Seasonal Variations In Species Composition And Community Structure In The Eastern Coast of South Korea


 The seasonal variations in species composition of set net fisheries were investigated in the eastern coast of Korea, from 2007 to 2008. In total, 51 species were found that were classified into 15 orders and 33 families. The water temperature of the study area was 0.1–2.1 °C during the study period, which was higher than the average water temperature in the last decade. Monthly variation in the number of species peaked twice, in May (spring) and November (autumn) when the water temperature increased and decreased, respectively, and monthly variation in the number of individuals showed a remarkably high trend in winter and autumn and was mainly caused by large migratory species. Based on the cluster analysis of the 18 most dominant species with more than 0.4% of the total number of individuals, we divided the species composition and community structure into three groups: fishes with temporary appearance (Group A), fishes with long-term appearance (Group B), and dominant pelagic fishes appearing with long-term appearance (Group C). We could conclude that seasonal variation in the fish community structure was mainly caused by pelagic migration of species under high water temperature conditions during the study period.


Introduction
and 28,468 individuals of S. quinqueradiata (20.8%) in October. In 2008, the number of 136 individuals ranged from 390 in September to 14 078 in April (Fig. 4). Further, January, 137 September, and November 2008, recorded more than 10,000 individuals (Supplementary   138   Table S1) Table S1). 143 The peaks in species diversity were recorded in June ( including the coastal waters of Gangwon-do, has a unique hydrology, with a combination of 173 both North Korean cold currents and Tsushima warm currents; therefore, the temporal and 174 spatial distribution of hydrological factors, such as water temperature and salinity, is 175 complex 11 . Short-and long-term information on changes in the fishery catches in this region 176 is required for sustainable resource management and utilization. Thus, this study analyzed the 177 seasonal variations in the fish species composition in the coastal waters of Gangwon-do for 178 two years (2007 and 2008) using set nets.

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A total of 51 fish species were identified during the study period ( Table 1). These species 180 can be divided into 19 pelagic fish species, including S. quinqueradiata, S. japonicus, and T. 181 japonicus, and 32 semi-demersal and demersal fish species, such as S. schlegelii, P. olivaceus, 182 and Pleuronectes schrenki (Supplementary Table S1). The set net method is a passive 183 fishing method that involves waiting for the fish to appear. It is strongly influenced by local  The dominant species (more than 0.4% of the total number of observed species) were 252 divided into three groups through cluster analysis. Group A included species that appeared 253 temporarily and sporadically in spring to autumn, and those that appeared intensively in 254 summer to autumn (Fig. 5). In this group, C. saira and T. japonicus were representative 255 migratory small pelagic fishes of the East Sea that migrate north in spring and summer and 256 south in autumn and winter 8,22 . A. schlegeli and K. punctatus observed in spring and autumn 257 was found to contribute to increasing the community similarity with C. saira, with a high 258 catch in spring, and with other main catch species, such as H. japonica, T. modestus, and T. 259 japonicas, in autumn. Group B comprised fish species that appeared for a long duration and 260 almost the entire study period, except summer (July to September); additionally, this group 261 included species that appeared intensively from winter to spring. In this group, small pelagic 262 fish species, such as M. cephalus and S. cirrhifer, whose distribution is highly affected by 263 warm currents 8,22 were found throughout the study period. Further, resident species, such as T.
residing species. S. quinqueradiata and S. japonicus appeared throughout the entire period, 276 except from February to April (Fig. 5). An increase or decrease in fish resources is related to 277 the water temperature and periods of plankton growth 29 ; additionally, it can be presumed that 278 there is a difference in the distribution of migratory species depending on the influence of a 279 warm current, which in turn is a critical aspect that should be considered during the study 280 period 25 . In previous studies, the water temperature was observed to increase by 2.59 °C in

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This study was conducted using three sets of set nets that were installed to capture fish 300 from the middle to upper regions of the sea in Yangyang, East Coast of Korea (37°58'27″ N, 301 128°47'18″ E; 37°58'21″ N, 128°47'24″ E; 37°58'18″ N, 128° 47'24″ E, respectively) (Fig. 1). 302 The dimensions of the fishing nets were 148 × 34.5 m (L× W), with a mesh size of 33 mm × 303 33 mm (Fig. 2). Fishing data from February 2007 to December 2008 were collected from 304 logbooks that had compiled information on set net fisheries at the three points. This study did Institute 34 . The daily number of individuals of the captured fishes was averaged for each 313 month and subsequently, the monthly averages were compared to assess the quantitative 314 changes. Further, Shannon-Weiner index (H'; 1963) 35 was used to calculate the fish species 315 diversity with the software primer 6 (Primer-E Ltd., Plymouth, UK).

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Out of the 51 species recorded, data of the 18 most abundant species, that is, species with 317 more than 0.4% of the total abundance, were used for cluster analysis based on the temporal 318 distribution of fish species composition and abundance. Cluster analysis was performed to 319 determine the groups of related species composition components (R-mode) and those of