Marine ecosystems, particularly the structure of fish assemblages are increasingly affected by human activity. We evaluated the structure and distribution of fish resources using data collected by trawl surveys in May and October of 2006 in the Yellow Sea off Shandong (35°00'-38°00'N, 120°30'-124°00'E). We collected samples at 45 sites and standardized the survey data using the sweep area and capture coefficient. The capture coefficient was set to 0.55 for pelagic fish, 0.35 for demersal fish, and 0.25 for benthic fish. The abundance index was much higher in the coastal waters than in the deeper, offshore waters in spring. During this time, most species migrate to the coastal regions to spawn. In addition, winter-spawning species, such as pacific sandeel (Ammodytes personatus), were still feeding in the coastal waters during the time of the surveys. In autumn, the abundance index was slightly higher in the coastal waters than in the offshore areas. The highest abundance index was measured in Haizhou Bay, both in spring and autumn. We collected a total of 61 species, 50 in spring and 50 in autumn. The structure of fish resources was analyzed based on economic value, habitat layer, and temperature-adapted components. The lower-valued species were dominant in spring and autumn. The lower-valued species constituted 91.0% of the biomass in spring and 80.9% in autumn. The demersal fish were dominant in spring (76.7% of the biomass) whereas pelagic fish, dominated in autumn (75.1% of the biomass). The biomass was dominated by cold-water species (75.0%) in spring and warm-water species (50.1%) in autumn. In spring, the top 10 species by biomass were pacific sandeel, Japanese anchovy (Engraulis japonicas), fang's blenny (Pholis fangi), pacific cod (Gadus macrocephalus), spotted mackerel (Scomberomorus niphonius), smallhead hairtail (Eupleurogrammus punctamanus), yellow croaker (Lahmichthys polyactis), silver pomfret (Pampus argenteus), scaly hairfin anchovy (Setipinna taty), and grassfish(Liparis tanakae). Conversely, the assemblage was dominated by Japanese anchovy, Japanese sardinella (Sardinella zunasi), pacific sandeel, yellow croaker, rednose anchovy (Thrissa kammalensis), silver pomfret, gizzard shad {Konosirus punctatus), smallhead hairtail, spotted mackerel, and scaly hairfin anchovy in autumn. We used the Normalized Biomass Size Spectra (NBSS) to compare the community composition between months and years. Species that contributed <0.01% to the total biomass were excluded. The slope was regressed by log2 (total biomass of every weight class/10) to log2 (upper limit of average individual weight class). The NBSS slope was <-l in both spring and autumn, suggesting the biomass decreased as individual body weight increased. The average individual body weight was 2.36 g/individual in spring and 3.34 g/individual in autumn. The proportion of species whose average individual body weight was <10 g was 95.74% in spring and 82.09% in autumn. Compared with the 1980s, we conclude that: 1) The low-valued species are more dominant, 2) though there has been a partial recovery in the fishery, the larger, high value species have not recovered at the same rate, and 3) the dominant species has changed significantly due to an increase in the number of fang's blenny. Given our results, we propose an earlier beginning to the closed fishing period during summer.%为了解山东近海渔业资源结构及数量分布现状,2006年春季(5月)和秋季(10月)利用疏目变水层双拖网对黄海山东海域进行了调查.数据分析结果表明,春季近岸浅水区资源量指数明显高于远岸深水区,以海州湾资源量指数最高；秋季,近岸浅水区资源量指数仍稍高于深水区,资源量指数以调查海域南部中间区域最低而海州湾最高.春、秋季调查各捕获鱼类50种.基于生物量的分析表明,按经济价值结构划分,春、秋季均以经济价值较低种类为主；按栖息水层划分,春季以底层鱼类为主,秋季以中上层鱼类为主；按适温类型结构划分,春季以冷温性种类为主,秋季以暖温性种类为主.春季生物量最高的3个种类为玉筋鱼(Ammodytes personatus)、鳀(Engraulisjaponicus)和方氏锦鳚(Enedrias fangi),秋季为鳀、青鳞小沙丁鱼(Sardinella zunasi)和玉筋鱼.春、秋季标准生物量谱的斜率均小于-1,表明种群生物量随着个体质量的增加而减少.鱼类资源组成以小型种类为主,春季鱼类平均体质量为2.36 g,秋季为3.34 g.春季平均个体质量小于10g的种类合计生物量占总生物量的95.74％,秋季则为82.09％.与20世纪80年代相比,本次调查期间鱼类的经济结构更加低质化；资源衰退的趋势虽有所遏制,但渔业资源尤其是传统经济种类资源并未根本恢复；优势种类更替明显,玉筋鱼的优势地位明显上升.根据研究结果认为,应将伏季休渔期提前.
展开▼
