# Presentation: 939314

## Preliminary observation of environmental factors

**Preliminary observation of environmental factors**
**around offshore cage system in Jeju island**

**18****th**** July 2005**
- Won Chan Lee, Rae Hong Jung, Hyun Taik Oh

##  Contents

**Offshore fish cage**

**NFRDI**

##   Fish culture in the coastal waters of many countries has grown dramatically 

**Offshore fish cage**

**Offshore fish cage**

**NFRDI**

-  **** Fish culture in the coastal waters of many countries has grown dramatically
-      in recent years, and further growth is expected in coming decade (FAO)
-      - Fish culture production : 2,000 ton (’96) → 37,000 ton (2003)

-  ****** **The  rapid growth  led to growing concerns on  environmental impact
-     1) Dispersion high organic and nutrients → Eutrophication, HAB
-           - 85% of  P, 80-88% of C, 52-95% of N as feed supply to environment
-           - add organic load of  cleaning fouled cage to water
-     2) Deposition high organic matter → anoxic, changing benthic ecosystem
-   - organic contents of sediment is10 times higher than another coastal zone
-   - macrofauna is lower species diversity & opportunistic species
-    3) Chemicals (therapeutants, vitamins and antifoulants) , pathogens and
-   new gene strains are raising environmental concerns

**Notes:**
High organic & nutrient loadings are mainly generated from feed wastage, fish excretion and faecal production. 

##       marine fish-farming offshore in USA, Scotland and Hong Kong etc

**Offshore fish cage**

**Offshore fish cage**

**NFRDI**

-  **** To prevent environmental effect of fish cage, there is a general tendency to force
-       marine fish-farming offshore in USA, Scotland and Hong Kong etc

-  ****** **to establish monitoring methodology for environmental impact of offshore
-      fish cage
-      - physical, chemical and benthic animal factors

##  Farm site : Hakdong, 16 net cage(6x6m wide, 5m deep)

**Offshore fish cage**

**NFRDI**

**** Farm site : Hakdong, 16 net cage(6x6m wide, 5m deep)
**** Culturing period : Feb. to Dec., 1998
**** N, P in fish and fish food : CHN analyzer/ Acid digestion
**** Sedimentation flux : U-type sediment trap, 10m, 1day
**** Benthic flux : Chamber (50cm x 7cm diameter)

_**Parameters used in mass balance**_
** ****** Total Environmental Loss (TEL)
-       :  (fish food and juveniles) – (harvest and fish loss)
** ****** Introduction Environmental Loss
-       :  TEL - sediment accumulation
** ****** Dispersion release from the cage
-      :  TEL - sedimentation
** ****** Sedimentation accumulation
-      :  Sedimentation - benthic flux

## Results

**Offshore fish cage**

**NFRDI**

- _Results_
- _Nitrogen is key element_ in aquatic environments and aquaculture systems
** ****** N contents is 3.5% of fish food and 2.5% of fish body
** ******** **Sedimentation flux : 1055 Nmg/m2/day** **
** ******** **Benthic flux : 47 Nmg/m2/day

- _Summary of  nitrogen mass balance in % of total input_   unit (kg N)
** ****** Fish food : 2,548 (95.5%), Juveniles : 121 (4.5%)
** ******** **Harvest : 704 (26.4), Fish loss : 63 (2.4%)** **
** ******** **Sedimentation flux : 218 (8.2), Benthic flux : 11 (0.4)
** **- Total environmental loss : 1,901 (71.3)
-  - Introduction environmental loss : 1,694 (63.5)
-  - Dispersion release : 1,683 (63.1)
-  - Sediment accumulation : 207 (7.8)

**Notes:**
N is considered to be the limiting nutrient for primary production in coastal areas.

## Fig. Nitrogen mass balance in the cage farm

**Offshore fish cage**

**NFRDI**

- - TEL : 71.3%

##      - visual diving survey, benthic faunal analysis, sediment chemistry, sediment profile imagery

**Offshore fish cage**

**NFRDI**

-  **** Monitoring method to assess the environmental impact by Carroll et al (2003)
-      - visual diving survey, benthic faunal analysis, sediment chemistry, sediment profile imagery
-       - All method is very well agreement on impact zone , but BFA is the most sensitive method

## Farm A

**Offshore fish cage**

**NFRDI**

**Farm** A

**Farm** B

**Numerical Composition of Major Taxonomic Groups**

## Distribution of Ecological Index

**Offshore fish cage**

**NFRDI**

**Distribution of Ecological Index**

## Distribution of 

**Offshore fish cage**

**NFRDI**

- Distribution of
-     dominant species

## Results of MDS (Multi-Dimensional Scaling)

**Offshore fish cage**

**NFRDI**

**Results of MDS (Multi-Dimensional Scaling)**

## Distribution of Infaunal Trophic Index (ITI)

**Offshore fish cage**

**NFRDI**

**Distribution of Infaunal Trophic Index (ITI)**

- Farm A

- Farm B

##   1st  monitoring : 15th – 16th June 2005

**Offshore fish cage**

**NFRDI**

-  **** 1st  monitoring : 15th – 16th June 2005
-       - physical factors : WT, salinity etc.
-        - current : draft (1hr), RCM 9 Mk II(25hr)

-  **** 2nd monitoring : 13th – 14th July 2005
-       - physical and chemical factors
-        - benthic fauna
-        - current : ADCP (16 days) 18th July

## Distribution of physical factors around offshore cage in June

**Offshore fish cage**

**NFRDI**

**Distribution of physical factors around offshore cage in June**

## Current speed & direction 

**Offshore fish cage**

**NFRDI**

- Current speed & direction
-   at 30m depth
-  - semi-diurnal
-  - 1.1m/s
-  - NE ~ NW

- Draft trajectory at 2m, 20m depth
-  - NE
-  - 1.12km of 2m, 0.55km of 20m
-  - 35cm/s of 2m, 14.3cm/s of 20m

##  establish monitoring methodology : 1st  stage

**Offshore fish cage**

**NFRDI**

**** establish monitoring methodology : 1st  stage
-      - gathering & analyzing previous research paper
-      - co-work with NOAA

**** assess environmental effect : 2nd stage
-      - sediment chemistry
-      - benthic fauna analysis

**** estimate mass balance : 3rd stage
-      - nitrogen or phosphorus

## Thank you for your attention !

**Thank you for your attention !**