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首页> 外文期刊>Marine ecology progress series >Seasonal and event-scale variation in growth of Calanus agulhensis (Copepoda) in the Benguela upwelling system and implications for spawning of sardine Sardinops sagax
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Seasonal and event-scale variation in growth of Calanus agulhensis (Copepoda) in the Benguela upwelling system and implications for spawning of sardine Sardinops sagax

机译：本格拉上升流系统中agalahensis（Copepoda）生长的季节性和事件尺度变化及其对沙丁鱼Sardinops sagax产卵的影响

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摘要

We investigated the growth rate and egg production of Calanus agulhensis, the dominant copepod on the western Agulhas Bank region of the southern Benguela upwelling system (South Africa), and assessed the implications for the spawning of sardine Sardinops sagax. Daily weight specific growth rate (SGR) of copepod developmental stages (N6 to female) was measured monthly between September and March 1993/94 and 1994/95. Seasonally, SGRs of small stages (N6 to C2) remained relatively constant. By contrast, SGRs of large stages (C3 to female) mirrored changes in chl a related to seasonal warming and wind patterns, with a moderate peak in September/October and a larger peak in January to March. Superimposed on this seasonal cycle were fluctuations in response to winds on the event scale. At the onset of upwelling, mean female SGR across the shelf was slow. During sustained upwelling, female SGR increased, with a peak associated with enhanced chl a in the upwelling front and slower rates inshore in newly upwelled water and offshore in oligotrophic water. Female SGR was fastest during prolonged guiescence when high chl a levels extended over most of the shelf. During downwelling, female SGRs decreased again, with fastest rates inshore. Overall, SGRs were not related to temperature, but were related to chl a, with stronger relationships for larger stages. This suggested food limitation of larger stages, which may be a consequence of their preference for larger phytoplankton cells that only occur at high concentrations in restricted locations in time and space in the southern Benguela upwelling system. The spawning of sardine varied seasonally and coincided with the maximum chl a concentration and production of C, agulhensis eggs (daily egg production x female density), both of which are a good source of food for fish larvae. Thus the timing of sardine spawning maximizes the food available to their larvae.
机译：我们调查了南部Benguela上升流系统（南非）的西部Agulhas Bank地区的主要co足类Calaus agulhensis的生长速率和产卵量，并评估了沙丁鱼Sardinops sagax产卵的意义。在1993/94和1994/95年9月至3月之间，每月测量growth足类发育阶段（从N6到雌性）的日体重比生长率（SGR）。季节性地，小​​阶段（N6至C2）的SGR保持相对恒定。相比之下，大阶段（从C3到雌性）的SGR反映了与季节性变暖和风型有关的chl a变化，9月/ 10月为中度峰值，而1月至3月则为较大峰值。在这一季节性周期上叠加了事件规模上随风而产生的波动。发生上升流时，整个大陆架上的女性SGR缓慢。在持续上升过程中，雌性SGR升高，在上升前沿中的chl a升高与峰值有关，而在新涌出水中的近岸速率和贫营养水中的近海速率降低。当高chl a水平延伸到大部分货架时，雌性SGR在长时间的衰老期间最快。在下沉期间，女性SGR再次下降，近岸速度最快。总体而言，SGR与温度无关，但与chl a相关，在更大的阶段具有更强的关系。这暗示了较大阶段的食物限制，这可能是由于它们偏爱大型浮游植物细胞的结果，而大型浮游植物细胞仅在本格拉南部上升流系统中的时间和空间有限的位置以高浓度出现。沙丁鱼的产卵随季节变化，并且与最大浓度的Chl产和产的C.agulhensis卵（每天的卵产量x雌性密度）相吻合，这两种都是鱼类幼虫的良好食物来源。因此，沙丁鱼产卵的时机使幼虫可获得的食物最大化。

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