Two fishing methods including gillnetting and trawling to estimate attributes of fish assemblage were compared in Dianshan Lake from August 2009 to July 2010. Species composition dif fered significantly between the ge...Two fishing methods including gillnetting and trawling to estimate attributes of fish assemblage were compared in Dianshan Lake from August 2009 to July 2010. Species composition dif fered significantly between the gears, with four significant contributors in gillnet catches and one in trawl catches. Trawling collected more proportions of benthic species by number and biomass than gillnetting. Size distribution was significantly influenced by fishing technique; gillnetting captured relatively less small-sized fishes and trawling captured less large-sized individuals. Trawling produced species richness closer to the one expected than gillnetting. On the whole, trawl catch was a quadratic polynomial function of gillnet catch and a significantly negative correlation was found between them, both of which varied as dif ferent polynomial functions of temperature. However, trawl and gillnet catches were significantly correlated only in one of five month groups. It is concluded that single-gear-based surveys can be misleading in assessments of attributes of fish assemblages, bottom trawling is a more ef fective gear for assessing fish diversity than benthic gillnetting, and using gillnet catches as an indicator of fish density depends on fishing season in the lake.展开更多
本文利用《中国渔业统计年鉴》数据,结合中国海洋捕捞业变化的相关研究材料,分析了改革开放四十年(1979-2019年)我国国内海洋捕捞渔船数量、捕捞机动渔船吨位和功率、捕捞年产量、单位功率和单位吨位年渔获量(Catch Per Unit Effort, CP...本文利用《中国渔业统计年鉴》数据,结合中国海洋捕捞业变化的相关研究材料,分析了改革开放四十年(1979-2019年)我国国内海洋捕捞渔船数量、捕捞机动渔船吨位和功率、捕捞年产量、单位功率和单位吨位年渔获量(Catch Per Unit Effort, CPUE)以及不同种类渔具(拖网、围网、刺网、张网、钓渔具和其他渔具)的捕捞产量和CPUE的变化。研究表明:我国国内海洋捕捞产量在1979-1998年逐年增加,1998年之后整体呈现下降趋势,国内海洋捕捞总量占海水产品总量的比例逐年下降,从1979年的74.8%下降到2019年的30.5%;虽然渔船总吨位和总功率保持着总体上升的趋势,但是2019年单位功率年渔获量与1999年相比减少了30.6%,单位总吨的年渔获量与1999年相比减少了45.4%。此外,不同种类渔具捕捞产量中,拖网产量一直处于主导地位(产量占比处于64%-42%之间);2000年后,刺网产量处于第二位(16%-22%),张网产量处于第三位(17%-11%),围网等渔具产量均不足10%;2003年后,除张网CPUE较为稳定之外,其它渔具CPUE都呈明显的下降趋势,CPUE的显著减少可能是由于渔船功率和吨位的不断增加及资源量的不断减少造成的。本文研究结果可为我国国内海洋捕捞业结构优化及相关管理政策制定提供参考。展开更多
基金Supported by the Science and Technology Commission of Shanghai Municipality(Nos.08DZ1203101,08DZ1203102)the Shanghai University Knowledge Service Platform,Shanghai Ocean University Aquatic Animal Breeding Center(No.ZF1206)
文摘Two fishing methods including gillnetting and trawling to estimate attributes of fish assemblage were compared in Dianshan Lake from August 2009 to July 2010. Species composition dif fered significantly between the gears, with four significant contributors in gillnet catches and one in trawl catches. Trawling collected more proportions of benthic species by number and biomass than gillnetting. Size distribution was significantly influenced by fishing technique; gillnetting captured relatively less small-sized fishes and trawling captured less large-sized individuals. Trawling produced species richness closer to the one expected than gillnetting. On the whole, trawl catch was a quadratic polynomial function of gillnet catch and a significantly negative correlation was found between them, both of which varied as dif ferent polynomial functions of temperature. However, trawl and gillnet catches were significantly correlated only in one of five month groups. It is concluded that single-gear-based surveys can be misleading in assessments of attributes of fish assemblages, bottom trawling is a more ef fective gear for assessing fish diversity than benthic gillnetting, and using gillnet catches as an indicator of fish density depends on fishing season in the lake.
文摘本文利用《中国渔业统计年鉴》数据,结合中国海洋捕捞业变化的相关研究材料,分析了改革开放四十年(1979-2019年)我国国内海洋捕捞渔船数量、捕捞机动渔船吨位和功率、捕捞年产量、单位功率和单位吨位年渔获量(Catch Per Unit Effort, CPUE)以及不同种类渔具(拖网、围网、刺网、张网、钓渔具和其他渔具)的捕捞产量和CPUE的变化。研究表明:我国国内海洋捕捞产量在1979-1998年逐年增加,1998年之后整体呈现下降趋势,国内海洋捕捞总量占海水产品总量的比例逐年下降,从1979年的74.8%下降到2019年的30.5%;虽然渔船总吨位和总功率保持着总体上升的趋势,但是2019年单位功率年渔获量与1999年相比减少了30.6%,单位总吨的年渔获量与1999年相比减少了45.4%。此外,不同种类渔具捕捞产量中,拖网产量一直处于主导地位(产量占比处于64%-42%之间);2000年后,刺网产量处于第二位(16%-22%),张网产量处于第三位(17%-11%),围网等渔具产量均不足10%;2003年后,除张网CPUE较为稳定之外,其它渔具CPUE都呈明显的下降趋势,CPUE的显著减少可能是由于渔船功率和吨位的不断增加及资源量的不断减少造成的。本文研究结果可为我国国内海洋捕捞业结构优化及相关管理政策制定提供参考。
