coagulants followed byobserved presumably due to the particle size anddewatering are necessary to harden the dredgedlack of organic matter. Leaf area index (LAI) for

sediments for easy handling. A new technology toeelgrass germinated both in the control andwhich the name Hi-Biah-System (HBS) was given,

dredged sediments without treatment were less

was developed in the project to perform thisthan that for samples treated with ARP and otheroperation. Main components of HBS are: main

hardeners.

stock tank, coagulant chamber, reactor, andBivalves are widely used as bio-indicators ofdewatering system. Continuous flow operation canheavy metals and other pollutants in coastal areas,

be achieved through a fully automatic system.

since bivalves are well known to concentrate these

Different coagulants were tested to check theircontaminants, providing a time integrated

abilities to form larger and more stable flocks.

indication of environmental contamination.

After coagulation and following the dewatering

Therefore, safety of treated sediments withprocess, water content of the original sediments

different coagulants was checked through thewas remarkably reduced. Treated sediment cakes

growth of short necked clams in the prepared

were applied in many ways for constructing

artificial tidal flats.

different types of artificial tidal flats (Figure 5).
Another application of HBS is to provide suitable

Five different experimental tidal flats wereprepared with use of; ARP, Pellets, Gypsander,

Fig. 5. Appearance of the automatic dewatering system of dredged sediment andscenes of dewatering processes.

14

Osamu MATSUDA

Ecorton, and sand only (without treatment). On

month. Fully matured seeds were preserved undereach flat, 200 short-necked clams were deployed

low temperatures of 0-4℃, which promoted

inside stainless steel cages covered with nylon net.

germination. In late autumn when water

After three months of deployment, sampling wastemperature decreases to less than 20℃, the seeds

carried out to monitor mortality, length, height,

begin to germinate. The Zostera mat system togrowth, and heavy metals in the clam tissues.

sow seeds for growing the plants was developed.

Maximum mortality was obtained with control flat

The size of the mat is 50x50 cm and is 2 cm in(16%), whereas minimum mortality was obtained

thickness and about 1.2 kg in weight. The mat iswith Pellets (0%). Reasonable growth, whichconstructed with four layers; those are iron net of

exceeed 50% from the original values, was

4 cm mesh, jute net of 2 mm mesh, jute fiber mat

observed for the clams in the different flats. Heavyof 5 mm in thickness and iron net of 4 cm mesh.

metals were measured by ICP-MS. Although

Seeds were sowed between jute mesh net and juteheavy metals in general showed a little increasefiber mat. Then, many bases were connected withafter three months of deployment, thecotton ropes in a row at intervals of 50 cm. Thus,

concentrations were below the level ofthe bases were easily settled on the sea bottom

international harmful standards.

continuously on the straight line from a small boat.
Many seeds germinated after a month, and grew

Development of aup after three months. We set 250 and 400 bases

new method for recovering Zostera bedof Zostera mat in 2004 and 2005, respectively.

Zostera marina Linnaeus is widely distributed in

Growth patterns and seasonal changes in density

the temperate zone of the northern hemisphere. It

of Zostera on the bed were surveyed. Optimal andgrows in calm and inner coastal areas and forms aupper limit temperatures for germination anddense populations called Zostera beds or Zostera

growth of this plant were also studied in thezones on sandy or muddy bottoms. This seagrasslaboratory (Figure 6).

bed performs a major role as a primary producer

Several advantages of the Zostera mat provedin the coastal ecosystem and serves coastal fish

are as follows. When seeds germinate, seedlings

and other animals with an important nursery andcan make root in the jute mat which helps

spawning ground. In Japan, Z. marina had longseedlings attach tightly to the bottom. By

been distributed in almost all coastal regions, butconnecting Zostera mat with ropes in a row, it issince the 1950s the beds have decreased

easy to set many bases on the sea bottom without

drastically. So, not a few recovering programs ofany kind of diving effort. Fisherman can do all the

Zostera bed have started since the 1960s in various

procedures, such as collecting mature plants,

regions for conservation of the coastal environment

promoting maturation of seeds, preserving seeds,

and the propagation of fishery recourses. Several

sowing seeds on the bases and deploying the bases

effective methods for recovering the beds haveon the sea bottom without special instruments andbeen developed, but the methods are generally

the use of difficult techniques. This base is madecomplicated and sometimes very difficult for

only of natural materials such as jute fiber androutine use by local people because of the need forcotton ropes, i.e. environment-friendly resources.

special instruments or technologies andconsiderable SCUBA diving effort. In this project,

Automatic environmental monitoring systema simple, convenient and effective method named

The automatic monitoring system in Ago Bay

the Zostera mat system that is applicable to local

consists of five sets of the automatic water quality

fisherman, was developed.

observation stations (WQOS) and two sets of the

Reproductive shoots of Zostera with developing

automatic flow observation stations (FOS). One ofseeds were collected from late spring to summer

the WQOS placed at the bay mouth collects

and were put in mesh bags for promoting

information closely related to open sea, while thematuration of seeds in sea water for about arest of the WQOS are established in the center

15

Fig. 6. Photographs showing the application of Zostera mats on which Zostera marina
germinated and grown.
and inner parts of the bay to get information on

The observation data of the WQOS and the FOS

the bay. The two FOS are established in line on

are transmitted to the Core Research Laboratory

the transverse section just inside the bay mouth.

of the project at one hour intervals, using a

The observation items of the WQOS are watercellular-phone network, and the data processed

temperature, salinity, chlorophyll fluorescence,with the personal computer of the laboratory are

dissolved oxygen and turbidity. The detector unit,

immediately distributed to the Internet throughin which the observation sensors are installed, goes

the Web server. The homepage is actively

up and down with a winch on the floating platform,

accessed not only by researchers but also by pearl

and acquires the data for every water depth. In

culture fishermen; consequently, it contributes toorder to prevent biofouling, the detector unit isadvertising the significance of the project to local

hauled up and is exposed to the air during theresidents (Figure 9).

time between operations and goes down into water

Another objective of the environmental

only during the time of measurement. This

monitoring system is a short-term prediction ofsignificantly reduced the frequency of maintenancewater quality. The observation data are used as

and contributed to raise the time of operation. The

the input data and the numerical simulation model

WQOS has already been operated for more thanunder development is expected to perform thethree years, and attained an high operation rate oftask. The dynamic behaviors of water quality in

90-95%, including the system stops at the time of

the bay have begun to be disclosed by thetyphoon attacks. The FOS consists of the seabedenvironmental monitoring system.

installation type ADCP and an acoustic modem
that performs communication with the floating

Development of hydrodynamic andplatform. The wireless communication systemecosystem model for Ago Bay

began to work in November 2005, however, theThree different models are under development.

two ADCP had already been collecting data since

They are a three-dimensional hydrodynamic model,

July 2003. The analysis of the recorded dataa water quality model and a sedimentation model.

showed the effectiveness of the FOS to predict the

The hydrodynamic model has characteristics thatvariation of water quality in the bay (Figures 7

the vertical grid interval shrinks toward the sea

and 8).

surface. This aims at improvement of16

Osamu MATSUDA

Fig. 7. Automatic environmental monitoring system of Ago Bay.

Fig. 8. Photographs showing the structure of a sensor unit.
computational accuracy of salinity, which has acompartments are included in the model, whichstrong vertical gradient near the sea surface.

allows the competition of phytoplankton species

According to the analyses already done, the river

between a diatom and a dinoflagellate. The

plume that spreads on a sea surface was clearly

concentration of carbon, nitrogen and phosphorus

captured, and density stratification in summer

are carefully implemented in the model so that theseason was reproduced quite accurately. Since thecomputational results can be utilized in the

nutrient inflow from the land area is conveyed byinvestigation of material circulation. The

the river plume, the models are also expected tosedimentation model also has 19 compartments

improve the accuracy of water quality calculation.

and takes into consideration the circulation of

The water quality model includes dynamics ofcarbon, nitrogen, phosphate, iron, manganese,plankton and nutrients, and the physiologicalsulfur and oxygen. It is one of the targets of thecharacteristics of pearl oysters. Nineteen

present study to couple the water quality model

17with the sedimentation model and to perform

planned in the project. The real time observation

analyses that reproduce the existing phenomenon

data of the environmental monitoring system is

as correctly as possible.

utilized and is read into the numerical models with

To obtain basic data for the numerical models,use of the data assimilation technique. This will beoceanographic observations and experiments withtried after the completion of the development of

the sediments have been conducted over three

the numerical models.

years. In addition to that, a biological experimentfor developing a physiological model for pearl

Closing Remarks

oysters has been conducted. The water quality

Results of the study and development of thedata measured by the environmental monitoring

technology during the course of the projectsystem since September 2003 also created a huge

including development of functional tidal flats, adata base. All of those data will be effectively

new method for recovering Zostera beds, real time

utilized to complete the integrated Ago Bay model

environmental monitoring systems and(Figure 10).

environmental forecasting technology to be

A short-term prediction of the water quality isestablished are expected to contribute to establish

Fig. 9. Display of monitoring data during three years (water temperature, salinity,
dissolved oxygen and chlorophyll from above) at Tategami Station.

Environmental
Monitoring System
Chlorophyll,
oxygen andturbidity
data

Weather Forecasting Data
Air temperature, solar radiation,
precipitation and Wind data

Water temperatureand salinity data

Hydrodynamic Model

River discharge data

Precipitation
data

Flow and vertical diffusivity data

Pelagic Ecosystem
Model
Flux data of organic matter,
nutrients, oxygen and others

Benthic and
Early Diagenesis Model
Fig.10.

Flux data of organic matterand nutrients

Watershed Area
Model

Flux data of organic matter, nutrients and oxygen

Physiology Model
Of Pearl Oyster

Fig. 10. Structure of prediction model by integration of the environmental monitoring
system and other models being developed.

18

Osamu MATSUDA

sustainable Sato-Umi through effective

1st International Workshop on Management

environmental restoration in the Ago Bay area.

and Function Restoration Technology for

Recent attempts of environmental restoration in

Estuaries and Coastal Seas (ed. by Jung K. T.),

this area with broader cooperation among a

KORDI, pp. 1-6.

variety of stakeholders can be a model of

Matsuda O. 2007. New approach for the integrated

environmental restoration of small scale enclosed

aquaculture management from the view point

coastal seas with particular emphasis toof multi-functional role of fisheries andenvironmental education for the next generationaquacultures. Bull. Fish. Res. Agen. No. 19, pp.

and sustainable environmental management by

167-171.

local people and local municipalities. The concept

Maegawa M. 2006. New technology for developingof Sato-Umi may help realize the motto of theZostera bed. Proceedings of the 16 th Joint

project: "Better life through wise and sustainable

Symposium by Cooperation Council for Coastal

use of coastal environments" in Ago Bay.

Environment-related Society in Japan(ENKANREN), pp. 34-36. (in Japanese)

Acknowledgment

Okumura H. et al. 2006. Environmental education

The author appreciates members of the project,in elementary school developed in Ago Bay

in particular of Dr. Tadaya Kato, Professor

area. Proceedings of the 16th Joint Symposium

Emeritus of Mie University, Dr. Miyuki Maegawa

by Cooperation Council for Coastalof the same university, Dr. Satoshi Chiba ofEnvironment-related Society in Japan

Yokkaichi University, Mrs. Hideki Kokubu and(ENKANREN), pp. 20-24. (in Japanese)

Hiroyuki Okumura of Mie Prefecture, Dr. Dabwan
Ahmed and Mr. Daizo Imai of Mie Industry andEnterprise Support Center, for providing valuable
information and data.
References
Chiba S. et al. 2006. Contribution of environmental
monitoring system to the solution ofenvironmental problems. Proceedings of the
16th Joint Symposium by Cooperation Council
for Coastal Environment-related Society inJapan (ENKANREN), pp. 5-12. (in Japanese)
Imai T. et al. 2006. New technology for treating
muddy dredged sediment. Proceedings of the
16th Joint Symposium by Cooperation Council
for Coastal Environment-related Society inJapan (ENKANREN), pp. 37-39. (in Japanese)
Kokubu H. et al. 2006. New technology fordeveloping tidal flat. Proceedings of the 16th
Joint Symposium by Cooperation Council for
Coastal Environment-related Society in Japan(ENKANREN), pp. 49-55. (in Japanese)
Matsuda O. 2007. Overview of Ago Bay restoration
project based on the new concept of "SatoUmi": a case of environmental restoration of
enclosed coastal seas in Japan. Proceedings of19

Utilization of Waste Porphyra Products as Eco-friendly Feed Ingredients
Tsuyoshi SUGITA＊1, Takeshi YAMAMOTO＊1, and Takao YASHIMATSU＊2
Abstract

We investigated the growth and hepatopancreatic enzyme activities in red sea

bream, Pagrus major, fed diets containing waste nori, Porphyra spp. (red algae, purple laver)with different protein to fat ratios. Fingerlings of 10.1 g average body weight were fed for 10
weeks on the optimum fat and protein (11 and 55 %) control diet (CTD) and two higher fat
and lower protein (19 and 42 % and 25 and 36 %, respectively) experimental diets (MFD and
HFD). All diets were supplemented with 5 % waste nori. Weight gain, specific growth rate
and feed efficiency in fish fed the CTD and MFD were higher than those in fish fed the HFD.
Plasma total cholesterol, phospholipid, and free fatty acid concentrations and whole body crude
fat content were increased as dietary fat level increased, whereas hepatopancreatic lipogenic
enzyme activities (glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase,NADP-isocitrate dehydrogenase and NADP-malate dehydrogense) were decreased as the
dietary fat level increased. Aspartate aminotransferase activity of the MFD group was
significantly lower than the activity of the CTD group. These findings suggest that dietary fat
content can be increased from 11% to 19% by supplementing 5% waste nori in fingerling red
sea bream diets.
Key words: Pagrus major, Porphyra, eco-friendly fish feed, high fat low protein diet,hepatopancreatic enzyme activity
Beamish and Medland 1986), yellowtail, Seriola
Introduction

quinqueradiata (Shimeno et al. 1980), Atlantic
salmon, Salmo salar (Hillestad and Johnsen 1994),

In recent years, environmental pollution by

and Atlantic halibut, Hippoglossus hippoglossus

nitrogen and phosphorus loading from fish farming(Aksnes et al. 1996), whereas no such effects

has become a serious social problem. These

were observed with tilapia, Oreochromis niloticus

pollutants are considered to originate mainly from

(Shimeno et al. 1993) or Japanese flounder,

fish meal, which is a main feed ingredient in fish

Paralichthys olivaceus (Kikuchi et al. 2000). In

feeds. Furthermore, the drastic decrease of feed-

our previous report ofnfingerling red sea bream,

grade fish landings worldwide and increasing

Pagrus major (Sugita et al. 2007a), a protein-demand of formula feed production for aquaculture

sparing effect by fat was not also found.

has made the market price of fish meal to increase.

Nori, Porphyra spp. (red algae, purple laver) are

Therefore, from the viewpoints of environmentcommercially and culturally important species usedand economics, dietary fish meal content should be

widely as traditional Japanese food. Nori products

reduced as much as possible.

contain high amounts of taurine, an important

The protein-sparing effects dietary of fat

amino acid for the growth of marine fish, as well as

have been demonstrated with rainbow trout,minerals and vitamins. In recent years, occurrence

Oncorhynchus mykiss (Takeuchi et al. 1978;of discolored nori with no commercial value

2009 年 8 月 10 日受理（Received. August 10. 2009）＊1
Feed Research Group, Aquaculture Systems Division, Inland Station, National Research Institute of Aquaculture, Fisheries Research Agency,
Tamaki, Mie 519-0423, Japan＊2
Feed Research Group, Aquaculture Systems Division, National Research Institute of Aquaculture, Fisheries Research Agency, Minamiise, Mie
516-0193, Japan

20

Tsuyoshi SUGITA, Takeshi YAMAMOTO, and Takao YASHIMATSU(i.e., waste nori) has become a serious problem.

crude protein, crude fat and crude sugar in the

Therefore, effective uses of the waste nori have

CTD were 55, 11, and 11%, respectively, which are

been sought. There have been several studies on

considered optimum (Furuichi et al. 1971, Yone etthe use of various kinds of algae meal in fish feedal. 1971, Yone 1976, Takeuchi et al. 1991). Crude(Stanley and Jones 1976, Tsai 1979, Appler 1985). It

protein contents were 42% in the MFD and 36%

has been confirmed that a small amount of algaein the HFD, and crude sugar contents were 9%

added to fish feed significantly improves growth,and 7%. On the other hand, crude fat contents

lipid metabolism, body composition, and disease

were 19% in the MFD and 25% in the HFD. The

resistance (Nakagawa and Kasahara 1986, Satohphosphorus content in the CTD was 2.8%, andet al. 1987, Xu et al. 1993, Mustafa et al. 1995).

the content decreased as the dietary BFM level

However, the supplemental effects of the waste

decreased (i.e., the dietary fat level increased),nori on the growth and lipid metabolism have notand the value was 2.4% (MFD) and 2.1% (HFD).

been studied in red sea bream. We compared theGross energy content in all diets ranged from 20.1-

growth and hepatopancreatic enzyme activities in

22.9MJ/kg.

red sea bream fed diets containing waste nori withdifferent protein to fat ratios.

Fish and Feeding Procedures
Fingerlings of red sea bream were obtained

Materials and Methods

from the Kinki University Fish Nursery Center,
Uragami, Wakayama, Japan and transferredExperimental Dietsto the Nansei Station of the National Research

The formulation and proximate composition of

Institute of Aquaculture, Minamiise, Mie, Japan.

the experimental diets are shown in Table 1. The

The fish were initially stocked in two 500 L fiber

control diet (CTD) contained 69% brown fish meal

reinforced plastic circular tanks, supplied with

(BFM), 4.7% pollock liver oil (Riken Vitamin, Tokyo,

sand filtered and aerated sea water. The fish wereJapan) and 10.5% gelatinized potato starch (Tokai

fed a commercial feed (Kyowa Hakko Kogyo Co.,

Denpun, Shizuoka, Japan) as the main protein, fat,Ltd., Tokyo, Japan) until they reached nearly 8.5

and carbohydrate sources, respectively. Medium

g. Then 20 fish of a similar size were selected

fat and medium protein diet (MFD) and the highest

and stocked in each of six 100 L plastic circular

fat and the lowest protein diet (HFD) containedtanks with duplication for each dietary treatment.

13.7 and 19.3% pollock liver oil. On the other hand,

Seawater was supplied at a flow rate of 3 L/

the BFM levels of MFD and HFD were reduced tomin, and the commercial feed was fed to the fish

53 and 45%. The gelatinized potato starch content

for another two weeks to acclimate them to thewas reduced to 9% (MFD) and 5.1% (HFD). All

experimental conditions. The water temperature

diets were supplemented with 5% waste nori,

during the experiment was 19.0±1.7℃.

which was supplied from Saga Prefectural Ariake

Just before the start of the feeding trial, theFisheries Research and Development Center,fish were weighed individually, and eight fish

Koshiro, Saga, Japan. Krill meal was supplemented

were randomly sampled from a surplus tank after

to all diets as a feeding stimulant. Chromium oxidebeing anesthetized in 0.01% 3-ethyl aminobenzoate

was included as a marker for nutrient digestibility

methanesulfonic acid (initial fish). In the eight fishmeasurement. Cellulose was used as a filler. All

sampled, four were used for proximate whole bodythe ingredients were thoroughly mixed, moistenedcomposition analysis. After taking blood from theby the addition of 35% water (w/w), and pelleted

other four fish, the hepatopancreas was taken forusing a meat chopper (Hanaki Mfg Co., Ltd., Tokyo,

analyses of proximate composition and metabolic

Japan). Then the pellets were dried at 50℃ for 6 h

enzyme activity. After measuring the hematocrit,and stored at -20℃ until fed to the fish.

the blood was centrifuged at 4,000 x g for five

Analytical nutrient and energy contents of theminutes to separate the plasma. All samples weretest diets are given in Table 1. The content of

stored in a freezer at -80℃ until analyzed. The





 

 DBCEFG$!A>@
21#&'0* 35180&7.32&2)453;.1&7*&2&0<6.63+7-**;4*5.1*27&0).*76
.*76

#









 



2,5*).*27:*7:*.,-7
53:2+.6-1*&0



%&67*235.

   

 3003(/0.9*53.0 

 *0&7.2.=*)437&7367&5(-

 

 *008036*?

3267&27(31432*276







   

2&0<6.6)5<:*.,-7'&6.6
58)*4537*.2;







58)*+&7

 



58)*68,&5 



 -364-3586

   

5366*2*5,</,).*7 



#(327530).*71*).81+&7).*7-.,-+&7).*758)*4537*.2(58)*+&7 /5.001*&0 1.2*5&01.;785*,.23*7&0   9.7&1.21.;785*"8,.7&*7&0 & (-531.(3;.)*(-531.(3;.)*(*008036*   ,8&5,81

experimental diets were fed to the fish with an
initial mean weight of 10.1 g to satiation, three

Blood Component Analysis

times daily (0900, 1300, and 1700), six days per

Blood was taken using a heparinized syringe.

week for 10 weeks. At the end of the feeding trial,

Hematocrit was measured using microhematocrit

the fish were weighed individually, and seven fishtubes. After sealing, the tubes were centrifuged

per tank were sampled after one day starvation. In

at 10,000 x g for 5 min. The contents of plasma

the seven fish sampled, four were used for whole

glucose, triglyceride, total cholesterol and total

body proximate composition analysis and theprotein were determined using an automaticother three fish were used for analyses of plasma

analyzer (SPOTCHEM SP-4410, Arkray, Kyoto,components and hepatopancreatic proximate

Japan). Plasma free fatty acid (FFA) andcomposition and enzyme activity.

phospholipid were measured using commercial kits

Another 38 fish (11.0±0.3 g) were selected from(NEFA C Test Wako and Phospholipids C Test

the surplus tank and stocked in each of six 50

Wako, Wako Pure Chemical Industries, Ltd., Osaka,

L tanks for fecal collection (Sugita et al. 2007b).

Japan) and free amino acid (FAA) was assayed

Seawater was supplied at a flow rate of 4.5 L/

using dinitrofluorobenzene (Goodwin 1968).

min, and the commercial feed was fed to thefish for another seven days to acclimate them to

Chemical Component Analysis

the experimental conditions. Each experimental

Determination of moisture, crude protein, crude

diet was fed to the fish to satiation twice in thefat, and ash in the test diets; feces; whole fish;morning. For the initial six days, the fish wereand hepatopancreas were assayed by 10 h drying

acclimated to the diets and fecal samples were not

at 110℃, semi-micro Kjeldahl method (N x 6.25),

collected. Feces excreted from 1730 on one day

diethyl ether extraction, and 5 h heating at 600℃,

to 0830 the next day, were collected immediately

respectively (Shimeno 1974). Crude sugar content

prior to the next satiation feeding each day forin the diets was determined by measuring simple

six days, pooled, and freeze-dried. The watersugar liberated in boiling 1N sulfuric acid for 4 h,temperature during fecal collection was 19.0±1.7℃.

based on the phenol-sulfuric acid method (Shimeno

22

Tsuyoshi SUGITA, Takeshi YAMAMOTO, and Takao YASHIMATSU

1974). Phosphorus contents of the diet, feces, andmeasurements of enzyme activities was measured

whole fish were determined using ammonium

using UVmini 1240 spectrophotometer (Shimadzu)

molybdate and ascorbic acid (Lowry and Lopez

equipped with a thermo-controlled cell positioner

1946). The gross energy content of the diets was

CPS-240A (Shimadzu). All the enzyme activities

measured using a CA-4PJ bomb calorimeter

were expressed as µmol of substrate or coenzyme(Shimadzu, Kyoto, Japan). The chromium oxide

converted per min per 100 g body weight.

contents of the diets and feces were measured
using a spectrophotometer (UVmini 1240,

Statistical Analysis

Shimadzu) after the samples were hydrolyzed

The effects of diet on growth, feed utilization,in nitric acid and perchloric acid (Furukawa andapparent digestibility and biochemical parameters

Tsukahara 1966).

were evaluated by one-way ANOVA and Fisher`sProtected Least Significant Difference test. A

Enzyme Activity Analysis

probability level of less than 0.05 was considered

Hepatopancreas samples were homogenizedsignificant. The statistical analyses were carried

with nine volumes of 3-morpholinopropansulfonicout using the Stat View program (SAS Institute,acid buffer (MOPS-buffer; 30 mM, pH7.0) using a

Cary, North Carolina, USA).

Polytron (Kinematica AG, Switzerland, PTA 10S).
Results

The homogenate was centrifuged at 12,000 x g for
30 min at 4℃. The resulting supernatant was used
to analyze the activities of the following enzymes:

Apparent Digestibility

phosphofructokinase (PFK, EC 2.7.1.11), glucose-

Table 2 shows the apparent digestibility of

6-phosphatase (G6Pase, EC 3.1.3.9), fructose-1,6-nutrients in the experimental diets in fingerlingbisphosphatase (FBPase, EC 3.1.3.11), glucose-6-

red sea bream. The apparent digestibility of crude

phosphate dehydrogenase (G6PDH, EC 1.1.1.49),

protein was not significantly different among the

6-phosphogluconate dehydrogenase (6PGDH, EC

dietary groups. The apparent digestibility of crude

1.1.1.44), NADP-isocitrate dehydrogenase (ICDH,

fat in fish fed the CTD and MFD was higher

EC 1.1.1.42), aspartate aminotransferase (GOT,than the digestibility of the HFD. The apparent

EC 2.6.1.1) and alanine aminotransferase (GPT,phosphorus absorption increased as the dietary

EC 2.6.1.2). These enzyme activities were assayed

fat level increased (i.e., the dietary BFM levelby the methods described previously (Sugita etdecreased).

al. 2001, 2007a). Pyruvate kinase (PK, EC 2.7.1.40)

Growth and Feed Performances of Fish in theactivity was measured as the rate of NADH

Feeding Trial

reduction (Moon and Johnston 1980). NADP-malate

Growth and feed performance are presented indehydrogenase (MDH, EC 1.1.1.40) activity was

Table 3. Weight gain (WG), specific growth rate

determined as the rate of NADP reduction (Ochoa(SGR), and feed efficiency (FE) in fish fed the CTD

1995). The absorbance of samples during theand MFD were higher than those in the HFD  <:;=>?968

!"*% ..!/%,1$)'%01)")*)15-&,21/)%,10-&1(%%4.%/)+%,1!*$)%10),&),'%/*),'
/%$0%!"/%!+
)%10















/2$%./-1%),7 77

/2$%&!17"7" 7!

!

" 7#(-0.(-/20  7

 7

 !*2%0!/%+%!,7-&13-0!+.*%0 !*2%0),1(%0!+%/-3&-**-3%$"51(%

0!+%*%11%/!/%,-10)',)&)#!,1*5$)&&%/%,1  %%1(%&--1,-1%-&!"*%23group. On the other hand, feed consumption rate

the final fish for each diet are shown in Table 5.

was highest in the HFD group. Protein efficiency

Moisture and crude protein contents decreased

ratio (PER) and protein retention in the fat-rich dietas dietary fat level increased, whereas crude fat(MFD and HFD) groups were higher compared

content increased as dietary fat level increased.

with those of the CTD group. Phosphorus retention

Ash and phosphorus contents were not significantly

was not significantly different among the dietarydifferent among the dietary groups. Table 5groups.

also shows the hepatopancreas composition of
fingerling red sea bream. Hepatopancreatic crude

Hematological Characteristics

protein and crude fat contents, and hepatosomatic

Table 4 shows the results of hematologicalindex (HSI) was not significantly influenced by theparameter analyses of fingerling red sea bream.

dietary treatment.

Plasma FFA, total cholesterol and phospholipid
Hepatopancreatic Enzyme Activity

concentrations increased as the dietary fat level
increased. Plasma glucose, triglyceride, FAA and

The hepatopancreatic enzyme activities of thetotal protein concentrations were not different

initial and final fish are shown in Table 6. The

among the dietary groups. Hematocrit level was

activities of G6Pase, FBPase, G6PDH, 6PGDH,

decreased as the dietary P/F decreased; however,

ICDH, and MDH were the highest in the CTD

it was not significantly influenced by dietarygroups, and those activities decreased as thetreatment.

dietary fat level increased. GOT activity of the
MFD group was significantly lower than that of body 
 IGHJKL%
"FCE
Whole
and Hepatopancreas Composition
the CTD
group, whereas GOT activity of the HFD
The whole body composition of the initial andgroup was not significantly different from that of$*+4. 97=;1*6-/..-8.9/795*6,.:7//260.942609.-:.*+9.*5/.-;1..>8.925.6;*4-2.;:
2.;:

$

!





 

D 





26*4'0/2:1

  D    D  ++  D   D + D * D *+  D + D  D 

..-,76:<58;2769*;.'-*?

 D *







D +


*

!"

D 

 D+#" 

62;2*4'0/2:1
'







D  +D   D * D *+  D    D    D  + D  *  D  +  D  + D 



".;.6;276
BBB!97;.26


BBB!17:8179<:

D 

 D 

&*4<.:*9.5.*6D#7/-<842,*;.;*63:&*4<.:26;1.:*5.97=/7447=.-+?;1.:*5.4.;;.9
*9.67;:2062/2,*6;4?-2//.9.6;!   
#..;1./77;67;.7/$*+4. 
'.201;0*26'

>/26*4'262;2*4'262;2*4'#8.,2/2,097=;19*;.#"

>89.::.-*:

>@46/26*4'46262;2*4'A9.*92608.927--*?:

>/..-26;*3.(@262;2*4'/26*4' A>9.*92608.927--*?:)

..-.//2,2.6,?

>/26*4'262;2*4'-9?/..-26;*3.



!97;.26.//2,2.6,?9*;27!"/26*4'262;2*4'-9?/..-897;.2626;*3.



>89.::.-*:

>@/26*4'>/26*4+7-?897;.26262;2*4'>262;2*4+7-?897;.26A;7;*4/..-26;*3.>/..-897;.26
>89.::.-*:
>@/26*4'>/26*4+7-?817:8179<:262;2*4'>262;2*4+7-?817:8179<:A;7;*4/..-26;*3.>/..-817:8179<:





 

24

 ECDFGH$!B?A
Tsuyoshi SUGITA, Takeshi YAMAMOTO, and Takao YASHIMATSU#&'0* *1&8303,.(&0(-&6&(8*6.78.(73++.2,*60.2,6*)7*&'6*&1+*)8-**<4*6.1*28&0).*87
.*87

#







 

2.8.&0>

#6.,0=(*6.)*1, 1>@15 



-374-30.4.)1, 1






.2&0

09(37*1, 1

#38&0(-30*78*6301, 1@>

> @>@&@  @ & @ 

&

>

@

 @@' @'@ '@ @  @ &''1, 1> @>#38&04638*.2, 1 > @> @> @*1&83(6.8



 @

 @


&' @ @ 

@ 

%&09*7&6*1*&2@"3+)940.(&8*8&2/7 +.7-8&2/%&09*7.28-*7&1*63;+3003;*)'=8-*7&1*0*88*6
&6*2387.,2.+.(&280=).++*6*28 

"**8-*+338238*3+#&'0* :*6&,*:&09*73+ +.7-


 
6**+&88=&(.)

 CABDEF# @=?

6**&1.23&(.)

"&'0* 53:.1&7*(31436.7.323+9-30*'3);&2)-*4&734&2(5*&63++.2,*50.2,5*)6*&'5*&1+*)
7-**:4*5.1*27&0).*76
.*76

"









 

2.7.&0.2&0%-30*'3);
3.6785*58)*4537*.2: 


58)*+&7  < > '<> &< >&'< >

&'<  > &<>

'<> '<  >

&< >

6- < >

< >

< >

-364-3586



< >

<>

< >

<

<

*4&734&2(5*&658)*4537*.2: 

<

58)*+&7  > 

> > 

 > > !

  <  >

< 

< > 

 > 

!**7-*+337237*3+"&'0* !**7-*+337237*3+"&'0* $&08*6&5*1*&2>!3+)840.(&7*7&2/64330*)6&140*6 +.6-6&140*$&08*6.27-*6&1*539
+30039*)';7-*6&1*0*77*5&5*2376.,2.+.(&270;).++*5*27  
$&08*6&5*1*&2>!3+)840.(&7*7&2/64330*)6&140*6 +.6-6&140*$&08*6.27-*6&1*539
+30039*)';7-*6&1*0*77*5&5*2376.,2.+.(&270;).++*5*27  *4&73631&7.(.2)*:! :-*4&734&2(5*&69*.,-7%$&08*6&5*1*&2>!3+)840.(&7*7&2/6 +.6-7&2/

>







 ECDFGH%"B?A
25$'(1++5'845'3)6+'8/)2+8'(41/)+3>=2+')8/:/8/+74,,/3-+61/3-6+*7+'(6+'2,+*8.++<5+6/2+38'1*/+87
/+87

$

!







 



2412/3 -(4*=;+/-.83/8/'1
!

 

!



!'7+
!'7+

 
 

!



!







/3'1
  @   @



@  @ @  @ 

(

@ 

'(

 @   @ (' @  @)

 @)



(

@   @

 $



!$



(@ '@ '

@ ( @ '

@ 

(

@'' @  '@ '@ '

  @  @ ( @ ' @ '(

 @

 @

 @

&'19+7'6+2+'3@#4,*951/)'8+8'307 ,/7.8'30&'19+7/38.+7'2+64;
,4114;+*(=8.+7'2+1+88+6'6+3487/-3/,/)'381=*/,,+6+38!  #++8.+,448348+4,$'(1+ #++8.+,448348+4,$'(1+ !!.475.4,69)840/3'7+!!=69:'8+0/3'7+!'7+19)47+5.475.'8'7+
!'7+69)847+ (/75.475.'8'7+!19)47+5.475.'8+*+.=*64-+3'7+!!.475.4-19)43'8+*+.=*64-+3'7+!74)/86'8+*+.=*64-+3'7+!'1'8+*+.=*64-+3'7+ $75'68'8+'2/3486'37,+6'7+!$1'3/3+
'2/3486'37,+6'7+

the CTD group. The activities of PFK, PK, andSince dietary protein contents of MFD and HFD

GPT were not significantly different among thewere lower than CTD, PER and protein retention

dietary groups.

of the MFD and HFD groups were higher than the
CTD group. WG, SGR, FE and apparent crude fat
Discussion

digestibility were not different between the CTD
group and the MFD groups, whereas those were

In our previous report on fingerling red sea

lowest in the HFD group. These results suggest

bream (Sugita et al. 2007a), growth and feedthat waste nori supplementation can improve

performances decreased as the dietary fat levelutilization of high fat and low protein diets toincreased (i.e., dietary protein level decreased).

some degree in fingerling red sea bream. The

Therefore, the authors concluded that fingerling

supplemental effect was not observed in fish fed

red sea bream did not effectively utilize the highthe high fat and low protein diet (HFD), because

fat diet. In the present experiment, crude protein

digestible energy intake for fish fed the HFD

and crude fat contents of the experimental diets

might have been reduced due to the decrease of

were similar to those in the previous experiment.

apparent fat digestibility.

However, growth and feed performances of the

Lipogenic enzymes (G6PDH, 6PGDH, ICDH and

MFD group were equal to those of the CTD

MDH) play an important role in the generation ofgroup. The difference between the present andreduced form nicotinamide adenine dinucleotide

previous experiments was just the waste nori diet

phosphate (NADPH) for lipid synthesis in the liver

supplementation. The present experiment clearly(Kheyyali et al. 1989). In the present experiment,

showed that supplemental waste nori enhanced thethe activities of these enzymes significantly

utilization of the higher fat and lower protein diet.

decreased in the MFD and HFD groups. On the

26

Tsuyoshi SUGITA, Takeshi YAMAMOTO, and Takao YASHIMATSU

other hand, the concentrations of total cholesterol,

Oreochromis (Tilapia) niloticus and Tilapia

phospholipid and FFA in the plasma, and thezillii. Journal of Fish Biology, 27:327-334.

content of crude fat in the whole body increased

Beamish, F.W.H. and T.E. Medland. 1986. Protein

as the dietary fat level increased. These results

sparing effects in large rainbow trout, Salmo

indicate that the accumulated body fat components

gairdneri. Aquaculture, 55:35-42.

did not originate mainly from dietary protein

Furuichi, M., K. Shitanda and Y. Yone. 1971.

and carbohydrate but from dietary fat. Similar

Studies on nutrition of red sea bream-V.

depression in hepatic lipogenic enzyme activity

Appropriate supply of dietary carbohydrate.

and increase in fat deposition by a high fat and low

Report of the Fishery Research Laboratory ofprotein diet was reported in yellowtail (Shimeno et

Kyushu University, 1:91-100.

al. 1980; Shimeno et al. 1981), carp Cyprinus carpio

Furukawa, A. and H. Tsukahara. 1966. On the acid

(Kheyyali et al. 1989), tilapia (Shimeno et al. 1993)

digestion method for the determination ofand Japanese flounder (Kikuchi et al. 2000).

chromic oxide as an index substance in the

Although the GOT activity of the HFD group
was not different from the CTD group, the activity

study of digestibility of fish feed. Nippon
Suisan Gakkaishi, 32:502-506.

of the MFD group was significantly lower than the

Goodwin, J. F. 1968. The colorimetric estimation of

CTD group. The response of GOT activity of theplasma amino nitrogen with DNFB. Clinical

MFD group meant the depression of breakdown

Chemistry, 14:1080-1090.

from protein to amino acid. These results suggest

Hillestad, M. and F. Johnsen. 1994. High-energy/

that protein-sparing effect by fat was demonstrated

low-protein diets for Atlantic salmon: Effects

with fish fed the MFD but the effect was limited

on growth, nutrient retention and slaughtercompared to the case in rainbow trout, yellowtail

quality. Aquaculture, 124:109-116.

and so on as mentioned in the introduction.

Kheyyali, D., S. Shimeno and M. Takeda M. 1989.

Judging from the growth performance andEffect of dietary carbohydrate and lipid levels

hepatopancreatic enzyme activities of the present

on hepatopancreatic enzyme and body

experiment and our previous report (Sugita et al.

composition in carp. pp. 451-460, In

2007a), the dietary fat content can be increased

Proceedings of the Third Internationalfrom 11% to 19%; i.e., dietary protein content

Symposium on Feeding and Nutrition in Fish.

can be effectively reduced from 55% to 42%, byKikuchi, K., H. Sugita and T. Watanabe. 2000.

supplementing 5% waste nori in fingerling red sea

Effects of dietary protein and lipid levels on

bream diets.

growth and body composition of Japaneseflounder. Aquaculture Science, 48:537-543.
Acknowledgements

Lowry, O. H. and J.A. Lopez. 1946. The determinationof inorganic phosphate in the presence ofThis study was financially supported in partby the Fisheries Agency, Ministry of Agriculture,
Forestry and Fisheries, Government of Japan.

labile phosphate esters. Journal of Biological
Chemistry, 162:421-428.
Moon, T. W. and I.A. Johnston. 1980. Starvationand the activities of glycolytic andReferences

gluconeogenic enzymes in skeletal muscle andliver of the plaice, Pleuronectes platessa.

Aksnes A., T. Hjertnes and J. Opstvedt. 1996.

Journal of Comparative Physiology, 136:31-38.

Effects of dietary protein level on growth andMustafa, M. G., S. Wakamatsu, T. Takeda, T.

carcass composition in Atlantic halibut

Umino and H. Nakagawa. 1995. Effect of algae(Hippoglossus hippoglossus L). Aquaculture,meal as feed additive on growth, feed

145:225-233.

efficiency, and body composition in red sea

Appler, H.N. 1985. Evaluation of Hydrodictyon
reticulatum as protein source in feeds forbream. Fisheries Science, 61:25-28.
Nakagawa, H. and S. Kasahara. 1986: Effect of Ulva

27
meal supplementation on the lipid metabolism

Influence of dietary phosphate sources onof red sea bream. Nippon Suisan Gakkaishi,

apparent phosphorus, protein and fat

52:1887-1893.

absorptions in fingerling red sea bream Pagrus

Ochoa, S. 1995. Methods in Enzymology, Volume 1.
Academic press, New York, USA.

major. Aquaculture Science, 55:in press.
Takeuchi, T., M. Yokoyama, T. Watanabe and C.

Ogino, C., L. Takeuchi , H. Takeda and T.

Ogino. 1978. Optimum ratio of dietary energy

Watanabe. 1979. Availability of dietary

to protein for rainbow trout. Bulletin of thephosphorus in carp and rainbow trout. Nippon

Japanese Society of Scientific Fisheries, 44:729-

Suisan Gakkaishi, 45:1527-1532.

732.

Satoh, K., H. Nakagawa and S. Kasahara. 1987.

Takeuchi, T., Y. Shiina and T. Watanabe. 1991.

Effect of Ulva meal supplementation on

Suitable protein and lipid levels in diet for

disease resistance of red sea bream. Nippon

fingerlings of red sea bream Pagrus major.

Suisan Gakkaishi, 53:1115-1120.

Nippon Suisan Gakkaishi, 57:293-299.

Shimeno, S. 1974. Studies on carbohydrate

Tsai, P., 1979. Evaluation of Spirulina platensis as ametabolism in fishes. Report of the Fisheryprotein source in fish and shrimp nutrition.

Research Laboratory of Kochi University, 2:1-

Aquqaculture Science, 2:2-39.

107.

Xu, B., S. Yamasaki and H. Hirata. 1993.

Shimeno, S., H. Hosokawa, M. Takeda and H.

Supplementary Ulva sp. var. meal level in diet

Kajiyama. 1980. Effects of calorie to proteinof Japanese flounder, Paralichthys olivaceus.

ratios in formulated diet on the growth, feed

Aquaculture Science, 41:461-468.

conversion and body composition of young

Yone, Y., M. Furuichi and S. Sakamoto. 1971.

yellowtail. Nippon Suisan Gakkaishi, 46:1083-

Studies on nutrition of red sea bream-III

1087.

Nutritive value and optimum content of lipids

Shimeno, S., H. Hosokawa, M. Takeda, S.

in diet. Report of the Fishery Research

Takayama, A. Fukui and H. Sasaki H. 1981.

Laboratory of Kyushu University, 1:49-60.

Adaptation of hepatic enzymes to dietary lipid

Yone, Y. 1976. Nutritional studies of red sea bream.

in young yellowtail. Nippon Suisan Gakkaishi,

Report of the Fishery Research Laboratory of

47:63-69.

Kyushu University, 3:87-101.

Shimeno, S., D.C. Ming and M. Takeda. 1993.
Metabolic response to dietary carbohydrate tolipid rations in Oreochromis niloticus. Nippon
Suisan Gakkaishi, 59:827-833.
Stanley, J. D. and J.B. Jones. 1976. Feeding algae tofish. Aquaculture, 7:219-223.
Sugita, T., S. Shimeno, Y. Ohkubo, H. Hosokawa
and T. Masumoto. 2001. Response of enzyme
activities and metabolic intermediateconcentrations to epinephrine administrationin hepatopancreas and muscle of carp.
Fisheries Science, 67:81-286.
Sugita, T., Y. Yamamoto and H. Furuita. 2007a.
Effect of partial replacement of dietary protein
by fish oil and palm oil on growth andhepatopancreatic enzyme activities infingerling red sea bream Pagrus major.
Aquaculture Sci.ence, 55:431-440.
Sugita, T., Y. Yamamoto and H. Furuita. 2007b.

29

The Effect of the Methods of Farming on the Environment and Growthof Cultured Red Sea Bream, Pagrus major
Takashi UEDE＊
Abstract The environment of fish farming areas and aquaculture production are considered to
be closely related. Therefore, to establish the efficient use of fish farming grounds, I conducteda research on the subjects in conjunction with the rearing of red sea bream.
The presence of waste feed is assumed to provide the majority of the total particulate nitrogen
discharged. The primary cause of eutrophication of fish farming grounds is excessive loadingof nitrogen and phosphorus. Therefore, reducing waste is an important countermeasure toexcessive nitrogen discharge. The chemical characteristics of phosphorus are different fromthose of nitrogen. Therefore, different measures are required to reduce phosphorus discharges.
In addition, it is suggested that rearing fish at low density is good for the growth of red sea
bream, though the accumulation of more data is necessary before a clear conclusion can bereached. Furthermore, mortality caused by Edwardsiella decreases when fish are reared at low
density. Thus, low density rearing is thought to be effective in reducing disease problems.
Key words: aquaculture, feeding frequency, rearing density, red sea bream, waste feed
Wakayama Prefecture. The southern part of theIntroduction

bay is a tranquil region with a complex coastline
comprised of five inlets and some small islands.

Wakayama Prefecture is located in the

The southern part of the bay is one of the largest

southwest of Honshu Island, Japan. The mainfish farming sites with the primary target fish

fisheries products are horse mackerel, mackerel,

being red sea bream. The aquaculture of yellow

and cultured red sea bream. Cultured red sea

tail started in the 1970s and that of red sea bream

bream, Pagrus major, ranks third in terms ofbegan in 1977. Production of both species increased

level of production. The species is cultured inevery year, peaking in the latter half of the

fish farming sites scattered along the coast of

1980s. Annual production decreased from the latethe prefecture. The aquaculture industry, which

1980s, and has fluctuated between 1,000 and 2,000

produces one quarter of the fishery products inannually since. Fluctuation in red tide, especiallythe prefecture, is important in Wakayama. The

associated with total duration, and fish farming

production of cultured red sea bream reaches

production reacted with each other from 1971 to

80% of total aquaculture production. In the 1980s,

2001 (Uede 2004a), when there was a decrease in

the deterioration of the sedimentary environment

fish farming caused by a depression in fish value

and the frequent occurrence of the red tides werethat began during the latter half of the 1980s,

observed in Tanabe Bay. In addition, there wasaccompanied with reductuion in the duration of

an increase in aquaculture production in the bay,

the red tide events (Uede 2004a, 2004b, 2008).

which today is one of the largest aquaculture sites
in the prefecture (Uede 2004a, 2004b).
Tanabe Bay is located in the central part ofWhen the aquaculture production increased
and peaked, the acid volatile sulfide (AVS)
increased and the dissolved oxygen (DO) in2009 年 8 月 10 日受理（Received. August 10. 2009）＊
Hidaka Promotions Bureau of Wakayama Prefecture, 651 Takara, Gobo, Wakayama, 644-0011, Japanuede_t0001@pref.wakayama.lg.jp

30

Takashi UEDE

summer season decreased (Uede 2004a, 2006).
An azoic zone appeared in the southern part,Materials and Methods

the most deteriorated area of the bay. However,improvements of AVS and DO were observed,

Rearing Experiment I

when production began to decrease in the 1990s.

The purpose of the rearing experiment was

There are significant relationships between

to demonstrate how much particulate carbon,

aquaculture production and the two parameters:

nitrogen, and phosphorus originated from the

AVS as a sedimentary environment factor anddischarge of fish feed and feces from the fish

the total duration of red tide events. Given thecages. The experiment was conducted with theresults presented, the environment of the bay andapparatus illustrated in Figure 1 from October 31

aquaculture production are regarded as being

to November 2, 2006. Red sea bream (55 individuals

closely related (Uede, 2004a).

with mean body weight 105g) were distributed

Aquaculture production should be controlled

in the tank (Figure 1) and the particulate matterto harmonize with the surrounding ecosystem.

discharged was collected. The diet type given to

Deterioration of the environment caused by

red sea bream was extruded pellets commerciallythe nutrient load discharged from aquaculture

available. The pellets were give to the fishes so

influences not only the productivity of aquaculturethat no waste feed as mach as possible. Sampling

itself but many other values of the coastal

was conducted 0.5, 3, 6, 24, and 48 hours after

environment as well (Brown et al. 1987, Weston

feeding, at which times water temperature was1990). For example, biodiversity, nutrition cycling,measured at the inflow. The settled particulate

and the value for tourism are all affected.

matter was collected by filtering the bottom water

To establish efficient use of fish farming grounds,

1.associated with the
I conducted a seriesFig.
of studies(100 liters) through a 229 µm mesh nylon net. Onerearing of red sea bream. This paper describes

passed through filter paper (GF/C) to collect thethe results of studies into the effects of farming

fine particulates. The particulates in the outflow

methods on the environment and the growth ofwater were collected in the nylon net during thered sea bream.

intervals between sample collections. The collected

liter of water that passed through the net wasparticulates were weighed after desiccation at
90℃. Total carbon and nitrogen levels in theFig. 1. Diagram of the experimental apparatus used to measure particulate compound dischargedof carbon, nitrogen and phosphorus. Arrows indicate the flowing of sea water.

31
samples were determined with an elemental
analyzer (Valio EL, Elementar). Total phosphorus

Results

was measured by the wet degradation method(The Japan Society for Analytical Chemistry 1987,

Rearing experiment I

Japanese Industrial Standard Committee 1998) The

Water temperature, salinity, and dissolved

introduction and discharge of particulate carbon,

oxygen ranged from 22.7-23.6℃, 33.69-33.92, andnitrogen and phosphorus were calculated from the

6.26-6.87 mg/l, respectively. The total amount ofdata collected.

extruded pellets fed was 68.4 g, and the carbon,
nitrogen, and phosphorus levels in the diet were

Rearing experiment II

532.9, 102.2, and 16.7 mg/g, respectively.

The organic load caused by rearing red sea

The amounts of particulate matter and levels

bream is related closely to the amount of foodof carbon, nitrogen, and phosphorus discharged

offered. Therefore, the feeding rate is thought(per 1 kg of red sea bream) are shown in Figure 2.

to be an important factor for environmental

Particulate matter discharged as waste feed andpreservation. To explore this, an experiment thatfeces were 367.7 and 1028.5 mg which correspondclarified how red sea bream's growth differed in

to 11.7% of the amount of diet fed. Carbon,

relation to feeding frequency was conducted. Red

nitrogen, and phosphorus discharged in waste feed

sea bream (130 individuals with mean body weight

were 167.4, 30.5, and 6.5 mg, respectively, while the190g) were distributed in three cages (volumelevels in the feces were 411.1, 32.9, and 27.1 mg.

3

22.5m ). The diet type given to red sea bream was

The particulate matter discharged and levels of

extruded pellets commercially available. Feedingcarbon and phosphorus in feces were more thanexperiments were conducted for 225 days, starting

71.1% of the total amounts discharged. Nitrogen

March 14, 2003. The feeding frequencies weredischarged as waste feed reached 48.1%, which isfour (experimental plot 1), three (experimental plot

greater than the level of particulate carbon and2), and two (experimental plot 3) times a week.

phosphorus discharged as waste feed. With respect

The results obtained from the experiment wereto the three elements discharged, the ratio of thecompared with fish growth obtained from threephosphorus discharged to the total phosphorus inprivate farms in the prefecture in 2002.

the diet offered was the largest.
C:N, C:P and N:P ratios as a function of time

Rearing experiment III

after feeding are shown in Figure 3. C:N was ≤6.5

Red sea bream (mean body weight 410 g)in the discharged particulates until three hours

were distributed in four cages (volume 22.5m3) atafter feeding. These values were similar to 6.1 of C:

densities of 2.4 (fish cage 1), 3.6 (fish cage 2), 4.7

N in the diet. C:P and N:P at 0.5 hours were 104.2(fish cage 3), and 5.7kg/m3 (fish cage 4). The feeding

and 16.1, whereas those ratios in the diet were

frequency was the same for all four cages. The

82.4 and 13.6. The values decreased sharply three

diet type given to red sea bream was extruded

hours after feeing. C:P and N:P were ≤47.6 and ≤3.6

pellets commercially available. The rearing

since six hours after feeding.

experiment was conducted over for 140 days from

Figure 4 shows the particulate carbon, nitrogen,

April 9, 2004. At the beginning, the purpose was toand phosphorus discharge levels in waste feed

demonstrate the relationship between growth andand feces in relation to feeding extruded pellets.

rearing density in red sea bream farming. But theWith respect to the particulate carbon andmortality of red sea bream in fish cage 4 increased

nitrogen discharged, the data obtained from therapidly due to an outbreak of Edwardsiella sincesimilar experiment by Uede (2007) were included.

day 100. As a result, I changed the purpose to

Particulate carbon discharged as waste feed anddevelop a relationship between mortality andfeces ranged from 1.9-3.2 and 4.7-6.5%. From 2.0-

rearing density.

3.5% of the dietary nitrogen was discharged aswaste feed and 2.2-2.7% was discharged as feces. In

Fig. 2.

32

Takashi UEDE

Fig. 3.
Fig. 2. Amounts of particulate matter, carbon, nitrogen and phosphorus discharged as waste feed
and feces (per 1 kg of red sea bream).

Fig. 3. C:N, C:P and N:P atomic ratio as a function of time after feeding.
△ shows each values in extruded pellets diet.

33
the case of phosphorus, the proportions discharged

The experiment was initiated at the same timein waste feed and feces were 3.3 and 13.6%.

that growout began on the private fish farms.
Rearing density was consistently lower in the

Rearing Experiment IIexperimental cages than on the private farms.

The summary of the rearing performance of therearing experiment II is shown in Table 1. Red sea

Rearing experiment III

bream growth improved with increasing feeding

Fish performance in conjunction with rearing

frequency. Daily feed consumption and growthexperiment III is summarized in Table 3. The

rate both increased with feeding frequency, whilechange in cumulative mortality and number ofthe feed to gain ratio decreased. Best growth was

survivors over time are shown in Figure 7 andobtained from experimental plot 1 which received

8. The mortality in cage 4 due to the outbreak of

the highest feeding frequency.

Edwardsiella increased rapidly from the 100th day.

Figure 5 indicates the growth of red sea bream

Best fish growth was maintained in cage 2 until

from rearing experiment II in comparison to thoseday 103 (2nd period). Mortality gradually spreadon private farms. Table 2 provides a summary of

to fish cage 3, and occurred in cages 1 and 2 after

the variables on three private farms compared to

day 130. As a result, when the rearing trial wasthose of rearing experiment II. Both sets of data

terminated, the number of individuals in cages 2, 3,

were compared after the same number of days

and 4 ranged from 160-172. Cumulative mortalities

of growth, though the times when the data werein cages 1, 2, 3, and 4 were 16.2, 11.8, 38.5, andobtained were different. Fish growth in plot 1 was

49.4%, respectively.

better than the average obtained from the threeprivate farms.

Change in the mean body weight of red sea
bream over time is shown in Figure 9. Growth

Figure 6 shows red sea bream growth inin fish cage 2 was best until day 103. However,conjunction with rearing density. In the prefecture,mean body weight decreased as a result of thegenerally, after initial rearing is conducted in a

Edwardsiella outbreak except in cage 1 when thesmall net pen, red sea bream of about 100 g orFig.
4.
more are distributed into net pens for growout.

rearing trial was terminated.

Fig. 4. Diagram showing particulate carbon, nitrogen and phosphorus discharge level in waste feed
and feces in relation to feeding extruded pellets to 1 kg wet weight of red sea bream. The
amount of extruded pellets to 1 kg wet weight of red sea bream was 11.9 g dry weight. With
respect to the particulate carbon and nitrogen discharged, the data obtained from the similar
experiment by Uede (2007) were included.

34

Takashi UEDE

Experimental plot

1

2

3

Feeding frequency(times/week)

4

3

2

No. of fish

Total fishweight(kg)
Average bodyweight(g)

Initial

130

130

130

1st period

124

127

126

2nd period

124

127

126

3rd period

120

127

126

Initial
1st period
2nd period

24.3
39.3
58.1

25.0
37.8
55.0

24.9
36.6
50.7

3rd period

123.5

112.8

92.6

Initial

186.9

191.9

191.5

1st period

316.9

297.6

290.5

2nd period

468.1

433.1

402.0

3rd period

1029.2

888.2

734.9

7.7

2.3

3.1

Mortality(%)
Feed supplied(kg)

1st period

17.7

15.8

13.0

2nd period

32.5

27.8

24.6

3rd period

89.7

81.0

66.1

Whole period

140.0

124.6

103.7

1st period

0.97

0.88

0.74

2nd period

1.19

1.07

1.01

Fig. 5. Whole period

0.86

0.85

0.81

0.82

0.80

0.78

1st period

1.07

1.16

1.02

2nd period

1.73

1.62

1.75

3rd period

1.31

1.40

1.58

Whole period

1.33

1.39

1.49

1st period

169.6

155.1

151.7

2nd period

147.7

145.5

138.4

3rd period

219.8

205.1

182.8

Whole period

550.6

462.8

383.7

Daily feed
consumption(%)

Feed to gain
ratio

Growth rate(%)

3rd period

Fig. 5. Red sea bream growth from rearing experiment II in comparison to those in private
farms. □ : Experimental plot 1, △ : Experimental plot 2, ○ : Experimental plot 3,■ : Private farm No.1, ▲ : Private farm No.2, ● : Private farm No.3.

35

Fig. 6.

Number of fish cage for the rearing experiment

Private farms

1

2

3

Initial

7 7 7

6 6 4

6 6 4

growout
No. of fish

15 15 912 12 713.5 13.5 9

14,0009,900

Size of cage

Date of beginning
Diet type

Aug. 4, 2002 Aug. 23, 2002
EP
EP MP

14,000Sep. 7, 2002
EP MP

1

2

3

3 3 2.5

3 3 2.5

3 3 2.5

130

130

130

Mar. 14, 2003 Mar. 14, 2003 Mar. 14, 2003
EP
EP
EP

Almost EP

Fig. 6. Red sea bream growth in conjunction with rearing density.
□ : Experimental plot 1, △ : Experimental plot 2, ○ : Experimental plot 3,■ : Private farm No.1, ▲ : Private farm No.2, ● : Private farm No.3.

Discussionthat conclusion. The C:P ratio in the particulatematter discharged at 0.5 hours after feeding was
higher than that in the diet. This indicates that

Particulate carbon and phosphorus in feces

phosphate, which forms the chemical union toaccounted for ≧71.1% of the total discharged. The

organic compounds in the diet by an ester bond, is

proportion in waste feed reached 48.1% of the total

immediately dissociated after feeding (Laws, 1993).

amount in particulate nitrogen discharged. Waste
feed is assumed to be the source of the majority of

Six hours later, the C:P ratio decreased sharply to≤47.6. The change in N:P was same as that of C:P.

the total particulate nitrogen discharged according

It is concluded that low values of C:P and N:P are

to Uede (2007b). That assumption is supported byassociated with high rates of carbon and nitrogenthe research reported here. Hence, it is concluded

absorption in the digestive tract of the fish. Onthat the reducing the amount of feed that is not

the other hand, calcium bond phosphorus, which

consumed by the fish is an effective way to reduce

composes a large part of phosphorus compounds,

the particulate nitrogen loading in the sediments.

is not highly absorbed. Uede (2007a) reported

With respect to the C:N ratio in particulate

there are high phosphorus concentrations, which

discharges, Uede (2007b) indicated that particulate

are predominantly composed of calcium bounddischarge for the first three hours after feeding

phosphorus, in the sediments in fish farming areas.

is primarily from waste feed, after which it isCompared with the ratios of C:P and N:P (≤25.5
and ≤2.82) in the sediments in fish farming areas,from feces. The results presented here support

36

Takashi UEDEthe values in feces found in this investigation (47.6

1, 2, and 3 were 0.61, 0.41, and 0.30 times a day,and 3.55) were higher. Reasons for this include

respectively. Feeding frequencies in conjunction

the fact that a large part of the phosphate, whichwith experimental plots 1 and 2, which had theis predominantly calcium bound phosphorus,

best fish growth rates, were similar to the rates

is discharged as feces. Moreover, calcium

used on the private farms, though the fish densities

bound phosphorus, which is a stable compound,in the experimental plots were lower than on theaccumulates in the sediments for long periods ofprivate farms. From these results, it is suggested

time. Hence, I need countermeasures, which arethat that rearing at low density promotes gooddifferent from those that may work with respect

growth in red sea bream.

to nitrogen discharges, to reduce the phosphate
discharge.

Mortalities from the Edwardsiella outbreakdecreased with decreasing fish density in rearing

In rearing experiment II, the best growthexperiment III. Therefore, it is thought that

rates and feed to gain ratios were obtained withresistance to fish diseases like Edwardsiellaincreasing feeding frequency. The growth inincreases when the fish are present at low density.

experimental plot 1 and 2 was better than on the

When the above-mentioned results are

private farms. The feeding frequencies on theconsidered together, it can be concluded that thethree private farms were 0.41, 0.70 and 0.53 times aamount of particulate nitrogen, which is discharged

day, while rate associated with experimental plots

primarily from waste feed, is more than that ofExperimental plot
Number of fish

Total body weight( Kg )

Mean body weight(g)

1

Feed to gain ratio

Growth rate(%)

4

Initial

130

195

260

318

128

195

259

310

2nd period

122

194

252

296

3rd period

109

172

160

161

Initial

53.8

80.4

106.3

129.0

1st period

70.7

113.1

146.0

173.1

2nd period

89.3

153.6

180.3

205.6

3rd period

85.2

128.8

110.5

107.7

Initial

413.8

412.3

408.8

405.7

1st period

552.3

580.0

563.7

558.4

2nd period

732.0

791.8

715.5

694.6

3rd period

781.7

748.8

690.6

668.9

1st period

Daily feed consumption(%)

3

1st period

Mortality ( % )Feed supplied
(g)

2

16.2

11.8

38.5

49.4

37.3

60.3

75.3

96.0

2nd period

41.6

63.2

82.2

97.6

3rd period

31.8

43.7

41.3

42.1

Whole period

110.7

167.2

198.8

235.7

1st period

1.13

1.18

1.13

1.20

2nd period

1.02

0.93

0.99

1.01

3rd period

0.96

0.82

0.75

0.71

Whole period

1.11

1.12

1.23

1.31

1st period

2.09

1.84

1.87

2.00

2nd period

1.85

1.53

2.12

2.36

3rd period

5.54

-5.57

-8.06

-7.18

Whole period

2.52

2.71

3.36

3.74

1st period

133.5

140.7

137.9

137.6

2nd period

132.5

136.5

126.9

124.4

3rd period

106.8

94.6

96.5

96.3

Whole period

188.9

181.6

168.9

164.9

37
feces. The primary cause of eutrophication in the

but also may improve the health of cultured fish,

fish farming areas is excessive loads of nitrogenthough the conclusions are based on limited data.

and phosphorus. Therefore, reduction in waste

I'm now trying to establish techniques to evaluate

feed is an important means of reducing nitrogen

the environment in fish farming areas. I want todischarges. Since the chemical characteristics ofdevelop the technologies that can provide harmony

phosphorus are different from those of nitrogen,between aquaculture and coastal ecosystems. I

so the different countermeasures are required forbelieve that the only way aquaculture can makephosphorus reduction in discharges. Finally, it is

strides forward in the future is for it to exist insuggested that rearing at low density promotes

harmony with the surrounding ecosystem.

Fig. 7.
the growth of red sea bream, though more data
are required for verification. Low density also

Acknowledgements

appears to increase resistance to Edwardsiella.
These results explain the opinion that reducing

I thank Dr. K. Ikuta and Dr. H. Yokoyama of

the nutrient loads discharged from aquaculture

the National Research Institute of Aquaculture,

can help to improve environmental conditions. It

Fisheries Research Agency, for continuousis thought that rearing in a low density is good

support. A very special thanks to A. Sasaki, S.

for not only the environment in fish farming areas

Komi, T. Tanaka and K. Takenaka for help in

Fig. 8.

Fig. 7. Change in cumulative mortality of red sea bream as a function of the day elapsed.
–––– Fish cage 1, ––--––Fish cage 2, ––––Fish cage 3, ------Fish cage 4.

Fig. 8. Change in number of survivors of red sea bream as a function of the day elapsed.
–––– Fish cage 1, ––--––Fish cage 2, ––––Fish cage 3, -----Fish cage 4.

38

Takashi UEDE

Fig. 9. Change in mean body weight of red sea bream as a function of the day elapsed. ● : Fishcage 1, ▲ : Fish cage 2, ■ : Fish cage 3, ○ : Fish cage 4
conducting the experiments in this study, and to M.

Research Center of Agriculture, Forestry and

Tanaka for help in working as my good assistant.

Fisheries, 7: 123-130.

This study was conducted by a grant from the
Fisheries Agency of Japan.

Uede, T. 2007a. Chemical characteristics and formsof phosphorus compounds in sediment of fish
farming areas. Nippon Suisan Gakkaishi, 73:

References

62-68.
Uede, T. 2007b. Postprandial changes indigesta,

Brown, J.R., R.J. Gowen and D.S. McLusky. 1987.

leftovers and feces in cultured red sea breams,

The effect of salmon farming on the benthos

Pagrus major. Aquaculture Science, 55: 409-

of a Scottish sea loch. Journal of Experimental
Marine Biology and Ecology, 109: 39-51.

415.
Uede, T. 2008. Occurrence and characteristics ofJapanese Industrial Standard Committee. 1998.

red tides in Tanabe Bay, Wakayama

pp.175-177, In Testing methods for industrial

Prefecture from 1971 to 2006. Nankiseibutu:

wastewater, JIS K 0102. Japanese Standard

The Nanki Biological Society, 50: 38-45.

Association, Tokyo.

Weston, D.P. 1990. Quantitative examination ofLaws, E.A. 1993. pp.21-40, In Aquatic Pollution: An

macrobenthic community changes along an

Introductory text, second edition. John Wileyorganic enrichment gradient. Marine Ecology& Sons, Inc., New York, USA.

Progress Series, 61: 233-244.

The Japan Society for Analytical Chemistry. 1987.
pp.301-303 In Handbook for experiments ofanalytical chemistry, Maruzen, Tokyo.
Uede, T. 2004a. Fluctuations of environment inareas of aquaculture farms in Tanabe Bay.
Bulletin of the Wakayama Research Center ofAgriculture, Forestry and Fisheries, 5: 117-124.
Uede, T. 2004b. Occurrences of red tide in the
coastal waters of Wakayama Prefecture from1981 to 2000. Bulletin of the Wakayama
Research Center of Agriculture, Forestry and
Fisheries, 5: 107-116.
Uede, T. 2006. Fluctuation in dissolved oxygen in
August from 1985 to 2000 in southern area of
Tanabe Bay. Bulletin of the Wakayama

39

Manila Clam and Pacific Oyster Culture in Isahaya Bay— For the Sustainable Production in Stressful Environment —Junya HIGANO＊1, Keiji HIRANO＊2, Shigeru KITAHARA＊2, Masahiko MATSUDA＊2,
Kohji MIZUTA＊2, Akihiko FUJII＊2, and Akira SＨINAGAWA＊3
Abstract

Isahaya Bay is a branch of Ariake Sound, Kyushu, where the tidal range is thelargest in Japan. Culture of Manila clam, Ruditapes philippinarum, commenced in the 1970s andis currently the most important industry in the Konagaicho Fisheries Cooperative. The
Cooperative introduced a demarcated fishery for Manila clam culture, so that the fishermen are
in charge of the management of their own culture grounds, such as sand placement on muddy
substrate, installation of facilities for accumulating the juvenile clams and preventing predators,
and registering landings under the cooperative sales. The annual landing normally reaches 400700 metric tons for about 100 individual fishermen. But Manila clam culture has occasionally
suffered from mass mortality during summer since 1998 when the barrage in the Isahaya
Reclamation Project closed the inner bay area in the previous year. We studied the massmortality from the aspects of environment and clam physiology and determined that the maincause of mass mortality was anoxia by means of continuous monitoring of water quality factors
and analysis of organic acids in the pallial cavity fluid of Manila clams. For sustainable andstable production of Manila clams, prediction and prevention of anoxic water intrusion to theculture grounds are of critical importance. Suspended culture of Pacific oyster, Crassostrea
gigas, was introduced in late 1990s in Isahaya Bay, which had naturally produced delicious
native oysters near the shoreline. The oyster culture industry has grown up to 175 metric tons
a year by 42 fishermen in 2005. However, there are several problems constricting the increasein production; namely, summer mortality after spawning, heavy fouling by barnacles, and lower
consumer demand in the local market. Increasing market demand and improvement of theculture technique are necessary.
Key words: Manila clams, Pacific oysters, pen shells, Ariake Sound, summer mortality
resonance of stationary waves (Inoue 1980). In
Introduction

Japan, the coastline has been artificially changed
for many years, especially in sheltered bays where

Isahaya Bay, a branch of Ariake Sound wherereclaimed lands and artificial structures such as

tidal range reaches ca. 5 m, possesses a large tidal

dikes, breakwaters, and jetties have replaced the22flat of 29 km out of 100 km in the total bay area

natural coastal line. Reclaiming tidal flats is the(Figure 1). The sediment of the tidal flat in Isahaya

easiest way to extend farmland, industrial zones,

Bay and Inner area of Ariake Sound mostly

and residential areas. Ariake Sound has been

consists of silt and clay (Kamata 1980). However,gradually reclaimed for a long time since the 6th

the tidal current in inner Ariake Sound is very

century in accordance with natural land forming.

strong because of tidal movement and theAfter the Meiji era (from 1868), a huge2009 年 8 月 10 日受理（Received. August 10. 2009）＊1
National Research Institute of Aquaculture, Fisheries Research Agency, 422-1 Nakatsuhamaura, Nansei, Watarai, Mie 516-0193 Japanhiga@fra.affrc.go.jp＊2
Nagasaki Prefectural Inst. of Fisheries, 1551-4 Taira, Nagasaki, Nagasaki 851-2213 Japan＊3
Gakushuin Women's College, 3-20-1 Toyama, Shinjuku, Tokyo 162-8650 Japan

40 Junya HIGANO, Keiji HIRANO, Shigeru KITAHARA, Masahiko MATSUDA, Kohji MIZUTA, Akihiko FUJII, and Akira SHINAGAWA
Saga

Fukuoka

Ariakesound
Kumamoto

KonagaiIsahaya-Bay

Takaki

Nagasaki
KunimiMoriyamai
MizuhoAzuma

Fig. 1. Location of Ariake Sound and Isahaya Bay. Ariake Sound is surrounded by four prefectures. In
Isahaya Bay, six fisheries cooperative had existed but three were abolished due to the construction ofFig.
1.
barrage in Isahaya reclamation project (arrow).
undertakings of reclamation was started and thePen Shell Fisheries in Isahaya Bay

shoreline moved forward up to 5 km (Satoh 2000).
In Isahaya Bay, construction of the Isahaya
Reclamation Project was started in 1989. A dike

Pen shell, Atrina pectinata, was a dominant

and water gate were constructed up to 1996

fisheries product in Konagai Fisheries Cooperative

without opening 1.2 km out of 7 km total width. In

and caught by means of diving. Figure 2 shows the1997 the opening was completely closed (Sasaki

annual production of A. pectinata in e a c h2005). In Isahaya Bay as well as other tidal flats ofprefecture surrounding Ariake Sound. Production

Ariake Sound, there was a good habitat for largeof A. pectinata periodically fluctuated presumably

amounts of filter feeding bivalves and fishes along

due to dominant year classes. Landing and sales ofwith laver, Porphyra yezoensis. culture (Coastal

A. pectinata in three fisheries cooperatives

Oceanography Research Committee 1985), so thatsurrounding Isahaya Bay are shown in Figure 3. In

a lot of fishing activity has occurred. However,

1989, annual landings of the adductor muscle

recent environmental changes including

valuable as edible meat, reached 300 metric tons.

reclamation, barrage construction, port

It corresponds to three thousands metric tons ofconstruction, seabed collapse by coal mining andtotal animal weight. As sales reached 800 million

excavation of the seabed, presumably broughtyen, pen shell was the most important fisheries

about negative ecological impact to indigenous

product in Isahaya Bay. Nevertheless, only four

marine organisms (Sasaki, 2005).

year after starting the construction of Isahaya

In this paper, Manila clam culture in KonagaichoFisheries cooperative is described as an ideal

Reclamation Project production was diminished in
1993.

example of development of a Manila clam
aquaculture system in the face of difficult

Manila Clam Culture in Isahaya Bay

conditions in an altered environment. Moreover,
we introduce the fact that hanging culture of

Figure 4 shows the annual production of Manila

Pacific oysters contributes to the production

clam in each fisheries cooperative surrounding

system in the bay.

Isahaya Bay. Takaki and Azuma occupied half oftotal production in the 1970s and 1980s, but bothwere diminished with the progress of reclamation

41
in the mid-1990s. Instead of these, Konagai became

placing sand on muddy substrate, developing

dominant after 1990. Manila clam culture

facilities for producing juvenile clams andcommenced in the 1970s and is currently the mostpreventing predators.

important industry in Konagaicho Fisheries

According to Mori (1982), introduction andCooperative in accordance with the decrease ofdevelopment of Manila clam culture in Konagaicho

pen shell landings. The annual landing in the

Fisheries Cooperative is as follows. Although the

Cooperative normally reaches 400-700 metric tons

substrate on most of the tidal flat in Konagai

by about 100 individual fishermen (Figure 4).

consists of silt and clay with high iron content,

The characteristics of clam culture in the

successful production of Manila clam has been

Cooperative are the introduction of a demarcatedpossible by placing sand placement on the muddy

area for Manila clam culture. Each member owns

substrate. Trial and error of sand placement led toan average of 1 ha of culture ground in thethe determination that a sand mound was suitableintertidal zone. Individual fishermen manage theirfor seawater circulation and prevention of mud

own culture ground by taking actions such as

accumulation. Thus sand placement contributes to(metric ton)

Annual production

35000
30000

NagasakiSaga

Fukuoka

Kumamoto

25000

Start reclamation

20000

Barrage closure

15000
10000
5000

0
1968 1973 1978 1983 1988 1993 1998 2003

Fig. 2. Annual production (with shell) of pen shell, Atrina pectinata, in Ariake Sound. EachFig . 2.in Figure 1.
prefecture was shown

Annual production(metric ton)

350

Konagai

KunimiMizuho

300
250
200
150
100
50

Annual sales(million yen)0
1989 1991 1993 1995 1997 1999 2001 2003 2005

900
Konagai Kunimi Mizuho
800
700
600
500
400
300
200
100
0
1989 1991 1993 1995 1997 1999 2001 2003 2005

Fig. 3. Annual production (edible meat: adductor muscle) and sales of pen shell, Atrina pectinata,in main fisheriesof Isahaya Bay
Figcooperative. 3.

42 Junya HIGANO, Keiji HIRANO, Shigeru KITAHARA, Masahiko MATSUDA, Kohji MIZUTA, Akihiko FUJII, and Akira SHINAGAWA
increase the area of high productivity, and theFisheries Cooperative is shown in Figure 5. Total

production reached up to 4.2 kg/m2 from 1.2 kg/m2

sales were affected by the total production andbefore sand placement. In addition, the following

unit price, but cost of seed has been constant anddevices have been used for maintaining

cost of sand has been increasing since the mid-productivity of the culture ground. Fine mesh net

1990s. So the benefit is extremely depressed in

was applied to prevent sand from sinking onlean years and recent decrease of total sales is

extremely soft substrate. Setting of sand bags on

disadvantageous for the business of Manila clam

the created sand flat can control bottom sandculture in the Cooperative. The proportion of the

movement and create a natural nursery. Rakes

production to the seed amount in each year is

and waterjets from submerged pumps areshown in Figure 6.

recognized as effective means of removing

1988, 1999, 1995, 1996, and 1997, but lower in 1991,

accumulated mud and dead shells from the bottom

1992, 1994, and after 1998. Recovery of released

substrate. Each culture ground is enclosed by net

seed should affect the budget of the culture

fence in order to prevent the invasion ofbusiness. In fact the ratio of production/seed islongheaded eagle rays, Aetobatus flagellum, whichsignificantly correlated with the benefit (r = 0.609,

are predators of shellfish (Yamaguchi et al. 2005).

p<0.05). Production is relatively low in comparison

The proportion is higher in

The cost of purchasing seed and sand againstwith the amount of seed released, so benefit only

annual total sales of Manila clam in Konagaichocomes from the increase in unit price after growth

2000
1800

Konagai(metric ton)

Annual production

1600

KunimiMizuhoAzuma

Takaki

1400
1200
1000
800
600
400
200
0
1975

1980

1985

1990

1995

2000

2005

350
300
250
200
150
100
50
0
-50
1988

Benefit Seed

1,000

Sand

Metric ton

Million yen

Fig. 4. Annual production of Manila clam, Ruditapes philippinarum, in main fisheries cooperative of
Fig . 4.
Isahaya Bay. Only Konagai, Kunimi and Mizuo were running at present.

1990

1992

1994

1996

1998

2000

2002

FigAnnual. 5.
Fig. 5.
balance of cost and benefit on Manila
clam culture at Konagaicho fisheries
cooperative. The upper line shows theannual total sales of Manila clam.

800

Production
Seed

600
400
200
0
1988 1990 1992 1994 1996 1998 2000 2002

Fig Annual. 6.
Fig. 6.
production and amount of seed forplanting to aquaculture ground on Manila
clam culture at Konagaicho fisheries
cooperative.

43of Manila clam seed. But Manila clam culture hasfrom 2003 to 2005, continuous real-time monitoringoccasionally suffered from mass mortality duringof water quality and periodic monitoring ofsummer since 1998 when the barrage in Isahaya

survival and physiological condition of Manila clam

Reclamation was closed in the preceding year.

on the culture ground were performed (Figure 7).

Actually, mass mortality on the Manila clam

Water temperature, salinity, and dissolved oxygen

culture ground in Konagai was reported in 1994,

were measured with a Hydrolab Co. DS-4 water

1998, 1999, 2000, 2001, 2002, and 2004.

quality meter connected with a cellphonetransmission module and a solar electric supplier.

Mass Mortality of Manila Clam on Culture Grounds

Data were transferred by cellphone communicationof Konagai and Search for a Causal Effect of Anoxia

to the mail server and recorded on a hard drive.
Manila clams were placed in plastic baskets with

The Manila clam is the most important productsand on the culture ground and checked forin the Konagaicho Fisheries Cooperative, but it

survival rate and carbohydrate contents

occasionally suffered from mass mortality during

fortnightly. In august 2004 we encountered highlysummer since 1998. It brought severe adverse

anoxic water and mass mortality of Manila clams

impact for production of the Manila clam for theduring normal monitoring and intensive

following couple of years. The certain fact wasobservation. From late July to early August inrecognized that only a pile of dead shells emerged

2004, it had been hot and dry. Red tide ofat ebb tide. The cause of the mortality had not

Chattonella marina and C. antiqua,

been understood, although anoxia and/or red tide

Raphidophyceae, had broken out on August 5, andhad been thought to be main factors associatedextremely low oxygen was observed from Augustwith mass mortality in Isahaya Bay.

11-14 intermittently (Figure 8). All the Manila

In order to make clear the possible cause ofclams in the area died during that period.

mass mortality and find out the appropriate

According to the monitoring of Manila clam inmanagement strategy for Manila clam culture, webaskets, carbohydrate contents of soft tissues

have been studying the relationship between thewere stable from May to July and still showedphysiological condition and environmental factors.

more than 30 mg/g wet weight of soft tissue andDuring the summer season (June - September)

80% survival on August 2. It is thought that the

Ariakesound
Isahaya-Bay

Fig. 7. Research site at Manila clam culture ground in Isahaya-Bay and scaffolding water quality
meter is equipped. Solar cell module and cell-phone module are installed on the top.

Fig . 7.

44 Junya HIGANO, Keiji HIRANO, Shigeru KITAHARA, Masahiko MATSUDA, Kohji MIZUTA, Akihiko FUJII, and Akira SHINAGAWA
Manila clams had conserved enough energy until

put in mesh bags placed on the bottom of themass mortality occurred.

culture ground at 1500 August 10 along with the

Figure 9 shows the survival rate and organic

record of dissolved oxygen. Both succinate andacid contents in pallial cavity fluid of Manila clams

propionate, which are known as end products of

WT（℃）・Sal（psu）

DO saturation
300

Red tide of Chattonella spp.

34

Depth（cm）

Sal

32

250

30

200

28

150

26

100

24

DO（％）

WT

50

22

20
400
300
200
100
0
8/7

0

Anoxic water appeared intermittently

Neap tide

8/8

8/9

8/10

8/11

8/12

8/13

8/14

8/15

8/16

Fig.
temperature, salinity, dissolved oxygen and depth in second week of August, 2004
Fig8.. Water
8.
on the bottom of Manila clam culture ground recorded by water quality meter.

80

Mortality

60
40

50

20
0

0

20

2.5

Succinate(µmol/ml)

15

Succinate2

Acetate

1.5

Propionate

1

10
5

0.5

0
8/10

0
8/11

8/12

Acetate ,Propionate(µmol/ml)

DO (%)

100

DO

Mortality (%)

100

150

8/13

2004
Fig. 9. Dissolved oxygen concentration at the Manila clam culture ground in Isahaya-Bay and theFig .mortality
9.
clam(upper), and organic acid contents in pallial cavity fluid of Manila clam placedin mesh bag on the bottom (lower). Organic acids significantly increased before rapid rise of
fatality (framed rectangle).

45
anaerobiosis (Hochachka 1984, Zwaan 1983)

bottom water and on a device to efficiently supply

significantly increased by 0600 on the 12th before aoxygen to the bottom layer where Manila clam

rapid rise of fatality. The propionate concentration

inhabits is currently progressing.

of 2 µmol/ml indicates no recovery state to the
Pacific Oyster Culture in Isahaya Bay

aerobic pathway in Manila clams even if they aresupplied sufficient oxygen (Shinagawa, personalcommunication). In fact, most of the clams died

In Isahaya Bay native oysters have long been

until 1400 on the 12th. Average water temperature

utilized at local retail shops and seafoodduring the period exceeding 30℃ even including

restaurants along the shoreside road before theanoxic water flowed into the culture ground. This

reclamation construction. The native oysters havefact demonstrates that the clams exposed tobeen in high repute with good flavor although theiranoxic water for 13 hours from the evening of thesize is quite small. But most of the oyster reefsth

had reached thewere diminished with the construction. Suspended

fatal step of anaerobiosis. The anoxic water had aculture of the Pacific oyster, Crassostrea gigas, wasstrong odor of hydrogen sulfide and the sulfide

introduced to Isahaya Bay in the late 1990s. Figure

concentration of the bottom water ca. 5 km from10 shows the increasing number of fishermen andthis site was 3 mg/l on 13 August. A tankfacilities for oyster culture in the Konagaicho

experiment in which Manila clams were exposed

Fisheries Cooperative and they reached ca. 40% of

to anoxic water and plus hydrogen sulfide at 30℃

the members and averaged 1.5 rafts in 2005. The

demonstrated that hydrogen sulfide increased

growth of cultured oysters is good and can bepropionate in the pallial cavity fluid within 13

harvested after only a half year of growout.

hours. Anoxia and (normoxia, sometimes hypoxia)

Annual production and sales of the oysters inalternated with the interval of 15 hr, (6 hr), 14 hr,

Konagaicho Fisheries Cooperative is shown in(13 hr), 12 hr within 60 hours from August 12 at

Figure 11. Production increased constantly except

0030 to the 14th at 1230. It is thought that thethin 2004 due to damage by a typhoon on the 18 of

combination of hydrogen sulfide generation with

September, 2004.

11

to the morning of the 12thanoxic water at high water temperature above

Production and the sales in 2005 reached 175

30℃ brought Manila clams to the fatal state oftons and 74 million yen. The spat of cultured

metabolite accumulation.

oysters were transported from Miyagi Prefecture,

The cultured Manila clam was lost by only anorthern Japan. The oyster rafts are placed 2-4 m

three days event, namely anoxia. It is foremostof the depth at low water spring tide in several

important to establish measures to prevent mass

locations of Isahaya Bay, so suitable area formortality by anoxia. Research on the development

culture are limited. They grow fast, but summerof simple facilities to prevent the invasion of anoxic

mortality occurs during the culture period by

Rafts

60

(metric ton)

Production

Number offarmers and rafts

Farmers40
20
01999 2000 2001 2002 2003 2004 2005

Fig. Fig
10.. 10Increasing
number of farmers and rafts.
on Pacific oyster culture at Konagaicho
fisheries cooperative.

Sales

200

100

150

80
60

100

40

50

20

0

0

Sales (million yen)

Production

1999 2000 2001 2002 2003 2004 2005
Fig . 11.

Fig. 11. Annual production and sales of Pacificoyster at Konagaicho fisheries cooperative.

46 Junya HIGANO, Keiji HIRANO, Shigeru KITAHARA, Masahiko MATSUDA, Kohji MIZUTA, Akihiko FUJII, and Akira SHINAGAWA
oysters weakened after spawning because of highCooperative so far. Nevertheless both Manila clamwater temperature and sometimes perhaps

and Pacific oyster culture haven't compensated for

hypoxic water. More effort to introduce native

the entire portion of the lost pen shell industry. In

oysters to hanging culture is essential not usingorder to increase the production of both species,

spat from coldwater areas in order to avoid

technical and administrative supports are

summer mortality. Heavy fouling by barnacles,

necessary. For Manila clam culture, establishment

ascidians and other animals is a constraining factor

of effective measures to prevent anoxic water isfor the management of oyster culture. Attachments

indispensable. Development of the reproduction

and/or settlement of larvae are inevitable insystem of natural seed on the culture ground isshallow water, so development of novel equipment

essential in order to reduce costs. Development ofand methods against fouling animals is necessary.

methods and devices for improving substrate on
the culture grounds is necessary for reducing theDiscussion and Conclusions

costs of sand. For oyster culture, improvement of
the culture technique including using local

After the crash of the pen shell fishery, Manila

broodstock is necessary. Exploit of the market

clam culture has been the most important industry

demand is inevitable for further increasing total

in Isahaya Bay. Oyster culture helps compensate

production. Furthermore, the problem is that thefor the reduction of Manila clam production

culture of both species is faced with the reduction(Figure 12). These transitions could support totalof productivity due to environmental factors.

income of the fishermen in Konagaicho Fisheries

Production(metric ton)

3,000

Pen shell

For sustainable shellfish production in Isahaya

Manila clam

OysterOthers

2,500
2,000
1,500
1,000
500
0

Sales
(million yen)

1989 1991 1993 1995 1997 1999 2001 2003 2005

700
600
500
400
300
200
100
0

Pen shell

Manila clam

OysterOthers1989 1991 1993 1995 1997 1999 2001 2003 2005
Fig. 12.Fig
The
breakdown of main fisheries products in terms of production and. 12.
sales at Konagaicho fisheries cooperative. The production of pen shell isexpressed as amount of edible meat.

47
Bay, a fundamental solution is necessary for

Responsible Marine Aquaculture. CABI

generation of hypoxic/anoxic water. Rapid

Publishing, Oxon, United Kingdom.

decrease of the nutrient removal from theMori F. 1982. Progressing the deployment of

ecosystem, i.e. fisheries production, may cause

Manila clam culture. pp. 169-173, In: National

increased harmful phytoplankton blooms andFederation of Fisheries Co-operative

anoxic water through collapse of the balance

Associations (Editors). Proceedings of the 28

between the inflow and the outflow of nutrients.

National conference of activities results on

Extractive culture, such as Manila clam and oyster

women's and young men's section of Fisheries

culture, must contribute to restoration of the

Co-operative (in Japanese).

thenvironment. So, we should make a great effort to

Sasaki K. 2005. Act of development. 39-48, In: The

enhance bivalve culture in Isahaya Bay. Both the

Oceanographic Society of Japan (Editors).

Manila clam and Pacific oyster are key species for

Aiming at ecosystem rehabilitation in Ariake

a balanced ecosystem through their filter feeding

Sound. Kouseisha Kouseikaku, Tokyo (inactivities and harvest without feeding in terms ofJapanese).

removing organic matter from the ecosystem

Satoh M. (Editor). 2000. Life in Ariake Sea:
Biodiversity in Tidal Flats and Estuaries.

(McVey et al. 2002).

Kaiyusha, Tokyo, 396 pp (in Japanese).
Acknowledgement

Yamaguchi A., I. Kawaura and S. Ito. 2005.
Occurrence, growth and food of longheaded

We thank Konagaicho Fisheries Cooperative foreagle ray, Aetobatus flagellum, in Ariake

providing the statistical data of shellfish cultureSound, Kyushu, Japan. Environmental Biology

and its cooperation on our research.

of Fishes, 74:229-238.
Zwaan A. de. 1983. Carbohydrate catabolism inReferences

bivalves. pp. 138-169, In: P.W. Hochachka(Editor). The mollusca, I, Academic Press,

Coastal Oceanography Research Committee. 1985.
Coastal Oceanography of Japanese Islands,
Tokai University Press, Tokyo, 815-878. (inJapanese).
Hochachka P.W. 1984. Biochemistry of adaptationof hypoxia - strategy of the organisms tosurvive without oxygen. Kouseishakouseikaku,
Tokyo 194 pp (translated in Japanese).
Inoue N., 1980: Oceanographic description of thecoast of Japan XIX: Ariake Bay (II) --Physicalenvironments--. Bull. Coastal Oceanography,
17(2), 151-165. (in Japanese).
Kamata Y. 1980. Oceanographic description of thecoast of Japan XVIII: Ariake Bay (I)-Geomorphology and geology of Ariake Bay.
Bulletin of Coastal Oceanography, 17:72-85 (inJapanese).
McVey J.P., R.R. Stickney, C. Yarish C. and T.
Chopin. 2002. Aquatic polyculture andbalanced ecosystem management: Newparadigms for seafood production. pp. 91-104,
In: R.R. Stickney and J.P. McVey (Eds.).

New York, USA.

49

New Technology for Developing Biologically
Productive Shallow Area in Ago Bay
Hideki KOKUBU＊ and Hiroyuki OKUMURA＊
Abstract

In Ago Bay, sediment eutrophication and frequent occurrence of hypoxia has caused

the deterioration of benthic ecosystem and decrease of biological productivity in recent years.
Furthermore, harmful algal blooms and infectious diseases make sustainable pearl culture
difficult. It is considered that one of the major causes of these phenomena are stagnation of thematerial circulation by reduction of the shallow coastal areas. The natural shallow coastal areas
were decreased everywhere in the inner parts of the bay by land reclamation and the dike
construction. Then we made clear that approximately 70% of the tidal flat and shallow areas
have already been decreased in Ago Bay. Therefore, for environmental restoration of Ago Bay
as a major site of pearl culture, it is necessary to enhance the biological productivity whichthese shallow areas provide and to enhance the material circulation around the shallow areas.
In this study, the suitable range of sediment quality of tidal flat for benthic species was foundto be 3-10mg/g dry weight for chemical oxygen demand and 15-35% for mud content ratio.
New technology for enhancing the biological productivity in the reclaimed shallow areas bycontrolling sediment quality was developed.
Key words: Tidal flat, biological productivity, Ago Bay, dredged sediment, macrobenthos
Bay. Therefore, for environmental restoration ofIntroduction

Ago Bay as the major site of pearl culture, it isnecessary to enhance the biological productivity

Ago Bay is located in Ise-Shima National Park

which tidal flats, seagrass and sea weed beds

and is famous for the cradle of the pearl culture.

provide, and to recover good material circulation

However, harmful algal blooms and infectious

around the shallow areas. New technology for

diseases make sustainable pearl culture difficult.

enhancing biological productivity by controlling

Furthermore, sediment eutrophication andsediment quality was developed.

frequent occurrence of oxygen-deficient water hascaused the deterioration of the benthic ecosystem

Experimental Suitable Sediment Conditionand decreased biological productivity in recent

for the Benthic Species

years. It is considered that one of the major causes

To determine the suitable sediment conditionof these phenomena is reduction of the material

for the benthic species, six experimental tidal flats

circulation by reduction of shallow coastal area

in which the organic content has changed, were

including a tidal flat, sea grass and seaweed beds.

set up in Ago bay. The sediment qualities and

The natural shallow coastal areas have decreased

benthic species of the experimental tidal flats wereeverywhere in inner parts of the bay due to landmonitored for three years. The results indicatedreclamation and the dike construction. Then wethat the suitable range of sediment qualities offound out by the multi-spectrum aerial photo

tidal flats for benthic species was 3-10mg/g dry

analysis that approximately 70% of tidal flat andweight for chemical oxygen demand (COD) and 15-

shallow areas have already been lost in Ago

35% for mud content ratio. By utilizing the above

2009 年 8 月 10 日受理（Received. August 10. 2009）＊
Fisheries Research Division, Mie Prefectural Science and Technology Promotion Center, 3564-3, Hamajima, Hamajima-cho, Shima, Mie 517-0404

50

Hideki KOKUBU and Hiroyuki OKUMURA

results, the two types of artificial tidal flats by

their chambers were measured for AVS, TOC,

controlling sediment condition were constructed inTN, chlorophyll a, DIN, and DIP (interstitial water).

Ago Bay.

These measurements were carried every month in2005. The primary production rate was calculated

Enhancing the Biological Productivity in theby subtracting the oxygen consumption rate in the

Relatively Oligotrophic Tidal Flat in Front of adark chamber from that in light chamber.

Dike by Using Dredged Sediment
In Ago Bay, natural tidal flats in front of thedike are relatively oligotrophic. Total area of theInvestigating Changes in Water Quality During
Ebb and Flow on the Artificial Tidal Flattidal flats is about 84 ha. The sediment of the tidal

The artificial tidal flat was enclosed in two

flats are gravel and contain low organic matterareas with polyethylene sheets. First was all the

because the dike shut out the nutrient supply from

artificial tidal flat area (DL = +1.5 m to about -1.5

the land. Thus, in these tidal flats, the abundancem) which contained a rich macrobenthos area (DLand diversity of benthos are very low. To enhance= 0 m to about -1.5 m). Second was a relatively

the biological productivity of such ecosystems,

shallow artificial tidal flat area (DL = +1.5 m to

new artificial tidal flat using muddy dredged

about 0 m) that did not contain an area of richsediment from Ago Bay was constructed. A total

macrobenthos (Figure 3). Water quality was2

area is about 7,200m . The artificial tidal flat wasinvestigated every hour for one day during ebb

constructed by mixing muddy dredged sedimentand flow conditions in the two areas. Those studies

with existing oligotorophic sediment in front of thewere carried on during the summer (21-22 Julydike (Figure 1). The construction of the artificial

and 4-5 August 2005), autumn (13-14 October andtidal flat was completed in March, 2005.

2-3 November 2005), and winter (26-27 January and

The sediment samples from the artificial
tidal flat and neighboring natural tidal flat were
measured for COD, TOC, TN, IL, AVS, ORP,
particle size, chlorophyll a, benthic abundanceExperimental siteAGO Bay

and species numbers every season for two years.
(Figure 1). In April 2004, before construction,
sediment samples were obtained and analyzed forsame characteristics. To analyze for chlorophylla, this sediment samples were sliced into the 1
cm sections from the surface. For analyzing other1st construction
constructionarea（2004.3）
area（2004.3）
Mud 50%sediment characteristics, samples were sliced up
to 12 cm from the surface.
Investigation of the Oxygen Consumption and thePrimary Production Rate on the Artificial andNatural Tidal Flats

2nd construction
construction
area (2005.3)(2005.3)

Mud 30%
Mud 30%

Two transparent chambers (made fromchloroethylene

diameter 25cm, height 20cm),

one each on the artificial and natural tidal flats

Zostera bed

in front of the dyke, were set on their sedimentsurface (Figure 2). The oxygen consumption rate
was measured continuously for two hours with
dissolved oxygen probes in both chambers. Solarradiation was measured continuously with a lightquantum sensor. The sediment samples underFig. 1.

Total area : 7200m2
Fig. 1. Outline of the artificial tidal flat.

51
16-17 February 2006), during flood tides. The study

Enhancing the Biological Productivity on theareas are shown in Figure 3. DO, salinity, turbidity

Hypertrophic Wetland Behind the Dike byand pH were measured by multi-sensor every

Promoting Water Exchange

hour. At the same time, sea water samples were

Behind the dike there were hypertrophic

collected. Water temperature, depth, and lightwetlands which in the past were a part of thewere measured on the artificial tidal flat every 10

natural tidal flats prevalent in Ago bay. Such

minutes with recording instruments. The water

areas add up to some 153 ha. The sediments ofsamples were filtered in the field and analyzed forthe wetland are muddy and contain high levels

SS，chlorophyll a，TOC，DOC，TN，DTN，

of organic matter because the dikes accumulate

TP，DTP，DIN，and DIP.

nutrients and organic matter due to runoff fromthe land. In these wetlands, the abundance anddiversity of benthos are very low. Attempts weremade to enhance the biological productivity by

Oxygen probeLight
condition

Mixing motor

Dark
condition

Fig. 2. Light and dark chambers on the tidal flat.
Fig. 2.

E nclosing area
Enclosingarea(DL:+1.5m
1.5m)
(DL:+
1.5m ～-1.5m)
E nclosing
nclosing area
area
(DL:+
(DL:+1.5m
1.5m ～0m)～0m)
S ampling
amplingpoint
point（S（S t.）

S tt.2.21-1Fig. 3. Outline of the flux investigation area.

Fig. 3.

S tt.1.11-1

52

Hideki KOKUBU and Hiroyuki OKUMURA

promoting water exchange between the wetland

bivalvia, gastropoda, crastacea, and ichthyoid.

and bay using pumps in conjunction with a

Immediately after the construction, the gastropoda

pipeline system. Improvements were evaluated byand the crastacea were dominant. After six months,

monitoring sediment quality, benthic abundance

the polychaetes and the bivalves had increased,

and species diversity seasonally.

and after 10 months, species numbers also
increased remarkably compared to the present

Results and Discussion

before construction, indicating increased diversity.
After four months, the abundance of macrobenthos

The Function of Habitat on the Artificial Tidal

had increased significantly, and after one year

Flat:

they had increased four-fold compared to before

Seasonal Changes in the Abundance andconstruction and had reached steady state.

Diversity of Macrobenthos

The recovery time for the macrobenthos in 30%

The seasonal changes in chlorophyll a in the

mud on the experimental tidal flat was faster thansediments (DL = +0.5m) on the natural and artificial

that of the community in 50% mud. Furthermore,

tidal flats containing 50% and 30% mud are shownaccording to the results of the carbon and nitrogenin Figure 4. After two months, chlorophyll a on

stable isotope analyses, the carnivores were notthe experimental tidal flat increased significantly

present on this tidal flat. Thus, the community wascompared to that of the natural tidal flat. One year

in a transition phase toward stability. Therefore,

after construction the chlorophyll a on the artificial

these results indicated that it takes more than one

tidal flat was about four times higher than before

year to develop a stable habitat on an artificial

construction. On the other hand, after one year the

tidal flat.

abundance of macrobenthos on the artificial tidal

It is clear from the study that after theflat had increased markedly and subsequently, theconstruction of tidal flats, benthic algae increasechlorophyll a was the same as before construction

first, followed by the macrobenthos. On thedue to greater grazing pressure. These results

other hand, after the dredged sediment was

indicated that benthic algae increased soon after

mixed, deposit and suspension feeders became

construction because dredged sediments contained

more abundant. Thus, the constructed tidal flatrich in organic matter.

ecosystem had changed to an ecosystem with highThe seasonal changes in abundance ofdiversity. For about one year the abundance andmacrobenthos on the artificial tidal flat sediment

diversity of benthos had increased more than four-(DL = +0.5m) comprised of 50% and 30% mud arefold compared with the pre-construction situation.

shown in Figure 5.
The macrobenthos were classified as polychaeta,

Before construction

Mud 30%

Mud 50%Chl. a（mg/m2）

50
40
30
20
10
0

Beforeconstruction

First Year

Second Year

Fig. 4. Seasonal changes of chl. a in artificial tidal flat.

53

600
400

Gastropoda

Bivalvia

Crustacea

Ichthyoid(Mud 30%)
Abundance

200

Species number of benthos（ species number /0.2m2）

Abundance of benthos（ ind. /0.2m2）

Polychaeta

0
40
30

Beforeconstruction

First year

Second year

(Mud 30%)
Species number

20
10
0

Beforeconstruction

First year

Second year

Fig. 5. Seasonal changes in abundance and diversity of the macrobenthos.
Fig. 5.

Tsopographic Change on the Artificial Tidal Flat

greater on the artificial flat than on the natural

The changes in elevation a year beginningone. These results indicated that under aerobic

immediately after construction of the artificial tidal

conditions, decomposition of organic matter wasflat are shown in Figure 6. The ground elevation

enhanced on the artificial tidal flat from spring toincreased from 30-40 cm below DL= 0 m, andautumn.

above DL = 0 m elevation had decreased 10-20

The monthly changes in the primary production

cm. It is thought that tidal flat sediments moved

rate and chlorophyll a on the artificial and natural

offshore. The inner part of Ago Bay in whichtidal flats are shown in Figure 8. The primaryartificial tidal flat was constructed is characterized

production rates were low during summer, thenby calm water, but it is possible that large

increased and reached its highest level in autumn

amounts of the tidal flat sediments can be moved(from September to November). The chlorophyllby turbulence caused by typhoons. Therefore, toa level in the tidal flat sediments was also low

estimate the topographic change in the artificial

during summer and highest during autumn. It

tidal flat, it is necessary to understand the patternis concluded that grazing of benthic algae byof change in wave patterns. To protect the loss ofmacrobenthic organisms and the inhibition ofsilt and clay, it is necessary to provide stability forprimary production by strong solar radiation

the tidal flat sediments.

caused the lower primary productivity in summer.
During August and November the primaryMonthly Changes in the Oxygen Consumption

productivity on the artificial tidal flat was higher

and Primary Production Rates on the Artificial

than on the natural tidal flat. It is concluded thatand Natural Tidal Flats

under aerobic conditions the rich organic matter inMonthly changes in the oxygen consumption

artificial tidal flat sediments decomposed and therate on the artificial and natural tidal flats arebenthic algae increased by taking up the nutrientsshown in Figure 7. During winter the oxygenthat were released. Subsequently, the diversity

consumption rate on the flats were not very

and abundance of the benthos on the artificial tidal

different. However, from May to October when

flat were enhanced over those on the oligotrophic

the water was warmer, the oxygen consumption

natural tidal flat.

rate on artificial tidal flat increased significantly. In
August and September, oxygen consumption was

54

Hideki KOKUBU and Hiroyuki OKUMURA

Fig. 6. The topographic change in the artificial tidal flat.

Oxygen consumption rate2
(mmol-O2/m h)

6.0

Artificial
Before construction
Water Temp.

35
30
25
20

4.0

15
10

2.0

5
0.0

Water Temp. (℃ )8.0
Fig. 6.

0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fig. 7. Oxygen consumption rate on the artificial and natural tidal flats.

6.0

35

Prod. rate(before construction)

30

Chl. a (artificial)

25

Chl. a (natural)

4.0

20
15
10

2.0

2

Fig. 7.

Prod. rate(artificial)

Chl. a (mg/m )Primary Production Rate
2
(mmol-C/m h)

8.0

5
0.0

0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fig. 8. Primary production rate on the natural and artificial tidal flats.
Fig. 8.

55
Nutrient Flux on the Artificial Tidal Flat

POP, and chlorophyll a) showed absorption into

To investigate the changes in diurnal water

the tidal flat, while dissolved inorganic nutrientsquality around the artificial tidal flat, the clock,(DIN and DIP) always flowed out of the tidal flat.

light, DIN, DIP , chlor ophyll a, D O, depth,

These results indicated that the offshore watertemperature, and turbidity were measured on 21-

which contains rich particulate organic matter

22 July 2005 (Figure 9) and 26-27 January 2006

(POM), such as phytoplankton, flowed into the tidal(Figure 10).

flat with the high tide, and they were removed byfilter feeders on the artificial tidal flat. This results

TP, DIP, POP, and chlorophyll a) under ebb andindicated that the dissolved inorganic nutrientsflow conditions were calculated by integrating theflowed out from the tidal flat by decomposition ofdata (Table 1). Negative values were indicated thatthe organic matter in tidal flat sediments and bymaterials were absorbed into the tidal flat, while

being discharged from the macrobenthos. These

positive values were indicated that the materials

phenomena were supported by increasing nutrient

were flowed out of the tidal flat. During every

levels in the interstitial water and elution rate fromseason, particulate organic matter indicators (PON,

tidal flat sediments (Kokubu et al. 2006). These

Light quantum

0 :0 0

4 :0 0

8 :0 0

Water depth

1 2 :0 0
2 .0
1 .5

2 .0

1 .0

1 .0

0 .5
0 .0

9

36

-1

34
7

-1

-1

2 .0

0

0 .0

50

3

40

2

30
20

200
150
100

1

DIN
DIP

10

0
20

DIN FLUXDIP FLUX

15
10

50

5

0

0
1 2 :0 0

1 6 :0 0

Chl.a ( μ gL )

4 .0

50

0
-2 -1

6 .0

Turbidity
Chl.a

100

DIN FLUX( μ molm h )

30

-1

150

DIN ( μ gL )Turbidity ( ppm)

5

32

DO
Water temp.

DIP ( μ gL )DO ( mgL )0 .0

Water temp.（ ℃ ）2 0 :0 0

2 0 :0 0

0 :0 0

4 :0 0

8 :0 0-2 -1

1 6 :0 0

DIP FLUX( μ molm h )-2 -1light quantum ( mmolm s )1 2 :0 0
3 .0

Water depth ( m)Then the flux of water quality (TN, DIN, PON,

1 2 :0 0

Fig. 9. Time course of the water quality during ebb and flow on the artificial tidal flat (4-5 Aug. 2005).

56

1 8 :0 0

2 2 :0 0

2 :0 0

6 :0 00 .0

1 0 :0 0
3 .0
2 .5
2 .0
1 .5
1 .0
0 .5
0 .0

10

10

Light quantum
Water depth
多 項 式 ( Water depth)

1 .5
1 .0
0 .5

8
6

9

0
2 .0
1 .5

25

1 .0
0 .5

0

0 .0

-1

DIP ( μ gL )

3

DIN
DIP

-1

2

25
1
0

0

50

5

-2 -1

DIN ( μ gL )

50

-2 -1

-1

Turbidity
Chl.a

Chl.a ( μ gL )50

2

DIP FLUX( μ molm h )Turbidity ( ppm)

4

DO
Water temp.

8

DIN FLUX( μ molm h )Water depth ( m)

1 4 :0 0

Water temp.（ ℃ ）1 0 :0 0
2 .0-1DO ( mgL )-2 -1

Light quantum ( mmolm s )Hideki KOKUBU and Hiroyuki OKUMURADIN FLUX
4
Table 1. The flux of water quality
DIPduring
FLUX ebb and flow on the artificial 3tidal flat.
25

2
1
0

0
1 0 :0 0

1 4 :0 0

1 8 :0 0

2 2 :0 0

2 :0 0

6 :0 01 0 :0 0

Fig. 10. Time course of the water quality during ebb and flow on the artificial tidal flat (26-27 Jan. 2006).

Table 1. The flux of water quality during ebb and flow on the artificial tidal flat.
Cal. Time

TN

DIN

PON

TP

PO4-P

POP

Chl.a

21.JUL

15:00-09:00

44.4

15.4

-52.2

-8.44

0.83

-1.67

-12.4

DL:+1.5m～+0m

04.AUG

13:00-10:00

-97.5

110

-109

4.95

7.62

-7.67

-23.1

DL:+1.5m～-1.5m

13.OCT

15:00-09:00

-55.0

13.8

-39.4

-2.00

1.44

-2.72

-10.3

DL:+1.5m～+0m

02.NOV

13:00-10:00

-60.9

30.9

-107

-4.71

6.14

-4.81

-14.2

DL:+1.5m～-1.5m

26.JAN

11:00-09:00

-38.2

3.41

-27.2

-0.18

0.55

-0.82

-2.36

DL:+1.5m～+0m

16.FEB

11:00-05:00

-69.3

5.83

-41.3

-1.50

1.39

-5.78

-5.67

DL:+1.5m～-1.5m

57
results corresponded with those from the Banzu

Development, 3:546-550 (in Japanese).

tidal flat in Tokyo Bay as reported by Nomura et

Kokubu, H., H. Okumura, S. Ueno, Y. Takayamaal. (2002). During all seasons the fluxes in waterand S. Yuasa. 2006. Characteristics of thequality when all the artificial tidal flat areas were

oxygen consumption rate and primary

enclosed were larger than when only the relatively

production rate in artificial tidal flat by using

shallow artificial tidal flat area was enclosed.

dredged sediment. Water Environment, 40:185(in Japanese).

Conclusion

Nomura, S., S. Onuma, A. Kuwae, E. Miyoshi and Y.

In the present work, the new technology for

Nakamura. 2002. Field study of the nutrient

enhancing biological productivity by controllingbalance in Banzu tidal flat. Technical Reportsediment quality was developed, and theof the Port and Airport Research Institute,function of habitat and material circulation were

1020:1-19 (in Japanese).

investigated. It was clear that the abundanceand diversity of macrobenthos and biologicalproductivity were enhanced by supplying nutrientsto a relatively oligotrophic tidal flat in the formof dredged organic matter-rich sediments.
Furthermore, the mechanism of enhancementof the biological productivity was clarified. Firstof all, the decomposition of the organic matterin added dredged sediment was rapid, resulting
in greater regeneration and release of dissolve
nutrients. The released nutrients were utilized
by benthic algae. Subsequently, the macrobenthos
increased more abundant by feeding on thealgae. Thus these results were supposed thatthe benthos are strongly linked with material
circulation on tidal flats, and artificial tidal flats
work as sinks for particulate organic mattersources of dissolved nutrient. However, in thepresent artificial tidal flat ecosystem, after up to
one year following construction, carnivores werestill not existed, so the ecosystem was considered
to still be in the transition phase. It was also
evident that the organic matter in the artificial
tidal flat was slightly decreased, so it is necessary
to consider the stability and durability of tidal flat
sediments. The present study is a part of the Ago
Bay Environmental Restoration Project under the
program of Japan Science and Technology Agency.
References
Katakura, N., Y. Takayama, S. Ueno, M. Kobayashi,
H. Kokubu and K. Okuda. 2005. The planningand constructing artificial tidal flat by using
dredged sediment. Journal of Marine

59

Stable Isotope Analyses of the Trophic Structure of Macrobenthos on an
Artificial Tidal Flat Developed Using Sediments Dredged from Pearl
Oyster Farms in Ago Bay
Yuka ISHIHI＊ and Hisashi YOKOYAMA＊
Abstract

In a study organized by the Mie Prefectural Government, an artificial tidal flat

was created on a sandy shore in Ago Bay using enriched sediments that had been dredged
from pearl oyster farms. The aim of the artificial tidal flat (ATF) was to remove enrichedsediments from pearl oyster farms and to re-mineralize the organic matter in the sedimentthrough the activity by the biota. We investigated the trophic structure of the macrobenthos
on the intertidal flat before (November, 2003) and after (November, 2004 and 2005) the ATF
was constructed using the stable carbon and nitrogen isotope technique in order to evaluate
the effect of the ATF. Before the ATF, the consumers were classified into four groups: groupA, which was composed of suspension feeders and characterized by depleted δ13C values(-19.5 to -18.0‰), group B, in which members had intermediate δ13C values (-14.8 to -12.1‰),
group C, in which members had enriched δ13C values (-11.5 to -10.7‰) and group D, in which
members had enriched δ15N values (11.9 to 13.7‰). The members of groups A, B, and C are
primary consumers and the food sources of each group are considered to have been a mixtureof coastal phytoplankton and benthic microalgae, benthic microalgae, and a mixture of benthic
microalgae and eelgrass or other unknown primary producers that have enriched δ13C values,
respectively. The members of group D are secondary consumers. Benthic animals collected
after ATF construction were also divided into four groups, however the number of species
in groups C and D decreased due to the change of sediment composition from sand to sandy
mud and to the short duration (8 months) after the completion of the ATF. After the ATF, thesuspension feeding bivalves were enriched in 13C by 0.6 to 1.4‰ and were depleted in 15N by 0.5
to 1.3‰, suggesting the increased dependency on benthic microalgae that had increased theirbiomass by utilizing the nutrients from the pearl-oyster farm sediments.
Key words: intertidal flat, stable isotopes, benthic microalgae, phytoplankton, suspension
feeders
have been based on engineering approaches, such
Introduction

as digging trenches to create water routes along
the seabed, widening the mouths of bays, aeration

Continuous culture of pearl oysters overor vertical stirring of the water, and dredging

extended periods within a confined farm area

enriched sediments from the seabed (Yokoyama et

generates a large amount of biodeposition, oxygenal. 2006). Among those measures, dredging

deficient bottom water, and free hydrogen sulfide

enriched sediments leads to an immediate effect,from the enriched sediments. Those conditions

however finding disposal sites for the enriched

often result in a decline in pearl oyster

sediments has been a major problem.

productivity (Sawada and Taniguchi 1965). Some

In a study organized by the Mie Prefectural

measures taken to improve farm environments

Government, an artificial tidal flat was created on

2009 年 8 月 10 日受理（Received. August 10. 2009）＊
Aquaculture Systems Division, National Research Institute of Aquaculture, FRA, 422-1, Nakatsuhamaura, Minami-ise, Watarai, Mie 516-0193

60

Yuka ISHIHI and Hisashi YOKOYAMAa sandy shore in Ago Bay using enrichedspread over the shore and were mixed with thesediments that were dredged from pearl oyster

existing sandy sediment to a depth of 1.0 m underfarms. The aim of the artificial tidal flat (ATF) was

the sediment surface, resulting in the emergence

to remove enriched sediments from the pearlof a tidal flat with an area of 5,000 m2. After theoyster farms and to re-mineralize sediment organic

ATF was constructed, the mud content of thematter through the activities of the biota at the

sediments changed from 12.1 to 29.8%, COD sed

oxygen-rich sediment-water and sediment-air

changed from 0.46 to 4.8 mg/g-dry, and theinterfaces.

chlorophyll a concentration on the sediment

The stable isotope technique has been usedsuccessfully to follow the flows of organic mattersurface increased from 0.9 to 1.9 mg/kg (Kokubu
2005).

and to point out linkages from primary producers
to higher trophic levels. Stable carbon isotope
13

Sampling and Isotope Analysis

ratios (δ C) have been extensively used toSurveys were conducted before and after the

elucidate the sources of nutrition of consumers

ATF was constructed. Before the ATF, webased on the close relationship between thesampled the reeds (Phragmites australis) in August

δ13C of the food items and that of the consumer

2003; particulate organic matter in surface(DeNiro and Epstein 1978). On the other hand,stable nitrogen ratios (δ15N) have been applied toinvestigations of the trophic levels because of thel a r g e a n d c o n s i s t e n t 15N e n r i c h m e n t w i t hincreasing trophic level (DeNiro and Epstein 1981,
Minagawa and Wada 1984). The coupling of δ13C
and δ15N values therefore results in a clear bidimensional separation of the different potential

Ago Bay

food sources for estuarine consumers. In thispaper, we report on the application of the stablecarbon and nitrogen technique to determine the1ｋｍfood sources and trophic levels of intertidal animals
before and after ATF construction in Ago Bay.
-1

Materials and Methods

0tStudy Area

oyster farming began in the bay in the 1900s. In
2004, 6,600 rafts for pearl oyster farming covered
620,000 m2 of the bay, and 2,000 kg of pearls were
produced (Tokai Regional Agricultural
Administration Office 2006).
The ATF was conducted at 34°18.0'N, 136°50.7'E

Fla

2
3
4m

Art

27 km2 and a mean depth of 10 m (Figure 1). Pearl

1

ific
ial
Tid
al

Ago Bay has a ria style coastline with an area ofin Ago Bay during the period from December 2003
to March 2005 using enriched sediments (CODsed,
12mg/g dry, mud content, 91.9％) that had been

050m

deposited on the seabed beneath rafts of pearloyster culture in Ago Bay (Katakura et al. 2005,
Kokubu et al. 2005). The enriched sediments were

Fig. 1. Map of Ago Bay showing the artificial tidal
flat with depth contours.

August, and November 2003; eelgrass (Zostera
marina) in July and November 2003; and intertidal
macrobenthos in November 2003 on and around3.4 ± 0.7 (5)6.1 ± 1.6 (40)8.1 ± 0.5 (16)5.6 ± 1.4 (20)4.6 ± 0.7 (38)May, July, and November 2003; seaweed in July,

Totalmean ± SD

seawater (coastal POM) and benthic microalgae in-26.7 ± 0.5 (5)-21.7 ± 1.2 (40)-16.7 ± 3.4 (15)-15.8 ± 1.8 (19)-9.2 ± 1.6 (38)61

the sandy shore in Ago Bay (Table 1). After the-23.1 (2)
δ13C（‰）
reed
phytoplankton
seaweedbenthic microalgae
eelgrass

were determined using a mass spectrometer(MAT 252, Finnigan MAT) coupled online via aFinnigan ConFlo II interface with an elemental
analyzer (EA 1110, ThermoQuest). Results are
expressed in the standard δ unit notation as δX= [(Rsamples / Rreference) - 1] × 103, where X is 13C or
15

N and R = 13C / 12C for carbon and 15N / 14N for

nitrogen. The values are reported relative to theVienna Pee Dee Belemnite standard (PDB) for
carbon and to air N2 for nitrogen.
Results and Discussion
Primary Producers
In the study area, there are various potential
food sources for benthic animals, which include
coastal phytoplankton (coastal POM), benthic
microalgae, eelgrass, and reeds. Figure 2 is a dual
isotope plot of the potential food sources. As the

5.8 (1)
3.9 (6)4.6 (24)

5.0 (16)4.2 (5)8.7 (2)

The 15N and 13C compositions of the samples

6.5 (4)fine powder.

7.1 (4)

plant samples were freeze-dried and ground to a

(4)
(3)
(3)
(4)

to remove traces of carbonates. The animal and

7.2
8.0
5.9
4.2

tissues were soaked in 1.2N HCl for a few minutes

3.4 (5)other animals were analyzed whole. The animal

(4)
(5)
(3)
(5)

and the soft tissues were used as the sample. The

7.4
8.3
6.5
5.6

analysis. For the molluscs, the shell was removed

8.5 (4)

Collected animals were kept frozen untilδ15N（‰）
reed
phytoplankton
seaweedbenthic microalgae
eelgrasswith distilled water, and dried at 60℃.

-8.9 (24)glass fiber filters, washed with 1.2N HCl, rinsed-7.2 (5)was filtered on pre-combusted Whatman GF/F

-23.1 (4) -21.5 (16)and Richard (1996). The seawater for coastal POM

-21.1
-16.3
-15.6
-11.6

procedure of Couch (1989) as modified by Riera-20.4 (4)extracted from the surface sediments following the-26.7 (5)2005 at the ATF. Benthic microalgae were

-14.3 (5)intertidal macrobenthos in November 2004 and

5.5 (3)-22.7 (3) -21.4 (3)-16.9 (5)
-14.6 (1) -15.6 (3)2005; eelgrass in February and May 2004; and-15.7 (4)benthic microalgae in January, July, and November(4)-21.9 (4)(5) -10.6 (2) -17.1 (3)(3)-18.0 (3)(5)
-10.4 (4)February 2006; seaweed in November 2005;

4.9 (3)8.1 (5)5.5 (3)and May 2004; July and November 2005, and

6.0 (2)

2006
Feb
Table 1. Isotopic compositions of primary producers. Mean values are indicated. Numbers in parentheses indicate sample size.
2003
2004
2005
May
Jul
Aug
Nov
Feb
May
Jan
Jul
Nov

ATF, we also sampled coastal POM in February

62

Yuka ISHIHI and Hisashi YOKOYAMA

isotopic compositions of the primary producers

ranged from -19.5 to -6.5‰, while the δ15N ranged

showed large temporal variations and we could notfrom 6.1 to 13.7‰. The animals were roughly

find any seasonal pattern (Table 1), a mean (±SD)

divided into four groups: A, B, C, and D, based onvalue for each producer was used for thethe δ13C and δ15N values.
Group A was constituted of 10 bivalves and one

identification of food sources. Among the primary13

producers, reeds had the most depleted δ C andpolychaete. Animals in this group were all15

δ N values, -26.7±0.5‰ and 3.4±0.7‰. The

suspension feeders. The δ 13C values for thateelgrass had enriched δ 13 C (-9.2±1.6‰) andgroup (range -19.5 to -18.0‰), was the most

15

comparatively low δ N (4.6±0.7‰) values. The δ

depleted among the four animal groups, and were

13

15

C and δ N values for phytoplankton were -21.7

intermediate between those of phytoplankton and±1.2‰ and 6.1±1.6‰. The values are within thebenthic microalgae. The δ15N values (8.7 to 9.9‰)

range of those previously reported for marine

for the group A were approximately 3-4‰organic matter in temperate regions (e.g. Fry andenriched relative to the phytoplankton and benthic

Sherr 1984, Owens 1987). The δ 13C and δ 15N

microalgae, suggesting that the members of Groupvalues of benthic microalgae were -15.8±1.8‰ and

A incorporated a mixture of these two primary

5.6±1.4‰. The δ 13 C value was significantly

producers.

different from that of phytoplankton (Mann-Group B was comprised of a variety of taxa,

13

Whitney U-test, p<0.05). The δ C of seaweeds

including eight gastropods (Nos. 5-7 and 9-13), two(-16.7±3.4‰) was close to the δ 13C of benthic

polychaetes (Nos. 30 and 33), six decapods (Nos. 39,

15

microalgae, whereas the δ N of seaweeds (8.1±

41 and 46-49) and one holothurian (No. 51). The δ

0.5‰) was significantly more enriched than the δ1315

N of benthic microalgae (Mann-Whitney U-test,-12.1‰, while the δ15N showed a large range (6.7

p< 0.01). Dual isotope plots of δ13C vs. δ15N for

to 10.7‰). Taking into account the small difference

consumers and their potential food sources at thein the δ 13 C between group B and benthic

sandy shore before the artificial tidal flat are

microalgae which are considered to be a major

shown in Figure 3.

food source of the members of group B. In group B,

C values of that group ranged from -14.8 tofour gastropods (Nos. 7, 9, 10 and 12) had relatively
depleted δ15N values (6.7 to 8.4‰), indicating thatFood Sources of Animals Before the ATF
Intertidal animals collected from the sandy shore

those animals are primary consumers. Animals

before the ATF were composed of 41 species,

showing the δ 15 N values of >10‰ (> 4.3‰

including two actinians (sea anemone), two chitonsenriched relative to benthic microalgae) are(Polyplacophora), nine gastropods, 10 bivalves, fiveconsidered to include omnivores and/or carnivores.

polychaetes, 12 decapods, and one holothurian (seaThe mean δ15N for seaweeds (8.3‰) was the same

cucumber, Table 2). The δ 13C of the animals

level as, or more enriched than those of theδ15Ｎ (‰)

10

SW
PP

5

BM

EG

reed
0

-25

-20

-15

-10

δ13Ｃ (‰）
Fig. 2. Dual isotope plot of δ13C vs. δ15N for potential food sources for consumers. Error bars are
SD. PP: coastal phytoplankton. BM: benthic microalgae. SW: seaweeds. EG: eelgrass.

63

14

δ15Ｎ (‰)

12

(a)

34

2

D

6 51 30 B
3346
16 44 39
11 47
17
24
49
41
22
5 48 13 4540 C
18
23 21
9
43
15
42
7
50
SW
10
3

A 3219 20

10
8
6

31
1

4
-22

4

12

PP

8

BM

-18

EG

-14

-10

-6

14

δ15Ｎ (‰)

12

(b)

1

D'

30 B'
35 33 36 37
44
51 41 29
A'17 16 38
11 7
27
39
4
14
15
C'
26
25 28 5
23 SW
40
22
8
31

10
8
6

PP

4
-22

6

BM

-18

EG

-14

-10

-6

δ13Ｃ (‰）
Fig. 3. Dual isotope plots of δ13C vs. δ15N for consumers (●) and their potential food sources (■)
at the sandy shore before the artificial tidal flat making (a) and at the artificial tidal flat (b).
See Table 1 for species identification numbers (1-51). Error bars are SD for the primary
producers. PP: coastal phytoplankton. BM: benthic microalgae. SW: seaweeds. EG: eelgrass.
primary consumers. Assuming a 3-4‰ shift in N

can feed on crustose algae growing on stones andassimilation per trophic level, seaweeds wererocks (Steneck and Watling 1982). Thus, weprobably not important in the diet of theconclude that their enriched δ13C values were notconsumers.

due to the assimilation of eelgrass. It may be that15

The depleted δ N values (7.5 to 8.8‰) for

crustose algae had more enriched δ13C values

animals in group C, which was composed of athan benthic microalgae, however we did notchiton (No. 3) and five crabs (Nos. 40, 42, 43, 45 andmeasure the isotopic compositions of crustose50), indicate that those animals are primaryalgae at that time.

consumers. Among the primary consumers, theGroup D was comprised of four species: twomembers of the group showed the most enrichedactinians (Nos. 1 and 2) and two polychaetes (Nos.

13δ C, ranging from -11.5 to -10.7‰. A possible
13

31 and 34). The range of the δ15N for the animals

explanation for the observed δ C is that group C

in the group was from 11.9 to 13.7‰, which was 4.2

feed on a mixture of benthic microalgae andto 8.0‰ enriched relative to phytoplankton oreelgrass. However, the chiton in group C,

microalgae, indicating that the animals in group D

Liolophura japonica, and the other chiton species,

were secondary consumers. The actinian

Acanthochitona sp. (No. 4), showed a more enriched

Haliplanella luciae showed a more depleted δ13C13

δ C value (7.0‰) than those of group C overall,value (-17.8‰) than the other animals (-15.5 to64

Yuka ISHIHI and Hisashi YOKOYAMA

Table 2. Isotopic compositions of consumers before and after the artificial tidal flat making. . The mean ± SD (n≧3) or the range(n=2) of the δ13C δ15N values. Numbers in parentheses refer to the species identification number.
BeforeAfter
13Species
δ15N
δ
C
δ15N
δ13C
n
n
(‰）
(‰）
(‰）
(‰）
Actinia(1) Haliplanella luciae-17.8 ±0.5
13.1 ±0.3
4-17.2 ±0.4
12.4 ±0.34(2) Edwardsia sp.
-14.4 to -13.5
11.9 to 12.4
2
Polyplacophora(3) Liolophura japonica-10.8 ±0.1
7.5 ±0.1
3(4) Acanthochitona sp.
-6.5
7.0
1
-15.0 to -13.0
7.9 to 8.92
Gastropoda(5) Batillaria cumingii-13.9 ±0.3
9.6 ±0.1
5-14.6 ±0.9
8.7 ±0.6
9(6) Reticunassa festiva-14.4 ±0.8
10.7 ±0.45-16.7 ±0.8
10.1 ±0.49(7) Lunella coronata coreensis-13.0 ±0.5
8.1 ±0.2
5-14.5 ±0.5
8.9 ±0.3
10(8) Patelloida pygmaea-9.7 ±1.5
6.1 ±1.1
5-14.9 ±2.9
7.1 ±1.6
10(9) Monodonta labio confusa-14.8 ±0.5
8.4 ±0.25(10) Notoacmea radula-14.6 ±0.8
7.7 ±0.3
5(11) Batillaria multiformis-14.0 ±0.4
9.8 ±0.3
3
-14.8
9.1
1
(12) Littorina brevicula-12.7 ±0.5
6.7 ±0.3
3-12.2 to -12.0
9.2 to 9.4
2(13) Cerithideopsilla cingulata(14) Clypeomorus coralia-14.7 ±0.7
8.5 ±0.4
5Bivalvia(15) Vignadula atrata-19.5 ±0.2
8.7 ±0.2
5-18.7 ±0.5
8.2 ±0.3
4(16) Anomalocardia squamosa-18.1 ±0.1
9.9 ±0.2
5-17.5 ±0.3
8.6 ±0.6
4(17) Crassostrea gigas-19.4 ±0.4
9.9 ±0.4
5-18.0 ±0.3
8.7 ±0.1
10(18) Hormomya mutabilis-19.5 ±0.3
8.8 ±0.1
5(19) Claudiconcha japonica-18.9 ±0.4
9.9 ±0.65(20) Barbatia virescens-18.8 ±0.3
9.6 ±0.25(21) Cyclina sinensis-18.7 ±0.2
9.6 ±0.44(22) Ruditapes philippinarum-18.1 to -17.8
8.9 to 9.4
2-17.5 ±0.2
8.4 ±0.2
5(23) Laternula limicola
-18.7
8.9
1
-17.3 ±0.2
8.0 ±0.2
3(24) Gafrarium divaricatum
-18.5
9.3
1
(25) Macoma incongrua
-14.5
8.2
1
(26) Pitar sulfreum-18.0 to -17.7
8.3 to 8.3
2(27) Musculus senhousia-17.0 ±0.3
8.2 ±0.15(28) Moerella rutila-14.2 ±0.6
7.9 ±0.4
8Sipunculida
9.01(29) Siphonosoma cumanense-12.7
Polychaeta(30) Notomastus sp.
-14.0 ±0.6
10.2 ±0.9
6
-13.4
10.1
1
(31) Lumbrineris nipponica-15.5 ±1.113.7 ±0.4
4
-17.7
10.4
1
(32) Chaetopterus cautus-19.4 to -19.3
9.6 to 10.1
2(33) Cirriformia tentaculata
-14.5
10.3
1
-15.1 ±0.5
9.6 ±0.510(34) Marphysa sanguinea
-15.1
12.2
1
(35) Perinereis nuntia var. brevicirris-15.9 ±0.4
9.6 ±0.93(36) Perinereis nuntia var. vallata-14.9 ±1.8
9.4 ±1.2
5(37) Ceratonereis erythraeensis-13.5 ±0.3
10.0 ±0.810Crustacea(38) Sphaeroma sieboldii-16.2 ±2.3
8.8 ±1.05(39) Hemigrapsus penicillatus-14.7 ±0.2
10.1 ±0.75-13.5 to -11.2
7.3 to 10.02(40) Ilyoplax pusillus-10.9 ±0.3
8.5 ±0.1
5-10.9 ±0.9
7.3 ±0.55(41) Pagurus dubius-13.5 ±0.6
9.7 ±0.3
5-13.9 ±1.2
9.3 ±0.69(42) Macrophthalmus japonicus-11.3 ±0.5
8.4 ±0.35(43) Scopimera globosa-10.7 ±0.4
7.9 ±0.753(44) Diogenes spinifrons-16.6 ±0.9
9.7 ±0.5
4-17.8 ±0.99.2 ±0.2(45) Macrophthalmus dilatatus-11.5 ±0.4
8.8 ±0.33(46) Charybdis japonica-13.3 to -13.1
10.5 to 10.5
2(47) Nihonotrypaea sp.
-14.4 to -13.5
9.7 to 9.82(48) Alpheus brevicristatus
-13.9
9.5
1
(49) Laomedia astacina
-14.3
9.7
1
(50) Macrophthalmus banzai
-10.7
7.8
1
Holothuroidea(51) Patinapta ooplax-14.4 to -13.8
10.5 to 10.7
2
-14.8
9.3
1

65
-14.0‰), suggesting that H. luciae depended on

all five species that occurred before and after thephytoplankton and that the other animals

A T F , t h e δ 13C v a l u e s i n c r e a s e d b y 0 . 6 ‰incorporated benthic microalgae through primary(Ruditapes philippinarum) to 1.4‰ (Crassostrea

consumers.

gigas and Laternula limicola), while δ15N values
decreased by 0.5‰ (Vignadula atrata) to 1.3‰

Food Sources of Animals After the ATF(Anomalocardia squamosa) after the ATF. There

Eight months after the completion of the ATF,

were significant differences (Mann-Whitney U-test,

we sampled animals from the artificial tidal flat.

all p < 0.05) in the δ13C and δ15N for Vignadula

The 30 species collected were composed of one

atrata, Crassostrea gigas, and Anomalocardia

actinian, one chiton, six gastropods, nine bivalves,squamosa before and after the ATF.

one sipunculid, six polychaetes, five decapods andGroup B' consisted of 16 species, including one

one holothurian. Benthic animals collected after thechiton (No. 4), six gastropods (Nos. 5-8, 11 and 14),

ATF were also classified into 4 groups: group A',

two bivalves (Nos. 25 and 28), four polychaetes

group B', group C', and group D', which(Nos. 30, 33, 36 and 37), two decapods (Nos. 39 andcorresponded to groups A, B, C and D before the41), and one holothurian (No. 51). Among the

ATF.

members of group B', nine species, including fourGroup A' included seven bivalves representing

gastropods (Nos. 5-7 and 11), two polychaetes (Nos.

five species (Nos. 15-17, 22 and 23) that had

30 and 33), two decapods (Nos. 39 and 41), and one

occurred before the ATF and two species (Nos. 26

holothurian (No. 51) were collected at both before

and 27) that did not occur before the ATF. Fiveand after the ATF. After the ATF, one gastropod

bivalves (Nos. 18-21 and 24) and one polychaete(No. 14), two bivalves (Nos. 25 and 28), two(No. 32) disappeared after the ATF. The δ13C andpolychaetes (Nos. 36 and 37) and one isopod (No.

15

δ N values of group A' ranged from -18.7 to38) were new to the area, while five gastropods-17.0‰ and from 8.0 to 8.7‰, of which the range(Nos. 9-13) and four decapods (Nos. 46-49)

shifted considerably after the ATF. That is, the δdisappeared. The change of species composition

13

C enriched, while the δ N values decreased.

may have been due to the change in the sediment

Figure 4 shows the shift of the isotopic

composition from sand to sandy mud. We excluded

compositions of five bivalves after the ATF. For

the gastropod Reticunassa festiva (No. 6), which

15

(a)
5
5

(b)
Vignadula atrata

4

Crassostrea gigas

10
5
2
1
-20

beforeafter-19

Anomalocardia squamosa

4

Ruditapes philippinarum

5

Laternula limicola

3
-18

-17

δ13C (‰）
13

15

-16

7

8

9

10

11

δ15N (‰）

Fig. 4. (a) δ C and (b) δ N values for 5 bivalve species of suspension feeders collected from the
sandy shore before the artificial tidal flat making (□) and at the artificial tidal flat (■).
Error bars are SD. Numerals denoted in italics indicate sample size (n).

66

Yuka ISHIHI and Hisashi YOKOYAMA

was a member of group B before the ATF, from
Referencesgroup B', because the species showed a markedly
13

depleted δ C after the ATF. On the other hand,the δ13C values of the chiton Acanthochitona sp.

Couch, C. A. 1989. Carbon and nitrogen stable(No. 4) and the gastropod Patelloida pygmaea (No.

isotopes of meiobenthos and their food8) shifted in the range of group B'. The range ofresources. Estuarine, Coastal and Shelf Science,13

15

the δ C and δ N of group B' was from -15.1 to

28:433-441.

-12.4‰ and from 7.1 to10.1‰, which was close to

DeNiro, J. M. and S. Epstein. 1978. Influence of dietthe range of group B before the ATF, suggestingon the distribution of carbon isotopes ina close similarity in the food item benthic

animals. Geochimica et Cosmochimica Acta,

microalgae between the members of groups B and

42:495-506.

B'.

DeNiro, J. M. and S. Epstein. 1981. Influence of dietGroup C' consisted of a single species, theon the distribution of nitrogen isotopes in

decapod Ilyoplax pusillus (No. 40) that showed a δanimals. Geochimica et Cosmochimica Acta,

13

15

C of -10.9‰ and a δ N of 7.3‰. The other five

45:341-351.
13

species in group C disappeared after the ATF,

Fry, B. and E.B. Sherr. 1984. δ C measurements

probably due to the change of the sediment

as indicators of carbon flow in marine andcomposition.

freshwater ecosystems. Contributions inGroup D' contained two species, the actinian
Haliplanella luciae and the polychaete Lumbrineris
13

15

Marine Science, 27:13-47.
Katakura, N., Y. Takayama, S. Ueno, M. Kobayashi,nipponica and had δ C and δ N values of -17.2‰

H. Kokubu, and K. Okuda. 2005. Design andand 12.4‰ for the actinian and -17.7‰ and 10.4‰

construction method of mixing dredging

for the polychaete. Two members in group C, theorganic sediment for tidal flat construction

actinian Edwardsia sp. and the polychaete

method by using dredging sludge. Proceedings

Marphysa sanguinea were not collected after theof Civil Engineering in the Ocean, 21:885-890

ATF.

(in Japanese with English abstract).

The most characteristic findings in the present

Kokubu, H., H. Okumura, S. Ueno, Y. Takayama,

study are that the dependency of suspension

and S. Yuasa. 2005. Characteristics of benthos

feeders on benthic microalgae increased after theand sediments in the artificial tidal flat with

ATF. It has been suggested that ATF resulted insalvaged sludge in Ago Bay. Annual Journal of

the enrichment of the sediments and increased the

Coastal Engineering, 52:1196-1200 (inbiomasses of benthic microalgae and macrobenthos

Japanese).

(Kokubu et al. 2005). The present study suggests

Minagawa, M. and E. Wada. 1984. Stepwisethat macrobenthic animals assimilated benthic

enrichment of 15N along food chains: Further

microalgae that increased their biomass using

evidence and the relation between δ15N andnutrients that were contained in the pearl oyster

animal age. Geochimica et Cosmochimica Acta,

farm sediments. Thus, the ATF may be effective

48:1135-1140.

from the viewpoint of giving the disposal site ofOwens, H.J.P. 1987. Natural variations in 15N in theenriched sediments that are produced frommarine environment. Advances in Marine

mariculture and of mineralizing the accumulated

Biology, 24:389-451.

organic matter in the sediment. On the other hand,

Riera, P. and P. Richard. 1996. Isotopic

we must note that the ATF may exert andetermination of food sources of Crassostrea

influence on the local biota as shown by the factgigas along a trophic gradient in the estuarinethat the macrofauna changed from thatbay of Marennes-Oléron. Estuarine, Coastal

characteristic of a sandy shore to one

and Shelf Science, 42:347-360.

characteristic of a mudflat after the ATF.

Sawada, Y. and M. Taniguchi. 1965. The
oceanographical studies on the pearl culture

67
ground, III. On the seasonal changes of sea
water constituents and of bottom conditions.
Bulletin of National Pearl Research Laboratory,
10:1213-1227 (in Japanese).
Steneck, R.S. and L. Watling. 1982. Feeding
capabilities and limitation of herbivorous
molluscs: A functional group approach. Marine
Biology, 68:299-319.
Tokai Regional Agricultural Administration Office.
2006. Statistical Report of Fisheries Classified
by Cooperative Associations in Mie Prefecture(2004). Mie Statistics Association ofAgriculture and Forestry, Tsu, 56 pp (inJapanese).
Yokoyama, H., K. Abo, K. Ikuta, T. Kamiyama, J.
Higano, and S. Toda. 2006. Country scenarios
for ecosystem approaches for aquaculture. 4
Japan. pp. 71-89. In: J.P. McVey, C.-S. Lee, and
P.J. O'Bryen (eds). Aquaculture andEcosystems: An Integrated Coastal and Ocean
Management Approach. The World
Aquaculture Society, Baton Rouge, Louisiana,
USA.

69

Introduced Species and Aquaculture
Cheng-Sheng Lee＊
Abstract

The yield from global capture fisheries is the current main sources of seafood forhuman consumption but has reached a plateau since 1990, and is not expected to have any
further significant growth. Aquaculture contributions have increased significantly since 1970
and now account for more than 32.3% of all fish consumed worldwide in 2004 (FAO, 2006).
From 1950 to 2004, a total of 442 aquatic species have been cultured at least one time in theworld (FAO 2006). In 2003, of these species, 314 had production of one tonne or more.
Problems associated with the culture of local species led culturists in many regions of the world
to seek related non-indigenous species as alternatives (Stickney, 2001). Aquaculture, then, has
become the main cause of the introduction of non-indigenous species, accounting for 38.7% of
introduced species recorded in the Food and Agriculture Organization (FAO) database (Garibaldi
and Bartley 1998). The practice of culturing non-indigenous species has existed for many
years to take advantage of existing markets, as well as available technology and resources.
Almost 10% of global aquaculture production came from introduced species (Garibaldi and
Bartley 1998). The pressure to culture non-indigenous species has increased, given expanding
aquaculture production and increasing demand for diversified seafood from consumers.
Aquaculture farms in the United States currently produce more than 100 different species ofaquatic plants and animals; most major aquatic species cultured in the U.S. are not native totheir farm sites (Naylor et al., 2001). Non-indigenous species have been introduced for farmingin particular regions because of the immediate social and economic benefits. Some nonindigenous species, however, have quickly adapted to their new environment, have become
established, and now compete with indigenous species for limited habitats.
Biological invasions are recognized as serious threats to marine biodiversity and ecosystem
structure and function (Frisch and Murray, 2002). In addition, introduction of non-indigenous
species for aquaculture has resulted in numerous unintentional introductions of pathogens,parasites, and pest species (Galil, 2000).
This presentation will review and provide several cases for the significance of introduced
species to total aquaculture production. The culture of marine shrimp will be used as an
example to explain the impacts on surrounding environments in both physical and biologicalaspects. To keep the contribution of introduced species in aquaculture a positive one, certain
measures must be developed to avoid any negative impacts. Thus, mitigation strategies andmonitoring capabilities for introduced species are very important.
in 2004 (Fig. 1). Total seafood supply in 2004
Introduction

was 150 million mt, of which 45 million mt camefrom aquaculture and 95 million mt from capture

According to statistical data released by thefishery. Even though the main source of theFood and Agriculture Organization (FAO) inworld's seafood is still from capture fisheries, the2006, aquaculture contributed to 32.3% of the total

total yield from this source has been in a plateau

global seafood supply (excluding aquatic plants)

since 1990, and no further significant growth is2009 年 8 月 10 日受理（Received. August 10. 2009）＊
Center for Tropical and Subtropical Aquaculture, Oceanic Institute, 41-202 Kalanianaole Hwy., Waimanalo, Hawaii, USA

70

Cheng-Sheng Lee

expected in capture fisheries.

species have been cultured at least once in theThus, it has been predicated that the world

world (FAO 2006). Problems associated with theincreasingly will have to rely on aquaculture inculture of local species led culturists in many

the future to match rising seafood consumption.

regions of the globe to seek related non-indigenous

Lester Brown at Worldwatch Organization statedspecies as alternatives (Stickney, 2001).

(2001) that fish farming might soon overtake cattle

the expansion of aquaculture production and theranching as the world's largest food source (http://increasing demand for diversified seafood fromwww.naia.ca/faq.asp). Jacques Cousteau (1973)

consumers, the pressure to culture non-indigenous

stated "we must plant the sea and herd its animals,

species has only increased. There were many

using the sea as farmers instead of hunters" andreasons identified as the cause of introduction

encouraged farming of the sea because of thewhich included aquaculture, aquarium trade,earth's burgeoning human population. Aquaculture,

biological control, boats and ships, channels,

in fact, is the fastest growing sector of worldwide

canals and locks, live bait, nursery industry,

agriculture with an annual growth rate of 8.9%

scientific research institutions, schools and publicduring the period of 1970 to 2002, compared toaquariums, recreational fisheries enhancement, and2.8% for livestock and 1.2 % for capture fisheries

restaurants, seafood retail and processing (Copping

production (FAO, 2004).

and Smith 2005). Aquaculture is the main cause

With

Issues, such as preservation of environmentalof non-indigenous species introduction, accounting

conditions, however, have challenged the expansion

for 38.7% of introduced species recorded in theof aquaculture. The quality of seafood has also

database of the FAO (Garibaldi and Bartley 1998).

been closely watched by the public. A report by

The practice of culturing non-indigenous species

Hites et al. (2004), for example, pointed out thathas existed for many years to take advantage oforganic contaminants in farmed salmon would

existing markets, as well as available technology

create poor public perception toward aquaculture.

and resources. Bartley and Casal (1998) reported

From 1950 to 2004, a total of 442 aquaticthat introduced species contributed about 17%

100000
90000
80000

60000
50000
40000
30000
20000
10000
0

19
80
19
81
19
82
19
83
19
84
19
85
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04

Yield (1000 MT)

70000

Year
Capture fishery

Aquaculture

Fig. 1. Production from capture fishery and aquaculture between 1980 and 2004.

Fig. 1.

71
of total global fish production in 1996. Whiledemand should require no additional investments

the use of introduced species has increasedin technology and market development. On

aquaculture production, it also might threaten

the other hand, species can also be introduced

aquatic biodiversity, transfer disease, alter habitat,with the intention to supplement food supplies,

and compete with native species on food andafter researchers determine that environmental

space. The estimated loss from introductions

conditions are suitable for an introduced species

was about $137 billion annually in the U.S. inand that production costs are lower than those2003 (Goldsborough 2003).. According to a U.S.

for other species. This type of introduction iscongressional report (1993), introduction of theusually carried out by government or nonprofit

zebra mussel resulted in a $3 billion loss. This

organizations. The following species are familiar topaper presents the significance of the contribution

many consumers, but they are an alien species tomade by introduced species to the total global

many locations where they have been introduced

production of several major cultured species.

for aquaculture purposes.

Given current production trends, it is anticipatedthat the world will have to continually rely

1. Tilapia (Oreochromis mossambicus, and O.

on introduced species to increase aquaculture

niloticus) are native to Africa but were brought

production.

At the same time, however, we

to many countries after the first introduction

have to devote part of our effort to conserving

to Java in 1939 (Atz, 1954; Riedel, 1965). The

biodiversity and otherwise reducing the potential

major producers for both tilapia species today

adverse effects of introducing alien species.

are located in Asia. In 2004, total production

R.L. Welcomme in the early 1980s initiatedwas 1,495,744 mt for Nile tilapia and 46,665 mt

a database on introductions of aquatic species

for Mozambique tilapia. Production sharply(DIAS) at FAO. This initial database, focusedincreased after 1980 (Fig. 2). The farmers inon freshwater species, became the basis for the

Asia produced 1.29 million mt of tilapia, but

1988 FAO Fisheries Technical Paper No. 294

farmers in Africa produced only 210,000 mt(Welcomme 1988). Currently, DIAS includes

or 16 % of total worldwide production (Fig. 2).

additional taxa, such as mollusks, crustaceans, andMany domesticated strains were developed atmarine species. Building on this knowledge, Froesemany farming locations. Demand for tilapia has

and Pauley (1997) developed a FishBase program,grown continually during the past few years.

which included more information about species

2. Atlantic salmon (Salmo salar) is found in the

introduction. This report compares the production

North Atlantic from New England to Ungava

data from the native and new locations for a few

Bay on the west, Iceland, Greenland, andcultured and introduced species, such as tilapia,

from northern Portugal to the Kara Sea on

rainbow trout, Atlantic salmon, common carp, andthe east (Laird and Needham, 1990). Farming

marine shrimp. Marine shrimp farming is used asof this species is done mainly in Norway andan example to demonstrate adverse effects that

Scotland, and in Chile where no native species

can result from species introduction.

were found. The first introduction of Atlantic
salmon eggs to Chile was in 1916, but the firstSpecies introduced as a new species

privately owned salmon farm was not started
until between 1975 and 1980 (Wurmann 2007).

The rationale behind the introduction of a

Production really started to bloom was the

species to a new location as a target farming

1990s. In 2004, Chile produced 349,329 mt or

species usually includes existing culture technology,

about 72% of total production in Norway or

existing market demand, and anticipated high

28% of total worldwide production (Fig. 3). If

profit. Fish farmers expect a quick profit, since a

its current growth rate of salmon production

species that can be mass produced with exisingcontinues, Chile in a few years may overtake

technology and already has proven market

Norway as the nation with the highest

72

Cheng-Sheng Lee
AfricaAsia

rest of the world

1800

1600

1400

Production (1000 MT)

1200

1000

800

600

400

200

0
1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Year

Fig. 2. Production of tilapia from Africa, Asia, and the rest of the world.

Fig. 2.
Chile

Norway600

500

Production (1000 MT)

400

300

200

100

0

1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Year

Fig. 3. Atlantic salmon production in Chile and Norway
production of Atlantic salmon worldwide.

Fig. 3.

continents except Antarctica for aquaculture

3. Rainbow trout (Oncorhynchus mykiss) was

and recreation purposes (FAO 2007). By

native to western North America from Mexico

2002, 64 countries were reporting rainbow

to the Bering Sea, Siberia (Laird and Needham,

trout farming production. The primary trout-1990). Since 1874, it has been introduced to all

farming countries were in Europe, North

2

73
America, Chile, Japan, and Australia. According

4. Common carp (Cyprinus carpio) has been reared

to statistics from FAO, total production in

in China for more than 200 years and currently

Europe accounted for 57.31% of the total global

is cultured throughout the world, with a yieldproduction of 504,876 mt in 2004 (Fig. 4). In

of about 5.8 million mt in 2004. More than 58%

contrast, production in the U.S. was less thanof that total production came from countries

30 thousands MT in 2004. .

other than China and Japan, where the carp is

600

500

Production (1000 MT)

400

300

200

100

0
1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Year
N. America

E uropeS . America

Asia

Fig. 4. Rainbow trout production in different continents.

Fig. 4.

4000

3500

Production (1000MT)

3000

2500

2000

1500

1000

500

0

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Year
China and J apan

Rest of the world

Fig. 5. Comparing common carp production in China and Japan to production in the rest of the world.

Fig. 5.
4

74Cheng-Sheng Lee

native. (Fig. 5). Domesticated carps have been

to conduct inter-country transfers of milkfish

produced in most of the carp producer nations.

fingerlings every year to meet demand. Genetic

Strains can be very different from each other

differences among different strains have beenin performance. Although it was considereddiluted or may no longer exist.

a luxury food in the middle and late Roman

This situation has not improved. Even after

period (FAO 2007), it has became a traditional

hatchery technology was established in thosefood fish and provided a very important animal

three countries (Lee 1995), fingerlings were still

protein source in many farming countries.

moved around the region to meet the needs offarming practice in terms of availability and cost.

The above information clearly indicates the

For example, Taiwanese milkfish farmers would

significance of the contribution made by thestock their ponds with fingerlings from Indonesia

aquaculture production of introduced species,

to extend their growing season after winter.

such as tilapia, Atlantic salmon, rainbow trout and

The danger in such transfers is that

common carp. Total aquaculture production frommicroorganisms, along with the fish, can be

the above species would be reduced by more thantransported from one region to another. Undesired

half, if they were prohibited from "introduction".

pathogens can be unintentionally introduced to a

It is not difficult to imagine the impact on market

new location and create other issues. Althoughprices from the elimination of the production

no major outbreaks of diseases were reported,

contribution from introduced species. No doubt, we

additional measures to prevent any negative

would all have to pay higher prices for the above

impacts should always be taken. After all, thespecies.

intra- and inter-regional transfers of shrimp stocks
were one of the causes for the collapse of shrimp

Species introduced to locations where they

farming industries in several countries in Asia andalready exist

other regions (Lin 1989).

Not all introductions involve bringing species
to locations where they are alien. Unlike theMarine shrimp aquaculture expanded

previously discussed species, the following species

significantly throughout Latin America andare examples of introductions to a location where

Asia during the 1980s (Moss, 2002). Black tiger

the same species already exists. The rationale

shrimp (Penaeus mondon) and Chinese shrimp

for this type of transfer can be either to meet

(Fenneropenaeus chinensis) were the two majora shortage of fingerling supply for farming

marine crustacean species commercially cultured

purposes or to introduce desired traits to a local

in Asia and China, respectively. Pacific whitestrain in order to improve its performance. The

shrimp (Litopenaeus vannamei) was the major

genetic structure of native strains will be alteredspecies cultured in Central and South America.

eventually.

During the peak of black tiger shrimp farmingin Taiwan, wild shrimp broodstocks were not

Milkfish (Chanos chanos) have a broadabundant to meet the demand and were imported

geographic d is tr ibution, exis ting v ir tuallyfrom different locations in Southeast Asia tothroughout the entire tropical Indo-Pacific Ocean

make up for local broodstock supply shortages.

and is a popular farming species in Southeast

Most of the transfers were carried out without

Asian countries, especially in Taiwan, theany examination of stock health conditions orPhilippines, and Indonesia (Lee, 1995). Before thegone through quarantine procedure. Pathogens

establishment of hatchery technology, milkfish

could be transferred to new locations if the

farmers had to rely on wild collection of fingerlings

transported stock carried any infectious disease.

to stock fishponds. Because of shortages andFurthermore, intensification of stocking densities

fluctuations in the number of fingerlings available

and deterioration of culture conditions provided

annually in the region, the milkfish industry had

favorable conditions for the outbreak of shrimp

75
diseases.

alarm for international trade.

Shrimp diseases caused by viral infection are

The most effective way to deal with viral

not easily treated under current technology andinfection is through prevention. The concept ofhave caused significant economic losses thatbiosecurity has been introduced to aquaculture

have affected industry survival in many countries

production systems through a variety of(Lightner, 2003). Shrimp viral disease outbreaks

management strategies and by following

have caused billions of dollars in lost revenue forinternationally agreed upon policies and guidelines

the global shrimp industry. Disease outbreaks(Lightner, 2003). The key elements of biosecurity

were one of the major reasons for the collapse of

can be summarized into this short list: reliable

the shrimp industry in Taiwan and China in thesources of specific-pathogen-free domesticatedlate 1980s and early 1990s (Fig. 6). Ecuador andstock, adequate diagnostic and detection methods

Thailand have longer coastlines, so the effect offor excludable diseases, disinfection and pathogen

disease outbreaks on total production in those

eradication methods, best management practices

nations were not seen right away.

to exclude diseases, and practical and acceptable

Because of the uncontrolled transfer of stock,legislation. In addition to biosecurity, stocka disease outbreak in one area could also cause

improvement can also combat the viral infection

unintended consequences in other parts of theissue. Disease-free stocks are not always possible

world though trade. The outbreaks of Tauraand are not the only tactic. Disease-resistant stocks

syndrome virus (TSV), white spot syndrome

should be used in any area where the exclusion ofvirus (WSSV), and infectious hypodermal anddisease is difficult.

hematopoietic necrosis virus (IHHNV) were found

Under these disease management guidelines andin one location but were identified later in otherwith the availability of specific pathogen free (SPF)

countries (Lightner, 2003).

Nunan et al.(1998)

shrimp stock from Hawaii, Pacific white shrimp (L.

reported that frozen shrimp from an infected areavannamei) was introduced to Asia and impressive

could serve as a vector for exotic shrimp viruses

production data-particularly in China-were reachedduring seafood trade. This report sent out anin less than four years and more than four times

300000250000

Production (1000MT)

20000015000010000050000

01980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
Year
E cuador

China

TaiwanFig. 6. Shrimp production in selected countries from 1980 to 1990.

Fig. 6.

Thailand76

Cheng-Sheng Lee

production levels in Central and South America

containing introduced species from escaping farm(Fig. 7).

areas and breeding with native species. Meanwhile,
all introduction and transfer should follow the code
Implications and conclusion

developed by ICES (ICES 1995).
Acknowledgements

The above examples clearly indicate that theculture of introduced species was a common
practice throughout the world. Exotic species

Preparation of this manuscript was supported

will be introduced whenever and wherever an

by a grant from the National Oceanic andaquaculture industry sees potential for making a

Atmospheric Administration (NOAA)

profit. To stop the importation of non-native species#NA05OAR4171169, the United States Department

for aquaculture purpose will not only reduce totalof Commerce. The author would like to thankproduction but also affect the stability of seafood

Kathryn Dennis for her assistance in editing.

spplies and prices. Still, environmental and socioLiterature cited

economic damage from farming introduced
species will expand if left without any controls.
Introductions, for example, will alter the aquaticAtz, J. M. 1954. The peregrinating Tilapia. Anim.
Kindom, 57(5): 148-155.

community structure and genetic composition ofnative populations, as well as reduce biodiversity

Beveridge, M.C.M., L.G. Ross, and L.A. Kelly. 1994.

(Beveridge et al., 1994; Goldburg and Triplett, 1997;

Aquaculture and biodiversity. Ambio, 23: 497-

Naylor et al. 2000). The current use of SPF shrimp

502.

stock and biosecurity practices in shrimp farming

Bartley, D. and C. Casal. 1998. Impacts ofare positive steps toward reducing potential

introductions on the conservation a n dnegative impacts of culturing foreign species.

sustainable use of aquatic biodiversity. FAO

Urgently needed, however, are other means ofAquaculture Newsletter, 20: 15-19

1200

1000

PRoduction (1000MT)

800

600

400

200

0

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Year
America

China

Asia

Fig. 7. Production of Pacific white shrimp in Central and South America, Asia, and China.

Fig. 7.

77
Copping, A.. and S. Smith. 2005. Pathways of

Hamilton, B. A. Knuth, and S. J. Schwager.

aquatic introductions. http://www.washington.

2004. Global assessment of organic

edu/outreach/mas/aquaculture/pathways.

contaminants in farmed salmon. Science, 303:html

226-229.

Jacques Cousteau. 1973. Statement cited by Justin

ICES. 1995. ICES Code of Practice on the

Henry at 2006 Legislative Session: Second

Introductions and Transfers of Marine

Session, 38th Parliament, Special Committee

Organisms. International Council for theon Sustainable Aquaculture British Columbia.

Exploration of the Sea, Copenhagen, Denmark.

FAO (Food and Agriculture Organization of the

5p.

United Nations). 2004. The State of World

Laird, L.M. and E.A. Needham. 1990. Seawater

Fisheries and Aquaculture 2004. Fisheries

culture of salmonids. P. 628-646. In: G. Barnabe.

Department, Food and Agriculture(ed.) Aquaculture (Vol. II). Ellis Horwood;

Organization of the United Nations, Rome,
Italy.

Chichester, UK.
Lee, Cheng-Sheng. 1995. Aquaculture of milkfish

FAO 2006. The state of world aquaculture 2006.

(Chanos chanos). 141 pp. published by

FAO Fisheries Technical Paper 500, 134 p.

Tungkang Marine Laboratory, Taiwan andFood and Agriculture Organization of the

Oceanic Institute, Hawaii, USA.

United Nations, Rome, Italy.

Lightner, Donald V. 2003. Exclusion of species

FAO 2007. Culture aquatic species fact sheets.

patchogens for disease prevention in a penaeid

http://fao.org/figis/cultured aquatic species.

shrimp biosecurity program. Page. 81-116. In:

Froese, R. and D. Pauly. 2000. FishBase 2000:

Lee, C.-S. and O'Bryen, PJ. (ed.) Biosecurity inconcepts, design and data sources. ICLARM,

Aquaculture Production Systems: Exclusion ofLos Banos, Laguna, Philippines. 344p. publishedpathogens and other undesirables. The Worldby the International Center for Living Aquatic

Aquaculture Society, Baton Rouge, Louisiana,

Resources Management, Philippines.

USA.

Garibaldi, L. and D. Bartley. 1998. The database on

Lin, C.K. 1989. Prawn culture in Taiwan. Whatintroductions of aquatic species (DIAS): thewent wrong? World Aquaculture, 20(2): 19-20.

web site. FAO Aquaculture Newsletter, 20:

Moss, Shaun M. 2002. Marine shrimp farming in

20 - 24.
Goldburg, R. and T. Triplett. 1997. Murky Waters:
Environmental effects of aquaculture in thethe Western hemisphere: past problems,present solutions, and future visions. Review
in Fisheries Science, 10(3&4): 601-620.

United States. The Environmental Defense

Naylor, R.L., R.J. Goldburg, J.H. Primavera, N.

Fund, EDF Publications, Washington, D.C., 196

Kautsky, M.C.M. Beveridge, J. Clay, C. Folke, J.

pp.

Lubchenco, H. Mooney, and M. Troell. 2000.

Goldsborough, W.J. 2003. Statement cited fromhttp://see-the-sea.org/topics/species/invasive_
species.htm.
Hershberger, W. K. 2002. Aquaculture: its role inthe spread of aquatic species. In: Kinnunen,

Effects of aquaculture on world fish supplies.
Nature, 405: 1017-1024.
Naylor, R.L., S.L. Willams, and D.R. Strong. 2001.
Aquaculture-A gateway for exotic species.
Science, 294(5547): 1655- 1656.

R.E. (ed.) Environmental Strategies for

Nunan, L.M., B.T. Poulos, and D.V. Lightner. 1998.

Aquaculture Symposium Proceedings.

The detection of white spot syndrome virus

Minneapolis, MN, 5-6 December 2000.

(WSSV) and yellow head virus (YHV) in

Information Development- Expanding

imported shrimp. Aquaculture, 160:19-30.

Awareness, Iowa State University, Ames,

Riedel, D. 1965. Some remarks on the fecundity of

Iowa, USA. http://www.idea.iastate.edu/aqua/

Tilapia (T. mossambica Peters) and its

pub07.pdf.

introduction into Middle Central America

Hites, R.A., J. A. Foran, D. O. Carpenter, M. V.

(Nicaragua) together with a first contribution

78

Cheng-Sheng Lee

towards the limnology of Nicaragua.
Hydrobiologia, 25: 357-388.
U.S. Congress, Office of Technology Assessment.
1993. Harmful non-indigenous species in the
United States. OTA-F-565. U.S. Government
Printing Office, Washington, DC. 391 pp.
Welcomme, R. L. 1988. International Introductionsof Inland Aquatic Species. FAO Fisheries
Technical Paper No. 294. Food and Agriculture
Organization of the United Nations, Rome,
Italy. 318pp
Wurmann, C. 2007. Salmon farming in Chile:
history, policies, and development strategies.
Paper presented at Socioeconomic Aspects ofspecies and system selection for sustainable
Aquaculture Workshop help from October 1720, 2005 in Honolulu, Hawaii.

79

Countermeasures against Alien Fishes(Largemouth Bass and Bluegill) in Lake Biwa
Atsuhiko IDE＊ and Shinsuke SEKI＊
Abstract

Lake Biwa is one of the world's most ancient lakes, with an origin going back four

million years. Many aquatic organisms, including more than 30 endemic species or subspeciesof fish and molluscs inhabit the lake, and various kinds of fisheries have targeted those animals
for centuries. Bluegill (Lepomis macrochirus) and largemouth bass (Micropterus salmoides) werefirst found in Lake Biwa in 1965 and 1974. While bluegill spread gradually through the shallow
water zones and into small lagoons surrounding the lake, largemouth bass increased explosively
in the 1980s. Simultaneously, native fishes such as crucian carp and bitterlings disappeared
from the coastal shallows. After that, the population of bluegill began to increase.
In recent years, bluegill has comprised over 90% of the fish fauna in Lake Biwa's south basin.
Since 1985, fishermen have been trying continuously to reduce these alien species by several
means. Fishing gear such as Eri (a set-net), gill nets, and pulling nets have been used. Recently,
over 400 metric tons per year of these alien fishes have been eliminated. At the same time,
the Shiga Prefectural Fisheries Experimental Station has tried to develop more effective gearto catch them. We have devised a pot trap, with its top covered by a sheet to provide shade,for efficient capture of the alien fishes, and a small beam trawl for use in beds of submerged
aquatic vegetation. Other methods for the eradication of the alien fishes are currently understudy.
Key words: Lake Biwa, Alien fish, Largemouth bass, Bluegill
plants, littoral gravelly areas, littoral rocky areas,
Introduction

offshore shallow and offshore deep water.
Various kinds of fisheries have existed over theLake Biwa, located on the main island of Honshu,

hundreds of years the lake has been fished. A gillis the largest lake in Japan. It is 63.5 km long andnet fishery, Okisukuiami (a scoop net in offshore)

has a maximum width is 22.8 km. Its maximum

fishery, Chubikiami (a pulling net) fishery, a shell

depth is 104 m. The lake has a north basin and adredge net fishery, and Eri (a labyrinth-like set-south basin, with mean depths of 43 m and 4 mnet) fishery are included among them. The total(Figure 1).

annual commercial catch of fish and crustaceans

Lake Biwa is one of the world's most ancientlakes with an origin going back four million years.

was about 4,000 metric tons during the 1970s and1980s.

Many aquatic organisms, including more thanThe populations of most native littoral fish

30 endemic species or subspecies of fish andspecies, including nigorobuna (Carassius carassius

molluscs, inhabit the lake. About 50 fish species or

grandoculis) and honmoroko (Gnathopogon

subspecies are distributed in the lake, and morecaerulescens), which are the most important

than 10 of them are endemic. The richness of thecommercial fishes in the lake, have decreased

fauna in the lake may be related to the variety ofgreatly in the past twenty years. The decrease was

habitats, including littoral areas with emergent

probably caused by increases in the populations

2009 年 8 月 10 日受理（Received. August 10. 2009）＊
Shiga Prefectural Fisheries Experimental Station, Hassaka, Hikone, Shiga 522-0057, Japan80

Atsuhiko IDE and Shinsuke SEKIof the alien fishes largemouth bass (Micropterus

Stomach contents of the alien fishes in Lakesalmoides) and bluegill (Lepomis macrochirus,

Biwa are shown in Figure 3.Bluegill feed on

Figure 2). This report describes countermeasuresaquatic plants, zooplankton and insects, in addition

against alien fishes in Lake Biwa.

to fish eggs and shrimp, while largemouth bass
prey mainly on fish and shrimp. The results

Invasion of Alien Fishes

indicate that bluegill influences other littoral fish

In Lake Biwa, largemouth bass were first foundspecies by the competing for food and consumingin the north basin in 1974. Their distribution

fish eggs, and largemouth bass affect fish andspread throughout the littoral areas by 1980, andshrimp through predation.

the population increased explosively in the 1980s.

After the population of largemouth bass

Bluegill were found in Nishinoko, one of lagoons

increased explosively, the catch of crucian carp

surrounding Lake Biwa, in about 1965, and the fish

decreased rapidly (Figure 4). At the same time,

spread gradually through the shallow water zones

most bitterling species (small native cyprinidin the 1970s (Terashima 1977). The population

fishes) disappeared from the littoral areas ofbegan to increase in about 1990, and increased

the lake. In addition, the population of bluegill

explosively in about 1993.

increased explosively after the catch of crucian

Hokkaido

Japan

North basin(Northern lake)

HonshuLake Biwa

Kyushu22.8km

63.5kmMean depth 43m

South basin(Southern lake)

Shiga Prefecture
Fig . 1 .

Mean depth 4m

Fig. 1. The outline of Lake Biwa.

Largemouth bass

Bluegill

Micropterus salmoides

Lepomis macrochirus

Fig. 2. Alien fishes affecting native fish fauna in Lake Biwa.

Fig . 2 .

81
sites. At present, the alien fishes are the dominantBluegill
27.7%

49.9%
12.7%

species in the littoral zones of the lake.
aquatic plants
zoo plankton
shrimpsfish eggs
insects
the otherElimination of Alien Fishes
The project to eliminate the alien fishes from
Lake Biwa was initiated by fishermen who have

1.1%

received administrative financial support since

0.2%

1985. The project was developed in order to

8.4%

protect the native fishes. Usual fishing gear such

Largemouth bassas Eri, gill nets, and Chubikiami are being used

18.3%
0.7%

37.7%

for the project. Eri has a structure that guides fish

fish
shrimps
insects
the other

into the main nets. Gill nets are used to capture
the alien fishes mainly in the south basin of Lake
Biwa, and most of the fish species captured are

43.3%. 3 . frequencies of stomach contents ofFig. 3. Fig
Weightthe alien fishes inhabiting
Lake Biwa studied in 2003.

bluegill. Many alien fishes can be captured by
Chubikiami in water 10 m deep in the north basinof Lake Biwa.
The administrative support for the project

carp became stable a reduced level. After that,was increased beginning in 2002. As the result,the annual catch of honmoroko began to decrease

the amount of alien fishes captured, which was

as well. The annual catch of littoral commercial

less than 300 metric tons annually before 2001,

species in the lake has decreased to half of that

increased to more than 400 metric tons annually

recorded in the 1970s and 1980s.

year since 2002 (Figure 6).

Fish Fauna in the Littoral Zones of Lake Biwa
The percentages of largemouth bass, bluegill
and other species captured by small set-nets at

The alien fishes captured by fishermen are

four littoral sites in Lake Biwa in 2002 or 2003 aretransferred in carts to a factory where they are

shown in Figure 5. The percentages of largemouth

processed into fish powder, which is used as anbass were greatest at the two sites in the northern

ingredient for animal feed.

part of the lake, while the of bluegill portion of

The usual fishing gear types used for capturing

the catches exceeded 90% at the two southernalien fishes have some problems. Those gears

Annual catch (m.ｔ.）

1,000
800
600
400

Explosive increase in
the population oflargemouth bass

200

Explosive increasein the population of
bluegill

0
1970

1975

1980

1985

1990

1995

2000

Fig. 4. Change
Fig . 4 .of the annual catch of crucian carp in Lake Biwa, and relationships
between the change and the increase in alien fishes.

82

Atsuhiko IDE and Shinsuke SEKI
6.8%

Largemouth bass
Bluegill
Other fishes

53.4%

39.8%

25.7%

Enshoji

Harie
11.9%

62.4%

2.1%

7.9%

1.2%

Yamanosita

Maki

1.2%

90.0%

97.6%

Fig . 5 .

Fig 5. Percentages of largemouth bass, bluegill and other fishes captured by small set-nets atfour littoral sites in Lake Biwa in 2002 or 2003.

Administrative support was increased.

Annual catch (m.t.)

521
427

408

423

277
188

2000

2001

2002

2003

2004

2005

Fig.
Fig
. 6 . 6. Annual catches of the alien fishes in Lake Biwa.
cannot be used in the shallow water zones that

The new gear devised for use in shallow water

many alien fishes inhabit because they are toozones is shown in Figure 7. We call this trap

big to set up in those zones. The gears are also

"Shading" Type Pot Trap. In the studies, we could

not easily used in areas where aquatic plants

capture the alien fishes, in particular bluegill,grow thickly because the plants obstruct setting

more efficiently with the gear during its spawningof the gears. Small (young) alien fishes are notseason. The maximum number of the alien fishes

efficiently captured by the traditional gear types, in

captured with one shading type pot trap set for 24

particular, gill nets. The solution of these problems

hours in shallow water zones of Lake Biwa or inis necessary to eliminate the alien fishes efficiently.

the lagoons surrounding the lake was 65.

In order to solve the problems, we devised two

The second new type of gear we developed

new types of fishing gear. Test results showed

is a small beam trawl which is effective in beds

that a covering sheet put on the top of a potof submerged aquatic vegetation (Figure 8). The

trap increased its effectiveness in capturing thegear was designed after gear used in the Japanesealien fishes when they gather in shaded areas.

coastal seas to capture shrimp (Tsudani 1978).

83
The trawl net has two beams. The length of the

The new fishing gears have been introduced

first beam is 3 m and that of the second beam is 2

for the project to eliminate the alien fishes inm. These two beams stabilize the net for towing

2005. The removal of those fishes from Lake Biwa

in beds of submerged aquatic plants. This net iswill probably proceed more efficiently by using

towed with mowing down the aquatic plants. The

the older and the new fishing gears in parallel.

maximum catch of alien fishes in test tows of three

Verification of the effect of the new gears to theminutes duration in Lake Biwa's south basin was

project will be reported on in the future.

1.7kg.

The Shiga Prefecture Government established

Figure 9 shows the length frequency

a new local ordinance "Biwa-ko Jorei" in 2003.

distributions of bluegill and largemouth bass

This ordinance asks recreational fishermen not

captured by the small beam trawl in the south

to release the alien fishes captured in Lake Biwa,

basin in 2003. As shown in the graphs, the small

in order to get their collaboration in helping tobeam trawl could capture young alien fishes of lesseliminate the alien fishes.

than 60 mm standard length, which are hard tocapture with other types of fishing gear.

73 cm

Fig . 7 .

Fig. 7. “Shading”Type Pot Trap for the alien fishes.

Rope(30m)

First beam
Second beam (Square lumber)(Plastic coated iron pipe)
Mesh size: 4mm
Float
Mesh size: 2mm
2m
3m
Ground rope
2.5m
1.8m

2.6m

Fig . 8 .Fig. 8. Appearance of a small beam trawl.

2.7m

1.1m

84

Ｎ=496

160

150

140

130

120

May 30, 2003

110

100

70

60

50

40

30

20

10

0
80
60
40
20
0

90

Bluegill

Young
fish

80

25
20
15
10
5
0

Ｎ=80

Largemouth bass June 19, 2003

Young
fish

0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200

Frequency(%)

Atsuhiko IDE and Shinsuke SEKI

Standard length(mm)Fig. 9. Length frequency distributions of the alien fishes captured by the small beam trawl net
Fig in. 9Lake. Biwa`s south basin.

Estimated biomass (m.t.)

2000
1500
Bluegill
Largemouth bass

1000
500
0
2004

2005

2006

Fig. 10. Biomass offishes estimated from the data on the fishes captured by the
Figthe. 10alien.
project to eliminate.
Future Plans
As the result of the project to eliminate thesinnyugyo. Tansuigyo (Fewshwater Fish), 3:3843.

alien fishes, the estimated biomass of bluegill in

Tsudani, T. 1978. Coastal small beam trawlers

Lake Biwa, tended to decrease recently, but that

(Kogi Ami). Illustrations of fishing boats,of largemouth bass continues to be stable (Figure

Tokyo. pp. 59-63.

10). It is, therefore, necessary to increase thecountermeasures against largemouth bass. As
the next step, we will study methods that might
be used to prevent breeding by largemouth bass.
The ultimate goal is to restore the Lake Biwa
ecosystem to one that has a fauna comprised onlyof native fishes.
References
Terashima, A. 1977. Biwako ni seisokusuru

85

Conservation Aquaculture Approaches for Hatchery Reform
Thomas A. Flagg＊1 and Lars E. Mobrand＊2

Development of the North Pacific salmonid
hatchery system began in the late 19th century

management of production hatcheries and the
traditional users of hatchery fish.

and has played a prominent role in enhancement

Since 1999, NOAA has been a partner in a formalof the salmonid fisheries in the Pacific Northwest

process of hatchery reform that has been ongoing(states of Washington, Idaho, and Oregon, USA)in the Pacific Northwest (Mobrand et al. 2005).

since the 1950s. Most public hatcheries in the

The Hatchery Scientific Review Group (HSRG) is

Pacific Northwest were originally built to mitigate

funded by the U.S. Congress and is a systematic,

for loss of natural spawning habitat. Hatcheryscience-driven redesign of how hatcheries will be

production goals focused on enhancing harvest

used to achieve the goals of: 1) helping to recoverof adults in commercial fisheries. The hatcheries

and conserve naturally spawning populations, andwere established at a time when many wild2) supporting sustainable fisheries. Initial worksalmon stocks were healthy and genetic diversity

by the HSRG included developing a Scientificof stocks was not a concern. Hatcheries have

Framework for Artificial Propagation of Salmon

played a major role in supplying salmon andand Steelhead, a Benefit/Risk Assessment

trout to the common property fishery, benefiting

Tool, Hatchery Operational Guidelines, andcommercial, sport, tribal, and nontribal fishers. In

Monitoring and Evaluation Criteria (see www.

fact, hatcheries are so instrumental in supplying

hatcheryreform.org; http://hatcheryreform.us;

fish that it is nearly impossible to separate theand www.managingforsuccess.us for information

management of the salmonid fisheries from theon the Hatchery Reform process). These tools

management of the hatcheries.

Today in theare being used by the HSRG in a comprehensive

Pacific Northwest, nearly 400 artificial production

Pacific Northwest region-by-region review that

programs for anadromous salmon and steelhead

evaluates hatchery programs for consistency with

(Onchorynchus spp.) are producing over 200 million

established scientific principles and the objectives

hatchery fish annually. These hatcheries now

of hatchery reform.

provide up to 80% of the fish in several of the key
fisheries.

Where hatchery operations conflict withrecovery of ESA-listed stocks, the options appear

Despite the great success of hatcheries into be either 1) isolation of hatchery production (e.g.,

supplying fish for fisheries, the philosophy ofnear-tidewater rearing/release and aggressive

salmonid resource management has changed

terminal harvest of hatchery fish) or 2) altering

to include a focus on resource management for

hatchery operation to include a conservation

wild stocks. A number of stocks of anadromous

mandate (see Flagg and Nash 1999, Flagg etsalmonids in the Pacific Northwest are currently

al. 2004, and Mobrand et al. 2005 for details oflisted by the National Marine Fisheries Service

conservation hatchery approaches). What follows(NOAA Fisheries) as threatened or endangered

is a brief discussion of major emerging issues

under the U.S. Endangered Species Act (ESA).

relating to the operation of hatcheries in the

The need to preserve biodiversity has brought

Pacific Northwest and examples of what we feel

about a new era of conservation of wild stocks

are critical needs for hatchery reform. These

that cannot help but impact the operation anddiscussions provide an example for Pacific salmon

2009 年 8 月 10 日受理（Received. August 10. 2009）＊1
NOAA Fisheries, Northwest Fisheries Science Center, Resource Enhancement and Utilization Technologies Division, Manchester, Washington,
WA 98353, U.S.A.
＊2
Hatchery Scientific Review Group, Mobrand-Jones & Stokes, Inc., Vashon, Washington, WA 98070, U.S.A.

86

Thomas A. Flagg and Lars E. Mobrandof the general shift in aquaculture philosophy fromconservation aquaculture approach (Mobrand et al.

a production-based focus to one that also considers

2005)

effects of the actions on health and sustainability of

Principle 1: Every hatchery stock must havethe natural ecosystem.

well-defined goals in terms of desired benefits andPotential Impacts of Hatchery Rearing--The

purpose. Well-defined goals provide both targets

overall impact of hatchery fish on wild populations

and measures for success. The goals for eachcan be divided into three broad categories. 1)

hatchery stock must reflect the purpose andOver-harvest of wild stocks in mixed stock

desired benefits of the program (e.g., harvest,

fisheries can have a profound impact on survival

conservation, research, education). Whereverof wild stocks. When productive hatchery stocks

possible, goals should be quantified.

are targeted for high harvest, less productive

Hatcheries should operate as part of an

wild stocks cannot withstand the high exploitation

integrated strategy that includes short-term

rates, resulting in under-escapement of wild fish.

and long-term goals for habitat and harvest.

2) A number of ecological interactions can occur

Goals should be related to measures of success,between hatchery and wild fish. These can takeincluding: (a) the desired number of fish to be

the form of: competition for food and territory,

harvested each year, (b) the number of fish

predation with larger hatchery fish preying on

returning to a hatchery or spawning naturally insmaller wild cohorts, and other negative sociala watershed (i.e., escapement), (c) the expectedinteractions when large numbers of hatchery fish

results of scientific research, and (d) theare released on top of small numbers of wild fish.

educational benefits to be derived from outreach.

3) Genetic risks associated with hatchery rearing,

Principle 2:

including intentional and unintentional events

scientifically defensible.

such as domestication selection, inbreeding, andand operations must be consistent with statedoutbreeding depression.

goals, and they must be defensible scientifically.

Hatchery programs must be
Hatchery programs

Traditional hatchery rearing for Pacific salmon

Once the goals for a program are established,is most commonly conducted in outdoor raceways

the scientific rationale for the design andand tanks over uniform concrete substrate. Fish

operation of the program must be explicitly

in rearing vessels are conditioned to minimal

stated and understood by all personnel. These

raceway flow regimes; provided no structure in

requirements may necessitate a written,

which to seek refuge from predators, or dominantcomprehensive management plan for every

cohorts; held at high, stress-producing densities;

hatchery program. Scientific oversight and peersurface fed; and conditioned to approach large,

review should be integral components of every

moving objects at the surface. The protective

hatchery program.

nature of hatchery rearing increases egg-to-smolt

Every hatchery program needs to havesurvival. However, the postrelease survival andoperational guidelines and standard operating

reproductive success of cultured salmonids is often

procedures (e.g., selection of adults for broodstock,considerably lower than that of wild-reared fish.

spawning protocols, feeding protocols, etc.) that

The hatchery practices mentioned above are often

are scientifically defensible. These guidelines

considered prime factors that may induce genetic

should include decision-making pathways forchange (e.g., domestication) and reduce fitness ofdealing with potential contingencies.

hatchery fish for natural ecosystems. However,Principle 3: Hatchery programs must respond

it is likely that the most immediate impact ofadaptively to new information. Scientifictraditional rearing practices is to disrupt innatemonitoring and evaluation (M&E) of hatcherybehavioral repertoires.

programs need to be increased. M&E should

Conservation Hatchery approach-Threeassess smolt-to-adult survivals, return rates offoundational principles (Table 1) have been

adults, contributions of adults to harvest anddescribed for operation of hatcheries under anatural spawning, the proportion of naturally

87

Table 1. Principles for hatchery management and system-wide recommendations
developed by the Hatchery Scientific Review Group (HSRG), modified from Mobrand etal. 2005.
1) Well-Defined Goals:• Set Goals for all Stocks and Manage Hatchery Programs on a Regional Scale• Measure Success in Terms of Contribution to Harvest, Conservation and Other
Goals• Have Clear Goals for Educational Programs2) Scientific Defensibility:• Operate Hatchery Programs within the Context of Their Ecosystems• Operate Hatchery Programs as either Genetically Integrated or SegregatedRelative to Naturally-Spawning Populations• Size Hatchery Programs Consistent with Stock Goals• Consider both Freshwater and Marine Carrying Capacity in Sizing Hatchery
Programs• Ensure Productive Habitat for Hatchery Programs• Emphasize Quality, Not Quantity, in Fish Releases• Use In-Basin Rearing and Locally-Adapted Broodstocks• Spawn Adults Randomly throughout the Natural Period of Adult Return• Use Genetically-Benign Spawning Protocols that Maximize Effective
Population Size
• Reduce Risks Associated with Outplanting and Net Pen Releases• Develop a System of Wild Fish Management Zones• Use Hatchery Salmon Carcasses for Nutrification of Freshwater Ecosystems,
while Reducing Associated Fish Health Risks
3) Informed Decision Making:• Adaptively Manage Hatchery Programs• Incorporate Flexibility into Hatchery Design and Operation• Evaluate Hatchery Programs Regularly to Ensure Accountability for Successspawning fish composed of hatchery-origin

structured adaptive management program

adults, and stray rates of adults to non-target

is necessary for the success of hatcheries.

watersheds.

Institutional resistance to programmatic flexibility

Where possible, M&E should

include assessments of genetic and ecologicaland change needs to be overcome.

interactions (e.g., interbreeding, competition,

Conservation Hatchery Operation--Flagg et

predation) between hatchery- and natural-al. 2004 described an operational approach fororigin fish. Centralized databases need to beConservation Hatchery rearing for Pacific salmon

developed for collating, storing, and retrieving(Table 2). The process requires application anddata. Results need to be evaluated annually tointegration of a number of rearing protocols, all ofallow programmatic adjustments.

which are known individually to affect the inherent

Hatcheries need to be flexible and managed

fitness of the creature to survive and breed in

adaptively. Many scientific uncertainties are

its natural ecosystem. A Conservation Hatcheryassociated with salmon hatcheries. Hatcheryapproach for salmonids will require a specialized

programs and facilities must respond to newrearing facility to breed and propagate a stock

goals, new scientific information, and changesof fish genetically equivalent to the native stock,in the status of natural stocks and habitat. A

and with the full ability to return to reproducestandard (typically smoothwith no internal structure)surface or wellstandard (designed tomaximize fish output)
variablenaturalup to maximum safe levels
use accepted guidelines for
species that maximize adultreturn.
maximum possible
none

temperature

vessel typetemperature

culturepond timing

photoperiod
density

growthsurvival
Prereleaseconditioningssurface or wellincubator type

Egg incubation

Fish rearing

use accepted guidelines for
speciesmating strategy

directed (probably large
number of eggs taken)
directed (for characteristics)

number

Egg fertilization

directed (e.g., early or latecomponent, etc.)

spawn timing

Egg collection

Objective

maximize output
maximize output

maximize output

provide ambient conditions
maximize space use

maximize culture opportunity

time rearing to productionneedsmaximize output

time hatch to productionneedsmaximize output

select desired attributes (e.g.,
return size and age)
maximize output

maximize output

synchronize adultreturn/harvest opportunities

Production Hatchery

FactorParameter

Actionuse substrates that enhancecrypsisuse growth modulation
targeted to approximate wild
rearing scenario at all cultured
life stages
maximum possible
provide antipredator
conditioning

naturaluse low rearing density

synchronized to wild

innovative (designed tomaximize fish quality)

altered to include enriched(seminatural) habitats withcover, structure, substrate, etc.
controlled to ambient for stock

controlled to ambient for stock

Objective

maximize output
reduce predator
vulnerability/
increase postreleasesurvival
reduce predator
vulnerability/increase
postrelease survival

synchronize rearing withwild stock
reduce domestic
conditioning and improve
fitness
approximate wild rearing
scenario
provide ambient conditions
minimize behavioral andhealth aspects of fish
qualitytarget fish growth to wild
size

approximate wildconditions/maximize hatch
size
synchronize hatch withwild timing
reduce domestic
conditioning

stage production to habitat
carrying capacity
maintain diversity

maintain wild timing

Conservation Hatcherysynchronized to wild,
representative numbers
collected over range of run
directed (relatively small
number of eggs needed)
directed (to maintain genetic
diversity)
include substrate

ActionTable 2. Operational comparisons between production and Conservation Hatchery strategies for rearing of Pacific salmon (modified from
Flagg et al. 2004).

88
Thomas A. Flagg and Lars E. Mobrand89
and operational approaches for a Conservation
Hatchery may be considerably different then fora standard production hatchery.

Therefore, aConservation Hatchery must be equipped with afull complement of culture strategies to produce
very specific stocks of fish with specific attributes.
Where and when implemented, fish rearing inprimary/secondary strategy

primary/secondary strategy

secondary strategy

release only healthy fisha Conservation Hatchery must be conducted ina manner that 1) mimics the natural life history
patterns, 2) improves the quality and survivalof hatchery-reared juveniles, and 3) lessens thegenetic and ecological impacts of hatchery releases
on wild stocks.
Operational guidelines for conservation
hatcheries to help mitigate the unnatural
conditioning provided by hatchery rearing
described in Flagg et al. 2004 include: 1) Mating

maximize output

maximize adult return
opportunity

and rearing designs that produce minimal genetic
divergence of hatchery fish from their wild
counterparts to maintain long-term adaptive traits;
2) Simulation of natural rearing conditions throughincubation and rearing techniques that approximate
natural profiles and through increasing habitat
complexity (e.g., cover, structure, and substrate inappearance, and with natural behaviors and higher
survival; 3) Conditioning techniques such as antinot used under mostcircumstances
not used under mostcircumstances
primary strategy

fish often released with
subclinical health problems

rearing vessels) to produce fish more wild-like inpredator conditioning to increase behavioral fitness;
4) Release of fish at a size, stage, and condition
which approximates the wild population to reduce
potential negative ecological interactions and topromote migratory homing; and 5) Aggressive
monitoring and evaluation to determine success of

smolt releasepresmolt release

fry releasediseasesconservation hatchery approaches.
Genetic Integration vs. Segregation of
Hatchery Broodstocks Relative to Natural
Populations--A first step towards "hatcheryreform" is to develop a detailed genetic
management plan or strategy for every hatchery
Fish releasebroodstock.
Healthprovide forage training

provide exercise conditioning

increase postreleasesurvivalincrease postrelease
growth and survival
maximize survival andminimize impacts to wild
fish
seed critical habitats at or
below carrying capacity
seed critical habitats at or
below carrying capacity
maximize adult return
opportunity

naturally in the habitat. The fish quality goals

Morbrand et al. 2005 described

two genetic management options: (1) manage ahatchery broodstock as a reproductively distinct
population that is genetically segregated fromnaturally spawning populations, or (2) manage ahatchery broodstock as a genetically integrated
component of an existing natural population. Each

90

Thomas A. Flagg and Lars E. Mobrandof these broodstock strategies leads to a different

term goal, a self-sustaining naturally spawning

set of operational guidelines (detailed information

population capable of providing adult fish foron integrated vs segregated approaches can be

broodstock each year. Integration thus requires

found on the HSRG websites described above).

suitable natural habitat capable of sustaining

Genetically segregated broodstocks area natural population.

Under this concept, an

generally derived strictly from hatchery-origin

integrated hatchery does not replace habitat

adults returning back to the hatchery each year.

but adds to existing habitat.

Segregated hatchery programs create a geneticallyof an integrated program is to demographicallydistinct, hatchery-adapted population. Segregatedincrease the abundance of a natural population

hatchery populations will diverge genetically fromwhile minimizing the genetic effects of artificial

naturally spawning populations over time because

propagation. The size of an integrated hatcheryof founder effects, genetic drift, and domestication

program will necessarily be limited by the habitat

selection in the hatchery environment.

An implicit goalSuchavailable to the natural populations with whichchanges may be intentional (e.g., via selective

it is integrated and by the ability of the hatchery

breeding) to maximize benefits or the operational

program to restrain natural spawning by hatchery-

efficiency of a hatchery program.

origin adults.

However,natural spawning by hatchery-origin fish from

Risks and Benefits--Salmon hatcheries area segregated program may pose unacceptablea major source of controversy in the Pacificgenetic and ecological risks to natural populations,Northwest. The HSRG was mandated by Congress

and the HSRG recommends for segregatedto identify potential solutions to widely-recognizedprograms the percent of hatchery origin spawners

problems to ensure that hatcheries contribute to(HOS) on the spawning grounds should be less than

supporting sustainable fisheries while supporting

five percent of the naturally-spawning populationconservation, restoration, and recovery of natural(pHOS < 5%).

Often, to achieve these goals

populations. The review focused on identifying

will require a combination of directed selective

scientific uncertainties and proposing solutions

fisheries and control structures such as weirs to

based on the best available science. The need toremove segregated populations prior to arrival ondevelop broodstock genetic management plans forspawning grounds.

every hatchery program with the goal of managing

Conversely, genetically integrated broodstocks

each broodstock as either a genetically segregatedsystematically include a prescribed proportion"hatchery population" or as a geneticallyof natural-origin fish in the broodstock each year

integrated component of an existing "natural

to maintain genetic integration with a natural

population" became a fundamental foundation for

population.

One goal of integrated hatcherythe recommendations. Both strategies require

programs is to minimize the genetic effects of

the ability to distinguish hatchery and natural-

domestication by allowing selection pressuresorigin adults, both in the hatchery when adults

in the natural environment to drive the genetic

are spawned for broodstock and on the natural

constitution and mean fitness of the population as

spawning grounds to assess the genetic risks anda whole. For an integrated program, the percent

gene flow rates of hatchery-origin fish to naturalof natural origin fish taken into the broodstock

populations. Commensurate with these reforms iseach year (NOB) must be greater than the percent

the need for increased monitoring and evaluation,of hatchery origin fish allowed to spawn in thescientific oversight, and accountability of hatcherywild (pNOB > pHOS). An integrated program

operations.

will require methods (such as those described for

In this context, hatcheries cannot be regarded

segregated populations) to remove hatchery origin

as surrogates or substitutes for lost habitat.

fish prior to spawning grounds to adequately

Hatcheries need to operate in scientifically-

control hatchery/wild fish ratios.

defensible modes with well-defined goals andIntegrated hatchery programs require, as a long-

substantially increased data collection and91
evaluation. Hatcheries also need to be flexible
and adaptable; that is, they need to operate andbe evaluated in the context of both the ecosystem(watersheds) in which the hatcheries occur andother ecosystems and ecological processes on
which hatchery-origin fish depend.
Scientific uncertainties associated with hatcheryoperations are numerous. The science to manage
these risks is still inadequate, and some of the risks
are still poorly understood. However, one point isclear. Maintaining healthy habitat is critical not
only for viable, self-sustaining natural populations,but also to adequately control risks of hatchery
programs and realize the benefits of hatcheries torecover populations and sustain healthy harvests
in increasingly populated environments.
References
Flagg, T. and C. Nash.

1999.

A conceptual

framework for conservation hatcherystrategies for Pacific salmonids. NOAA Tech.
Memo. 38.
Flagg, T., C. Mahnken, and R. Iwamoto. 2004.
Conservation Hatchery Protocols for PacificSalmon. Am. Fish. Soc. Symp., 44:603-619.
Mobrand, L., J. Barr, D. Campton, T. Evelyn, T.
Flagg, C. Mahnken, L. Seeb, P. Seidel, and W.
Smoker.

2005.

Hatchery Reform in

Washington State: Principles and Emerging
Issues. Fisheries, 30(6):11-23.

93

Accounting for Economic Risk and Uncertainty in Offshore
Aquaculture: A Case Study of Korean Rock Bream Production
Douglas W. Lipton＊1 and Do Hoon Kim＊2
Abstract Interest is growing in offshore aquaculture as a means of overcoming environmental
concerns that plague nearshore and coastal aquaculture production. The challenge of dealing
in the offshore environment adds expenses that are not present in other aquaculture production
systems. We collected financial and production performance data from a commercial scale
offshore aquaculture production system for rock bream off the coast of Korea. Financial
performance of the system was evaluated using Aquasim, a stochastic financial simulator. To
compare performance, we focused on the ten year internal rate of return and net present value
based on different assumptions regarding fish survival rates and market prices. The baselinemodel which used the observed survival and market prices had a high probability of financial
success and an internal rate of return of 18%.

Financial performance became a lot riskier

when we assumed that survival rates followed a triangular distribution with a 25% minimum
survival that increased 5% per year, even when the mean survival rate was as high as 97%.
Rock bream aquaculture could be successful under that survival scenario if prices are high forthe first five years and then start declining due to the industry expanding. In that case, theinternal rate of return is around 14%, but with greater variability than the baseline. If prices
fall from the initial baseline level in the early years of production, then the operation has little
chance of surviving.
et al. 2006; Goldburg et al. 2001). Offshore ocean
Introduction

aquaculture systems, within the high energy
marine environment and deeper waters, may

The continued development of aquaculture as

ameliorate some of the environmental problems

a means of increasing the world's fish supply isof the current systems which tend to be more

a balance between cost efficiency in production

nearshore and in shallower water (Kalantzi andand environmental costs that are external to

Karakassis 2006). However, these environmental

the operation. At one extreme are recirculating

gains may be offset by higher investment costs,

systems that are greatly isolated from thehigher operating expenses and greater risk.

environment, but have high investment andAs with any new production process, there

operating costs that, at present, are mostly

is little data available about the economic

economically viable for high-valued species.

performance until a sufficient size industry

These systems have a relatively low impact

develops from which to gather data. Potential

on the environment since there is little, if any,

investors and government agencies that seek towater exchange, and the effluent can be easily

support the development of aquaculture must rely,

managed. More open systems such as shrimp

at best, on data from experimental or pilot-scale

ponds or coastal net-pen systems have lower costs,

systems, or expert opinion on which to base their

but are experiencing growing concerns about

decisions. Economic analysis of the performanceenvironmental impacts (Naylor 2006; Whitmarshof two offshore aquaculture systems in the United

2009 年 8 月 10 日受理（Received. August 10. 2009）＊1
Department of Agricultural & Resource Economics, University of Maryland, College Park, MD 20742＊2
National Fisheries Research & Development Institute, Busan, Korea 619-902

94Douglas W. Lipton and Do Hoon Kim

States, one off of Puerto Rico (Brown et al. 2002)

production levels and feed costs.

and one placed off of Hawaii (Kam et al. 2003), haverequires the user to specify ranges or standard

been conducted based on just such speculative

deviations for a variety of variables related to thedata. In this paper, we base an economic analysis

production process and for input and output prices.

of rock bream, Oplegnathus fasciatus, culture in(Table 1)

Aquasimthe offshore waters of Jeju Island, Korea, on the

In addition to incorporating risk and uncertainty

actual performance of a privately owned andvia Monte Carlo simulations, Aquasim provides

operated aquaculture enterprise. Since the data is

for a more realistic investment scenario thanlimited to one year of operation, we use stochastic

developed in typical enterprise budgets. The user

simulation to project the necessary conditions forcan specify initial loans and terms, as well as terms

long term success for similar offshore operations.

for new loans that may be initiated within the time
horizon should the cash flow situation require or

Methodology

when capital equipment needs to be replaced asindicated by the depreciation schedule. New loans

Financial Analysis

are allowed during the simulation as long as the

A basic accounting approach is standard for

operation meets standard equity ratio tests. If theexamining farm enterprises in general and has

operation runs out of money and borrowing is notbeen applied widely in aquaculture.

Greaterallowed due to insufficient equity, the simulation

attention has been paid to accounting foris declared insolvent. The number of insolvencies

uncertainty and risk, particularly when dealingis tracked during the simulations to generate awith relatively new aquaculture operations.

probability of survival for the operation. Standard

Examples of incorporating risk in aquaculture

measures of performance such as internal rate ofinclude studies on salmon (Kumbhakar 2000),

return and ending net worth are tracked for all

catfish (Kazmierczak and Soto 2001; Nelson et al.

the solvent iterations, and the mean values, ranges

2001), crawfish (McCullogh et al. 2001) and shrimp

and coefficients of variation are provided for the(Valderrama and Engle 2001). Sottorio collectedscenario being tested.

data from 16 companies in Spain involved in

Another feature of Aquasim is that it is aaquaculture production of eight finfish species.

dynamic model with up to a ten year time horizon.

Lipton and Gempesaw (1997) used a softwareThus, the user can specify different parameter

program they specifically developed for evaluating

values for all ten years. For example, survival

risk in aquaculture enterpises, Aquasim, torates may increase or feed efficiency increase due

compare production technologies for hybrid striped

to an assumption about the firm moving up thebass.

learning curve of production (Sotorrio 2002). The

Aquasim was used in this analysis of offshore

variance or ranges of the specified parameters canaquaculture of rock bream. Aquasim is derived
from Chicksim, a stochastic financial simulation

TABLE
1. Financial
information
usedininAquasim.
Aquasim.
Table
1. Financial
information
usedprogram originally designed for analyzing chicken
production (Gempesaw et al 1988). Aquasim iscapable of simulating four discrete stages of fish
production for a single species.

The model isalso capable of simulating multiple production
cycles simultaneously, allowing for continuous
stocking on up to a monthly basis.

Fish aregrown in the simulation based on user specified
ending and starting weights and stage length inmonths. User specified stage-specific mortalities
and feed conversion rates are applied to determineMarket Price

US$12.94/kg

Tax

10%

Discount rate

8%

Loan

US$150,000

Interest rate of loan

2.8%Life of loan

2years95
also increase or decrease over the time horizon.

Rock bream was selected as the species to be

For example, experience may not lead to a higher

farmed due to its high market price comparedmean survival rate, but it could lead to lessto other major species such as the flatfish,variability in the survival rate.

Paralichthys olivaceus, and the rockfish ,Sebastes

A baseline scenario using Aquasim is developed

schlegelii. 1 Rock bream fingerlings are readilyusing the actual data obtained from a commercial

available, and it has performed well in otherscale operation discussed below. Once the baselineaquaculture systems. A total 677,467 fingerlings,

performance is established in terms of net present

weighing 5-10g per fingerling were stocked at thevalue (NPV) and internal rate of return (IRR),

end of June 2005.

several other scenarios are run for comparison.

Production costs for the first 12 mo nth

In particular we look in detail at a more realistic

production cycle were obtained from the Noahprice scenario over the ten year time horizon, as

Offshore Farm.

well as a more realistic fish survival scenario. We

performance of the fish within the system in terms

then run the price scenario and survival scenario

of growth and survival. Financial parameters forin a combined scenario that we feel most closely

the production of rock bream offshore farming

approximates the expected performance of theare summarized in Table 2. Parameters include

offshore rock bream system. We also conduct

market sale price, tax rate, discount rate, and loan

sensitivity analysis for key production parameters

terms. The price of rock bream during the period

such as feed and seed costs.

was estimated to be relatively high (US$12.94/kg)

JFRI provided data on thecompared to other farmed species. A discount rate
Aquaculture Operation Description

of 8% is used to calculate the Net Present Value

The offshore rock bream cage production(NPV). The Noah Offshore Farm Co. Ltd. borrowed

system was initially introduced in the Pyo-Sun

US$150,000 from the National Federation ofarea of Jeju Island in Korea on April 2005 as part

Fisheries Cooperatives (NFFC) at a 2.8% interestof a commercial farming pilot project (Figure 1).

rate during a 2-year period.2

The Pyo-Sun area is close to port facilities and

The overall survival rate was 97%, and we

fingerling production facilities. A consortium for

initially assumed it ranged from 90-100%). The

the commercial project was formed by the Jeju

feed conversion rate (FCR) was 1.3 with an

Fisheries Research Institute (JFRI), a regional

assumed standard deviation of 0.2.

institute of the National Fisheries Research &had an average weight of 175g with an assumed

Development Institute (NFRDI) of Korea and astandard deviation of 0.14g after the 12-monthprivate aquaculture enterprise, Noah Offshore

production period. The survival rate is relatively

Farm Company Limited.

high compared to other species farmed in Korea

Thee fish

The city of Jeju issued a permit to conduct

in land-based raceways or in coastal cage systems.

the offshore farming in an area covering 10 ha of

For example, the average survival rate of flatfish

surface water, 4.5 km off Pyo-Sun for three years

in the land-based farms is 80%. The difference(May 2005 to May 2008). The offshore cage system

might be because there were no serious naturalTM3, a 3000 m biconical sea

disasters such as a typhoon or red tide during the

cage. This is the same cage system as is being

last 12-month farming period and no problems withused in Hawaii, Puerto Rico, and New Hampshire.

diseases that may occur in cage farming. This high

The cage system was imported from the United

rate of survival might be a significant advantage

States and currently, three cages are beingof an open ocean cage system in comparison toemployed.

coastal cage systems or land-based cage systems.

is the Seastation 3000

1

The production of flatfish and rockfish accounted for 75.4% of Korea's total farmed finfish production in 2005. The annual average price perkilogram of a flatfish and a rockfish in 2005 was US$8.76 and US$9.26, respectively.
2
This is a government subsidized rate, and other firms would expect to pay higher interest rates. However, the results that follow were notgreatly sensitive to the interest rate used.

Fig.1.
96

Douglas W. Lipton and Do Hoon Kim

Fig. 1. Map of Jeju Island in South Korea and sight of offshore aquaculture facilities.

TABLE
2. Production
parameters for
culture.
Table
2. Production
parameters
for offshore
offshorerock
rockbream
bream
culture.

3

PARAMETERMEAN VALUE

DISTRIBUTIONTime to market

12 months

Not Applicable

Initial stocking

677,467 fingerlings

Not Applicable

Survival Rate

97%

Triangular (min=90%; max=100%)

Feed Conversion Ratio

1.3

Normal (s.d.=0.2)3

Average Market Size

175 gs.d. = standard deviation

1

Normal (s.d.=0.14)

97However, since these potential natural disasters

cost (22.8%), and depreciation (10.5%). These costs

and disease outbreaks may eventually occur inrepresent 82% of total annual operating costs.

future offshore farming production, we will focus

This indicates fingerling and feed have the largest

some attention to a sensitivity analysis on the rate

potential for reducing annual operating costs.

of survival. The FCR is also significantly lower

Recurring energy costs (US$14,400) consist

than in other types of cage systems (for example,of fuel for boats and trucks. Lease rent cost of

the FCR averaged at 3.5 in the land-based cage

US$41,250 per year includes the full-time lease of asystem for flatfish), giving the offshore cage

boat and additional lease costs for boats and trucks

system a decided advantage in this important costrented temporarily during the time of stocking

category.

fingerlings and harvesting. Interest is incurred

A total of nine full-time employees (includingfrom US$150,000 that is borrowed from NFFC

three owners) were hired to run the three cagewith a 2.8% interest rate during the life of 2 years.

offshore production system. Among them, one

Due to the short production history of offshore

salaried person is in charge of an office work andfarming, it is difficult to estimate an exact repair/the other five people are used as divers. Diver

maintenance costs. Thus, the cost of maintenance

operations include repair and maintenance, feeding,is a provisional estimate that is charged atharvesting and stocking. Salary per worker

US$10,000 per cage (Kam, et al., 2003).

was US$2,200 per month and the total annual
Results and Analysis

labor cost total was US$237,600, which includes
US$79,200 that represents the opportunity costsof the three owners' time devoted to the project.

Baseline Scenario

Part time labor was used for stocking, harvesting

The baseline model suggests that the production

and miscellaneous tasks. A total of 16 part-timeof rock bream offshore farming is profitable over

employees were hired: one carpenter, five fora 10-year time horizon (Table 3). A 10-year cash

stocking and harvesting, and ten divers. The total

flow based on an 8% discount rate indicates

part-time labor costs were US$10,860. For future

a positive NPV of US$3,151,402 (ranging fromyears, we assumed that labor costs varied with a

US$2,159,171-US$4,111,452). In addition, the IRR

standard deviation that was 10% of the observed

value was high at 18% (ranging from 12%-28%).

costs from the actual operation.

At this level of performance there is virtually no

The initial investment for the operation wasrisk of economic failure; all the iterations remained

US$869,273. The three submersible cages andsolvent throughout the time horizon and all had aassociated gear (e.g., anchors, buoys, regular fish

positive return. The price of rock bream in thisnets, harvest/stocking bin, spar, and rims etc.)

scenario is assumed to have a mean on US$12.94/

cost a total of US$809,103, 93% of the initial capitalkg and a standard deviation of $2.46 for all ten

outlay. Additional items included US$16,170 for

years.

nursery nets (2%), a feed storage warehouse for
US$ 4,000 (0.4%), scuba gears at US$20,000 (2.3%);

Market Price Scenarios

and a truck, US$20,000 (2.3%). All asset costs are

Two alternative scenarios of rock bream prices

annualized using straight-line depreciation. Annual

over the ten years were analyzed (Table 4).

operating expenses include the cost of fingerling,

These scenarios were developed based on priorfeed, energy, labor (including owners/managers),

experience with other Korean farmed species.

lease rent, interest, insurance, repair/maintenance,

Scenario one mimics the price path of flatfish

depreciation, and supplies, and are summarized in

and rockfish, which decreased by about 5% per

Table 6. The largest costs contributing to annual

year once farming began. The second scenario

operating expenses of US$1,043,056 during fullreflects what happened to average annual prices

operation are fingerling (26%), feed (22.9%), full-for sea bream and other breams with the onset oftime labor including farm owners opportunity

aquaculture. For breams, prices initially increased

98

Douglas W. Lipton and Do Hoon Kim
TABLE
Results ofof themodel
Table
3. 3.Results
thebaseline
baselinemodel
Coefficient
Performance Indicator

Min

Mean

Max

of
Variation

Net Present Value (NPV)

2,159,171

3,151,402

4,111,452

14.51

0.12

0.18

0.28

19.34

Ending Net Worth

3,238,416

3,938,428

4,685,190

9Ending Total Debt

0

0

0

0

Leverage Ratio (debt/equity)

0.00

0.00

0.00

0.00

Equity/Asset Ratio

1.00

1.00

1.00

1.00

Cash Receipts

1,369,010

1,495,614

1,630,364

3

Cash Production Costs

945,043

984,030

1,019,412

1

Net Cash Income

389,469

511,583

632,868

11

Net Income

308,344

430,459

551,74413

Internal Rate of Returns (IRR)

Average Annual

Table 4. Results of different price scenarios on the performance of
TABLE 4.offshore
Results ofdifferent
price
scenarios on the performance of offshore rock bream culture.
rock
bream
culture.
Scenario 1

Performance Indicator
Net Present Value (NPV)

CV4

Mean

Mean

CV

1,131,419

35

3,805,201

12

0.01

300

0.24

15

12

4,231,567

7

1,194,617

3

1,673,018

3

Cash Production Costs

977,1031

1,021,986

1

Net Cash Income

217,51419

698,4748

Net Income

136,38931

617,349

10

Internal Rate of Return (IRR)
Ending Net Worth

2,099,660
18

AnnualCash Receipts

4

Scenario 2

CV = coefficient of variationby almost 6% annually for the first four years as

the mean NPV decreased by 62% to US$1,131,419.

demand expanded, but prices decreased by 5%

The IRR decreased from a mean of 18% and aas production increased in years six through ten.

range of 12%-28% to a mean of 1% and a range

When Aquasim was run using the first scenario

of 0%-8%. The mean net annual income dropped

99
accordingly from US$430,459 to US$136,389. The

effect of increasing skill and knowledge by theeffect of changes in market price of Scenario

operators which make it less likely for there to

2 is summarized in Table 4. The mean NPV

be a major mortality as experience is gained. For

increased from US$3,151,402 of the baseline modelcomparison, we also run a scenario where theto US$3,805,201 when the price increased by 6%

most likely survival rate is lowered from 97% toannually for the first 4 years and then decreased

85%, with a minimum of 70% and a maximum of

by 5% for the later 6 years. The IRR also increased

97%.

from 18% (12%-28%) in the baseline model to 24%

Of the survival rate scenarios run, only the(15%-33%). The mean net annual income rose

one representing a decrease in the minimum

accordingly from US$430,459 to US$617,349.

survival rate to 25% over the entire time period
significantly lowered the probability of economic

Survival Rate Scenarios

success of the enterprise, from 100% in the

The results above are based on the actual

baseline scenario to 76%. The internal rate ofperformance of the Korean rock bream aquaculture

return for the operation drops to only 3% and has

operation, but we feel that the survival rates

a high coefficient of variation of 75% (Table 5).

experienced may represent an overly optimistic

The probability of economic success increases toscenario. While the results may represent actual

97% if the minimum survival is allowed to increasesurvival rates under ideal conditions, it is likely

by 5% per year, but the internal rate of return is athat problems would arise over the ten year timemodest 8% with a coefficient of variation of 75%.

horizon that would result in periodic mortalities ata much greater level than observed. To capture

Combined Price and Survival Scenario

the possibility of occasional larger scale mortalities,

To obtain a more realistic and conservative

we change the minimum survival rate for the

scenario for rock bream offshore aquaculture intriangular distribution of survival from 90% to 25%,

Korea, we combine the two price scenarios with

but keep the most likely value at 97%. We also

the scenario of a minimum survival rate of 25%

run a scenario in which the minimum survival ratethat increases 5% per year.

in the first year is 25%, but the minimum survival

survival rate remains at 97% with a maximum

rate increases 5% a year over the ten year timeof 100%. Results from the two model runs arehorizon. This scenario is used to simulate thegiven in Table 6. For the declining price scenario,

The most likely

TABLE 5. Results of different survival scenarios on the performance rock bream culture.
Table 5. Results of different survival scenarios on the performance rock bream culture.
Min, Mean, Max Survival (%)

25, 97, 100

25(+5%/yr), 97, 100

70, 85, 97

Performance Indicator

Mean

CV

Mean

CV

Mean

CV

Net Present Value (NPV)

504,669157

1,235,332

53

1,717,098

23

0.03

157

0.08

75

0.09

45

1,982,738

30

2,648,968

17

2,898,548

10

Cash Receipts

1,150,761

9

1,268,728

6

1,311,277

4Cash Production Costs

946,7982

958,7592

963,022

2

Net Cash Income

203,96346

309,97022

348,254

13

Net Income

121,860

81

228,84730

267,130

17

Internal Rate of Return (IRR)
Ending Net WorthAnnual100

Douglas W. Lipton and Do Hoon Kim

Table 6. Results of combining price scenarios with survival
TABLE 6. scenario
Results of(25+(5%/yr),combining pricescenarioswith survival scenario (25+(5%/yr), 97%, 100%)
97%,
100%)
Price Scenario 1

Price Scenario 2

Performance Indicator

Mean

CV

Mean

Net Present Value (NPV)-533,005-126

1,828,001

38

0.00

0

0.14

50

98201049

2,904,044

16

1,008,643

7

1,314,568

6

Cash Production Costs

958,6892

757,752

2

Net Cash Income

49,953

127356,81620

Net Income-33,289-209

275,692

25

Internal Rate of Return (IRR)
Ending Net WorthCV

AnnualCash Receipts

the added risk due to a lower minimum survivalof the baseline value to a 50% increase over therate results in only a 22% probability of financial

baseline. The feed cost range examined is a little

success of the enterprise. The average net present

narrower, ranging from -20% to a 20% increasevalue is negative. The modeled firm has sufficient

over the baseline.

capital and profitability in the first three or four

Figures 2 and 3 show the effect of changing

years to avoid bankruptcy 92% of the time. The

fingerling and feed costs on overall production

situation is much improved for the scenario wherecosts and IRR. IRR is slightly more sensitive toinitially prices rise and then decline because theassumptions about fingerling costs which is notprice rise offsets the lower survival in the earlysurprising given that it makes up a slightly higher

years. For this scenario, probability of financial

percentage of the annual operating costs. IRR

success is again near 100% with a 14% IRR. The

for a 20% decrease in fingerling costs increases

results are more variable than the price scenario

to 21%, and for a decrease of 20% in feed costs,

or survival rate scenario alone.

IRR increases to 20%. A price increase of 50%
for fingerlings reduces the IRR to 11% and a 20%

Sensitivity to Feed and Fingerling Costs

price increase for feed reduces the IRR to about

Fingerling and feed costs are the first (26%) and16%. For a 20% decrease in fingerling price, it issecond (23%) largest percentages of average annual

indicated that the production cost per kilogram

operating cost expenditures in the baseline model.

of rock21bream decreased by US$0.46/kg, from

Because of their importance, we briefly examine

US$9.02/kg of the baseline model to US$8.56/

sensitivity of the baseline model results to different

kg. Accordingly, the resultant changes for the 10-

assumptions about fingerling and feed costs using

year mean IRR yields about 3% more than the

total production costs and internal rate of return asbaseline model, from 18% to 21%. On the otherthe primary indicator of farm performance. Kam

hand, a fingerling cost increase of 50% corresponds

et al. (2002) discuss the important role of having a

to US$135,493 annual cost increases in production

ready and appropriately priced source of seed forcost. That is, the production cost per kilogram ofa successfully aquaculture production industry.

Ifrock bream increased by 13%, from US$9.02/kg in

seed is difficult to come by, this will be reflected in

the baseline model to US$10.21/kg. The resultant

higher fingerling costs to the producer. Fingerlingchanges for the 10-year mean IRR yields about 7%

costs are varied in 10% increments from -20%

less than the baseline model, from 18% to 11%.

101

10.00

20%

9.50

15%

9.00
10%

8.50

9.60

5%

8.00
7.50

0%
-20% -10% 0% 10% 20% 30% 40% 50%
Fingerling Cost (% of Baseline)
Production cost per kg

10-year IRR

Fig. 2. Results of sensitivity analysis of different
fingerling costs.

25%

9.40

20%

9.20
9.00

15%

8.80

10%

8.60

IRR(%)

25%

Production Cost (US$/kg)

10.50

IRR(%)

Production Cost (US$/kg)

Fig.2.

5%

8.40
8.20

0%
-20%

-10%

0%

10%

20%

Feed Cost (% of Baseline)
Production cost per kg

10-year IRR

Fig. 3. Results of sensitivity analysis for changing
feed costs.
cause a large loss of fish. Nets can be torn andDiscussion

fish escape, storms can cause problems and humanerror, particular with a new technology can lead

Data collected from the Korean offshore

to large mortalities. Although these systems areaquaculture farm for rock bream suggests that

3 they still exist,
designed to minimize these risks,

under ideal conditions this enterprise could be

and when something does go wrong, it can have a

low risk and highly profitable. The combination

big impact. We chose to model this by extendingof extremely high survival rates, fast growth tothe left tail of the triangular distribution of fish

market size, and a high market price are the major

survival so that there was a small chance that only

factors contributing to the predicted success.

25% of the fish would survive during a production

However, if the na_ve assumption about constantcycle. Even when keeping the most likely survival

market prices for the ten year planning horizon

rate as high as 97%, this introduction of increased2
is replaced with a more realistic
expectation ofrisk had a profound effect on the results. Only if

price declines as the industry expands, growers

compensated for by higher fish prices in the firstwill face lower returns and higher risk. A better

five years of production, does the performance

understanding of the market situation in Koreaof the operation remain economically viable. If

is necessary to evaluate which of the three priceinstead, a scenario of fish prices falling from thescenarios is more likely to occur: the baseline

baseline level holds, the operation has virtually no

scenario of constant high price; the optimistic

chance of being financially successful.

scenario of higher prices in the first few years, andWe briefly touched on other factors such as feed

then declining prices; or the pessimistic scenario ofand fingerling costs which can affect the financial

immediate price declines as the industry grows.

performance and probability of success of the

The price decline scenarios that investors

operations. While they both have similar effects

choose to believe become more important whenon internal rates of return and net present value,

more realistic assumptions about fish survival

predictions about the time path of these costs

rates in these systems are introduced. The one

will be affected by different factors. Fingerlingyear experience with this operation off the coast

costs and production will be much more of a local

of Jeju Island experiences almost no mortality or

issue. A growing offshore rock bream industry

loss of fish. This demonstrates that with luck andshould lead to expansion of fingerling production,ideal conditions, these systems perform very well.

economies of scale and cost-saving technological

What is not captured in this single observation isadvancement. Some of those cost savings might

the small chance of a major disaster that would

be offset by increased demand for rock bream

102

Douglas W. Lipton and Do Hoon Kim

seed.

Feed costs are much more susceptible

Molnar. 2002. Size economies of a Pacificto world-wide changes in fish meal and grain

threadfin, Polydactylus sexfilis, hatchery inmarkets, and thus, are less dependent on local

Hawaii. Journal of the World Aquaculture

market conditions..

Society, Vol. 33, No. 4, pp. 410-424.

Our initial results are encouraging that offshore

K a zm i e rc z a k , J r ., R . F. a n d P . S o t o.

2001.

rock bream culture can provide a significant return

Stochastic economic variables and their effecton investment. However, as was demonstrated,on net returns to channel catfish production.

there is no escaping the uncertainties in fish prices

Aquaculture Economics and Management,

and other factors that can impact performance.

5(1/2), 15-36.

The excitement that often accompanies any

Kumbhakar, S.C.

2000.

Risk preference anddiscussion about the potential for offshore

technology: A joint analysis. Marine Resource

aquaculture needs to be tempered by these

Economics, 17 (2), 77-89.

economic realities. It has potential, but it is far
from a sure thing.

Lipton, D.W. and C.M. Gempesaw. 1997. Chapter
12. Economics and Marketing. In : StripedBass and Other Morone Culture. (R. M. Harrell,

Literature Citeded.)

Developments in Aquaculture andFisheries Science, 30. Elsevier, New York.
Brown, J.G., C.C. Goller, T.L. Peters, A. Olean, S.

pp. 315-328.

Vernon-Gerstenfeld, and A. Gerstenfeld. 2002.

McCullough, A. C.M. Gempesaw, W. Daniels andEconomics of cage culture in Puerto Rico.

J.R. Bacon. 2001. Simulating the economic

Aquaculture Economics and Management,

viability of crawfish production: a two-stage

6(5/6), 363-372.

modeling approach. Aquaculturre Economics

Delgado, C.L., N. Wada, M.W. Rosegrant, S. Meijer,

and management, 5(1/2):69-80.

and M. Ahmed. 2003. Fish to 2020: Supply

Naylor, R.L. 2006. Environmental safeguards forand Demand in Changing Global Markets.

open-ocean aquaculture. Issues in Science andInternational Food Policy Research Institute,

Technology. Spring, 53-58.

Washington, DC. 226pp.

Nelson, R.G., S.A. Duarte and M.P. Masser. 2001.

Gempesaw II, C.M., I.C. Munasinghe and JW.

Financial risk analysis of three aeration

Richardson. 1988. Description of Chicksim:

regimes in catfish cage culture. Aquaculture

A computer simulation program for broiler

Economics and Management, 5(3/4), 171-177.

growers. Agricultural Experiment Station,

Whitmarsh, D.J., E.J. Cook and K.D. Black. 2006.

University of Delaware, Bulletin No. 477.

Searching for sustainability in aquaculture: an

183pp.

investigation into the economic prospects forGoldburg, R.J., M.S. Elliott and R.L. Naylor. 2001.
Marine Aquaculture in the United States:
Environmental Impacts and Policy Options.

an integrated salmon-mussel production
system. Marine Policy, 30. 293-298.
Valderamma, D. and C.R. Engle.

2001.

Risk

Pew Oceans Commission, Arlington, VA.

analysis of shrimp farming in Honduras.

34pp.

Aquaculture Economics and Management,

Kalantzi, I. and I. Karakassis.

2006.

Benthic

impacts of fish farming: Meta-analysis ofcommunity and geochemical data. Marine
Pollution Bulletin, 52, 484-493.
Kam, L.E., P.S. Leung and A.C. Ostrowski. 2003.
Economics of offshore aquaculture of Pacificthreadfin (Polydactylus sexfilis) in Hawaii.
Aquaculture, 223, 63-87.
Kam, LE., P.S.Leung, A.C. Ostrowski and A.

5(1/2), 49-68.

103

An Economic Evaluation of Various Roles and Functions of
Propagation and Aquaculture: A Case Study
Yasuji TAMAKI＊
Abstract

I performed an economic evaluation of various roles of aquaculture, apart fromits primary role in supplying marine products. I defined these secondary roles as provision offood security, environmental improvement, exchange between urban and fishing communities,
maintenance of traditional culture, and formation and maintenance of local communities.
In 2005, aquaculture without the use of prepared feeds removed 6,090 metric tons of nitrogenand 595 metric tons of phosphorus from Japan's coastal seas. The economic value of the
reduction in pollution was equivalent to 1,298 hundred million yen by the replacement cost
method (the cost of sewage treatment for that amount of waste). From the results of aquestionnaire-based investigation of the general public, I estimated by the CVM (Contingent
Valuation Method) that non-use value of seaweed grounds around Japan was 553 to 2,109
hundred million yen.
Key words: aquaculture, roles and functions, replacement cost method, CVM
In addition, aquaculture produces the types
Introductionof products that are particularly in demand.
In fact, certain species are characterized by

Various examples of propagation andhigh production ratios, such as 100% for laver,aquaculture functions from the literature wereoysters, pearls and common scallops (including

examined, and economic estimates were made offisheries catch by propagation) ; 94% for Undaria,

some of those examples. The aquaculture industry

85% for red sea bream, 69% for yellowtail,has various functions. Each of them has been

64% for shrimp(Penaeus japonicas), 47% for

explained on the basis of the classification of theflatfish(Paralichthys olivaceus), 39% for globefish,

work of Tamaki (2004).

and 34% for Laminaria. In freshwater culture, thevalues are 97% for eel, 88% for landlocked trout,

Food security
Unlike ordinary fishing, where fish are caught as

68% for carp, and 50% for sweetfish (Plecoglossus
altivelis).

a natural resource, aquaculture can reliably supply

There are many fish species that would

selected fish species with the help of appropriate

disappear from the market or be in very shorttechnology. Some life stages used for stocking, suchsupply if it were not for aquaculture (Figure 1).

as those of yellowtail, oyster, or common scallop,

Given these circumstances, it is logical to conclude

may have to be taken from natural resources, butthat aquaculture plays a major role in foodothers, such as red sea bream, shrimp, or laver,security.

can be artificially produced. Even when culturing
natural larvae and fry, taking special care of life

Environmental Improvement (Table 1)stages at which the organisms have a high natural

Cultured seaweeds convert carbon dioxide inmortality rate can reduce the death ratio andthe seawater into oxygen through photosynthesis.

minimize loss of resources.

They also prevent eutrophication of the2009 年 8 月 10 日受理（Received. August 10. 2009）＊
National Research Institute of Fisheries Science, FRA, Fukuura, Kanazawa, Yokohama 236-8648, Japan

104

Yasuji TAMAKI

Ee
Tr l
ou
Sw
ee C ttfi ar
sh p
(A
yu
)

La
v
O y er
st
Co
er
m
P
m
on earsc ls
a
Re U llop
d nd
se ar
a
i
b a
Pr
aw Ye reamn( l l o
Fl Kur wta
Gl atf um il
ob ish aeef (H bi
ish ir )
(T am
or e)
a
La fugu
m )
in
ar
ia

100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%

Fisheries
Aquaculture

Note:Common Scallop contains fisheries production under propagation of seed

Fig. 1.

Fig. 1. Production Relation of Japanese Aquaculture in 2004.
Table1 Environmental
improvementsby aquaculture
Table1.
Environmental
improvementsby aquaculture

Aquaculture species Example
Seaweeds

Bivalves and sea
squirts
Silver carp andwhite crucian carp
Aquaculture
facilities (rafts
and net pens)

Convert carbon dioxide in the seawater into
oxygenImmobilizing nitrogen and phosphorus
Provide shelter to young creatures
Filter sea water and reduce organics in thewater
Filter water and reduce organics in the water
Provide shelter for natural fish
Stop the fisheries operation of natural
resources and provide nursary groundSource:Tamaki(2004)

seawater by immobilizing dissolved nitrogen andWhen filter-feeding marine species, such as

phosphorus. On cultured seaweed grounds, unlike

bivalves and sea squirts are cultured, they filter

natural seaweed grounds, we can recover most of

seawater and simultaneously reduce the level ofthe immobilized nitrogen and phosphorus before

organic compounds in the water. Silver carp andthe elements are eluted into the water.

white crucian carp produced in freshwater culture

Seaweed also provides shelter for young fish andfeed on phytoplankton and do not need to be

the larvae of many other creatures, contributing

provided with prepared feed, thereby reducing theto biodiversity.

pollution load on lakes. One kilogram of silver carp

In addition to the benefits obtained fromseaweeds themselves, there are cases where thefilter a cubic meter of water and eat 20 grams ofphytoplankton daily (Ibaraki Prefecture, 1996).

bamboo poles used in aquaculture for attachmentof laver can serve as substrates for the larvae ofProviding Recreational Opportunities,

short-necked clams, promoting favorable growth of

Exchanges and Learning

shellfish. In waters where aquaculture facilities are

Aquaculture promotes exchange between urban

set up, rafts and net pens can also provide shelter

and fishing communities. For instance, a fisheries

for wild fish. It is impossible to carry out seine

cooperative in Kagawa Prefecture has a cultured

fishing or trawl netting in the areas with rafts

oyster ownership system in which consumers buy

or net pens, thus promoting the preservation ofoyster spat. Later, they are entitled to experiencemarine resources.

the harvesting of the harvestable oysters or have

105
the oysters delivered directly to them. In thissurface in Mie and Hyogo Prefectures, or freshsystem, an aquaculture rope with some 70 oysters

water in other prefectures. Fishing ponds are very

attached is sold at 2,200 yen. Orders for some 1000

popular among experienced anglers, not to mention

ropes are received annually. They even come frombeginners and children who tend to be seasick in

outside the prefecture, such as from Okayama or

open waters, because they can experience fishing

Tokyo. This cooperative has also discovered thatin a safe and unthreatening environment. Many

many consumers prefer to come to get the oystersof the fish caught from the ponds are cultured

themselves rather than having them delivered.

species. Aquaculturists facilitate exchanges

Another fisheries cooperative is advertising for

between cities and fishing villages by stocking

purchasers of oyster culture ropes, at 2,500 yen

fishing ponds and opening them to the public.

each, but only accept orders from consumers

Aquaculturists can also obtain a profit by sellingwithin the same prefecture. In 2000, they received

fish for stocking the ponds.

some 500 orders.

Oyster culture rafts are ideal nests for black sea

In Kagawa Prefecture, some culturists, including

bream, a popular fish with anglers, for their shadethe said cooperative, have their own small

and the plants and animals that cling to them. In

restaurants that serve grilled oysters during

Ishikawa Prefecture, oyster rafts are provided by

the winter. A different cooperative offers "allsome culturists for sport fishing.

the oysters you can eat" at 2,500 yen per person

A fishermen's cooperative in the Oki Islands,

and, in 1999, achieved sales of 10 million yen. In

Shimane Pref., who know that large wild fish are

Kanagawa Prefecture, a "hands-on experience"

attracted to their fish culture grounds, take anglers

program that offers a course in Undaria culture

aboard recreational fishing boats to the waters

was provided for 100 groups at a fee of 3,000 yen

near their aquaculture grounds. These anglers pay

per group. Visitors took part in seeding of Undaria

10,000 yen per person for this experience and are

and studied the details of seaweed aquaculture

allowed to take home up to three red sea bream.

and its environmental advantages, including how

The cooperative had some 250 customers in fiveit purifies water. In November, they learned how

months in 2002.

to culture seaweed and in February experienced

Freshwater culturists often release cultured

harvesting of the seaweed, took classes on thefish for sport fishing. According to the census,

nutrients in Undaria, and learned how to use it in

the total number of sport fishers in freshwater

cooking.

in 2003 was 7,770,000 (excluding those for bass).

There are also exchange promotion programs inThus, aquaculture plays numerous roles, includingwhich elementary and junior high school students

exchange between urban and fishing communities

visit a fishing village as one of their schooland provision of recreational opportunities toexcursion destinations and take part in various

urban dwellers (Table 2).

events alongside the people of the village to gaina closer and more personal understanding of how

Maintenance of Traditions (Table 3)

they live. Since the culture grounds are close toI have already pointed out as one of the features

the port and located in calmer waters than in theof aquaculture that it provides types of fish thatcase of offshore fishing, programs that feature

would run short if we relied exclusively on naturalactual experiences with aquaculture are very

resources. Providing these fish also helps keep

popular with city people and are seen as safe andalive Japanese culinary traditions. For example, it

accessible opportunities. It is a valuable experienceis a custom to enjoy eel on certain days in summer.

for young people to actually feed cultured fish

Without aquaculture, however, the lack of eelsand see how shellfish species and seaweeds arewould lead to this custom's disappearance. Red

cultured. They can actually see for themselves

sea bream is very popular to the Japanese stylewhat the sea has to give them.

wedding reception. Laver, indispensable for rice

Another example is fishing ponds using the sea

balls and sushi, is 100% supplied by aquaculture.

106

Yasuji TAMAKI

Table 2. Providing recreational opportunities, exchanges and learning

Table 2

Providing recreational opportunities, exchanges and learning

Area
Kagawa Prefecture

ExampleCultured oyster ownership system

Kagawa Prefecture

Small restaurants that serve grilled cultured oyster

Kanagawa Prefecture

Experience of brown seaweed( Undalia ) aquaculture

Mie Prefecture and Hyougo Provide cultured fishes to "fish ponds"
Prefecture
Ishikawa Prefecture
Oyster culture rafts are provided for sport fishing
Shimane Prefecture

Takes anglers aboard recreational fishing boats to thewater near their aquaculture grounds

Freshwater

Fishermen’s cooperative release cultured seeds for sport
fishing
School excursion

Fishing village
Revised Tamaki(2004)

3. Maintenance of traditions
Table 3 Maintenance Tableof traditions
ExampleCultureEnjoy eel on specific days in summer
Maintain Japaneseculinary traditions
Laver for Rice ball(Onigiri) and Riceroll(Norimaki)

Japanese garden
Local festivals

Sushi
Fancy carp
Goldfish scooping

Revised Tamaki(2004)

Yellowtail, red sea bream, and common scallop are

Economic Evaluation of Various Functions

also essential ingredients for sushi and are supplied

Economic evaluation of the removal of nitrogenby aquaculture. Fancy carp (nishiki-goi) are an

and phosphorus by aquaculture without artificial

invaluable part of many Japanese gardens. Without

feedingaquaculture, "goldfish scooping," an essential andWhen shellfish and seaweed are cultured, noentertaining part of local festivals and a traditional

artificial feeding is provided, but nutrient salts,

festive pastime for children, would disappear.

such as nitrogen and phosphorus, are absorbed

These aquarium fish species are also the products

from the sea. Harvesting of cultured fish involvesof aquaculture.

the harvesting of nitrogen and phosphorus fromseawater. Their quantities may be estimated based

Formation and Maintenance of Local Communities

on the production of major aquaculture products

Aquaculture needs calm waters and clear

and their food composition table. According to thisfreshwater and is thus often conducted in places

estimation, 6,090 tons of nitrogen and 595 tons offar from major cities. The economy of many suchphosphorus were recovered from culture without

places relies entirely on fisheries and related

artificial feeding in 2005.

industries. Aquaculture helps dilute the otherwise

The unit cost of recovering nitrogen andconcentrated populations in cities and settle people

phosphorus, based on the Tokyo Metropolitan

in remote areas by providing economic security. At

Sewerage Works Annual Report 2004, wasthe same time, it plays other associated roles, suchcalculated using the method adopted by

as monitoring of national borders, preservation of

Suidosha Co., Ltd. (2003) and the recovery costnational land and protection of the landscape.

of nitrogen and phosphorus was calculated using
a replacement cost method. The results showedthat the nitrogen recovery cost is ¥129.8 billion
and the phosphorus recovery cost is ¥87.7 billion.

107
Table 4. The amount of removed nitrogen and phosphorus and estimated costof sewage treatment of this amount of waste.
Table4 The amount of removed nitrogen and phosphorus and estimated cost of sewage treatment of this amount of waste.
cost of sewage
cost of sewage
Amount of Amount oftreatment of thistreatment of thisnitrogen( phosphorus
amount of nitrogenamount of phosphorust)(t)（million yen）
（million yen）
Common scalop
4,907 (with shell）
5,299.6
515.2
112,958
75,985Oyster340 （without shell）
359.0
34.0
7,653
5,014
Other bivalves
20 (with shell）
21.6
2.1
460
310
Sea squirt
90 (with shell）
72.0
5.0
1,535
730
Laver
3,871 （wet weight）
134.4
14.7
2,864
2,169
Laminaria
450 （wet weight）
3.3
0.6
71
94
Undaria
637 （wet weight）
193.6
22.9
4,128
3,382
Nemacystus
130 （wet weight）
6.2
0.3
133
38
Total
10,445
6,089.8
594.8
129,80287,722
Note：The content of nitrogen and phosphorus from Food composition Database JapanThe content of Other bivalves used Common scarop
The content of shell and internal organ of sea squirt used edible partWet seaweeds contain 90% of water
The content of Laminaria used 7 species average
The cost of seawage treatment used Suidosya(2003) and "Annual report of sewage of Tokyo in 2004"
Amount ofproduction(2005)(100t)

Table5

Motherseaweedplanting

Table 5. Methods of transplanting seeds

Methods of transplanting seeds
Methods
Breed of seaweed
Direct fixation Laminariales, Sargasso
Sargasso
Net fixation
Laver net fixed
Sargassoin middle layer
Spore bags

Rope fixation
Seeding yarn
Seedling
plantation Seeding block
Seeding net

References
Nakazima(2003)
Yoshikawa(1985･1986･1997)
Kagoshima Pref.Fis.Exp.Sta.(2006)

Laminariales, Sargasso,
Gelidales

Oshima Branch, Tokyo Fis.Exp.Sta(2004)、
Tanaka(2002)、Nakabayashi & Akiyama(2004)、
Chuyo Branch, Ehime Pref. Fis. Exp. Sta(2000)、
Oita Fis. Exp. Sta.(2006)

Laminariales
Laminariales, Sargasso
Laminariales, Sargasso
Sargasso

Kikuchi(1976･1978)、Sawada et al(1981)
Nakashima(2003)、Nakahisa(1981)、Toyama(1981)
Nakashima(2003)、Toyama(1981)
Toyama(1981)

Since nitrogen and phosphorus are simultaneously

There are various methods of transplanting

recovered in sewage treatment, the higher cost ofseaweeds, as shown in Table 5. When seaweeds¥129.8 billion may be used as the recovery cost of

are transplanted to denuded rocky shores, animals

nitrogen and phosphorus by aquaculture without

feed on them, preventing the establishment ofartificial feeding (Table 4).

young plants. For this reason, transplantation isoften accompanied by the removal of sea urchins.

Economic evaluation of the functions of seaweed
beds

Mother seaweed plantings are particularly
effective with Laminariales seaweeds, which

Substrates for seaweed beds are sometimes

generate large numbers of planospores. For

constructed as part of public works in Japan. The

Undaria, one gram of sporophylls releases 1 million

Fisheries Agency creates seaweed beds with theto 10 million planospores; however, Sargasso

direct aim of harvesting the grown seaweed andhas smaller numbers of productive cells to be

the indirect aim of increasing fish resources bydischarged, and the discharge distance is short.

offering cultured seaweed as food or as spawning

Planting of Sargasso is therefore reportedly not

grounds and rearing places for young fish. The

as effective as of Laminariales (Tanaka, 2002).

agency also transplants seaweeds to restore dying

However, Nakabayashi and Akiyama (2004) reportbeds and preventing rocky-shore denudation. The

successful cases for Sargasso, in which the supply

Ministry of Land, Infrastructure and Transportof 5 kg of mother seaweed, coupled with theconducts public works, including the development

removal of sea urchins, successfully restored aof seaweed beds to compensate for beds lost due

Sargassum horneri marine forest 6 m in diameterto industrial development or reclamation.

(about 28 m ) centered on the installation spot

2

108

Yasuji TAMAKIof spore bags. At the Ehime Chuyo Fisheries

functions, similar results were generated byExperimental Station (2000), they put Hizikia

both the visitor questionnaire and the Internet

fusiformis in spore bags, placed them in the water,questionnaire. The top choice was food for fish andand successfully settled Hizikia fusiformis in theshellfish and a nursing ground for the young fish,area within 1 to 1.5 m from the spore bags.

followed by maintenance of biodiversity, fixation ofcarbon dioxide, scenery with rich seaweed growth,

Questionnaire survey

absorption of nutrient salts, and place for biologicalSeaweed beds are known to have a range of

observations. Each alternative had only a single-

functions. A questionnaire survey was conducted

digit rate for being selected for the top (Table 6).

to find how the general public, other than those

CVM is often used in Japan to assess the value

engaged in fisheries, value the seabed. The surveyof public goods for which no market actually exists.

was conducted with people aged 20 or over who

In the questionnaire, to calculate the value of an

were visitors to the National Research Instituteimaginary market, the question was asked aboutof Fisheries Science on October 22, 2005 andhow much the respondent would be willing to pay

also to people with Internet accounts aged 20 orinto an imaginary fund, or WTP (willingness toover on November 15 and 16, 2005. Out of 755

pay). To apply CVM, estimation was made based

visitors on October 22 (including those aged 20

on the assumption that a person who selected aand over, who accounted for 66%), 292 answered

certain amount to donate would also be willing to

the questionnaire. For the Internet questionnaire,

pay any amount less than that. The amount wasa service contractor sent the questionnaire to aestimated by means of the least squares method

total of 3,000 people, who were selected at random

using a semilogarithm of the acceptance rate = a

from about 220,000 registrants (three times a total+ blog (amount of donation, Table 7). The amountof 1,000 selected by gender and area), and received

obtained from the simple average of the answers

1,367 valid responses, excluding abnormal answers.

and the amount calculated as the median of the

One thousand responses selected at random were

equation estimated from the least squares method

then sent back to the author.

were extended to the Japanese population aged

In one of the two questions on seaweed beds,

20 or older. As a result, the maintenance cost of

the respondent was asked to select three functions

seaweed beds was evaluated as between ¥55.3

that he or she regarded as most important. The

billion and 210.9 billion (Table 8). That amountother question was on how much they would

may be regarded as the evaluated "non-utility

personally be prepared to donate to a maintenancevalue" held by the general public for maintaining

fund for seaweed beds to evaluate their value

a variety of ecosystems by maintaining seaweed

using the Contingent Valuation Method (CVM).

beds. The value may represent the view of theConcerning awareness of the seaweed bed

general public about the "non-utility value" of theTableof6.seaweed
Awarenessof seaweed bed functions
Awareness
bed functions
Visitors to the NRIFSInternet
open dayFirst Second Third Total First Second Third Total
Food for fish and44%
20% 13%
77% 38%28%
17%83%
shellfish and a nursing
ground for the young fish
Maintenance of
34%
20% 14%
68% 33%32%
19%
84%
biodiversity
Fixation of carbon
20%
12% 14%
45% 21%
21%
29%
70%
dioxideScenery with rich seaweed
7%
6% 10%
22%
3%
4%
8%
16%
growthAbsorption of nutrient
6%
9% 11%
26%
3%
10%
16%
29%
salts
Place for biological6%
4% 10%
20%
2%
4%
7%
14%
observations
Table６

109
preservation of diverse ecosystems achieved byfunctions for the seaweed bed fund. Consequently,

the maintenance of seaweed beds. "Non-utility

responses such as want to clean up the beach next

value" here includes "the value of simply being

year, Cleaned up the beach, did beach seine fishing,

there," which makes people feel privileged by justwant scuba diving next year, went bird watchingknowing there are a variety of ecosystems andat the beach, and age were found to be significant

the "value of endowment" in which people may notas parameters. Only the value for cleaned up theobtain any direct benefits but can leave a variety

beach was negative. The reasons for this may beof ecosystems to future generations. Two biases

that they carried out a cleaning activity, so they

are assumed: the sample bias and strategic bias.

thought that they did not want to pay into the

The Science Council of Japan said in 2004

fund, or their experience of beach cleaning, inthat for various functions of fisheries and fishing

which enormous amounts of seaweed had washedcommunities, if investigations are conducted onashore, had made them think it unnecessary to

many such functions, particularly using CVM, thedonate anything to the fund (Table 9).

research on them will reveal the importance of
their economic value, which will then feed throughto government policy. In that sense, evaluation
based on CVM is in line with the policy of the
Science Council of Japan.

Comparing the amount of donations to the fund,visitor respondents gave amounts that were 50 to

The Internet questionnaire also asked about

70% higher than the average amount suggested

any marine or seashore recreation that theby Internet respondents. This indicates the highrespondents had engaged in from 2000 to 2005,

awareness on the part of visitors of the importanceor wanted to do in 2006, and the questionnaireof seaweed beds or the successful results ofresult data were used to estimate the pricing

education by means of posters or pamphlets.

Table 7. Estimated with semilogarithm formula

Table７ Estimated with semilogarithm formula（Acceptance
rate =a+boflog(amount（Acceptance
rate =a+b log(amountdonation) of donation)
Standard
Parameter
Estimate Error
t-statist P-value
Interneta(constant)
1.316
0.089
14.848 [.000]b(Amount of-0.1300.013 -10.118 [.000]
donation)
NRIFS open a(constant)
1.813
0.183
9.930 [.000]dayb(Amount ofTable８-1-0.1920.026-7.262Results[.000]of the questionnaire survey about
donation)"Maintenance fund for seaweed beds"（yen）
Internet
NRIFS open day
Average
1,334
2,055Median539
946

Table 8-1.
Table 8-2.
Results of the questionnaire survey about
Extended to the Japanese population aged
Table８-1 Results of the questionnaire survey about Table8-2 Extended to the Japanese population aged
"Maintenancefundforseaweedbeds"（yen）
20 or older (billion yen)
"Maintenance fund for seaweed beds"（yen）
Average
MedianInternet NRIFS open day
1,334
2,055
539
946

20 or older(billion yen)Internet
NRIFS open day
Average136.9
210.9
Median55.3
97.1
Note：102,636,961（2005/3/31）

Table8-2 Extended to the Japanese population aged
20 or older(billion
Table 9. yen)
Estimate the pricing functions for the seaweed bed fundInternet NRIFS open day
Average136.9
210.9
Median55.3
97.1
Note：102,636,961（2005/3/31）

110

Yasuji TAMAKIFisheries Research Center, Fisheries Research
References

Institute. 2006. Reference materials for the 2nd
National Assembly of the Review Committee

Ehime Chuyo Fisheries Experimental Station. 2000.

on the 2005 Seaweed Bed and Tidal Wetland

Results of Seto Inland Sea block area fisheries.

Productivity Improvement Model Project

1999. National Research Institute of Fisheries(Project for Modeling Emergency Strategies

and Environment of Inland Sea website (inagainst Denudation of Rocky Foreshores). 2

Japanese). http://www.nnf.affrc.go.jp/seika/

pp. Fisheries Agency website (in Japanese).

h11/feis1123.html.

http://www.jfa.maff.go.jp/gyokogyojo/index.

Ibaraki Prefecture Inland Water Fisheries

htm.

Experiment Station. 1996. p. 10, In: Biology ofOshima Branch, Tokyo Fisheries Experimental

the fish of lakes Kitaura and Kasumigaura,

Station. 2004. Today's Hirome (Undaria

Ibaraki (in Japanese).

undaroides) of Oshima Island-Gone for 6

Kagoshima Prefectural Fisheries Technology andYears. Oshima Branch Topic, No. 302, Tokyo

Development Center. 2006. Reference

Fisheries Experimental Station website (inmaterials for the 2nd National Assembly ofJapanese).

the 2005 Seaweed Bed and Tidal Wetland

http://www.ifarc.metro.tokyo.jp/

Productivity Improvement Model Project, 2
pp. Fisheries Agency website (in Japanese).

info/2004/302.pdf.
Sawada, M. ,F. Miki and M. Asuke. 1981. Laminaria

http://www.jfa.maff.go.jp/gyokogyojo/index.

seaweed beds. pp. 135-137, In: Seaweed Beds

htm.

and Marine Forests. Science of Fisheries

Kikuchi, S. 1976. Marine afforestation experimentusing abalones and sea urchins at Enoshima

Series, No. 38, Koseisha Koseikaku Co., Ltd. (inJapanese).

Island, Miyagi Prefecture. p. 299 , In: New

Suidosha Co., Ltd. 2003. Investigative report on

edition of Creative Fisheries, Agricultural andvarious functional evaluations, 2004. pp. 66-68,

Forestry Statistics Association (in Japanese).

In: Commissioned Projects for Investigating

Kikuchi, S. 1978. Marine afforestation and its

Various Functional Evaluation, Suidosha Co.,

theory, foundation and theory of propagation

Ltd. (in Japanese).

technology. pp. 73-76, In: Science of Fisheries

Tamaki ,Y. 2004. Direct payment system toSeries No. 23. Koseisha Koseikaku Co., Ltd. (inpromote the appropriate management ofJapanese).

aquaculture grounds, ecosystem and carrying

Nakabayashi, N. and S. Akiyama. 2004. Amount ofcapacity of aquaculture ground. Proceedings

mother seaweed in spore bags for repair of aof the Thirty-Third UJNR Aquaculture Panel

Sargassum horneri marine forest, Akita

Symposium.

Prefectural Office website (in Japanese).

Tamaki, Y. 2006. Quantitative evaluation of various

http://www.pref.akita.lg.jp/www/

functions of fisheries and fishing villages,

contents/1131329992182/files/16047.pdf.

centering on activities that maintain

Nakahisa,,Y. 1981. Eisenia bicyclis (Kjellman)

environmental preservation: Analysis of a

Setchell and Ecklonia cava (Kjellman) seaweed

questionnaire survey. Report of the 2005

beds and marine forests. Science of Fisheries

Fisheries' and Fishing Villages' Multi-faceted

Series, No. 38, Koseisha Koseikaku Co. Ltd.,

Function Promotion and Education Project.

119 pp (in Japanese).

National Research Institute of Fisheries

Nakashima, Y., 2003. Germ cells and seeds. pp. 174-

Science. 12pp (in Japanese).

178, In: Seaweed in Seaweed Beds andTanaka, T. 2002. Development of seaweed beds.

Construction Technology, Seizando Shoten (inJournal of Fisheries Experimental Station, No.

Japanese).

218, Wakayama Prefectural office website (inOita Prefectural Agriculture, Forestry andJapanese).

111
http://www.pref.wakayama.lg.jp/
prefg/070109/news/008/news218_3.htm.
Toyama, A. 1981. Garamo beds, seaweed beds, andmarine forests. Science of Fisheries Series, No.
38, Koseisha Koseikaku Co. Ltd. 119 pp (inJapanese).
Yoshikawa, K. 1985. Studies on the formation ofSargassum beds I. Bulletin of the Nansei
Regional Fisheries Research Institute, 18:22-23(in Japanese).
Yoshikawa, K. 1986. Studies on the formation ofSargassum beds II. Bulletin of the Nansei
Regional Fisheries Research Institute, 20:144145 (in Japanese)
Yoshikawa, K. 1997. Effect of the supply of natural
thalli and the shelter methods on theformation of beds of Sargassum giganteifolium
Yamada. Bulletin of Nansei National Fisheries
Research Institute, 30:160-161 (in Japanese).

113

Risk and Risk Management for Feed and Seedfor Marine Fish Raised in Off-shore Aquaculture.

Michael B. Rust＊

For open ocean aquaculture of marine fish, theprovision of feed and seed occurs externally to thetrue when governments do not fund such researchand development.

actual fish culture operation. How such external

Potential up-stream ecological impacts associatedactivities are conducted and applied determines

with feed and seed from culture of marine fish

the potential ecological impact for the industry as

include over-fishing due to demand for wild

a whole.

juveniles for grow-out, and harvesting industrial

Ecological risks associated with marine

aquaculture may be addressed using a framework

fisheries for feeds (Nash et al. 2005).

similar to that used for assessment of risks in

simple equation, risk of over-fishing (R) is aother areas of our lives. The use of a framework

function of fisheries management (M) with thedeveloped for the World Health Organization

effectiveness of management subject to demand [R(WHO) for assessment of risk to human health= f(M)].

from various threats has been proposed for

demand), fisheries management has been shown toassessment of risk to the environment from marine

be effective, however management can only

aquaculture (Nash et al. 2005). The identification

produce some fraction of what exists naturally,

and characterization of risk are the first steps in

and wild fisheries are not able to increase

determining what risk management strategies

production beyond naturally set limits. At harvest

might be the most productive in developing

levels higher than a stock can recover from, over-supplies of feed and seed for offshore aquaculture

fishing occurs. When there is a high demand,

that are low risk and will be stable and dependable

fisheries management becomes increasingly

over the long run. For each risk, the WHO risk

difficult so alternatives need to be found thatassessment framework may be applied to focus

reduce or eliminate demand for both wild feed andresearch and development on strategies that could

wild seed. Management to reduce the risk of over-be used to reduce or eliminate risk. In most cases,

fishing due to feed includes the development ofmultiple options exist for risk reduction, however I

alternative protein and lipid sources (especiallysuggest that risk management strategies thatlong chain n-3 fatty acids) and for seed, theimprove economic gain and reduce or eliminate

development of hatcheries. In both cases, complete

multiple ecological risks, are preferred and have areplacement leads to elimination of the risk due tomuch higher chance of resulting in meaningfulactivities associated with offshore aquaculture andimprovements. Furthermore, strategies which

partial replacement leads to demand reduction

allow improvement, or change over the long term,

potentially to sustainable levels at least until theprovide more flexible and ultimately sustainableindustry grows again. In addition, hatcheries andsolutions. In most cases, research is needed toalternative feedstuffs can provide economic

develop better risk management strategies. Up-

benefits (in the way of lower prices and better

front costs associated with research, development

quality) and thus have a greater potential forand implementation often limit application of risk

adoption by industry once a critical size of an

management strategies to industries large enoughindustry is reached.

Stated as a

On some low scale of harvest (lowto afford such costs even if there are long-term

Potential downstream ecological risks associatedeconomic benefits associated. This is especiallywith feed include organic loading and benthic

2009 年 8 月 10 日受理（Received. August 10. 2009）＊NOAA Fisheries Service, Northwest Fisheries Science Center, 2725 Montlake Blvd E., Seattle, WA, USA

114
impacts.

Michael B. Rust

In this case risk (R) is a function of the

reduced by maintaining wild stocks at high levels

quality and quantity of feed used (F), the organism

relative to the number of escapes.

under culture (O) and management (M) within theaddressed by industry by raising a portion of thecontext of the specific site chosen for offshore

species they produce under stock enhancementaquaculture [R = f(F x O x M) ].

protocols for release (likely to have negative

Activities which

This may be

improve 1) the efficiency of the diet (for example

economic implications).

moving from wet fish to pelleted feeds, defining

combines several of these strategies may be thenutrient requirements, improved pelletingmost effective.

An approach thattechnologies, better feed formulation, feedstuffs

Risks can be interactive and need to be viewed

processing and so on), 2) the efficiency of the

as a set for a given activity to guide management

organism (species choice, selective breeding,and research. Often new risks can be created

improved husbandry, and so on) and/or 3) thewhen a different risk is solved, or the choice of amanagement systems (optimal feeding regimes,

risk management strategy that reduces or

improved fish health management, protection from

eliminates one risk may or may not also reduce or

predators and diseases, better husbandry,

eliminate another risk.

improved systems engineering, and so on), willdevelopment of a hatchery to reduce the risk of

reduce environmental risks. In most cases, theseover-fishing to provide seed, potentially creates theefforts will also improve economic return once a

genetic risk of escaped fish on their wild

critical level of production is reached by theconspecifics. If wild fish were used, then ∆G = 0

industry.

and the genetic risk from escapees would not exist.

For example, theDownstream risks associated with seed areThis has led some to call for only using local fish

associated with the potential ecological and genetic

as broodstock for hatcheries producing seed for

impacts of escapes on conspecific wild stocks if theoffshore aquaculture and actively maintaining acultured fish is native or ecological impacts on

wild-like genetic make-up in the hatchery.

native species if the escapees are non-native.

For

However to do this would forgo the positive

the sake of this paper I will only deal with the firstecological risk reduction that selective breedingrisk. Risk (R) associated with the escape of acan produce in terms of seed that uses feed

native species is a function of the number ofresources more efficiently, that makes better use

escapes relative to the number of wild conspecifics

of alternative feedstuffs, has better disease(Pe/Pw), the differences in genetic structure

resistance and so on. Maintaining a wild genotype

between the wild and escaped organisms (∆G) andfor fish used in offshore aquaculture would also

the fitness (Fe) of the escapees to reproduce in theforgo economic gains and puts environmental andwild [R=f(Pe/Pw)( ∆G) (Fe)]. Risk associated witheconomic goals at odds, reducing the chance for

escapes can be managed at the hatchery byadoption and meaningful environmental risk

several strategies. For example, either raising fish

reduction.

with the same genetic make-up as wild stocks

Governments can create win-win situations by

where ∆G = 0, or by domestication of the farmed

fostering research and development where

species which reduces escapees' fitness (Fe) in theecological risk management and economic gains

wild. In this case, economic gains would favor

are in line and both considered.

domestication and not maintaining a wild stock

feed and seed, this would include development ofgenotype. Risk can also be reduced by raisinghigh quality compound feeds from alternativesterile fish (where Fe = 0 ) which may or may notfeedstuffs, and hatcheries with associated selective

be economically beneficial, or by maintaining a low

breeding programs for new and existing marine

number of escapes (for example by betterfish industries.

engineering or management practices) relative toimprove the potential for the adoption of preferred

the size of the wild population.

Note that therisk management strategies by first identifying

converse is also a possible strategy, risk can bethose strategies that provide the best overall

In the case of

Governments can hasten and115
options and then by funding the up-front researchand development costs to put those practices inplace.
References
Nash, C. E., P. R. Burbridge, J. K. Volkman. (eds.)
2005. Guidelines for ecological risk assessmentof marine fish aquaculture. U.S. Dept. ofCommerce, NOAA Tech. Memo., NMFSNWFSC-71, 90 p

117

Ecological Risk Assessment of Marine Fish Aquaculture
William T. Fairgrieve＊ and Colin E. Nash＊

The following is taken in its entirety from NOAA Technical Memorandum NMFSNWFSC-71, entitled: "Guidelines for Ecological Risk Assessment of Marine Fish Aquaculture",edited by Colin E. Nash, Peter R. Burbridge, and John K. Volkman. It was prepared fromtechnical contributions by the editors and Kenneth M. Brooks, Stefano Cataudella, Brett R.
Dumbauld, William T. Fairgrieve, John R. M. Forster, Robert N. Iwamoto, David F. Jackson,
Sadasivam J. Kaushik, Michael B. Rust, Philip A. D. Secretan, Karl D. Shearer, Ole J. Torrissen,and Masashi Yokota, at the NOAA Fisheries Service Manchester Research Station International
Workshop, 11-14 April 2005. The technical memorandum is available online (http://www.
nwfsc.noaa.gov).
although aquaculture remains a crucial cornerstone
Introductionof rural life in many countries, its modern practices
and array of commercial end-products are, to the

The Environment and the Intervention ofMarine Aquaculture

rest of the world, dependent more on human life
style decisions governed by social choice.

Few, if any, human interventions in the

Fortunately, an important factor in social choiceenvironment fail to have impact. In some cases

as aquaculture emerges in the twenty-first century

interventions are potentially so damaging that they

is not only to minimize the impact of all humanmust be eliminated.

On the other hand, theinterventions on the environment but also tomajority of human interventions are purposefulsustain the existing integrity of its manyand designed to be of benefit to humans, so it isecosystems in perpetuity.

necessary that they proceed responsibly, sharing

challenge to all resource-based industries, not only

equitably in the use of nature's vital resources. It

marine aquaculture.

is thus important that these interventions areaquatic ecosystems in which aquaculture

carefully managed with good stewardship tointervention is feasible. Each and every ecosystem

ensure that benefits can be achieved over time

has its own very specific and desired values, andframes of many decades.

therefore for the stewards of these resources toThis has become a

There are innumerable

Aquaculture, together with fisheries andset specific goals around these values it isagriculture, has long been a provider of food fornecessary for them to know in advance 1) what

human consumption. For over three millennia it

integrity means for each ecosystem and what

has been a necessary and often the only source ofspecifically needs to be protected; and 2) whichanimal protein for pastoral communities living at

ecological resources and processes have to be

subsistence levels. But within the last century its

sustained and for what reason. Compared withhistory has dramatically changed, and science andthat of terrestrial ecosystems, comprehensive

technology have propelled modern aquacultureknowledge of aquatic ecosystems is severely

into semi-intensive and intensive farming systems.

constrained. Partly this is because much of the

These systems have greatly increased its degree

ecosystem lies below water and is thus not readilyof exposure to the environment. Consequently,

observable, but also the need for extensive

2009 年 8 月 10 日受理（Received. August 10. 2009）＊NOAA Fisheries Service Manchester Research Station, Manchester, Washington 98353, U.S.A.

118

William T. Fairgrieve and Colin E. Nashenvironmental research of marine ecosystems is

Using the Guidelines Document

only now becoming recognized in many countries.

Before any decisions can be made with regard

Many aquatic and terrestrial ecosystems can beto the siting or operation of a marine aquaculture

said to be equally fragile, but the factors differ as

facility, the first responsibility of risk managers,

do the mechanisms available for remediation.

and that includes both managers of resources as

Most human interventions in aquatic ecosystems,

well as managers of aquaculture operations, is tosuch as mineral extraction, fishing, and now

draw their conclusions from all informationaquaculture, may induce more lasting far-fieldprovided by the risk assessors that a perceived

effects unless properly managed. Nonetheless,risk to a particular ecosystem has validity or not,these and any other industries that integrate withand if so to estimate its degree of adverse effect.

open waters, such as tourism and recreational

This may or may not be a straightforward task.

boating, all have a right to exist equitably as

In some cases the information reported to them bystakeholders; the effects on the aquatic ecosystem

the risk assessors may be an excellent combination

by one should not eliminate the existence ofof field and laboratory data to compare withanother.

recognized benchmarks of stress, while in others it

In enabling aquaculture to share aquatic
resources responsibly, the stewards of these

may be no more than the long-time experience ofpractitioners.

resources are faced with many options. Invariably

Irrespective of the final detail, it is importantthese options cannot be quantified adequately, andthat the information is considered, collected,

thus managers must estimate their potential

analyzed, characterized, and reported in aecological risks through individual risk

structured fashion. This ensures that the risk

assessments.

Nonetheless, although ecologicalassessment report is not only complete as far as it

risks are a paramount concern, the final decision iscan be (Table 1), but also that it can be comparedfrequently decided by other factors brought todirectly with similar risk assessments made bybear by social choice, such as economic benefits toother individuals elsewhere.

a local community, or issues of public health.

These guidelines for the risk assessment ofmarine fish aquaculture attempt to facilitate theTable 1. Possible contents of a risk assessment report.

Table 1. Possible contents of a risk assessment report.

•
•
•
•
•
•
•
•

Description of the preliminary objectives and plans
Description of the environmental setting for the planned development
Description of the proposed aquaculture practice and species to be cultured
Review of the conceptual model and the assessment end points
Discussion of the major data sources and analytical procedures used
Review of the stressor response and exposure profiles
Description of the risk to the assessment end points, including risk estimates and adversity
evaluations
Review and summary of major areas of uncertainty, and their direction, and approaches used
to address them, such as:
o Discussion of the degree of scientific consensus in key areas of uncertainty
o Identification of major gaps and, where appropriate, indicate whether gathering
additional data would add significantly to the overall confidence in the assessment
resultso Estimation of the risk probability by combining numerical datao Discussion of science policy judgments or default assumptions used to bridge
information gaps and the basis for the assumptionso Discussion of how elements of quantitative uncertainty analysis are embedded in theestimate of risk

119work of risk assessors and risk managers to

but later nonhuman-oriented environmental risk

achieve these objectives. In brief, the guidelines:

assessments were included.

◦identify the 10 areas of substantive risk in theconsidered the risk to entire communities andinteraction between marine fish aquaculture

addressed any number of selected end points, but

operations and the environment;

they also included the possible effects of◦identify the biological end points or entities andtheir attributes, both locally and far field, thatmight be affected in those areas of risk;

These not only

nonchemical stressors.
In order to accommodate the sudden burst ofdifferent views and approaches to environmental◦identify methodologies for measuring or

risk assessment by its member countries, themonitoring the effects of exposure to each area

United Nations (UN) World Health Organizationof risk;(WHO) developed a common analytical framework.

◦provide a common framework, or step-by-step

The WHO Framework is adopted here forprocess, to estimate the degree of potential

developing Guidelines for Ecological Risk

adversity of each area of risk, together with its

Assessment of Marine Fish Aquaculture (thismitigation; andtechnical memorandum) because it provides a◦provide a concept of the physical andgeneric analytical framework that has been widely

environmental demands of marine fish

reviewed and accepted by international experts inaquaculture sites, and a matrix to suggest

UN-sponsored workshops.

different orders of relevance for the application

The WHO Framework (Figure 1) represents theof each area of risk in different global

scope of the guidelines for undertaking ecologicalecosystems.

risk assessments.

In planning a risk assessment, it isdimensional figure, with planes surrounding therecommended that the risk managers and risk

actual risk assessment to depict the total process.

assessors, together with others with experience in

These planes represent the continuum for all thosemarine fish aquaculture, first review the areas of

who are involved in the decision-making process,risk identified as priorities in the guidelines, andand includes not only the interactions between risk

establish their relevance in their own geographic

managers and risk assessors (the scientific andregion and to the particular local ecosystem where

technical experts), but also their interaction withmarine aquaculture facilities are to be sited. It is

stakeholders who may be affected by any decision.

very probable that not all areas of risk will be

For marine aquaculture, participating stakeholders

applicable to every development site, and therefore

are typically the fish farmers and their tradea matrix has been developed as part of theassociations, waterfront property owners,

guidelines to suggest some of the more common

recreational users of waters, other fishing anddifferences (see "Near-field and Far-field Effects").

aquaculture bodies, and environmental advocacy

For those that are important, the respective

groups. The extent of stakeholder interaction, andtemplates (as described in Appendices A-J of theat what point it is considered in the decision-

full document) can be used.

making process, is the prerogative of the decision-

It represents a three-maker, and varies from one country to another in
Ecological Risk Assessment ofaccordance to the regulatory, legal, and decision-

Marine Fish Aquaculture

making climate. Furthermore, stakeholders might
perform their own risk assessments with orFramework
For more than 20 years, countries have beendeveloping national guidelines for environmental
risk assessment.

without the help of technical consultants, withdifferences arguable in court.
The risk assessment process is itself divided into

At first their focus wasthree segments. These segments represent three

predominantly on environmental risks to a single

distinct phases of work, but once again there is a

species (humans) and one end point (human health),

continuum of interplay between the persons

120

William T. Fairgrieve and Colin E. Nash

Discussion
between
Risk Assessor&
Risk Manager(P lanning)

P ROBLE M FORMULATIONP ROBLE M
ANALYS IS
CharacterizationofE xposure

CharacterizationofE cological E ffects

Data
Acquisition,
Verification,
andMonitoring

RIS K CHARACTE RIZATION

Discussion between the
Risk Assessor & Risk Manager(Results)

RIS K MANAGE ME NT

Fig.1.

Fig. 1. The WHO framework for ecological risk assessment.

involved.

water quality, avoidance of low dissolved oxygen,

The following sections describe in broad terms a

avoidance of eutrophication, etc.);

generic risk assessment process but without direct◦a conceptual model or diagram of how theapplication to any specific category of risk.

system being assessed is thought to be

Detailed processes can be found for all theorganized; and finally,

principal categories of risk from marine fish◦the plan for analyzing the information andaquaculture in Appendices A-J of the fullconducting the rest of the assessment.

document.

Problem formulation can be a long and difficult

Problem Formulation for Marine Fish

1

process. It depends on the degree of familiarity
with the particular field of aquaculture, how

Aquaculture (Phase 1)

contentious are any issues, and finally who is

The first phase is problem formulation, or the

involved. Unfamiliar problems, such as the location

identification of key factors to be considered in theof marine fish cages in the migratory routes orrisk assessment. Here all the necessary plans are

breeding grounds of cetaceans, unquestionably

made by the risk managers and risk assessors totake longer to formulate compared with, say, thedetermine how the analysis will be performed.

location of a land-based marine fish hatchery

These include, for example:

adjacent to an existing recreational marina or fish◦the scope, focus, and sources to be considered

processing plant.

(such as the type of marine aquaculture, andspecies);Modern marine fish aquaculture has been
evolving for almost 50 years.

Consequently,◦the biological or ecological end points and theirconsiderable experience has been building withattributes that are the concern for protection

regard to any real or perceived impact on marine(such as sea grass preservation, maintenance of

ecosystems all over the world.

Most of the121practical knowledge and experience by fish
farmers themselves has never been recorded,
although some has been documented in grayliterature, but a considerable volume of scientificand technical research can now be found in peer-

mammal, reptile, or bird,◦the immune resistance of demersal and pelagic
fishes,◦the number and fitness of the natural(conspecific) population,

reviewed journals. With this growing background◦the fitness of another fish population, andinformation to draw on, it is possible for risk◦the abundance of the industrial fisheries.

managers and risk assessors to undertake a very
comprehensive problem formulation.

The choice of species may be guided by whether
one is looking for a surrogate for system stressors,

For the purpose of these guidelines the possible

system response, or protection of some desirable

observed or perceived effects of marine

biological attribute. Thus, one might measure aaquaculture have been summarized in 10

toxic phytoplankton species because of the desirecategories (Table 2).

Within these broad

to avoid blooms of harmful or nuisance species, ordesignations it is not possible to include all theone might choose a species that is indicative of

possible effects which might be identifiable

degraded environmental condition (e.g., capitellid

globally, and consequently the guidelines

worms or the presence of Beggiatoa spp. inconcentrate on the sources of effects, and the end

sediments), or one might measure sea grass

points or entities of concern together with theirdistribution because of its high protection status.

attributes, of known importance to the majority ofmarine ecosystems. A risk assessment can include

Problem Analysis for Marine Fish Aquaculture

any number of other effects, but practical(Phase 2)experience suggests that the 10 categories andProblem analysis is the second phase of risk

their contents illustrated here provide a strong

assessment when all available scientific information

starting point. The biological end points of these

relevant to the issue is collected and applied. For

possible effects are generalized in the following

the most part it is carried out by technical experts.

paragraph.

Problem analysis is divided into two parts. The

Biological end points of marine fish aquaculture

first is the analysis of exposure, which predicts orand their attributes can be described in collective

measures the spatial and temporal distribution of aterms (such as the species abundance of thestressor and a point of concern; the second is theinfauna), or very specifically by location (such as

analysis of effects (sometimes called the exposure

the discovery of giant tubeworms at hydrothermal

response), which identifies and quantifies any

vents). They may also be assessed generally (suchadverse effects caused by a stressor.

as by the presence of certain species in theepifauna), or by specific measurements (such as byn, µg/g, or µg/L).

Characterizing the Background of an
Aquaculture Site

The end points identified in these guidelines for

It is important to know the characterization ofprotection from marine fish aquaculture activities

the marine site(s) where the stressor originates

may include:

and where it may have its adverse effects.

◦the species richness and abundance of the

Therefore the first step is a baseline survey, or

seston, nekton, or infauna,◦the abundance of a specific species in the seston,nekton, or infauna,◦the species richness and abundance of theepifauna,

stock-taking, of information about the near field,
and in some cases the far field. The survey is in
two parts, namely, collecting information through aliterature search followed by assembling current
information and data by field work.

◦the abundance of a specific species in theepifauna,◦the abundance of a specific species of marine

Historical information
A valuable part of the baseline survey is aWilliam T. Fairgrieve and Colin E. Nash
122
Table 2. Categorization of observed or perceived effects associated with marine fish aquaculture, and theTable 2. Categorization of observed or perceived effects associated with marine fish aquaculture, and theidentifiable sources of the stressor.
identifiable sources of the stressor.

Effects

Sources

1. Increased organic loading••

Particulate organic loadingo Fish fecal materialo Uneaten fish feedo Debris from biofouling organismso Decomposed fish mortalities on the farm
Soluble organic loadingo Dissolved components of uneaten feedo Harvest wastes (blood)

2. Increased inorganic loading••

Nitrogen and phosphorus from fish excretory products
Trace elements and micronutrients (e.g., vitamins) infish fecal matter and uneaten feed

3. Residual heavy metals•••

Zinc compounds in fish fecal material
Zinc compounds in uneaten feed
Copper compounds in antifouling treatments

4. The transmission of disease organisms••

Indigenous parasites and pathogens
Exotic parasites and pathogens

5. Residual therapeutants•••

Treatment by inoculation
Treatment in feed
Treatment in baths

6. Biological interaction of escapes withwild populations

•
•
•
•

Unplanned release of farmed fish
Unplanned release of gametes and fertile eggs
Cross infection of parasites and pathogens
Planned release of cultured fish for enhancement or
ranching

7. Physical interaction with marine
wildlife•••

Entanglement with lost nets and other jetsam
Entanglement with nets in place, structures, andmoorings, etc.
Attraction of wildlife species (fish, birds, marine
mammals, reptiles)
Predator control

8. Physical impact on marine habitat••

Buoyant fish containment structures and mooring lines
Anchors and moorings

9. Using wild juveniles for grow-out•

Harvest of target and nontarget species as larvae,juveniles, and subadults

10. Harvesting industrial fisheries for fish
feed•

Increased fishing pressure on the shoaling small pelagic
fish populations•

search of existing literature of water and sediment

phytoplankton species and chlorophyll, sedimentquality parameters. These include, for example,

grain size, and organic matter content. In thosedata on water temperatures, salinity, dissolved

cases where information is not available, then aoxygen, stratification, bottom currents, water
depth, background nutrient concentrations,

2

program of data collection should be initiated to fill
the gaps.

It is hard to be prescriptive about

123
spatial and temporal scales of measurement, but

the macrobenthic communities. This may bemeasurement of some water quality parameterscarried out by stratification, or by the type of

may need to be taken on a weekly basis during

habitat.

seasons of high phytoplankton productivity.

4. The hydrographic variables, such as currents,

Some additional information might be available

tides and residence times, including acoustic

on the background levels of contaminants in both

doppler current profiler (ADCP) data collected

the water and in the sediments. These include, forover at least one lunar cycle, and bathymetry

example, metals, and organics such as

within 500 m of the proposed site.

hydrocarbons, pesticides, polychlorinated biphenyls

5. A profile of water quality, including temperature,(PCBs), and polycyclic aromatic hydrocarbons

salinity, and the potential for stratification as a

(PAHs), etc.

function of season (pycnoclines and haloclines).

This information is particularly

important (and more likely to be available) in near-

6. A profile of primary productivity, including

shore coastal areas where there are significant

major species (including any toxic species),

anthropogenic inputs from agricultural and urban

chlorophyll (Chla), phaeophytin, and dissolved

areas. In open waters there is little potential forthe accumulation or discharge of these types ofcontaminants, and the need is reduced.

oxygen (DO).
7. If possible, underwater surveys recorded on avideo or a series of photographs to provide an

Finally, any documentation providing a broad

overall, semiquantitative assessment of thedescription of the natural history of the area,

benthic environment of the site, especially in

together with any reports or local knowledge ofdeep water.

the potential for noxious phytoplankton blooms or

8. Finally, identification of activities by otherthe prevalence and intensity of known parasites

resource users, such as marine sanctuaries,

are potentially useful. Information on the incidence

marine protected areas, fishing grounds,of blooms and parasites is more likely if there arerecreational areas, navigational channels, oilcommercial shellfish resources in the area.

and mineral extraction, military training areas,
and approved dumping grounds, etc.

Current information
A typical baseline survey of current information

The grid on which this information for thebaseline survey is to be collected depends on thefor the lease area will include most of the items

homogeneity of the system.

A regression

from the following checklist:

approach is recommended with single samples

1. Identification of sensitive habitats. These may

collected at intervals on four orthogonal transects

include, for example, beds of macroalgae andbeginning at the center of the proposed farmeelgrass, coral reefs, commercially valuable

location. Samples should extend at least 500 m

shellfish beds, spawning grounds and breedingfrom the center. If video surveys are conductedareas, migratory pathways of aquatic species,

first, the grab collections can be focused in areas

rocky reef communities, and all otherwhere samples are possible, namely soft to mixed

structures valuable as nurseries. Such habitats

substrates. About 24 samples are adequate.

within 500 m of a proposed intensive farm site

The profile of the macrobenthic community canshould be mapped, with the intention of

be reduced in cost by using the smaller petite

avoiding them whenever possible.

ponar grab (with a 0.0225 m2 footprint) rather than

2. The background physico-chemistry of thethe more standard van Veen grab (0.1 m2).

sediments. This may include, for example, total
volatile solids (TVS) or organic matter content,
redox potential (Eh), sediment grain size (SGS),=

Near-field and Far-field Effects
Effects of aquaculture interventions on thefree sulfide (S ), and the two inorganic metals

ecosystem are spatial and temporal. They can becopper and zinc.

localized and immediate, or distant and sometime

3. An inventory of the species and abundance ofin the future. However, both near-field and far-

124

William T. Fairgrieve and Colin E. Nash

field effects have to be considered in the risk

particle tracking with empirical relationships

assessment process.

between the spatial distribution of solids andchanges in the structure of the benthic community.

Near-field effects

Near-field effects are usually limited or managed

The near field can be defined as that areaby regulatory authorities setting performanceencompassing the limit of directly measurable

standards, which are appropriate for the location

effects. In the marine environment, the majority ofor the region as a whole. Typically, under thehuman interventions, such as sand mining,terms of a permit or license, the producer isdredging, drilling, waste disposal, fish processing,

responsible for conducting the necessary

and recreational boating, etc., all have instant near-

monitoring and complying with the management

field effects, particularly on the sediments andpractices adopted to enable the performance

their benthic communities in the immediatestandards to be met.

vicinity of the source. Consequently, because of
the long history of these activities in marine

Far-field effects

waters, the extent and diversity of their effects are

Far-field effects are those effects that occur

well known. They can be measured with accuracy,

outside that area where statistically significant

and the particulate data and benthic biological dataclines in relationship with the source cannot belinked in a number of empirical or mechanistic

measured.

models to assess potential risk.

normally can only be detected by long-term

These are cumulative effects that

With regard to the relatively recent intervention

monitoring programs at locations not directlyof aquaculture in the marine environment, and its

influenced by local effects. Assessment of far-field

most localized and instant impact of wastes andeffects associated with aquaculture becomes

contaminants accumulating on the bottom

increasingly important as the industry expands.

sediment beneath fish enclosures or in solution,

The maximum spatial extent of far-field effects

there is a wealth of comparative information about

is a hydrologic unit that includes all inputs

the measurement of near-field effects on which topotentially affecting the unit. It may include, fordraw. For example: 1) in terms of sedimented

example, a single bay, several bays, or an entire

organic waste, the near field describes that area inestuary or delta.

which statistically significant differences (t-tests,

increasingly difficult to measure in open bodies of

ANOVA, etc.) or significant clines (statisticallywater, such as those offshore where aquaculture

significant coefficients on dependent variables in

may occur. However, even in large open bodies oflinear or nonlinear regression analysis) in either

water the same definitions could be applied.

Far-field effects become

physico-chemical or biological end points associatedBecause of the vast scope of far-field effects,

with aquaculture-related effects can betheir potential is normally best assessed throughdemonstrated at the peak of farm production; andcomputer models.

2) in terms of reduced concentrations of dissolved

consortiums of contributors to the cumulative

contaminants or effects of metabolic waste, theeffects in coordination with some level ofnear field describes that area in which statistically

government. Management of far-field effects issignificant increases or decreases in the end point

normally a public function in cooperation with allof interest can be measured in comparison withthe contributors. With regard to organic loading,

local reference conditions.

for example, from a number of marine fish farms

These are monitored by

Because of the extent of good data, near-field

into a bay 10 km distant, the regulatory authority

effects are generally assessed using local computer

may set Total Maximum Daily Loads (TDML) for

models to predict the deposition of organic

the far field of interest (the bay), and apportion thematerial released by the producer.

The

TMDL to individual producers or farm complexes.

DEPOMOD computer modeling tool, for example,

The authority then manages the far-field effects bymodels benthic enrichment effects by combining

manipulating the respective TMDLs to meet one

125stated objective.

formulation. This is because issues might havearisen which necessitate a reiteration of problem

Risk Characterization forformulation and a repeat of the problem analysis.

Marine Fish Aquaculture (Phase 3)
Risk characterization is the final phase when the

Risk Communication

two analyses of exposure and effects are brought

A final responsibility for everyone involved in

together.

It is best performed using models

managing risk is risk communication. This is andeveloped to estimate effects from hypotheticalongoing process at the local level and usuallyrisks.

involves a government agency, represented by risk

In a number of fields, such as the pharmaceuticalindustry or chemical engineering, risk
characterization can be straightforward.

managers, industry and other stakeholders, andthe public at large.

The

The objective of risk communication is topoint estimate of exposure is compared with the

maximize the transparency of every activity

point estimate of the threshold of effects, and if therelated to the risk through interaction with theratio is greater than one then an effect is assumed.

broadest range of interested parties (Figure 2).

It can be taken further with an exposure-response

This objective includes risk identification, analysis,model, when the distribution of the exposure andassessment, implementation of the decision, andeffects can be shown to accumulate over a period

subsequent monitoring. It is important that theof time.

However, in the marine aquaculturecommunication process is begun as soon as

industry the process of risk characterization ispossible, preferably with an announcement of thecomplicated by the fact that most of the effects areproject itself.

interactive. Such complexity could be dealt with

Risk communication is carried out in a variety ofby modeling, but quantifiable information for many

ways. Productive communication is invariably

aspects of marine aquaculture is extremely scarce.

conducted at public hearings when, in theory,

Consequently, for risk characterization the only

everyone listens carefully to each other without

recourse at present is either to make use of aany prejudgment of the issue. But this is notmechanistic model for a particular site, providing

always the case, and it is important for the risk

the assumptions are reasonable and that the model

managers representing government agencies atcan be adequately calibrated and validated, or tosuch hearings to maintain public trust by theirrely on all existing information and especially the

independence and impartiality.

classical "dose and response" laboratorycommunication is also achieved by regularly

information.

circulating published materials.

Good

In assessing a risk it is important both to qualify

Some aspects of risk assessment are scientificand quantify, where possible, the associatedand very technical, and therefore it is important

uncertainty. For example, the uncertainty could

that the data and all methods of collection, any

be described by probabilistic factors, bymodels and assumptions that have been applied,

semiquantitative factors, or entirely qualitative

and any conclusions drawn are reviewed by peers.

factors, such as high, medium, or low. Whateverfactors are chosen, it is important to include theMonitoring for Subsequent Risk

uncertainty with any risk assessment. In addition,

Decisions can be made by the risk manager

it is important to explain any assumptions whichbased on the historical and current information

were used in the analysis, the scientificgathered by the team of risk assessors anduncertainties, and their strengths and weaknesses.

stakeholders. If the potential risk is assessed as

Risk characterization is carried out by scientificbeing unlikely, or small, then the risk manager canand technical experts, but it is not limited to them.

authorize the project to go ahead. However, it is

Risk assessors and risk managers are again

important that the baseline does not change inactively involved in the process, as during problem

such a way that the risk can in fact occur at a

126

William T. Fairgrieve and Colin E. Nash

THE RIS K AS S E S S ME NT
P ROJ E CT

RIS K AS S E S S ME NT
RE S ULTS

RIS K COMMUNICATIONInternal P lanning andP reparation

E xternal Coordination
and Collaboration(i) P eer review of results(ii) Review and discuss withagencies and other credible
resources

E xternal Interface with P ublic(i) Meet, involve, listen anddiscuss with all stakeholders(ii) Distribute information
through appropriate media

Reiteration as Necessary

FINALIZING AND
IMP LE ME NTING THE
DE CIS IONS

Fig. 2. The process of risk communication for the project and the results.
Fig.2.

later time, and therefore the risk manager usually

points (such as the perimeter of a facility), and all

qualifies any decision with the requirement for thebased on the predominant direction of the current.

continual monitoring of certain site parameters.

In addition, the frequency and methods of sampling

The task of carrying out the monitoring program

will be specified, and the methods of analysis will

may be the responsibility of the regulatory agency,

be identified together, where necessary, withthe owners or managers of the project in question,

laboratory instrumentation.

or both.
It is important that any monitoring program is

2

Global Application of the Framework

designed around the measurement of:◦standards identified by national legislation andregulation, andPhysical Demands of Marine Fish Aquaculture
For the foreseeable future, intensive marine fish

◦those parameters relevant to the indication of

aquaculture will be limited to waters of the

any increasing risk to the biological end points

continental shelf, which is often defined as lyingthat have been identified.

above the 200-m contour.

However, for theFundamental also to every monitoring program

practical reasons of engineering cost, operational

is an exact specification of the methodology. This,

management, and profitability, marine fishfor the most part, should have been establishedaquaculture takes place reasonably close to shore,during the baseline survey.

In other words,

provided that water quality conditions are suitable.

reference stations and site stations will be locatedSelection of a location depends on the proposedand fixed along transects on the seabed or at set

fish farming system and practice. Again, because

surface or mid-water distances from identifiableof the investment cost, only intensive fish

127
production is economically feasible, and the options

life history and physiology of the species of fish inare floating net-pen complexes and buoyant

culture, and the operator must provide an

individual cages designed to remain at the surface

appropriate living space for the fish, meet all theiror to be submerged as required.

Net-pennutritional requirements, and maintain their health.

complexes are therefore usually located in coastal

Site selection for an aquaculture facility isestuaries, sounds, and lagoons that have rapid

therefore a critical task.

marine water exchange, have some shelter, andbecause the range of marine ecosystems in which

provide anchorages that are less than 40 m deep.

it may be located is diverse, and the suitability ofIndividual buoyant cages can be located in less-their physical and chemical properties depend

sheltered waters, and submersible cages can besignificantly on the species and culture practice todeployed in deeper water to avoid storms.

be implemented. For example, there are different

However, submersible cages have limitations.

site demands for submersible cages containing

Although wave energy attenuates with depth, thecobia 3-5 km from the coast of Puerto Rico, pensscale of each unit is limited by potential fatigue offor growing-out tuna in coastal waters within 2 km

the materials, the capacity of the automatedof the shoreline of Australia, and enclosures forfeeders, and the need for regular surveillance andrearing sea bream in shallow marine embayments

service operations by scuba divers. Scuba divers

in the Mediterranean.

It is made difficult

can operate safely down to a depth of 30 m, but

The hydrodynamics, nutrient levels, types ofoperate most economically around 10-15 m, andpollution, and other environmental parameters

working in pairs. Currently, submersible cages

found in these locations are all very different.

are being operated at depths of less than 100 m,

Consequently, there will be differences in the

but this may still be up to 30 km offshore.

biological end points and their attributes resulting

Net-pen complexes are anchored by manyfrom aquaculture operations that characterize theseparate cables, depending on their formation andpotential risks to the environment. For example,

size. Additional lines may anchor predator nets.

the risk of eutrophication and change in species

Individual buoyant cages are anchored by four

diversity in the benthic environment in the poorly

discrete lines which maintain tension all aroundflushed lagoons of the Mediterranean is higher

continuously. Single-point anchor systems havethan the offshore waters of either Puerto Rico oralso been used, but at some time the line will

Australia where there are greater depths and highbecome slack, which puts a burden on the cage/water exchange rates.

line interface. The preferred substrate for the

Because of all these differences, each ecologicalanchors themselves is sand or mud. Anchors canrisk assessment has to be tailored to an individual

be bolted into rocky substrates, but the practice islocation, and an individual species and aquaculture

costly.

practice. However, the categories of potential

Buoyant cages are designed to operate inecological risks and their fundamental methods ofcurrents up to 90 cm/sec, or about 1.74 knots.

assessment are common, and it is only theirThis is above what is desirable for the fish, which,relative importance that will vary.

when confined in strong currents, expend too
much energy maintaining their position in the cage
instead of growth.

A Matrix Approach to Guide
the Application of Risk Assessments
In selecting a suitable site for marine fish

Environmental Demands ofculture, the ideal requirement is a pollution-freeMarine Fish Aquaculture

environment in the epipelagic zone with good

Successful marine fish aquaculture depends on awater quality parameters. Primarily this meanssynergism between the aquaculture site and theyear-round high ambient levels of oxygen

farmer.

The environmental qualities or

combined with salinities and temperatures that are

parameters of the site must be conducive to thebetween the middle and upper end of the ranges

128

William T. Fairgrieve and Colin E. Nashtolerated by the respective farm species, andwith intrusions of some colder waters from themaintained by a modest current and average tidal

subtropics. Tropical waters are biologically veryrise and fall.

rich but nutrient poor and characterized by high

Unfortunately the ideal cannot

always be found, and the parameters are solight levels.

diverse that most sites are selected for reasonsmigratory populations.

somewhere between ideal water quality

The three epipelagic ecosystems are:Tropical waters often support

parameters and operational cost and convenience.

1. Offshore waters. Typically 3 km or more from

As marine fish aquaculture is still in its infancy

the coast, or up to 100 m in depth, and suitablein most countries, and the locations where it isfor submersible cages.

practiced at the present time are few, for the

2. Coastal waters. Typically less than 3 km frompurpose of these guidelines it is proposed tothe coast, or up to 30 m in depth, suitable forclassify the typical marine aquaculture

submersible cages and floating cages, withenvironment into categories of biogeographicalstrong tidal interchange.

regions or zones and categories of marine

3. Inshore water bodies. Typically semienclosed

epipelagic ecosystem. The definitions of the zones

but large coastal sounds, lagoons, and estuaries,

and categories are as follows:

relatively shallow in depth, suitable for floating

The two biogeographical zones suitable for marine

cages and fixed enclosures, with good tidal

aquaculture (as illustrated in Figure 3) are:flushing.

◦Temperate waters (10-18℃).

Typically cold

The 10 categories of risk can then be evaluatedwaters with intrusions of some warmer waters

in broad terms against each of the 6 generalized

from the subtropics. Temperate waters can bemarine ecosystems in the form of a matrix (Table

rich in nutrients and highly productive (waters

3). The objective is to indicate probable differences

off Australia being an exception), andin priority relative to each type of ecosystem, andconsequently characterized by low light intensity

to assist risk managers and risk assessors withlevels.

their problem formulation.

Temperate waters often support

However, thesubstantial fisheries, together with theirinformation presented in the matrix does not ruledependent populations of birds and marine

out the uniqueness of some ecosystems, and thismammals.

most always be considered.

◦Tropical waters (>18℃). Typically warm waters

Fig. 3. Broad biogeographical zones for marine aquaculture(courtesy of the Gulf of Maine Research Institute).

Fig.3.

Table 3. Matrix to guide the application of risk assessments in the waters of different biogeographic
129

zones.

Table 3. Matrix to guide the application of risk assessments in the waters of different biogeographic zones.

Category of observed or
perceived risk
1. Increased organic loading
2. Increased inorganic loading
3. Residual heavy metals
4. Transmission of diseaseorganisms
5. Residual therapeutants
6. Biological interactions ofescapes with wild populations
7. Physical interactions withmarine wildlife
8. Physical impact on marine
habitat
9. Using wild juveniles forgrow-out
10. Harvesting industrial
fisheries for fish feed

Epipelagic ecosystem intemperate waters(10–18˚C)InshoreCoastalOffshore

Epipelagic ecosystem intropical waters(>18˚C)
InshoreCoastalOffshore

*****
*****
*
***

**
**
*
**

*
*
*
**

*****
*****
**
***

***
***
*
**

*
*
*
**

**
**

*
**

*
*

**
**

*
**

*
*

**

**

*

**

**

*

**

*

*

**

*

*

**

**

*

***

***

**

**

**

***

***

***

***

Key: Potential for ecological change without management action*****
Significantly
high for ecological change without management action
Key:
Potential**** High*** Medium** Low***** Significantly high* Little or none

****

High

of the escapees) than to other fish populations at

Risk Assessment Example***

large.

Medium** Biological
Low Interaction of

Background Experience

Escapes with Wild Populations*

Little or none

The practices of both freshwater and marine
fish culture for stock enhancement or ranching

Risk Hypothesis

have benefited from years of effort to improve theEscaped farmed fish, or their gametes liberated

cultured stocks.

In addition to the results offrom a farm, may pose a risk to wild populations

traditional genetic techniques used by hatcherywhen they interact biologically.

managers, such as trait selection, inbreeding, andPotentially

deleterious genetic impacts are perceived to be:

out-breeding, there are also the genetic influences◦interbreeding andof simply surviving in the wild. On the other hand,◦competition for mates or nesting sites.

commercial fish culture is a relatively new field

Potential ecological risks from escaped farm fish

and the present generations of farmed species areare perceived to be:

still closely allied to the original wild parents. Fish

◦competition for habitat and forage,

populations bred in captivity have already been◦increased predation (if piscivores),subjected to similar stock-improvement practices◦the introduction of exotic pathogens andwhich, however small, have probably begun toparasites, and◦amplification of endemic pathogens, some ofchange their genetic makeup. Consequently, when
cultured fish are released intentionally or escapewhich may be antibiotic-resistant.

3from farm enclosures into the ecosystem, they

All these possible risks are believed to pose acarry with them a genetic profile that can have agreater threat to natural populations (conspecifics

deleterious effect should they interact again with

130

William T. Fairgrieve and Colin E. Nashnatural populations.

dormant pathogens and cause the same diseases

There are a number of ways for biologicalendemic to these fish in their native habitat.

interactions to occur in an aquatic ecosystem

Outbreaks of disease can occur at fish hatcheries,

where aquaculture activities are practiced. Firstly,

and transfer of infected fish may facilitate disease

farmed fish can escape directly from net-pens andtransfer between stocks.

other enclosures due to human error, damage fromoccurrence of endemic pathogens in wild fish isa catastrophic natural event such as a severecommon, it is difficult to determine the extent thatstorm, or following damage to the structure by apathogen transfer occurs. Similarly, it is difficult topredatory marine mammal.

Secondly, somedetermine the extent to which amplification of

species of finfish and shellfish that spawn freely inendemic diseases occur. It has been suggested

captivity and produce pelagic eggs may releasethat populations of sea lice (such as Caligis andfertilized gametes into the surrounding

Lepeophtheirus spp.) are transferred and amplified

environment. Thirdly, domestically cultured fish

between farmed salmon and their wild populations,and shellfish raised in hatcheries can be released

but no scientific evidence has been found (seeintentionally on a large scale in annual stock

Appendix D).

However, as theenhancement or sea-ranching programs, leaving
them to migrate freely and interact with wild
populations.

Building the Conceptual Model
Escapes may occur with varying frequency and

There is evidence that farmed fish are capable

intensity. Therefore, the two sources of biologicalof breeding with their conspecific naturalinteractions from the escape of cultured fish or

populations in the wild. Therefore escapees may

their gametes from aquaculture facilities arepresent a genetic threat to a locally adapted

catastrophic releases, or periodic natural eventsnatural population through intraspecificsuch as storms, and chronic releases.

hybridization, resulting in a reduction in overall

impact, however, is modified by a number ofreproductive fitness and recruitment to the wildthings, amongst which importantly are thepopulation. Some interspecific hybridization might

numbers and the genetic characteristics of bothalso occur should farmed fish escape into an

the escapees and their resident indigenous wild

ecosystem where there are very closely related

populations.

Theirspecies. The use of reproductively sterile farm

Catastrophic releases are unique as they arefish has been proposed as one means of preventing

rare and not planned, and they could involve a

genetic interactions with wild populations, andlarge number of escapees. Invariably they can beconsequently reducing their ecological impacts, but

avoided or controlled if appropriate guidelines arethis practice is still a matter of priority research.

followed for risk management (disaster prevention)

The introduction of exotic pathogens by theand the subsequent recovery of inadvertently

transfer and escape of farmed fish is an issue of

released animals. Although it may be impossible

lessening concern. This is because most countries

to anticipate the occurrence of a 100-year climatic

have adopted the international protocols regarding

event, a range of possible disasters can be avoided

the movement of terrestrial and aquatic species

with the selection of a site concomitant with thefor almost any reason, and they have stringent

engineering technology, and away from shipping

regulations in place regarding the importation ofand navigation lanes and fishing grounds, forexportation of fish or their eggs specifically to

example. The effects of a catastrophic releaseminimize the risk of transferring exotic diseases.

may also be reduced by having a plan and theSuch precautions, however, have not always been

appropriate equipment for retaining or recapturing

effective. Wild fish are the reservoirs of a wide

escapees.

variety of common pathogens, and when certified

Chronic releases may be planned or unplanned

disease-free fish or shellfish are introduced into an

and may involve large numbers or small numbers

area for the first time they are infected by theseof escapees.

Planned releases include stock131
Catastrophic
event

Chronic
event

Unplanned
releaseof gametes

Unplanned
releaseof fishInterbreeding withconspecifics

P lannedreleaseof fishP redation
on wild fauna

Competition
for habitat

Introduction of*
disease and parasites

Competition formates /nests

Number and fitnessof the wild (conspecific)
population

Fitness ofanother fish
population*
Key:

S ourceD

S tep

P rocess

E nd point

Link

Fig. F-1. A conceptual model for biological interaction of escapes with wild populations.
Fig.F-1.

enhancement and ranching programs by fisheriesof genetic variance between the two populations,managers; unplanned releases include the loss of aand out-breeding depression. Some other indirect

few fish through a hole in a net made by aconsequences in the short-term may be throughpredator, or the release of fertilized gametes fromcompetition with all species for forage and habitata captive stock as a consequence of uncontrolled

space, by predation on endemic fish populations,

breeding.
Chronic releases, even due to predator attacks,

and the introduction of bacterial or viral pathogens
4or parasites. The effects of these processes can be

are therefore often seasonal, but their potential

a reduction in the genetic integrity of a community

effects for detrimental genetic and ecologicalor an ecosystem, and they may of course beinteractions may be accumulative. On the otherpositive or negative to both. In brief, the outcome

hand, the effects of planned releases of cultured

can be a reduction in the numerical or genetic

fish are often minimized simply because they arestrength (fitness) of the wild population, andtarget fisheries for commerce or recreation, andpossibly a reduction in fitness in other fish

this reduces their potential to interact with the

populations.

natural population.
Regardless of the manner of escape, escapees

Analysis and Characterization

may affect the natural population in a number ofThe biological end points and their attributes forways. The most important and direct consequence

protection are:is interbreeding, followed by the indirect1) the numerical or genetic strength (fitness) of theconsequence of competition for mates and nestingwild (conspecific) population, andsites. The effects of interbreeding are a reduction2) the fitness of another fish population.

132

William T. Fairgrieve and Colin E. NashModern methodologies for measuring the size

increased significantly by a technique to extract

and genetic parameters of fish populations are all

genetic information from stored samples, which

now carried out at the molecular level by

are usually otoliths and scales, where they exist.

analyzing markers, such as mitochondrial DNA

The polymerase chain reaction (PCR) techniqueand microsatellites. Consequently the techniques

can target a DNA molecule in small and old

are sophisticated and require laboratories well-

samples and amplify its genetic information.

equipped with costly instrumentation. Protein

Unfortunately, fisheries biologists archived material

electrophoresis continues to be a reliable method

more from freshwater and anadromous fishes thant o detect gen etic v ar iation b y i dentifying

marine fishes, and therefore comparative material

differences in protein allele frequencies between

might be difficult to obtain.

stocks.

More recently, however, protein

Fitness is a measure of breeding success orelectrophoresis has been complemented by studies

survival. Relative lifetime fitness (%) is thereforeof the genome and the genetic information thatthe breeding success or survival of one generation

can be carried and detected in a small piece ofto the next.

material, such as tissue from liver or muscle, forcalculation is masked by several possible variables

DNA identification.

associated with any planned or unplanned releases,

However, the simplicity of thissuch as the number and timing of the release, andFitness of the Wild Population

the suitability of the receiving ecosystem.

Genetically effective population size (or Ne) is theAnnual demographic data about the population

most important factor to sustain a high level ofin question is also important, such as the year-classgenetic variation within a fish population. This is

strength of successive generations. Here, there isbecause in the actual total population (N), only apotentially more information available for marine

proportion (the Ne) will pass on their genetic profile

species than freshwater species, as demographic

to the next generation. If the total population isdata has been required for some time by fisheries

reduced for some reason, such as the suggested

managers. It is also important to know when acompetition with cultured fish, then its original

population has substructures, as these cangenetic profile may drift further and further away

influence allele frequency changes and misdirectfrom the original. By measuring this drift, thenany conclusions.

the genetically effective population size can becalculated and conclusions drawn from the results.

Fitness in Another Population

However, calculating the genetically effective

The same procedures will be used to determine

population size is not particularly simple.

A

any reduced fitness in another fish population.

difficult starting point is having a uniform
Biological Opinion

population, so that selected fish are representativeof that population with the same genetic diversity

Escaped farm fish are not in the economic

and any local adaptations. For marine fish this isinterest of producers, and there continues to bemade easier by the fact that few species have been

improvements in the design and operations ofsubjected to the same practices of hatcherymarine fish farms to prevent escapes occurring

propagation, restocking, and enhancement as havealtogether.

freshwater fish and anadromous fish, and therefore

notification of escapes, existing records show thathave little or no introgression.

the incidence and numbers of escapees continue toAs many regulators now requireN e can be estimated directly by sampling adecline. However escapes can and do occur, andpopulation at two or more points in time, andthe escapees may interact biologically with theseparated by a specified number of generations,wild population by changing their genetic integrity

and it is possible to estimate Ne by the changes inor profile, introducing new or unusual genotypes,

allele frequencies in the interval between sampling.

or by eroding their reproductive fitness,

The usefulness of this temporal method has been

particularly if they are originally from nonlocal

133
stock or selected by the breeders for certain farmvariability is partitioned at the population level ortraits.

on a geographical basis, then the natural population

Fortunately the statistical chance of thesestructure is particularly at risk from interbreeding

interactions occurring is affected by a number ofwith escaped conspecifics. This applies to species

factors, the most important of which is opportunity.

of Atlantic (Salmo sp.) and Pacific (Oncorhynchus

Escapees are rarely sexually mature, as they aresp.) salmon, which are highly structured, and someharvested by the commercial growers before

Mediterranean species, such as sea bass (Sparus

nutritional energy is directed to the development

auratus).

of gonads. The few that might be selected as

Because of the apparent continuum of the

future broodstock at harvest time would be moved

marine environment, it has been thought for someelsewhere-usually to a land-based hatchery.

time that most populations of marine fish species

Therefore, at the time of escape, escapees are notare not structured, and therefore their capacity tonecessarily mature enough to breed. Secondly, theexert genetic effects is greatly reduced. Species

escapees might not last long enough to mature insuch as the sea bream in the Mediterranean, for

the wild and interbreed. There is considerable

example, appear to lack structure at the population

evidence for a variety of species that the majority

level, and gene flow across the range of suchof escapees, being raised in captivity on a daily

species appears extensive. Although farmed sea

routine of artificial diets, invariably remain in thebream outnumber wild fish, the presence of an

vicinity of the site to be recovered or fall easy

undifferentiated stock reduces the potential for

victims of predators. Thirdly, the timing of theadverse interactions. However, the increasing

escape might not be coincidental with the naturalinterest in the genetics of marine fish species forbreeding season of the wild population.

fisheries management, and increasing skills in

Catastrophic events may be large but they are

DNA analysis, now suggest subpopulations of somealso very rare, and chronic events may bemarine species might in fact have remained

continual but usually involve very few fish.

localized for sufficient time to have developed

Consequently the timing of an escape, the numbers

small genetic differentiation that now areof escapees, and the size of the wild population aredetectable. This adds to the genetic implications

all variables which play a role in defining thefor releases and escapees mixing with aopportunity for biological interaction.

subpopulation of conspecifics, although, as noted

This is not the same for a planned release ofabove, escapees tend to remain close to the culture

cultured fish from a hatchery, or an unplannedsite, therefore selection of broodstock within therelease of fertile gametes from captive adults on a

vicinity of the site would be an appropriate

farm. Such events involve the release of a large

practice to reduce this possibility.

number of juveniles or gametes that could mature

There is evidence that fish reared in captivity

and breed, or a few mature breeders in acan lose any natural undiminished capacity torestocking program in the hope that they willcapture prey, and when released or escape they dobreed. The opportunities for biological interactions

not compete for forage too well. Escaped fishfrom planned releases of juveniles or broodstock,when recaptured invariably have empty stomachs.

or unplanned releases of fertile gametes, areIn summary, ecological risks from the biologicalobviously considerable, and may be magnified

interactions of unplanned releases with wild

further by the degree to which they have been

populations can be greatly reduced, as they cannot

selected to enhance certain traits.

be deleted altogether, by good management

The potential genetic effects of biologicalpractices, such as:interactions of planned and unplanned releases◦careful choice of the site;

may also be modified by the population structure◦constant vigilance of all structures, moorings,of the wild population. For populations with a highdegree of local adaptation, among which genetic

and anchorages;◦regularly cleaning nets and predator nets;

134

William T. Fairgrieve and Colin E. Nash◦maintaining all navigational requirements (lights
and foghorns);◦conducting any transfers with great care; and◦having a plan for escape recovery.
Genetic risks from the biological interactions of
unplanned and planned releases with wild
conspecific populations can be reduced by:◦selecting broodstock from within the ecosystemof the site;◦selecting marine species for farming, which havelittle or no substructure; and◦raising sterile animals.
Further Information◦ICES. 2002. Working Group on the Applicationof Genetics in Fisheries and Mariculture. ICES
CM 2002/F:03, Ref. ACFM, ACME.
◦ICES. 2003. Working Group on the Applicationof Genetics in Fisheries and Mariculture. ICES
CM 2003/F:01, Ref. ACE, 1.
◦ICES. 2003. Working Group on Environmental
Interactions of Mariculture. ICES CM 2003/
F:04, Ref. ACME.
◦ICES. 2004. Working Group on the Applicationof Genetics in Fisheries and Mariculture. ICES
CM 2004/F:04, Ref. ACFM, ACME 1.
◦Journal of Applied Ichthyology (2001) 17:153-162.

135

The Measures for Sustainable Marine Aquaculture in Japan
Ikuo TAKEDA＊
Abstract

Marine aquaculture in Japan has developed steadily since the 1960s, and it occupies

an important position in the Japanese marine fisheries at this stage. In 2004, it accounted
for 21.4% of the total production and 29.0% of the total value. Accordingly, the achievementof sustainable marine aquaculture is one of the important issues when considering Japanesefisheries policy. This paper outlines several measures and a basic plan related to sustainable
development of Japanese marine aquaculture..
Key words: sustainable aquaculture, regulation, seafood safety

Outline of Marine Aquaculture in Japan

Dividing Japanese marine fisheries into four
major sectors: distant-water, offshore, coastal and

Aquaculture has a very long history in Japan,

aquaculture, aquaculture production exceededththat of the distant-water fishery and was nearlycentury. The artificial feeding of marine species

equal to coastal fisheries. The value of aquaculture

was said to initiate in 1927 with yellowtail inproduction has exceeded that of the distant-water

Kagawa Prefecture. The aquaculture of yellowtail

fishery since 1988 and that of the offshore fishery

was suspended in World War II, but had comesince 1992 (Figure 1).

beginning with nori seaweed culture in the 16

back in the decade following the War. And new
aquaculture technologies were gradually applied to
an increasing number of species. At present, it issaid that about 30 species are cultivated in Japan;

Today, marine aquaculture is a major fooda part of those comprise most of the domestic

production industry in Japan. Some big companies,

production. In 2004, cultivated nori, oysters ande.g., Nihon Suisan, Maruha and foreign-affiliatedcoho salmon accounted for 100% of the domestic

firms such as Norwegian companies have enteredsupply of those species, and cultivated yellowtail

into aquaculture through subsidiaries. Aquaculture

and red sea bream account about 70 or 80% of the

products generally meet the tastes of consumers

domestic supply of those species. Aquaculture andand consist mainly of medium- to high-quality

fisheries production levels in Japan during 2004 areproducts. As marine aquaculture continues

presented in Table 1.

to develop and expand, protecting the marine
environment from the effects of water pollution
is vital to the health of the industry. At the sametime, Japanese consumers have been concerned

In 2004, marine aquaculture production in Japan

about "Anzen" and "Ansin" on food including

amounted to 1.2 million metric tons valued at

cultured seafood since the discovery of outbreak

436 billion yen and represented 21.4% of the totalof Bovine Spongiform Encephalopathy, i.e., BSE in

Japanese marine fisheries in volume and 29.0% ofJapan. In English, "Anzen" can be translated into

the total in value (Table 2).

"safety" and "Ansin" can be translated into "trust."
Accordingly, aquaculture policy of Japan has to2009 年 8 月 10 日受理（Received. August 10. 2009）＊
Fish Ranching and Aquaculture Division, Fisheries Agency, 1-2-1 Kasumigaseki Chiyoda-ku, Tokyo, Japan 100-8907

136

Ikuo TAKEDA

Table
of of
Aquaculture
FisheryProduction
Productionin in
2004
Table1.1 Rate
Rate
Aquacultureto
to Total
Total Fishery
2004
SpeciesAquaculture (A)Fishery

Total (C)

(ton)

(ton)

(ton)

A/C

Yellowtail

150,101

66,345

216,446

69.3%

Red Sea Bream

80,957

26,161

107,118

75.6%

Coho Salmon

9,607

-

9,607

100.0%

Olive Flounder

5,241

5,917

11,15847.0%

Globefish

4,329

6,704

11,033

39.2%

Scallop

215,203

313,800

529,003

40.7%

Oyster234,151-

234,151

100.0%

Kuruma Prawn

1,818

1,044

2,862

63.5%

Nori(Laver)

358,929-358,929100.0%

Wakame Kelp

62,236

3,673

65,90994.4%

Konbu Kelp

47,253

91,122

138,375

34.1%

Source: MAFF

Source: MAFF

Table
2. PositionofofAquaculture
Aquaculture ininJapan
in 2004
Table
2 PositionJapan
in 2004

Marine Fishery(A)

Distant-water Fishery
Offshore Fishery

VolumeValue1000 ton

Billion Yen

5,670

1,500

535

169

2,406

396

Coastal Fishery

(B)

1,514

500

Aquaculture

(C)

1,215

434

Inland Fishery

106

103

Fishery

60

51

Aquaculture

(D)

46

52

Total

(E)

5,776

1,604

C/A

21.4%

28.9%

(C+D)/E

21.8%

30.3%

C/(B+C)

44.5%

46.5%

Source: MAFF

Source: MAFF

point to the preservation of the environment of

Measures for Conservation of

aquaculture grounds and the safety of aquaculture

the Environment of Aquaculture Grounds

products.

In the course of aquaculture development,
environmental problems have occurred. The fact
is that aquaculture grounds, the environmental
condition of which is suffering from excessive

137

Billion Yen

900

Coastal

800
700
600
500
400

Aquaculture

Offshore

300
200

Distant- water

100
01985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Fig. 1. Trend of the value of Japanese Fisheries.
Fig.1.
organic sediment, are expanding. Excessive

program" shall indicate the goal of theorganic loading of the sediments is primarily

improvement and indicate measures to be takencaused by high-density farming and excessive

for the improvement of environmental conditions,feeding, both of which are aimed at increasing

and shall also be authorized by a prefectural

production. In order to resolve the situation,

Governor (Figure 2).

the "Law to Ensure Sustainable Aquaculture

To be concrete, an "aquaculture ground

Production" was established in 1999 with a view

improvement program" for fish aquaculture shallto facilitating voluntary actions by fishermen toreport fish population density in the fish preserve,

promote sustainable aquaculture by improving

promote the use of assorted feeds and avoid using

and maintaining environmental conditions, and byharmful materials for livestock and so on. The

preventing the spread of fish diseases.

program for seaweed contains weed population

According to the law, the Minister for thedensity in the seaweed preserve and avoids using

Ministry of Agriculture, Forestry and Fisheries

harmful materials for livestock and so on. Whenshall develop a "Basic Guideline" which establishes

the "aquaculture ground improvement program"criteria for environmental indicators required foris not carried out, the Governor recommends

sustainable utilization of aquaculture grounds. The

the cooperative to develop thep rogram in case"Basic Guideline" established thus far contains theits aquaculture ground is recognized to befollowing three categories as the criteria:

conspicuously deteriorated, and can make it public

1. Water quality.
2. Sediment condition on the bottom ofaquaculture grounds.

if there no compliance.
In the past, farmers used fresh fish as feed, but
this leads to environmental degradation because

3. Health condition of cultured fish, includingof wastage. Now, according to the guideline

mortality rate of cultured fish by diseases.

and programs, the use of fresh fish as feed andEach fisheries cooperative that conducts

assorted feed of a type that mixes fish with dry

aquaculture, will voluntarily establish an

ingredients that is made into moist pellets has"aquaculture ground improvement program"been decreasing. The use of dry pellets which doindividually, or in cooperation with a neighboring

not incorporate fresh fish has increased in Japan

cooperative or cooperatives, for its or their(Figure 3).

aquaculture grounds, based on the "Basic

The Acid Volatile Sulfide in mud of seabed has

Guideline." The "aquaculture ground improvement

decreased after establishment of the "aquaculture

138

Ikuo TAKEDA

Fig. 2. Conceptual flowchart of the law to ensure sustainable aquaculture production.

ground improvement program" (Figure 4). Thisaquaculture production by establishingis just one example of how the environment ofand implementing the "aquaculture groundmany aquaculture grounds has been improved

improvement program" for all aquaculture grounds

since the establishment of the "aquaculture groundaround Japan.

improvement program."
Currently, nearly 85% of the production of

Measures for Ensuring Food Safety

cultured fish is farmed on aquaculture grounds

In aquaculture, residual medicines brought on

where the "aquaculture ground improvement

much criticism because it is said that aquaculture

program" has been established (Table 3). The

farming uses to much medication. To resolve thisFisheries Agency has promoted sustainable

matter, the amount and usage of medications are

139

ton

180,000

80.0%

160,000

70.0%

140,000

60.0%

120,000

50.0%

100,000

40.0%

80,00030.0%

60,00040,00020.0%

20,000

10.0%
0.0%

0
1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

"moist pellet""dry pellet"

ratio of dry pellet

AVS (Acid Volatile Sulfide) in mud of seabed

Fig. 3. Trend of production of assorted feed: distinct by form.
Fig.3.

m g/ g (m ud)

0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Fig. 4. Example of improvement of aquaculture ground.
governed by the "Pharmaceutical Affairs Law."

prevention officials use medicines and vaccines

This law regulates the usage of medicine, e.g.,in accordance with "Law to Ensure Sustainableantibiotics, in conjunction with all aquatic animals.

Aquaculture Production." As a result, the amounts

Recently, the development of vaccines for fishof damage caused by fish diseases and the salesdiseases has changed the situation with respectvolume of medicines for fish diseases havefish diseases. Furthermore, Governors can prevent

declined.

the movement of cultured organisms in caseOn the other hand, the quality of farmed fishof specific diseases outbreaks, and fish disease

is not ranked high by the public because it is felt

140

Table 3 Settlement of "Aquaculture Ground Improvement Program"
Ikuo TAKEDA

Table 3. Settlement of "Aquaculture Ground Improvement Program"

Cover Ratio*
number of "Program"
Fish

367

Shellfish

84.4%

Seaweed

48.3%

65.7%

*:"Cover ratio" is calculated as follows;
Volumein theratio"
aquaculture
ground settledof "Program" / Total aquacuture volume × 100*:"Coveris calculated
as follows;in theaquaculture
ground bysettled of the"Program"
100 was an
to be much too Volume
oily. This
problemis causedsafety /ofTotal
foodaquacuturesince 2001volume
when×there

the excessive feeding of fresh sardines. Today,

outbreak of BSE in Japan. Now, there are two key

the quality of farmed fish is improved by thewords associated with food: Those are "Anzen"

promoting the use of assorted feeds, especially dry(safety) and "Ansin" (trust). Consumers demandpellets. But the consumer's deep-seated distrust

the information about the production so they

has not been easily dispelled. Therefore, supplying

can judge whether a food is "Ansin" or not. No

correct information to consumers about the way

information means it is not "Ansin." In any case, it

fish are produced in aquaculture is very importantis thought to be important for aquaculture to farmfor increasing the market for farmed fish. Many

fish properly according to the laws and regulations

consumers who visit fish farms say that they haveand supply information about production widely.

changed their opinion about farmed fish and that

Therefore, the introduction of a traceability system

their misunderstandings were wiped away (Figure

has been favorably received by consumers. It is

5).

quite possible that farmed fish for which there is
InJapan, consumers have been concerned about

no access to information about production will be
excluded from market since consumers will not
buy them. Supplying information may become
very important to achieve sustainable aquaculture
production in Japan. A new type of Specific Japan
Agriculture Standard with Production Information
was established in 2003. In that program thevalidity of production information is certified byRegistered Certifying Bodies. Now, there are threeStandards with Production Information for beef,
pork and agricultural products. MAFF's staffs havebeen working for introduction of the standard for
cultured fish. The private sector, including farmers
and retailers, are interested in the traceability
system. Some groups consisting of farmers andretailers or farmers by themselves have alreadyFig. 5. Change of evaluation of consumers on
aquacultured fish after communication
with farmers.

established and are applying a similar system on
their own.

141
Conclusion
Marine aquaculture provides various
nutritional, social, and economic benefits tosociety. Aquaculture is and will continue to be anincreasingly important food production industry
for Japan. The Japanese experience is evidence
how uncontrolled industrial growth, including
aquaculture itself, can pollute coastal waters anddestroy valuable aquaculture food resources, but
this can be prevented by proper regulation. On theother hand, the environments that were damaged
can be recovered through proper management
and great effort. Furthermore, acquiring theconfidence of consumers is very important forsustainable aquaculture production. Regulation
alone may not produce consumer confidence;that can only be gained through the provision of
accurate information on production methodology
and product healthfulness.