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首页> 外文期刊>Marine ecology progress series >Influence of salinity on life history traits of the bonga shad Ethmalosa fimbriata (Pisces, Clupeidae): comparison between the Gambia and Saloum estuaries
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Influence of salinity on life history traits of the bonga shad Ethmalosa fimbriata (Pisces, Clupeidae): comparison between the Gambia and Saloum estuaries

机译：盐度对邦加sha鱼Ethmalosa fimbriata（双鱼座，lu科）生活史特征的影响：冈比亚和萨卢姆河口的比较

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The common West African bonga shad represents a large part of the fish biomass in 2 neighbouring estuaries that function in different ways. The Gambia estuary has a normal salinity gradient, while the Saloum has an inverse gradient. Bonga shad Ethmalosa fimbriata were collected in both ecosystems during a 16 mo period (June 2001 to September 2002) at 5 locations, to investigate the role of salinity on life history traits. The main traits were studied at a spatio-temporal scale: reproduction from macroscopic examination of the gonads, oocyte counting and measuring, and growth from interpretation and measurements of a sub-sample of otoliths. Analysis of genetic differentiation at 3 intronic and 1 anonymous nuclear gene loci was also carried out to investigate differences between estuaries and among locations. The results did not show any allelic frequency heterogeneity between populations, indicating that populations of both estuaries represent 1 single panmictic unit, and that selection is not significantly acting on these loci. Hence, the response of the different traits to environmental variation may primarily represent phenotypic plasticity. The seasonal cycle of reproduction was clearer in the Saloum, occurring during a long period (January to August). The calculated size at maturity was reduced for both sexes in the upper Saloum, where the salinity was highest. The relative fecundity and the oocyte size were larger in the Saloum. On the otoliths, translucent zones, formed each year at the end of the rains (September to October), were used to estimate the age in months. Growth rates were reduced in the hypersaline environment of the Saloum, whereas growth differences were smaller between the Gambia and the pooled Saloum data, with a salinity < 60 psu. Growth was faster in the lower parts of the Saloum, related to better conditions for fish. The results illustrate that an environment with high salinity (> 60 psu) affects the growth, reduces the size-at-maturity and increases the fecundity of E. fimbriata.
机译：常见的西非邦加sha鱼在两个相邻河口中以不同的方式起作用，代表了鱼类生物量的很大一部分。冈比亚河口具有正常的盐度梯度，而Saloum具有反梯度。在16个月期间（2001年6月至2002年9月）在5个地点的两个生态系统中收集了Bonga shad Ethmalosa fimbriata，以研究盐度对生活史特征的作用。在时空尺度上研究了主要特征：生殖腺的宏观检查，卵母细胞计数和测量的繁殖，以及耳石子样品的解释和测量的生长。还对3个内含子和1个匿名核基因位点的遗传分化进行了分析，以研究河口之间和位置之间的差异。结果未显示种群之间的任何等位基因频率异质性，表明两个河口种群均代表一个单一的全景单元，并且选择对这些基因座的作用不明显。因此，不同性状对环境变化的响应可能主要代表表型可塑性。萨洛姆（Saloum）的繁殖季节周期性更清晰，发生在很长一段时间（1月至8月）。盐度最高的上萨卢姆州，男女双方的成熟时计算出的大小都减小了。 Saloum中的相对繁殖力和卵母细胞大小较大。在耳石上，每年降雨结束时（9月至10月）形成的半透明带用于估算月龄。在Saloum的高盐环境中，生长速率降低，而冈比亚和所收集的Saloum数据之间的生长差异较小，盐度小于60 psu。 Saloum下部的生长较快，这与鱼类的良好条件有关。结果表明，高盐度（> 60 psu）的环境会影响生长，降低成熟时的大小并增加大肠杆菌的繁殖力。

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