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

Preliminary observation of environmental factorsaround offshore cage system in Jeju island

18th July 2005

Won Chan Lee, Rae Hong Jung, Hyun Taik Oh

Contents

I. Introduction

III. Preliminary observation

IV. Future work

II. Case Study

Offshore fish cage NFRDI

Ⅰ. IntroductionⅠ. Introduction

Offshore fish cageOffshore 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

Offshore fish cageOffshore 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

Ⅰ. IntroductionⅠ. Introduction

Ⅱ. Case study : Mass balanceⅡ. Case study : Mass balance


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)

Fish cage

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



ResultsNitrogen 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)



Fig. Nitrogen mass balance in the cage farm

- TEL : 71.3%

Ⅱ. Case study : Spatial extentⅡ. Case study : Spatial extent


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



0%

20%

40%

60%

80%

100%

0m 2m 5m 10m 15m 20m 30m 60m

Distance(m)

0%20%

40%

60%

80%100%

0m 5m 15m 30m 50m

Distance

TS

0%

20%

40%

60%

80%

100%

0m 5m 15m 30m 50m

Distance

TE

Polychaeta Crustacea Mollusca Echinodermata Others

Farm A

Farm B

Numerical Composition of Major Taxonomic Groups


0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 2 5 10 15 20 30 60

Distance(m)

Div

ersi

ty(H

')

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 5 15 30 50

Distance(m)

TS TE

Distribution of Ecological Index

0

5000

10000

15000

20000

Abu

ndan

ce(in

d./m

2 )

0

10

20

30

40

50

Num

ber

of S

peci

es

0

5

10

15

20

25

0

1000

2000

3000

4000

5000

6000

7000

Farm A Farm B




0

400

800

1200

1600

2000

0 2 5 10 15 20 30 60

Distance(m)

Cirratulidae sp.

0

200

400

600

800

0 5 15 30 50

Distance(m)

Sigambra tentaculata

0

5000

10000

15000

20000

Capitella cpitata

0

400

800

1200

1600

2000

Lumbrineris longifolia

0

400

800

1200

1600

2000

Tharyx multifilis

0

200

400

600

800

Ab

un

da

nce(i

nd

./m

2 )

Dorvillea rudolphi

0

100

200

300

400

500

Mediomastus californiensis

0100200300400500600

TS TE

Capitella cpitata

0300600900

120015001800

Lumbrineris longifolia

0

1000

2000

3000

4000

5000

6000

Tharyx multifilis

0

50

100

150

200

250

Dorvillea rudolphi

0

30

60

90

120

150 Mediomastus californiensis

Distribution of dominant species



T-0mT-2m

T-5m

T-10m

T-15m

T-20m T-30m

T-60m

TE-0mTE-5m

TE-15m TE-30m

TE-50m

TS-0mTS-5m

TS-15m

TS-30mTS-50m

Stress: 0.05

Farm A

Farm B

Highly enriched Slightly enriched

Results of MDS (Multi-Dimensional Scaling)



0

20

40

60

80

100

0 2 5 10 15 20 30 60

Distance(m)

ITI

Ind

ex

0

20

40

60

80

100

0 5 15 30 50

Distance(m)

ITI

Inde

x

> 50 : little effect, 20 – 50 : enriched, < 20 : degraded

N1 : suspension feederN2 : surface detritus feederN3 : surface deposit feederN4 : subsurface deposit feeder

Distribution of Infaunal Trophic Index (ITI)

Farm A Farm B


Ⅲ. Preliminary observation Ⅲ. Preliminary observation

1st monitoring : 15th – 16th June 2005 - physical factors : WT, salinity etc.

- current : draft (1hr), RCM 9 Mk (25hr)Ⅱ

2nd monitoring : 13th – 14th July 2005 - physical and chemical factors - benthic fauna

- current : ADCP (16 days) 18th July



W.T. (oC)

16 18 20 22 24

Dep

th (m

)

50

40

30

20

10

0

(Cage)

W.T. (oC)

16 18 20 22 24

50

40

30

20

10

0

(100m)

W.T. (oC)

16 18 20 22 24

50

40

30

20

10

0

(500m)

Sal.

31.5 32.0 32.5 33.0 33.5 34.0 34.5 35.0

Dep

th (m

)

50

40

30

20

10

0

(Cage)

Sal.

31.5 32.0 32.5 33.0 33.5 34.0 34.5 35.0

50

40

30

20

10

0

(100 m)

Sal.

31.5 32.0 32.5 33.0 33.5 34.0 34.5 35.0

50

40

30

20

10

0

(500 m)

Distribution of physical factors around offshore cage in June



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


Ⅳ. Future workⅣ. Future work

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 !

Documents

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