采用声学方法研究2016年秋季布兰斯菲尔德海峡南极磷虾群昼夜垂直移动特征及其影响因素

Diel vertical migration of Antarctic krill(Euphausia superba) swarm in the Bransfield Strait during austral autumn 2016 inferred from acoustic data and its relations to environmental factors

近年来,南极磷虾渔业过于集中于布兰斯菲尔德海峡,这也使得该海区磷虾资源状况及其生态学特征日益受到关注。南极磷虾群具有较为明显的昼夜垂直移动特征,开展此方面的研究可为探索其渔场形成机制提供基础数据,并为磷虾渔业反馈式管理提供参考。基于磷虾渔船上Simrad EK80记录的相关声学数据,使用Echoview软件判别声学数据中的磷虾群体,对2016年秋季布兰斯菲尔德海峡南极磷虾群昼夜垂直移动特征进行分析,并进一步分析影响磷虾群昼夜垂直移动的因素。结果显示,3月和4月磷虾群深度基本维持在250 m以浅,虾群最大深度出现在日升时分的频次最高(22.9%),而最浅深度出现在夜间时分的频次最高(36.0%),同时在日升时分,虾群厚度达到最大值;白天磷虾群多集中在较深水层,夜间会上浮到较浅水层。随着月份的推移,磷虾群平均深度总体呈现加深的趋势。光强和海底深度是影响磷虾群深度变化的2个主要因素。

Recently,krill fishery has concentrated increasingly in the Bransfield Strait,and krill abundance and ecological characteristics have received much attention.Antarctic krill(Euphausia superba)presents significant diel vertical migration(DVM)pattern,such studies were conducted to provide the basic data for exploring the formation mechanism of fishing ground and the reference for feedback management of krill fishery.Scientific acoustic device mounted in fishing vessels can reflect directly the distribution and vertical movement of krill in the water column.Based on the acoustic data recorded by Simrad EK 80 used in krill fishing vessel,krill swarms were identified using Echoview software.The present study analyzed DVM of krill in the Bransfield Strait during the austral autumn 2016 and the factors that impact DVM of krill were further explored.The results indicate that the depth of krill swarm maintained to above 250 m,the highest frequency of average deepest(shallowest)krill swarm occurs at sunrise(at night).The largest thickness of krill swarm presents at sunrise.Krill swarms are distributed in the deeper water column in the daytime,but move to the shallower depth at night.Compared to March,the average depth of krill swarms increased in April.Brightness and bottom depth are the main factors that impacted depth change of krill swarms.