Swarm characteristics of Antarctic krill Euphausia superba relative to the proximity of land during summer in the Scotia Sea

被引:31
作者
Klevjer, T. A. [1 ]
Tarling, G. A. [2 ]
Fielding, S. [2 ]
机构
[1] Univ Oslo, Dept Biol, N-01316 Oslo, Norway
[2] British Antarctic Survey, NERC, Cambridge CB3 0ET, England
关键词
Acoustics; Southern Ocean; Distribution; Vertical migration; Predation; Seals; Penguins; Fishery; DIEL VERTICAL MIGRATION; SOUTH-GEORGIA; FUR SEALS; MACARONI PENGUINS; TARGET-STRENGTH; AGGREGATION CHARACTERISTICS; MEGANYCTIPHANES-NORVEGICA; ACOUSTIC OBSERVATIONS; SPATIAL-DISTRIBUTION; SOCIAL AGGREGATION;
D O I
10.3354/meps08602
中图分类号
Q14 [生态学(生物生态学)];
学科分类号
071012 ; 0713 ;
摘要
We studied the relationship between the proximity of land and the distribution and swarming characteristics of Antarctic krill across the Scotia Sea in January and February 2003. Krill swarms identified with a Simrad EK60 (38 kHz, 120 kHz) echosounder were grouped into 4 categories according to distance from shoreline: 0 to 50 km, 50 to 100 km, 100 to 200 km and >200 km. Cross-sectional areas of swarms were significantly larger inshore, with a mean value of 120 m(2) in the 0 to 50 km zone compared to < 80 m(2) further offshore. The packing concentration of krill within inshore swarms was also significantly greater, with an average density of 95 ind. m(-3) compared to between 24 and 31 ind. m(-3) elsewhere. A large proportion of the biomass was concentrated into a small number of large, dense swarms throughout the survey area, and this trend increased with decreasing distance from shore. The highest median number of swarms per km and krill acoustic biomass per km was found in the 50 to 100 km zone. However, a significantly greater number of large, biomass-rich swarms occurred in the 0 to 50 km zone compared to all other zones. Swarms in the 0 to 50 km zone were also significantly further apart. The majority of swarms were located in the upper 50 m during the daytime although they were marginally deeper in the night in offshore regions. Krill are likely to move between inshore and offshore environments continuously over their lifetimes. The change in krill behaviour between environments could be a response to local predatory threats over short spatial and temporal scales.
引用
收藏
页码:157 / 170
页数:14
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