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Busan, South Korea

Kim J.Y.,Gyeongnam Development Institute | Jeong H.C.,University of Suwon | Kim H.,Southwest Research Institute | Kang S.,NFRDI
Fisheries Research | Year: 2015

Japanese anchovies, Engraulis japonicus, have exhibited substantial fluctuations in production in Korean waters. Anchovy drag net and drift gillnet fisheries are the major types of fishery that target different sizes of anchovies during different fishing seasons. We analyzed the monthly catch per unit effort (CPUE) for 1987-2012 using exponential smoothing methods, seasonal autoregressive integrated moving average (SARIMA), autoregressive neural network (ANN), and autoregressive recurrent neural network (ARNN) models to forecast the abundance of anchovies based on the fishing conditions. For the drag net fisheries, SARIMA provided better statistical insight than the other models, but the ARNN model was best for future forecasting (r2=0.819, PI=0.733). Additive Winters' exponential smoothing (AWES) was the most effective of the three smoothing methods, but its validation was poor compared with SARIMA and the other neural network models. AWES, SARIMA, ANN and ARNN were less suitable for the drift gillnet fisheries. A comparison of the CPUE of drift gillnet fisheries to that of drag net fisheries showed that the data had been contaminated by factors such as periods when anchovy fishing was prohibited or a fishery had been abandoned due to economic reasons, rather than biological factors. Nevertheless, ARNN proved to be an effective and accurate model in the training phase, and its forecasts showed a comparatively strong statistical performance (r2=0.797, PI=0.662) in the context of short-to-medium-length time periods. Additionally, whereas SARIMA performed worse than ANN or ARNN, its forecasting capability was comparatively satisfactory (r2=0.713, PI=0.584). Finally, SARIMA has the advantage of providing statistical descriptions of the catches. © 2014 Elsevier B.V. Source

Jun J.-C.,NFRDI | Chung E.-Y.,Kunsan National University | Lee K.-Y.,Kunsan National University | Lee C.-H.,NeoEnBiz
Invertebrate Reproduction and Development | Year: 2014

The gametogenic cycle and number of spawning seasons per year of the female Chlamys (Azumapecten) farreri farreri were investigated by qualitative and quantitative analyses, and also the size at 50% of group sexual maturity (the size of first sexual maturity) was calculated to inform natural living resource management. In qualitative histologic analysis, the gametogenic cycle of this species can be classified into five successive stages: early active stage, late active stage, ripe stage, partially spawned stage, and spent/inactive stage. The spawning season occurs annually from July to September. In quantitative statistical analysis using an image analysis system, the patterns of monthly changes in reproductive cells were shown to be maximum in June and then dropped sharply from July to September. From these data, it is apparent that the C. (A.) farreri farreri has a unimodal annual gametogenic cycle. Shell heights at 50% of group sexual maturity were estimated as 51.47 mm and was 100% for scallops over 61.0 mm. © 2014 Taylor & Francis. Source

Jin J.W.,Pukyong National University | Kim K.I.,NFRDI | Kim J.K.,Pukyong National University | Park N.G.,Pukyong National University | Jeong H.D.,Pukyong National University
Aquaculture | Year: 2014

Megalocytivirus is a major viral agent that affects fresh and marine fish, and causes serious economic losses in aquaculture in Asian countries. As filter-feeding organisms, bivalve molluscs may act as viral transmitters following the capture of a released virus into seawater from infected fish. We identified megalocytivirus, rock bream iridovirus (RBIV) type in Pacific oysters (Crassostrea gigas) and blue mussels (Mytilus edulis) inhabiting the areas around rock bream farms in Korea. In artificial viral-depuration analysis, the concentration of iridovirus Sachun (IVS) particles, which is a major RBIV strain in Korea, decreased more rapidly in seawater than in the digestive glands of mussels. Cohabitation of mussels with IVS-infected rock bream (Oplegnathus fasciatus) resulted in the presence of viral particles in the gill, mantle and digestive gland of the mussels. In addition, the virus was retained in the digestive gland for 28. days, regardless of water temperature. Infection with IVS derived from the digestive gland of cohabitating mussels also led to 100% cumulative mortality in rock breams. In this study, we investigated megalocytivirus carried by bivalve molluscs inhabiting the vicinity of rock bream farms, and revealed the potential risk posed by these viral particles by modelling the cohabitation of mussels with RBIV-infected rock bream. © 2014 Elsevier B.V. Source

We compiled and analyzed past time-series data to evaluate changes in oceanographic conditions and marine ecosystems near the Ieodo ocean research station (IORS) in the East China Sea (N 31°15′-33°45′, E 124°15′-127°45′) in relation to longterm changes in climate and global warming. The environment data we used was a depth-specific time-series of temperature and salinity for the water columns at 175 fixed stations along 22 oceanographic lines in Korean waters, based on bimonthly measurements since 1961 taken by the National Fisheries Research & Development Institute. As an indicator for the ecosystem status of the waters off Ieodo, we analyzed species composition in biomass of fishes caught by Korean fishing vessels in the waters near the IORS (1984-2010) and summarized the data in relation to the environmental changes using canonical correspondence analysis (CCA). To detect step changes in the time-series of environmental factors, we applied a sequential t-test analysis of regime shift. Correspondence analysis detected a major shift in fish assemblage structure between 1990 and 1993: the dominant species was filefish during 1981-1992, but chub mackerel during 1992-2007. This shift in fish assemblage structure seemed to be related to the well-established 1989 regime shift in the North Pacific, which was confirmed again with respect to temperature in the Yellow Sea and the Korea Strait (but not in the waters off the IORS). In overall from 1984 to 2010, salinity was more important than water temperature in CCA, implying that the fluctuation of the Tsushima warm current is a most important force driving the long-term changes in fish assemblage structure in the waters off the IORS. Further multidisciplinary researches are required to identify oceanographic and biological processes that link climate-driven physical changes to fish recruitment and habitat range fluctuations. © 2012 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Netherlands. Source

Kang H.J.,Pukyong National University | Zhang C.I.,Pukyong National University | Lee E.J.,NFRDI | Seo Y.I.,NFRDI
Ocean Science Journal | Year: 2015

Hairtail (Trichiurus lepturus) has been traditionally harvested by multi-gear types in the Yellow Sea and the East China Sea, except for the East Sea (Sea of Japan) in Korean waters. Six different fishery types such as offshore stownet fishery, offshore longline fishery, large pair-trawl fishery, large purse seine fishery, large otter trawl fishery and offshore angling fishery target to harvest the hairtail stock accounting for about 90% of the total annual catch. We attempted to develop an ecosystem-based fisheries assessment approach, which determines the optimal allocation of catch quotas and fishing efforts for major fisheries. We conducted standardization of fishing effort for six types of hairtail fisheries using a general linear model (GLM), and then estimated maximum sustainable yield (MSY) and maximum economic yield (MEY). Estimated MSY and MEY for the hairtail stock were estimated as 100,151 mt and 97,485 mt, respectively. In addition, we carried out an ecosystem-based risk analysis to obtain species risk index (SRI), which was applied to adjusting the optimal proportion of fishing effort for six hairtail fisheries as a penalty or an incentive. As a result, fishing effort ratios were adjusted by SRI for the six fisheries types. Also, the total allowable catch (TAC) was estimated as 97,485 mt and the maximum net profit at TAC by the hairtail fisheries was estimated as 778 billion won (USD 765 million). © 2015, Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht. Source

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