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首页> 外文期刊>Estuarine Coastal and Shelf Science >Larval fish assemblages across an upwelling front: Indication for active and passive retention
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Larval fish assemblages across an upwelling front: Indication for active and passive retention

机译：上涌锋面的幼体鱼群：主动和被动滞留的指示

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In upwelling areas, enrichment, concentration and retention are physical processes that have major consequences for larval fish survival. While these processes generally increase larval survival, strong upwelling can also increase mortality due to an offshore transport of larvae towards unfavorable habitats. In 2013 a survey was conducted along the Senegalese coast to investigate the upwelling effect with regard to larval fish assemblages and possible larval fish retention. According to water column characteristics two distinct habitats during an upwelling event were discriminated, i.e. the inshore upwelled water and the transition area over the deepest part of the Senegalese shelf. Along the two areas 42,162 fish larvae were collected representing 133 species within 40 families. Highest larval fish abundances were observed in the inshore area and decreasing abundances towards the transition, indicating that certain fish species make use of the retentive function of the inner shelf area as spawning grounds. Two larval fish assemblages overlap both habitats, which are sharply delimited by a strong upwelling front. One assemblage inhabited the inshore/upwelling area characterized by majorly neritic and pelagic species (Sparidae spp., Sardinella aurita), that seem to take the advantage of a passive retention on the shelf. The second assemblage consisted of a mix of pelagic and mesopelagic species (Engraulis encrasicolus, Carangidae spp. and Myctophidae spp.). Some species of the second assemblage, e.g. horse mackerels (Trachurus trachurus and Trachurus trecae), large finned-lantern fish (Hygophum macrochir) and foureyed sole (Microchints ocellatus), revealed larval peak occurrences at intermediate and deep water layers, where the near-ground upwelling layer is able to transport larvae back to the shelf. This indicates active larval retention for species that are dominant in the transition area. Diel vertical migration patterns of S. aurita, E. encrasicolus and M. ocellatus revealed that a larval fish species may adapt its behavior to the local environment and do not necessarily follow a diurnal cycle. Field observations are essential to be integrated in larval drift models, since the vertical and horizontal larval distribution will have major consequences for survival. Comprehending larval survival mechanisms is necessary for the ultimate goal to understand and predict recruitment. (C) 2016 Elsevier Ltd. All rights reserved.
机译：在上升流地区，富集，浓缩和滞留是对幼体鱼类生存产生重大影响的物理过程。虽然这些过程通常会提高幼虫的存活率，但由于幼虫向不利栖息地的近海运输，强烈的上升流也可能增加死亡率。 2013年，塞内加尔海岸沿线进行了一项调查，以调查有关幼体鱼类组合和可能的幼体鱼类滞留的上升效应。根据水柱特征，区分出上升流事件中的两个不同的栖息地，即近岸上升水和塞内加尔大陆架最深部分的过渡区。在这两个地区，共收集了42162个鱼幼体，代表40个科中的133种。在沿海地区观察到最高的幼体鱼丰度，并且在过渡期时丰度逐渐降低，这表明某些鱼类利用内架区的保持功能作为产卵场。两个幼虫鱼群在两个栖息地上都​​重叠在一起，它们被强烈的上升流锋线清晰地界定。一种组合栖息在沿海地区/上升流地区，其特征是主要是中性和浮游性物种（Sparidae spp。，Sardinella aurita），它们似乎利用了被动保留在架子上的优势。第二种组合包括中上层物种和中上层物种（Engraulis encrasicolus，Carangidae spp。和Myctophidae spp。）的混合物。第二种组合的某些种类，例如竹荚鱼（Trachurus trachurus和Trachurus trecae），大型翅鳍鱼（Hygophum macrochir）和富足的（Microchints ocellatus）在中层和深水层均出现幼虫高峰，近地上升流层能够运输幼体。回到架子上。这表明在过渡区占优势的物种的活跃幼虫保留。 S. aurita，E。encrasicolus和M. ocellatus的Diel垂直迁移模式表明，幼鱼可能会使其行为适应当地环境，并且不一定遵循昼夜周期。实地观察对于将幼体漂移模型整合起来至关重要，因为垂直和水平幼体分布将对生存产生重大影响。理解幼虫生存机制对于理解和预测募集的最终目标是必要的。 （C）2016 Elsevier Ltd.保留所有权利。

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