Satoumi approach for realizing sustainable
coastal use in a rias-type bay:a case of Shizugawa Bay in Sanriku Coast hit
by the huge tsunami on 11 March 2011
Teruhisa Komatsu, Shuji Sasa
(The University of Tokyo)
Shigeru Montani(Hokkaido University)
Osamu Nishimura, Takashi Sakamaki(Tohoku University)
Chihiro Yoshimura, Manabu Fujii(Tokyo Institute of Technology)
andTetsuo Yanagi(EMECS Center)

Sato-umi“Sato-umi” ：Coastal waters of which theproductivity and biodiversity are increased byhuman activities(Yanagi, 1998)

Why did we start to study Shizugawa Bay after thehuge tsunami?

5 km

1. Typical rias-type bay along Sanriku Coast with spatial scale suitablefor our study
2. Watersheds flowing into the bay located only inside Minami
Sanriku Town
3. Local fishermen’s request for us to provide an optimal number anddeployment of aquaculture facilities
4. NPO’s cooperation for sampling river and sea waters

Huge tsunami on 11 March 2011
14.4m

Huge tsunami hit
mainly Sanriku CoastMovement of fishermen toward sustainable coastal
fisheries after 2011 andJapanese Ministry of Environment initiative to useSatoumi activities for realizing the healthy coastal sea
since 2013
1.
2.
3.
4.

Initiative of President of Shizugawa Bay Management Committeeof Miyagi Fisheries Cooperative and representatives of oyster
culture in Shizugawa Branch area and Tokura Branch area
Gambaru Fisheries policy by Fisheries Agency to promote rapid
recover of coastal fisheries by supplying fishing gears and funds togroups of fishermen
Gambaru Fisheries stimulating discussion among fishermenthough sharing all boats and fisheries facilities
Research groups on Satoumi activities organized by the Japanese
Ministry of Environment have been initiated since 2013

S13-2

Framework of research
Establishment of relation between people and healthy marine environments with richbiodiversity in open type semi-enclosed sea
Development of monitoring system of coastal ecosystem and management system ofcoastal waters
Quantitative evaluation of “a forest is a lover of the sea “ hypothesis underlying a projectof cooperation among forests, villages, rivers and the sea to ensure a healthy material flow
Consensus building to decrease aquaculture facilities using ecological modeling codesigned by stakeholders

Enhancement of productivity andbiodiversity by satoumi activities

Realize sustainable and prosperous human society basedon healthy coastal waters with rich biodiversity

Monitoring a recovery process of seagrass and seaweed
beds with satellite remote sensing
Nov. 2009

Seagrass beds

Feb. 2012

Jan. 2014(ha)

Seaweed beds
Recovered seagrass beds

Growing on
hard debris

Removal ofhard debris

Seagrass beds not recovered yet

Nov. 2009 Feb. 2012

Jan. 2014

Visualization of devastated seaweed beds withsatellite remote sensing
2014年から各所でウニによる磯焼けの発生
Importance ofmonitoring of atransitional
coastal ecosystemSeaweed bed:
Sargassum horneri
ShizugawaPort

Seaweed bed:
Saccharina japonica

Devastated seaweed
beds by sea urchins

Seagrass bed
Muddy bottom
1 km（GeoEye-1 shot on 12 Feb. 2015）

Sea urchin fisheries to support biodiversity incoastal waters: Satoumi activity
(t)

2500
2000
1500
1000
500
02000

PrefectureIwate
岩手Miyagi
宮城

2005

2010

2015

Landing of sea urchins (t) Statistics of agriculture,
forestry and fisheries

Explosive increase in sea
urchins due to stop offisheries

Trophic cascade

West of Tsubaki Island in January 2015

Mapping aquaculture facilities in inner area of Shizugawa
Bay where oyster culture is very active
Shizugawa Branch area

Tokura Branch area

3 February 2009

Shizugawa Branch area

Tokura Branch area

15 January 2014

Red and blue polygons indicate aquaculture areas permitted to Tokura Branch andShizugawa Branch of Shizugawa District Fishermen’s Cooperative
Green, red and yellow are seaweed, oyster and salmon aquaculture, respectively

Rafts (num)Rafts (num)Temporal changes in aquaculture facilities of oyster andseaweed in Tokura (red) and Shizugawa (blue) areas

OysterSeaweed

Decreasees of rafts toDecrease of rafts to
30% in Tokura and 50%
30% in Tokura
in Shizugawa
Sustainable production and environment

Why did the fishermen’s cooperative succeed todiminish oyster rafts
1. Experience of slow growth of oysters before the tsunamithat need more than three years for landing
2. Experience of rapid growth of oysters after the tsunami
because small number of rafts had been deployed andmore than 10 months culture is sufficient for landing

3. Gambaru Fisheries policy by Fisheries Agency to promote
rapid recover of coastal fisheries by supplying fishing gears
and funds to groups of fishermen
4. Discussion among fishermen who shared fishing gears,
funds and boats

Growth of oysters
Wet weight of flesh (g/ind)
C-0m
D-0m

Shizugawa Branch area

Decrease in rafts to 50%

BD

B-0m
A-0m

AC

Decrease in rafts to 30%
Tokura Branch area

A-0m
B-0m
C-0m
C-8m
D

Oysters in Tokura grow better than in Shizugawa

Organic carbon content in feces and pseudofeces of oyster
depending on age
Increase in growth of oyster due todiminution of rafts shortens culture
duration from more than 18 months
to more than 10 months
Increase in flesh of oyster（>20g/ind）

We compared the oxygen consumption rates offeces and pseudofeces from oysters withdifferent ages, 4 – 28 months.

Increase in oxygen consumption rate due toincrease in organic carbon content in feces
and pseudofeces through decrease inassimilation rate by aging

Diminution of rafts
combining increase inproductivity of oysterwith decrease inenvironmental load
14

Assessment of oyster culture impact on dissolved oxygenand oxygen demand of sedimentwith a bottle method
Oxygen budget of water column
Bay head

1993年

Bay head

Water way

Oyster culture

Bay head

15 September 2015

Oxygen demand of sediment is decreased from 1993 to 2015 due to diminution ofrafts and amelioration of bottom sediments by the tsunami in 2011: Monitoring!

Afforestation by fishermen’s cooperativein mountains around Shizugawa Bay
Afforestationarea

Fishermen believe that forests of broad-leaved trees supply more Fe to the bay
through the river, which is indispensable for marine plants based on Prof.
Mtsunaga’s hypothesis.
Good effects of the forest on organic matters and nutrients are also expected.
One fisherman Mr. Hatakeyama in Sanriku Coastnamed it “the forest is the lover ofthe sea”.

Preliminary overview on standing stocks and flux of nutrients S13-2-(2)in inner area of Shizugawa Bay in October 2015
Landing

DIN controls primary production
Transfer rate of C: 2%

Standingstock(mg/m2)
Flux (mg/m2/d)+: into the system-: out from the system

Inflow from rivers
DIN: +8.1
DIP: +0.2
DSi: +55.1

Microalgae
POC: 1055
PON: 182
PP:25
Primary
productivity
C: +1058
N: + 168
P: + 26
SuspendedparticlesSedimentation
C: -1245
N: -167
P: -29Macroalgae etc.

Oyster
C: 2109
N: 491
P:?

Regeneration
rate of urine
DIN: +1.6
DIP: +0.2

Nutrients
DIN: 184
DIP:73
DSi: 9792

Waterexchange
DIN: +54.5
DIP: +0.4
DSi: +1599

Feces andpseudofeces
Regeneration rate
DIN: +0.08
DIP: +0.002

DIN from the rivers is a quarter of that from the open sea
DIN from oyster is 7% of its standing stock in the bay headPreliminary overview of standing stock and flux of Fe in inner area ofShizugawa Bay in July2014

With freshwater from land
3.4 kg/d

To the bay
Sedimentation 0.31 kg/d
in estuaries
3.1 kg/dRiver discharge supplies
22% of Fe for Fe requiredby phytoplanktons

Phytoplankton
5.0 kg*Feeding
0.03 kg/d

Intake of Fe
1.4 kg/day
Dissolved Fe
130 kg? ？？

Oyster andother bivalves
0.5 kgOpenseaPreliminary overview of particulate organic matter (Carbon t/d) in July 2014
Exchange with atmosphere

LandRiversRiver
discharge
0.26

Open ocean

Dissolved
inorganiccarbonPOM, DOM,
Zooplankton andphytoplankton
42.80

inflow
outflow

Feeding 0.70 Oysters andothers
12.83
Feces and pseudofeces
0.14

sedimentation
0.51

Net
1.91

outflow
10.32

inflow
8.41

Resuspension
海底泥Supply of POM from the rivers is little due to small
quantity of water discharge
Primary production is the most important for POM

Standing stock：tflux：t/d

Results from Shizugawa Bay• Monitoring ecosystems and fisheries activities is important• Sea urchin fisheries as human activity is indispensable forseaweed beds that foster many marine organisms• DIN controls primary productivity• Cultured oysters influence greatly nitrogen flow in inner bay• Fe from the rivers is small relative to requirements• Diminution of oyster rafts contributes to amelioration of marineenvironment• Oysters may be landed in one year culture rather than threeyears culture to decrease environmental load under small
number of rafts

Reproduction and prediction of marine environments
in Shizugawa Bay by using ecological simulation
Co-design with Fishermen, administrators of MinamiSanriku Town and Miyagi Prefecture and us
Reproduction：
Marine environments before and after the tsunami
for tuning the modelPrediction：
Number of rafts and their deployment, and land use
including forests for examining sustainable fisheries toharmonizing healthy marine environments

Co-design: discussion for developing an
ecological model of Shizugawa Bay on 14 July

Discussion among Minamisanriku Town, Shizugawa Bay
Management Committee of Miyagi Fisheries Cooperative to explore
the number of rafts and deployment for sustainable aquaculture andhealthy marine environments

The first council for examination of future Shizugawa Bay
１．Date 30 April 2015
２．Place Public hall of Shizugawa Town
３．Organizer Committee for examination of future Shizugawa Bay
４．Participants： 16 fishermen, 3 cooperative officers, 3 Miyagi Prefectureofficers, 2 Minami Sanriku Town officers, 1 journalist, 1 WWF officer and10 researchers
５．Objective Introduction of project of Shizugawa Bay Research anddiscussion on the research results and environments of Shizugawa Bay inthe future.

The second council for examination of future Shizugawa Bay
１．Date 19 May 2016
２．Place Conference room of Shizugawa Branch, Miyagi PrefecturalFisheries Cooperative
３．Organizer Council for examination of future Shizugawa Bay
４．Participants： 6 fishermen, 3 cooperative officers, 2 Miyagi Prefectureofficers, 1 Ministry of Environment officer, 1 Ishinomaki City officer, 1WWF officer and 11 researchers
５．Objective Introduction of project of Shizugawa Bay Research anddiscussion on the research results, environments of Shizugawa Bay in thefuture and ASC certificate with marine environments.

Co-design, co-production, co-delivery

S13-2Co-production with Fishermen’s Cooperative and ＷＷＦ

Providing rafts data for acquisition of ASC certificate that proves
sustainable aquaculture and respect for healthy environments

Our results can apply to rias-type
enclosed bays open to the ocean
Discharge from the river is small
DIN that controls primary productivity in a bay
Active aquaculture of bivalves

Ago Bay in Shima Peninsular

Misho Bay in Shikoku IslandБольшое спасибо!
Thank you very much!

Prosperous Satoumi villages with healthy coastal sea withhigh biodiversity and productivity, and sound marine
environments
http://www.jarlchiba.com/2009/%E5%A4%A7%E6%A9%8B%E4%BA%8B%E5%8B%99%E5%B1%80%E9%95%B7/%E8%8A%B120.htm