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首页> 外文期刊>ICES Journal of Marine Science >Distribution, feeding behaviour, and condition of Cape horse mackerel early life stages, Trachurus capensis, under different environmental conditions in the northern Benguela upwelling ecosystem
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Distribution, feeding behaviour, and condition of Cape horse mackerel early life stages, Trachurus capensis, under different environmental conditions in the northern Benguela upwelling ecosystem

机译：本格拉北部上升流生态系统中不同环境条件下海角鲭鱼鲭鱼早期生命阶段的分布，摄食行为和状况

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摘要

Early life history (ELH) traits are key to understand variable recruitment success and hence the stock size of marine fish. One of the currently most puzzling ecosystems in this regard is the northern part of the Benguela Current upwelling system off Namibia. Here, populations of the formerly dominant pelagic species, sardine and anchovy, failed to recover during the last three decades after a dramatic decline. In contrast, Cape horse mackerel, Trachurus capensis, maintained a constant population size. Warming of the system and shoaling of hypoxic zones together with feedback loops within an altered foodweb are discussed to be responsible for this regime shift. In this study, we address the role of larval traits for the successful performance of the T.capensis population under the present environmental conditions with the focus on feeding ecology. We investigated seasonal variations of the geographical distribution, growth rate, feeding ecology, and nutritional condition of their ELH stages and examined relationships with water temperature, dissolved oxygen concentration, and micro-zooplankton composition. T. capensis' ELH stages showed a wide spatial and seasonal distribution, a preference for higher water temperatures (18-21 degrees C) and presence over a wide range of dissolved oxygen concentrations (0.13-6.35 ml O-2 l(-1)). Feeding success was high and mainly different groups of Copepoda were targeted, which were strongly size selected. The high dietary importance of micro-copepods during large parts of the larval phase indicates successful exploitation of this food source, which has increased in abundance during the last decade. It also explains observed best nutritional conditions at temperatures between 18 and 21 degrees C, since these small copepods are commonly associated with warmer temperatures. Altogether, these traits enhance the species' probability to encounter suitable environments for the survival of their ELH stages, which is likely to lead to their high recruitment success in the northern Benguela ecosystem.
机译：早期生活史（ELH）特征对于了解可变的募集成功率以及因此而引起的海水鱼类种群数量至关重要。在这方面，目前最令人费解的生态系统之一是纳米比亚附近本格拉水流上升系统的北部。在这里，曾经占主导地位的远洋鱼类沙丁鱼和an鱼的种群在急剧下降之后的过去三十年里没有恢复。相比之下，开普角鲭鱼Trachurus capensis保持不变的种群规模。讨论了系统变暖和缺氧区的散布以及食物网改变后的反馈回路，都是造成这种状态变化的原因。在这项研究中，我们着眼于饲料生态学，探讨了幼虫性状在目前环境条件下对美国山毛榉种群成功表现的作用。我们调查了ELH阶段的地理分布，生长速度，摄食生态和营养状况的季节性变化，并研究了与水温，溶解氧浓度和微浮游动物组成的关系。 T. capensis的ELH阶段显示出较宽的空间和季节分布，更喜欢较高的水温（18-21摄氏度），并且存在较大范围的溶解氧浓度（0.13-6.35 ml O-2 l（-1） ）。饲喂成功率很高，主要针对不同种类的Co足类动物，它们的大小均经过严格选择。在幼虫期的大部分时间里，微型脚足纲动物的饮食重要性很高，这表明该食物来源的成功开发，在过去十年中，这种食物来源的数量大量增加。它还解释了在18至21摄氏度之间观察到的最佳营养条件，因为这些小co足类动物通常与温度升高有关。总而言之，这些特征增加了该物种遇到适合其ELH阶段生存的环境的可能性，这很可能导致其在本格拉北部生态系统中的高募集成功率。

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