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 I. Introduction III. Preliminary observation IV. Future work II. Case Study Offshore fish cageNFRDI

Ⅰ. Introduction 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

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 Ⅰ. Introduction

Ⅱ. Case study : Mass balance Offshore fish cageNFRDI  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

Ⅱ. Case study : Mass balance Offshore fish cageNFRDI 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  S edimentation flux : 1055 Nmg/m 2 /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)

Ⅱ. Case study : Mass balance Offshore fish cageNFRDI Fig. Nitrogen mass balance in the cage farm - TEL : 71.3%

Ⅱ. Case study : Spatial extent Offshore fish cageNFRDI  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

Ⅱ. Case study : Spatial extent Offshore fish cageNFRDI Farm A Farm B Numerical Composition of Major Taxonomic Groups

Offshore fish cageNFRDI Distribution of Ecological Index Farm A Farm B Ⅱ. Case study : Spatial extent

Offshore fish cageNFRDI Ⅱ. Case study : Spatial extent Distribution of dominant species

Offshore fish cageNFRDI Ⅱ. Case study : Spatial extent T-0m T-2m T-5m T-10m T-15m T-20m T-30m T-60m TE-0m TE-5m TE-15m TE-30m TE-50m TS-0m TS-5m TS-15m TS-30m TS-50m Stress: 0.05 Farm A Farm B Highly enrichedSlightly enriched Results of MDS (Multi-Dimensional Scaling)

Offshore fish cageNFRDI Ⅱ. Case study : Spatial extent > 50 : little effect, 20 – 50 : enriched, < 20 : degraded N 1 : suspension feeder N 2 : surface detritus feeder N 3 : surface deposit feeder N 4 : subsurface deposit feeder Distribution of Infaunal Trophic Index (ITI) Farm AFarm B

Offshore fish cageNFRDI Ⅲ. Preliminary observation  1 st monitoring : 15 th – 16 th June physical factors : WT, salinity etc. - current : draft (1hr), RCM 9 Mk Ⅱ (25hr)  2 nd monitoring : 13 th – 14 th July physical and chemical factors - benthic fauna - current : ADCP (16 days) 18 th July

Offshore fish cageNFRDI Ⅲ. Preliminary observation Distribution of physical factors around offshore cage in June

Offshore fish cageNFRDI Ⅲ. Preliminary observation Current speed & direction at 30m depth - semi-diurnal - 1.1m/s - NE ~ NW Draft trajectory at 2m, 20m depth - NE km of 2m, 0.55km of 20m - 35cm/s of 2m, 14.3cm/s of 20m

Offshore fish cageNFRDI Ⅳ. Future work  establish monitoring methodology : 1 st stage - gathering & analyzing previous research paper - co-work with NOAA  assess environmental effect : 2 nd stage - sediment chemistry - benthic fauna analysis  estimate mass balance : 3 rd stage - nitrogen or phosphorus

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