Pennahia Argentata Research Articles

낙동강 하구역에 출현하는 보구치 (Pennahia argentata)와 청보리멸 (Sillago japonica)의 섭식관계

낙동강 하구역에 출현하는 보구치 (Pennahia argentata)와 청보리멸 (Sillago japonica)의 섭식관계

The breadth and overlap of ecological niche of major fish species in the Minjiang River Estuary, China.

Based on the seasonal bottom trawl surveys in the Minjiang River Estuary in 2015, the breadth and overlap of ecological niche of major fish species were analyzed. Those fish species were identified based on the index of relative importance (IRI). A total of 137 species belonging to 37 families and 16 orders were collected. Fifteen major fish species were determined by the IRI, including six dominant species Polydactylus sextarius, Harpadon nehereus, Pennahia argentata, Secutor ruconius, Cynoglossus abbreviates, Coilia mystus, and nine important species Collichthys lucidus, Amblychaeturichthys hexanema, Upeneus japonicas, Lagocephalus spadiceus, Pampus argenteus, Larimichthys crocea, Thryssa kammalensis, Takifugu oblongus, Lepturacanthus savala. Seven species whose spatio-temporal niche breadth was higher than 1 in a declining order were C. abbreviates, C. lucidus, S. ruconius, A. hexanema, T. kammalensis, C. mystus, H. nehereus. The ecological niche of major fish species in the Minjiang River Estuary showed obvious seasonal dynamics. The percentage of species pairs with spatio-temporal niche overlap at the meaningful level was as high as 81.9%. Six species pairs reached significant ecological niche overlap, indicating that major fish species had similar distribution at the spatial and temporal scales and the existence of resource utilization competition. The species pairs of U. japonicus-L. savalawas had the highest spatio-temporal niche overlap value, whereas U. japonicus-C. lucidus had the lowest niche overlap value. The spatio-temporal niche overlap of major fish species in the Minjiang River Estuary had substantial seasonal variation.

The effects of endogenous proteases within abdominal muscle parts on the rheological properties of thermally induced gels from white croaker (Pennahia argentata)

Three types of material meats were prepared from a so-called normal muscle part of white croaker (Pennahia argentata) containing 0, 4.2 and 8.4% of an abdominal muscle part. Thermally induced gels were then prepared from these materials by pre-heating at 65 °C for 30 or 60 min and subsequent heating at 85 °C for 20 min. The breaking strength and breaking strain rate of thermally induced gels decreased with increasing contamination levels of the abdominal muscle part, in which degradation of myosin heavy chains was observed. The proteolytic activity in the abdominal muscle part homogenate was highest at 62.5 °C. These results suggest that the abdominal muscle part contains proteases that induce the modori phenomenon. Technical experts assume that a contaminated abdominal muscle part leads to quality deterioration in surimi production industries. Our findings will aid the production of high-quality surimi-based products.

莱州湾鱼类群落优势种生态位

PDF HTML阅读 XML下载 导出引用 引用提醒 莱州湾鱼类群落优势种生态位 DOI: 10.5846/stxb201408281711 作者: 作者单位: 山东省海洋资源与环境研究院,山东省海洋资源与环境研究院,山东省海洋资源与环境研究院,烟台市水产研究所 作者简介: 通讯作者: 中图分类号: S931.1 基金项目: 山东省渔业资源增殖效果评价（SD-XGPJ-2012-2）；山东省优秀中青年科学家科研奖励基金（BS2012HZ030） Ecological niche of dominant species of fish assemblages in Laizhou Bay, China Author: Affiliation: Shandong Marine Resource and Environment Research Institute,Shandong Provincial Key Laboratory of Restoration for Marine Ecology,Shandong Marine Resource and Environment Research Institute,Shandong Provincial Key Laboratory of Restoration for Marine Ecology,Shandong Marine Resource and Environment Research Institute,Shandong Provincial Key Laboratory of Restoration for Marine Ecology,Yantai Fisheries Research Institute Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根据2011年5月、8月、10月和12月莱州湾底拖网调查资料，对该海域鱼类群落优势种的生态位进行了研究。结果表明，全年调查共捕获鱼类49种，各季节优势种种类数分别为春季3种，夏季5种，秋季3种，冬季4种。夏、冬季优势种的丛生指数较低，春、秋季较高；冬、春季优势种的平均拥挤度较低，夏、秋季较高。基于欧氏距离的优势种丰度聚类结果同优势度排序结果吻合。主成分分析（PCA）表明，青鳞小沙丁鱼（Sardinella zunasi）和赤鼻棱鳀（Thryssa kammalensis）分别是影响第一轴和第二轴的主要种类。绯鱼衔（Callionymus beniteguri）、鲬（Platycephalus indicus）、髭缟虾虎鱼（Tridentiger barbatus）和短吻红舌鳎（Cynoglossus joyneri）是时空二维生态位宽度最高的种类（>2）。时空生态位显著重叠（>0.6）的种类有7组，其中银姑鱼（Pennahia argentata）和皮氏叫姑鱼（Johnius belengerii）重叠值最高（0.798）。δ13C值变幅（CR）最大的种类为斑鱼祭（Konosirus punctatus），δ15N值变幅（NR）最大的种类为青鳞小沙丁鱼；青鳞小沙丁鱼和鱼祭生态位总面积超过20，皮氏叫姑鱼生态位总面积最小（1.38）且与其他优势种营养生态位重叠较高。等级聚类、排序、PCA和优势种排序结果较一致，而与时空生态位宽度分析结果差异较大，表明莱州湾鱼类群落结构受洄游鱼类的影响较大。时空生态位宽度较高的种类主要为集群特征不明显的周年定居种（绯鱼衔、鲬、短吻红舌鳎等底层鱼类），而季节洄游种（青鳞小沙丁鱼、鱼祭、赤鼻棱鳀等中上层鱼类）因时间生态位宽度较低导致时空生态位宽度较低。时空生态位和营养生态位分析表明，生态位重叠导致的资源利用性竞争并不是导致莱州湾鱼类群落结构现状的决定性因素，而更多可能是人为干扰形成的。 Abstract:Laizhou Bay, an estuary of the Yellow River, is one of the three most important bays of the Bohai Sea, China. It is characterized by a high level of primary productivity and is one of the most important spawning and feeding grounds for most fish species in the Yellow Sea and Bohai Sea. After decades of overfishing, the dominant species of the fish assemblage have been altered. Ecological niche describes how an organism or population responds to the distribution of resources. Therefore, studies on ecological niches are extremely important to clarify the ecological dynamics of different species and the mechanism of interspecific coexistence and competition, as they are a fundamental tool for the conservation and assessment of fish stocks, as well as for the analysis of the ecosystem as a whole. Data were obtained from a bottom trawl survey conducted in Laizhou Bay (119°05'-120°00'E, 37°12'-37°40'N) in 2011. The most dominant species that contributed to 97.2% of biomass and 98.4% of abundance were used for the hierarchical cluster analysis, non-metric multidimensional scaling (NMDS), principal component analysis (PCA), and spatio-temporal niche analysis. Tissue samples were collected from the 12 most dominant species recorded in the trawl-survey catches. δ13C and δ15N stable-isotope analyses were performed to assess the trophic niche. A total of 49 fishes were collected. The assemblage density of dominant species was low in the summer and winter and high in the spring and autumn. The mean crowding of the dominant species was low in the spring and winter, and high in the summer and autumn. The results of the hierarchical cluster analysis based on the Euclidean distance showed a similarity with the results of the ecological dominance analysis. The PCA showed that Sardinella zunasi was one of the species that mostly affected the first axis, and Thryssa kammalensis mostly affected the second axis. Callionymus beniteguri had the highest value of tempo-spatial niche width, followed by Platycephalus indicus, Tridentiger barbatus, and Cynoglossus joyneri. Significant overlap of spatio-temporal niche occurred between the seven groups:Pennahia argentata vs. Setipinna taty (0.798), S. taty vs. Johnius belangerii (0.793), C. joyneri vs. J. belangerii (0.771), Chaeturichthys stigmatias vs. J. belangerii (0.770), Konosirus punctatus vs. Scomberomorus niphonius (0.763), and K. punctatus vs. C. joyneri (0.625). Konosirus punctatus had the highest δ13C range (CR=9.2), and J. belangerii had the highest δ15N range (NR=7.1). The total area (TA) of the trophic niche of S. zunasi and K. punctatus were the highest, both being larger than 20. Johnius belangerii had the lowest TA (1.38); however, it had a significant overlap with other species, such as C. stigmatias, C. joyneri, and P. argentata. The results showed a similar trend with cluster analysis, NMDS, and PCA; however, the trend was different with the tempo-spatial niche analysis. The non-migration species, which lives throughout year in the bay, with lower assemblage densities had a higher value of spatio-temporal niche width. The seasonal migratory species had a lower tempo-spatial niche width because of the low temporal niche width. The high spatio-temporal niche overlap between the most dominant species found in this study also reflected a high degree of homogeneity of fish assemblies in the Laizhou Bay. Competition owing to niche overlap was not the decisive factor that formed the community structure of nekton in the Laizhou Bay. The community structures might be most affected by anthropogenic activities. 参考文献 相似文献 引证文献

Larval Fish Assemblages and Hydrographic Characteristics in the Coastal Waters of Southwestern Taiwan during Non- and Post-typhoon Summers.

Hung-Yen Hsieh, Wen-Tseng Lo, Hsiao-Hao Chen, and Pei-Jie Meng (2016) Although research on the larval fish assemblages in the Taiwan Strait has progressively developed in the last two decades, it is difficult to study typhoons' impacts on larval fish assemblages due to (1) the occurrence and path of a cyclone cannot be predicted accurately and (2) the severe weather condition makes shipboard measurements extremely difficult. Larval fish and zooplankton were sampled and hydrographic variables and chlorophyll a were measured in the waters of southwestern Taiwan during September 2009 (non-typhoon) and September 2012 (post-typhoon Tembin). Data from these collections were used to elucidate the effects of hydrographic dynamics after the typhoon event on species assemblage and abundance. The results showed that after the typhoon Tembin, the surface temperature and salinity decreased slightly, but the values of the measured chemical and biological parameters were much greater than those derived from the non-typhoon period due to enriched nutrients from entrainment of river runoff of the Kaoping River. Meanwhile, the abundance of larval fish also increased significantly, but the species composition became less diverse. Multivariate statistical analyses revealed two distinct larval fish assemblages that were closely correlated to sampling cruise. The dominant taxa of larval fish changed from Encrasicholina heteroloba, Nuchequula nuchalis, unidentified Sparidae, Equulites rivulatus, and Cyclothone spp. during the non-typhoon period to Engraulis japonicus, unidentified Engraulidae, Sillago sihama, Pennahia argentata, and E. rivulatus during the post-typhoon period. Canonical correspondence analysis revealed that, in the waters of southwestern Taiwan, the horizontal distribution of larval fish in late summer may be explained by the food availability. The magnitude of the enhancement of measured variables changed with sampling periods, suggesting the study area was at an unsteady status after the passage of the typhoon Tembin. The coastal ecosystem became more productive after the typhoon event.

Age, growth, mortality and population structure of silver croaker Pennahia argentata (Houttuyn, 1782) and red bigeye Priacanthus macracanthus Cuvier, 1829 in the north-central Taiwan Strait

Summary The main objectives of this study were to estimate the age, growth, mortality and population structure of silver croaker Pennahia argentata (Houttuyn, 1782) and red bigeye Priacanthus macracanthus Cuvier, 1829 and to explore the factors causing the fluctuation of the fish populations and the ecological parameters. The two species were randomly sampled, with 80~120 individuals of each species captured every month from a single trawler fishery (mesh size 250 mm), March to November 2006, in the north-central Taiwan Strait. A total of 994 speciments of silver croaker and 851 speciments of red bigeye were collected. Compared with previous studies, the mean length and weight, mean age, the minimum size at first sexual maturity, the asymptotic length (L∞) and weight (W∞) of the two species has decreased in recent decades, indicating that the populations were younger, smaller and earlier in sexual maturity. Meanwhile, the growth coefficient (K) increased, the mortality coefficients (Z, F, M) were higher, and the exploitation rate (E) indicated overfishing. Fishing is a key driving force that can cause abundant fluctuations and changes in ecological characteristics in these two demersal fishes in this area. Accordingly, the traditional fishery management approach, such as the reduction in fishing effort, coupled with the Ecosystem-based Fishery Management (EBFM) should be implemented to achieve sustainable demersal fisheries.

Deterioration of white croaker (Pennahia argentata) meat thermally-induced gel products caused by proteolytic enzymes in the contaminated intestine and kidney

Thermally-induced gels were made from white croaker (Pennahia argentata) meat in the presence of its organ extracts by pre-heating at 40 and 65°C for 20min and subsequent heating at 85°C for 20min. The breaking strength of the gels decreased with increasing concentrations of the intestinal extracts accompanying decomposition of myosin heavy chains. However, no significant changes in the gel strength occurred when the kidney extract was added. The proteolytic activity in the intestinal extracts examined in the meat homogenate had a maximum at 60°C and pH 8.90. These results suggest that the intestinal rather than kidney proteolytic activities are responsible for gel softening known as a modori phenomenon. Thus, the removal of intestinal tracts is essential to maintain a high quality of surimi-based products.

The role of molecular methods to compare distribution and feeding habits in larvae and juveniles of two co-occurring sciaenid species Nibea albiflora and Pennahia argentata

In Ariake Bay, Japan, two sciaenids Nibea albiflora and Pennahia argentata spawn in the same season and their larvae and juveniles are believed to co-occur. We developed a molecular method to identify larvae and early-stage juveniles of N. albiflora and P. argentata using multiplex polymerase chain reaction (PCR) due to difficulties of species identification using morphological keys and compared the ontogenetic distribution and feeding habits in larvae and early-stage juveniles of both species. N. albiflora spawn in the shallow water of the inner part of the bay, and P. argentata spawn in the deeper waters from the middle to the outer part of the bay. As a result of inter-species difference in their preferred spawning areas, P. argentata larvae were more common than N. albiflora in the southern part of the bay. The larvae of both species tended to emerge in shallower waters toward the inside of the bay and juveniles were observed exclusively in the lower reaches of the inflowing rivers, suggesting that larvae and juveniles could be successfully transported to their nursery ground or retained in the bay without seaward dispersion. In Ariake Bay, the maximum turbidity zone is around the mouth and estuarine areas of the rivers in the innermost part of the bay and these areas are important nursery grounds for both study species during their early life stages, especially the early juvenile stage. For N. albiflora, pre-flexion and flexion larvae fed exclusively on small copepods, mainly Oithona davisae, whereas post-flexion and juveniles fed mainly on a large copepod, Sinocalanus sinensis, and mysids. P. argentata larvae and juveniles consistently fed on copepods, mainly Paracalanidae. Both species consumed small prey throughout the larval stages and the smallest prey consumed by juveniles was larger than that consumed by larvae. The size of the largest prey consumed by larvae and juveniles of both species tended to increase throughout development. The similarity of morphological features and ontogenetic distribution patterns between species suggest that the observed differences in diet composition of both species may result from differences in selective feeding by larval and juvenile N. albiflora and P. argentata.

Distribution of Chitinolytic Enzymes in the Organs and cDNA Cloning of Chitinase Isozymes from the Stomach of Two Species of Fish, Chub Mackerel (<i>Scomber japonicus</i>) and Silver Croaker (<i>Pennahia argentata</i>)

Chitinolytic activities were measured in two fish species having different feeding habits, chub mackerel (Scomber japonicus) and silver croaker (Pennahia argentata). Chitinase (an endo-type chitinolytic enzyme) activity was measured using pNP-(GlcNAc)n (n = 2, 3) as substrates; its level was significantly high in the stomachs of both species, as well as in the gills, intestine, pyloric appendage, testis, and liver of chub mackerel and in the spleen, kidney, pyloric appendage, ovaries, heart, and liver of silver croaker. β-N-Acetylhexosaminidase (an exo-type chitinolytic enzyme) activity was measured using pNP-(GlcNAc) as a substrate; it was detected at high levels in many parts apart from the digestive tracts of both species. The optimum pH for chitinase activity was 3.0 - 5.0 in the stomachs of both species, 4.0 in the liver of chub mackerel, and 4.0 and 8.0 in the kidney of silver croaker. Full-length cDNAs encoding two chitinase isozymes were obtained from the stomachs of the two fish species: SjChi-1 (1604 bp) and SjChi-2 (1512 bp) from chub mackerel and PaChi-1 (1630 bp) and PaChi-2 (1606 bp) from silver croaker. Expression analysis of these genes in the organs of the two species revealed strong expression of SjChi-1 in the stomach of chub mackerel and that of PaChi-1 andPaChi-2 in the stomach of silver croaker. The difference in the expression pattern of these genes is likely attributed to the difference in the feeding habits of the two fish species. Our results suggested the presence of novel chitinases in the two species.

The pepsin digestibility of thermal gel products made from white croaker (Pennahia argentata) muscle in associating with myosin polymerization levels.

Thermal gels were made from white croaker (Pennahia argentata) surimi at various polymerization levels of myosin heavy chains induced by suwari treatment at 38 °C for various time periods and subsequently heated at 85 °C for 20 min. Myosin heavy chain polymerization levels were also achieved in the presence of microbial transglutaminase (MTG) added at various concentrations in the surimi. The breaking strength and breaking strain rate were markedly increased during suwari treatment up to 60 min in accordance with the increased levels of myosin heavy chain polymerization. MTG enhanced myosin heavy chain polymerization during suwari treatment for 15 and 30 min, resulting in the increase of breaking strength. The solubilization in 8 M urea and pepsin digestibility of these gels as well as angiotensin I-converting enzyme (ACE) inhibitory activity of their pepsin digests were decreased with the increased levels of myosin heavy chain polymerization. These results suggest that myosin heavy chain polymerization affects not only rheological properties of thermal gels but also their functional properties for human health.

거문도 주변 해역에 출현하는 저어류 군집의 종조성

The study aims at analyzing a species composition of the fish live in bottom of the coastal waters off Sejon island, Korea. To reach the goal of the study, a species composition and it's seasonally fluctuation, a seasonally fluctuation of the dominant species and it's appearance type were analyzed with the fishes caught by the bottom trawl in the coastal waters off Sejon island from May, 2011 to March, 2012. The results obtained can be summarized as follows; Fish caught in this area composes 10 orders, 25 families, and 37 species. The most dominant species in an number of fish was Pennahia argentata which was occupied at 42.1% from the whole number, the second most dominant species was Konosirus punctatus which was occupied at 14.2%. The most dominant species in a biomass of fish was Pennahia argentata which was 31.3% out of the whole catch, the next dominant species was Lophius litulonwhich which was 18.2%. The first group (Trichiurus lepturus, Zeus faber, Pennahia argentata, Chelidonichthys spinosus and Lophius litulon) was appeared at May, August, October, the second group (Sphyraena pinguis) was appeared at May and November, the third group (Pampus argenteus) was appeared at August, the fourth group (Pampus echinogaster, Leiognathus nuchalis, Konosirus punctatus and Engraulis japonicus) was appeared at March.

한국 남해안 세존도 주변 해역에 출현하는 보구치 (Pennahia argentata)의 식성

Feeding habits of white croacker, Pennahia argentata, were analyzed by using the stomach contents of 153 specimens caught by bottom trawl from May 2011 to March 2012 in the Sejon island, Korea. To know feeding habits of the white croacker, P. argentata, a species composition and it's fluctuation were analyzed based on growth. White croacker, P. argentata caught in the area composes 15 species. The most species in an number of the prey was Macrura which was occupied at 66.4% from whole prey, the second most species was Pisces which was occupied at 20.3%. The most species in an wet-weight of the prey was Pisces which was 49.3% out of the whole specimens. The second most species was Macrura which was 43.3%. The frequency occurrence of the prey was Macrura which was 68.6%, the next one was Pisces which was 28.8%. The highest Index of Relative Importance (IRI) of the prey was Macrura which was 78.2%, the next one was Pisces which was 28.8%. A number of the prey per specimen of small, middle and large class were 1.3, 1.5, 1.7, respectively. A wet weight of the prey per specimen of small, middle and large class were 0.2, 0.6, 0.2 g, respectively.

Phylogenetic estimation of Sciaenidae in the East China Sea inferred from nuclear EPIC DNA sequence variation

Here we describe a phylogenetic analysis of sciaenids of the East China Sea based on nuclear exon-primed intron-crossing genes (EPIC markers) and a mitochondrial gene (CO1). Separate analyses of the two data partitions resulted in mostly congruent trees. Although there were some differences in the classification of these species, the main difference between trees obtained by the mitochondrial gene (CO1) and nuclear DNA sequences was the position of Miichthys miiuy and Johnius belangerii. In the mitochondrial phylogeny, Johnius belangerii was placed at the most basal position forming an individual clade, while other species formed another large cluster. Miichthys miiuy formed an independent basal sub-clade grouped with Larimichthys and Collichthys. Collichthys lucidus was grouped with Larimichthys crocea and Larimichthys polyactis. Trees based on the nuclear genes differed somewhat from those based on the CO1 mitochondrial gene. In this analysis, two groups resulted, the Larimichthys and Collichthys clade, and another clade including a total of five species: Johnius belangerii, Nibea albiflora, Pennahia argentata, Sciaenops ocellatus, and Argyrosomus japonicus; Johnius belangerii clustered with Nibea albiflora. Miichthys miiuy was placed at the basal position of the other cluster because it was an independent basal sub-clade grouped with Johnius belangerii, Nibea albiflora, Pennahia argentata, Sciaenops ocellatus, and Argyrosomus japonicus. Many aspects of the phylogeny of the Sciaenidae remain unresolved, and further analysis based on more molecular information and extensive taxon sampling is necessary to elucidate the phylogenetic relationships among the major lineages within Sciaenidae.

Dual isotope study of food sources of a fish assemblage in the Red River mangrove ecosystem, Vietnam

The food source utilization and trophic relationship of the fish assemblage in the Red River mangrove ecosystem, Vietnam were examined using dual isotope analysis. The carbon and nitrogen stable isotope signatures of 23 fish species ranged from −24.0 to −15.7‰ and from 8.8 to 15.5‰, respectively. Cluster analysis based on the δ13C and δ15N signatures clearly separated the mangrove fish into five feeding groups, representing detritivores, omnivores, piscivores, zoobenthivores, and zooplanktivores, which concurred with the dietary information. The results suggested that mangrove carbon contributed a small proportion in the diets of the mangrove fish, with dominant food sources coming from benthic invertebrates, including ocypodid and grapsid crabs, penaeid shrimps, bivalves, gastropods, and polychaetes. The δ15N values showed that the food web structure may be divided into different trophic levels (TLs). The lowest TLs associated with Liza macrolepis, Mugil cephalus, and Periophthalmus modestus; 18 fish species had TLs between 3.0 and 3.8; and Pennahia argentata had the highest TL (c. 4.0).

Mitochondrial genome sequence of the Japanese white croaker Pennahia argentata (Perciformes: Sciaenidae)

Through primer walking method, the mitochondrial genome sequence of white croaker (Pennahia argentata) from Japanese coastal water was obtained in this study. The mitogenome length of Japanese white croaker was 16,486 bp. The genome contains 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes, a control region (CR) and a dominating non-coding region. The termination-associated sequence, the central conserved domain, and the conserved sequence blocks were identified in the control region. The origin of L-strand replication was located in a cluster of five tRNA genes between tRNA-Asn and tRNA-Cys.

Length-weight relationships for 14 fish species of the Suer River estuary in southern Korea

Summary Length–weight relationships were estimated for 14 species belonging to 13 fish families from the Suer River estuary, Korea. These 14 species are: Callionymus valenciennei, Konosirus punctatus, Conger myriaster, Cynoglossus joyneri, Tribolodon hakonensis, Thryssa hamiltonii, Acanthogobius flavimanus, Paratrypauchen microcephalus, Hexagrammos agrammus, Nuchequula nuchalis, Pseudopleuronectes yokohamae, Pennahia argentata, Sillago japonica and Takifugu niphobles. Between April 2009 and January 2010, samples were caught by commercial trawl net at depths of <20 m. Estimates for parameter b of the length–weight relationship (W = aLb) ranged between 2.510 and 3.149.

Feeding Habits of Yellow Goose Fish Lophius litulon and John Dory Zeus faber in the South Sea of Korea

The feeding habits of yellow goosefish Lophius litulon and John Dory Zeus faber were studied by analyzing the stomach contents of specimens collected in the South Sea of Korea. In total, 132 hauls were taken during six experimental trawl survey (Tamgu 1) cruises conducted on a seasonal basis (March 2005-October 2007). The main prey items of the two species were similar. Fishes and crustaceans were the most important prey, with neither species showing ontogenetic changes in preferred species. Specifically, Pennahia argentata was the preferred prey item of L. litulon, whereas Trichiurus lepturus and Engraulis japonicus were preferred by Z. faber. Larger Z. faber (>24 cm) preferred bigger prey such as T. lepturus and Larimichthys polyactis, while smaller Z. faber preferred E. japonicus and Acropoma japonicum.

트롤 어구에 부착된 쐐기형 해파리 분리배출장치의 성능 연구

In order to describe the performance of a wedge type jellyfish excluder device, a series of fishing experiments was carried out in the coastal areas of Yokji Island, southern Korea in 2009, using a trawl net with a cover net. The body size and weight of each individual (fish or jellyfish) caught in the experimental fishing were measured. In the case of giant jellyfish the bell diameter and weight were measured. The catch species was composed of giant jellyfish (Nemopilema nomurai), silver croaker (Pennahia argentata), yellow croaker (Larimichthys polyactics), finespotted flounder (Pleuronichthys cornutus), largehead hairtail (Trichiuruslepturus), melon seed (Psenopsisanomala) and so on. The weight ratio and individual ratio of total fish escaped through the outlet of the excluder device were 0.322 and 0.320, respectively. The weight ratios of giant jellyfish excluded from the trawl net ranged from 0.740 to 0.921 (average 0.852/haul). It means that the wedge type jellyfish excluder device performed well and allowed the most of the giant jellyfish to exclude through the trawl net. The approximately 70% of fish entered in trawl net was caught. The wedge type excluder device needs some improvements to minimize the fish escape from the trawl nets in the future.

사천바다목장해역 어류군집의 변동특성

Species composition and seasonal variation of fish assemblage in Sacheon marine ranching, Korea were examined. Sampling was seasonally made by a shrimp trawl from February 2009 to November 2009. A total of 55 species were collected. Of these, five species was dominant species comprising 51.1% of the total number of individuals. Nine species represented 57.3% of the total biomass. While total abundance (number of individuals) was high in spring, total biomass and species richness (number of species) and diversity were high in autumn. Cluster analysis, based on seasonally abundance data of the 21 most common species, showed that the species were separated into 4 different groups. Group A composed of Pholis nebulosa, Pleuronectes yokohamae, Hypodytes rubripinnis, Hexagrammos otakii, Tridentiger trigonocephalus and Paracercis sexfasciata, which were year round residents, group B Congr myriaster, Leiognathus nuchalis, and Platycephalus indicus, which were abundant in autumn, group C Sillago japonica, Pseudaesopia japonica, Zoarces gilli, Pholis fangi, and Pleuronichthys cornutus which were abundant in spring, and group D Sillago sihama, Cociella sp., Johnius grypotus, Cynoglossus joyneri, Cynoglossus robustus, and Pennahia argentata, which were abundant in summer. Principal component analysis revealed that seasonal variation in the fish assemblage was attributed to the abundance of temporal species such as conger and sand smelt fishes, which were abundant in summer, due to seasonal variation of water temperature.

Degree of intraspecific genetic divergence and variability in three Sciaenid species

Abstrllct Genetic variations in Nibea mitsukurii, N. albijfora and Pennahia argentara from different localities were assayed electrophoretically. The genetic variability in N. mirsukurii was relatively high. According to the chi-square values for heterogeneity between two localities and genetic distance (D) values, N. albijfora from the Ariake Sea and the Inland Sea or the East China Sea (D=O.OO92 in average), and N. misukurii, from Tosa Bay vs, Atsumi Bay (D=~O.OO67) were considered to be independent subpopulations, The D value in N. albifiora from the Inland Sea VS, the East China Sea was quite small (D=O.OOlO), In P. argenrara populations, the D values were also small. Further, the relationship between genetic and geographic distances observed in the three species were discussed, P. argenrata showed a positive relationship between these two factors as compared to N. mirsukurii or N, albifiora. It seemed that the lower level of genetic divergence might be due to the frequent gene flow within the large-scale and wide distributional range of the population. During the past decade the application of gel electrophoresis coupled with selective enzyme stain­ ing has shown that a large amount genetic variation exists in natural populations of many species (Allen­ dorf and Utter, 1979). Phenotypes of allozyme can be scored during most stages of their life cycle and their genetics more easily interpreted than the pro­ portional and meristic characters employed in fish taxonomy. Genetic differences among populations within a defined body of water may conceivably decrease with time, due to gene flow by migration within sub­ populations. Alternatively, genetic differentiation could become· accentuated through time, perhaps because subpopulations become increasingly associ­ ated with discrete breeding areas (Felley and Avise, 1980). The fishes of the family Sciaenidae contribute sub­ stantially to the fisheries of the warm and shallow seas and estuaries of the world. Nibea mitsukurii (Jordan et Snyder) commonly known as nibe croak­ er, extends along the coast of the Pacific Ocean from Sendai Bay in the north to Hyuga Basin (an open bay) in the south. Nibea albiflora (Richardson), commonly known as roncader, occurs in Hong­ kong, the East China Sea and northwards to Port Arthur and southern Japan. Pennahia argentata (Houttuyn), commonly known as white croaker, is widely distributed in Japanese, Korean and Chinese waters (Trewavas, 1977).