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111.
112.
Data sets for two bottom trawl fisheries, the coastal pair-trawler fishery and offshore single-trawler fishery in the Tsushima Warm Current (TWC) region of the Japan Sea, were compiled and analyzed for the last three decades (1974-2006). These data sets were used to (1) identify and compare the variability in demersal fish assemblages, and (2) relate these to water temperature to examine the impacts of climate regime shifts. Principal component analysis (PCA) of catches of target species in the two trawler fisheries showed synchronous decadal variability with step changes around 1986/1987 and 1996/1997. These step changes strongly suggest the effect of the late 1980s climate regime shift, which was characterized by an abrupt change from a cool to a warm condition in the TWC. The first and second principal components (PC1 and PC2) for both trawler fisheries agreed closely with winter and summer water temperature in the Japan Sea, respectively, suggesting PC1 (PC2) was associated with cold- (warm-) water species. However, between warm- and cold-water species the response pattern to water temperature was different. CPUE (catch per unit effort) of warm- (cold-) water species correlated positively (negatively) with water temperature, indicating the increase in water temperature has a positive (negative) effect on warm- (cold-) water species. Cold-water species decreased (increased) both in biomass and distribution during the warm (cold) regime, while warm-water species increased in biomass and/or distribution during the warm 1990s. These results suggested that the demersal fish assemblage structure changed abruptly as a consequence of the late 1980s climate regime shift. Impact of fishing was unclear on the demersal fish assemblage as a whole, but fishing pressure has been intensified for specific species under unfavorable climate regimes even with a declining fishing effort. Differing response patterns between warm- and cold-water species to climate regime shifts suggest the importance of integrated assessment and ecosystem-based management for the whole trawl fishery rather than only for individual target species. 相似文献
113.
为探究筏式贻贝养殖生境鱼类资源养护功能,于2020年9-12月对枸杞岛筏式贻贝养殖生境(分表层区和底层区)及周边岩礁生境的鱼类进行了多网目组合刺网采样。应用相对重要性指数IRI、多样性指数并结合等级聚类、非度量多维标度排序(nMDS)分析鱼类组成和群落结构。结果显示,在2种生境中共采集鱼类55 种,隶属于10目34科47属,其中贻贝养殖生境采集到37种(底层和表层分别为29和20种);岩礁生境共采集到40种。在鱼类组成上,中国花鲈和鲻是贻贝养殖生境表层区的典型优势种,而黄姑鱼和褐菖鲉是贻贝养殖生境底层区的典型优势种;褐菖鲉同时也是岩礁生境的典型优势种。多样性分析表明,贻贝养殖生境的总体鱼类多样性要高于岩礁生境,但尚不显著。多元分析显示,各月份2种生境中的鱼类群落格局均可分为3种类型,虽与养殖表层区、养殖底层区和岩礁区并非严格一致,但各群落间差异依然显著。研究表明,大规模筏式养殖设施的存在吸引了众多中上层鱼类及底层鱼类,也为岩礁生境优势鱼类提供了额外的栖息环境,发挥了近似于浮鱼礁系统的资源养护作用。研究结果可为岛礁海域海洋牧场目标种的选择和人工生境构建模式的应用提供重要参考。 相似文献
114.
为探讨金沙江下游溪洛渡、向家坝水电站蓄水运行对下游江段鱼类早期资源群聚动态的影响,本文基于2016-2020年宜宾江段鱼类早期资源调查数据,对鱼类早期资源种群结构和年际变化趋势进行了研究。宜宾江段共计采集鱼卵20种,主要优势种为吻鮈和寡鳞飘鱼;估算出鱼卵年平均径流量为15.07×106粒,漂流性卵为9.89×106粒,年际间总体呈增加趋势;推算采样点以上分布有产漂流性卵鱼类产卵场3处;从多样性指数和相似度指数看,宜宾江段鱼卵种类组成结构较为稳定,年际间变化不大。尽管受到金沙江下游水电工程开发的影响,宜宾江段作为长江上游珍稀特有鱼类国家级自然保护区的重要组成部分,仍是产漂流性卵鱼类产卵繁殖的重要分布区,但主要以产漂流性卵小型鱼类为主,圆口铜鱼、长鳍吻鮈等长距离洄游性鱼类鱼卵没有监测到。建议继续加强圆口铜鱼、长鳍吻鮈等鱼类的增殖放流,同时,针对产漂流性卵小型鱼类的生态需求,开展金沙江下游梯级水电开发对其生态效应影响的监测研究。 相似文献