Young-Il Seo

Four cDNAs encoding lipoprotein receptors from shrimp (Pandalopsis japonica): structural characterization and expression analysis during maturation.

As in all other oviparous animals, lipoprotein receptors play a critical role in lipid metabolism and reproduction in decapod crustaceans. Four full-length cDNAs encoding lipoprotein receptors (Paj-VgR, Paj-LpR1, Paj-LpR2A, and Paj-LpR2B) were identified from Pandalopsis japonica through a combination of EST screening and PCR-based cloning. Paj-LpR1 appears to be the first crustacean ortholog of insect lipophorin receptors, and its two paralogs, Paj-LpR2A and Paj-LpR2B, exhibited similar structural characteristics. Several transcriptional isoforms were also identified for all three Paj-LpRs. Each expression pattern was unique, suggesting different physiological roles for these proteins. Paj-VgR is an ortholog of vitellogenin (Vg) receptors from other decapod crustaceans. A phylogenetic analysis of lipoproteins and their receptors suggested that the nomenclature of Vgs from decapod crustaceans may need to be changed. A PCR-based transcriptional analysis showed that Paj-VgR and Paj-LpR2B are expressed almost exclusively in the ovary, whereas Paj-LpR1 and Paj-LpR2A are expressed in multiple tissues. The various transcriptional isoforms of the three Paj-LpRs exhibited unique tissue distribution profiles. A transcriptional analysis of each receptor using tissues with different GSI values showed that the change in transcription of Paj-VgRs, Paj-LpR2A and Paj-LpR1 was not as significant as that of Vgs during maturation. However, the transcriptional levels of Paj-LpR2B decreased in ovary at maturation, suggesting that their transcriptional regulation is involved in reproduction.

Study for fishery management measure on gape net with wings with catch composition in the water of Jin-do

In this study, we conducted field surveys to investigate and analyze species and length composition of catch from gape net with wings being set in two areas - Masari, Supomri - located in southern part of Jin-do for understanding fishing characteristics of gape net with wings fishery from March to September of 2011. And with those results, we attempted to propose fishery management strategy to harvest fisheries resources continuously. Catch obtained from field surveys comprised total 78 species, which accounted for 53 species of fish, 20 species of crustacean, 4 species of cephalopod and one of polychaete. As to species composition in weight, it showed that there was 88.5% for pisces, 9.0% for cephalopoda and 2.5% for crustacea. As to catch specifics by area, there was 36 species (596,891 individual, 456,551g) of pisces, 17 species (35,815 individual, 12,909g) of crustacea and 3 species (2,876 individual, 3,004g) of cephalopoda in Masari area. In Supumri area, there was 41 species (396,898 individual, 281,457g) of pisces, 15 species (16,113 individual, 7,772g) of crustacea and 4 species (6,792 individual, 72,329g) of cephalopoda and one polychaeta (36 individual, 11g). Catch of anchovy by month recorded on high level on June, July, September in both areas. When considering size composition by month, it was found that new populations recruit to these fishing grounds on June and September. Most of bycatch species including hairtail (Trichiurus lepturus), dotted gizzard shad (Konosirus punctatus), conger eel (Leptocephalous), Pacific sandlance (Ammodytes personatus), horse mackerel (Trachurus japonicus) were juvenile, and grass puffer (Takifugu niphobles), Kammal thryssa (Thryssa kammalensis), Japanese sardinella (Sardinella zunasi) were also small in size. As a result, it is considered that gape net with wings fishery which is likely to catch juvenile needs to be set fishing prohibit period for conserving above stocks during the period excluding main fishing periods of anchovy or fisheries management such as expanding mesh size for preventing juvenile catch.

A Study on Fisheries Management of Ecosystem-Based TAC using a Linear Programming

This study aimed to empirically investigate the applicability of ecosystem-based TAC (Total Allowable Catch) fisheries management targeting the large purse seine fishery where multi-species are regulated by TAC. Using a linear programming, the optimal fishing effort and the catch amount by species which maximize fishing profits were analyzed under the constraint condition of catch limits by species. Analytical results showed that an application of TAC on only chub mackerel would have negative impacts on fish stocks such as hairtail and jack mackerel by increasing the level of fishing effort to achieve its allocated catch limit. However, under the constraint condition of catch limits of all species, it was shown that optimal catches of all species were achieved within their catch limits. It implies the importance of ecosystem-based management considering biological and technical interactions of species those were excluded in the traditional single species fisheries management.

Distribution characteristic of Octopus minor in the Tando Bay on the southwest coast of Korea

This study is to find out the distribution characteristic of Octopus minor in the Tando Bay on the southwest coast of Korea with conducting surveys from May of 2006 to April of 2007. Surveys were carried out at 20 stations on 2 and 3 tide time in the low speed of high tide at night and conducted during 30minutes (4 times fishing) per station. Catch per unit effort (CPUE) was estimated by total catch per 500hooks at each station. Monthly CPUE showed that they put highest in October, November, April and June at 10.4, 10.5, 9.4 and 7.7 individuals respectively. On the other hand, CPUE put lowest in January, the coldest month, and August, the hottest month, at 0.2 and 0.3 individuals respectively. As for geographical mantle length distribution, average mantle length ranged from 6.2cm to 7.3cm at stations near the tidal channels (St. 1, 4, 5, 6, 8, 9, 10, 13, 14, 15, 18, 19 and 20), and was smaller than 6.0cm at stations located inside of bay (St. 2, 3, 7, 11, 12 and 17). In terms of geographical distribution density, CPUE showed higher than 8.0 at St.4 in Changmaeri, St.8 in Taecheonri, St.13 near Seondo, St.18 in Naeri and St.14 in western part of Tando which are located near the main tidal channels. And distribution density showed low that CPUE was lower than 5.0 individuals at stations located inside of bay (St. 1, 3, 5, 6, 7, 11, 12, 16 and 20). Through the results, the difference of distribution density reflects that distribution of Octopus minor is affected by direction of current and inflow of pollutant from land in direct. Therefore, it is considered that bottom composition of tidal flat and distribution of live food are the crucial cause of identifying the distribution characteristics of Octopus minor. For this reason, it is judged to need additional research on it.

A modified von Bertalanffy growth model dependent on temperature and body size

Fish growth models are widely used in fisheries as well in aquacultures and ecology. Water temperature is one of the most important factors determining the growth of fish. In the present study, we propose a growth model that includes the effect of water temperature on the growth in the von Bertalanffy growth model. Our model was applied to fit the growth data of bullhead (Cottus gobio), brown trout (Salmo trutta L.), juvenile salmon (Salmo salar), and Araucanian herring (Strangomera bentincki). The model reproduces the growth patterns of each species and fits a set of appropriate parameter values for each species. Moreover, the model reflects the seasonal growth rates quite well.

Fishing characteristics of small yellow croaker drift gill net by net height

Small yellow croaker is one of the important stocks in Korean waters. In this study, we conducted sea trials to estimate optimum height of a drift gill net for effective fishing of small yellow croaker. In the trial using existing net which has 9.2m in height, there was 22 species (1,180 fishes, 99.9kg) caught. The catch (in individuals) of small yellow croaker, especially larger fishes (over 22cm in FL), was higher as part of net height is higher, while the number of species bycaught and the catch of those species were higher as part of net height is lower. In the trial using extension net which has 18.4m in height, there was 27 species (2,030 fishes, 151.7kg). It showed same pattern with existing net in the section I to III, however, in the section IV which is over 13.8m of net height, the catch sharply decreased. The number of species bycaught and the catch of those species using extension net were also same as results using existing net. It showed that section III (9.2-13.8m) where is upper-middle part of the net has caught most of catch and large fishes having over 22cm in length. Through these results, it is judged that the setting depth of the net where is 4.6-13.8m above the sea bottom is the best to reduce bycatch and catch much more large size fishes, and the catch per net is proportional to filtering area of net. Therefore the Fisheries Resource Management Act (the clause 1, article 10) on the amount of usage for offshore drift gill net need to be considered not only length of a net but also net height.

Estimating the Economic Effectiveness of Increasing Mesh Sizes in the Small Yellow Croaker Gillnet fishery

For rebuilding and managing fish stocks and fisheries, the biological and socioeconomic evaluations on fisheries management regulations are important. This study aimed to estimate the economic effectiveness of different mesh sizes in the yellow croaker gillnet fishery. In particular, by comparing economic effects of mesh sizes, 50mm and 52mm, it aimed to provide the economic validity for increasing mesh sizes. Analytical results showed that the fishing revenue was higher in the vessels using a mesh size over 52mm than that in the vessels using a mesh size less than 50mm. In addition, the effect of fishing cost reduction was also larger in the vessels using a mesh size over 52mm than that in the vessels using a mesh size less than 50mm.