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Larval fish assemblage structure at coastal fronts and the influence of environmental variability
Frontiers in Ecology and Evolution ( IF 3 ) Pub Date : 2021-05-10 , DOI: 10.3389/fevo.2021.684502
Paula Pattrick , Nicolas Weidberg , Wayne S. Goschen , Jennifer M. Jackson , Christopher D. McQuaid , Francesca Porri

Within the coastal zone, oceanographic features, such as fronts, can have major effects on the abundance and distribution of larval fish. We investigated the effects of fronts on larval fish assemblages by jointly collecting physical (ADCP and CTD) and biological (larvae) data in the nearshore waters of the south coast of South Africa, on four separate neap-tide occasions. Accumulation of fish larvae at predominantly internal wave-associated fronts was observed, with higher larval densities inshore of and within the front than farther. On each occasion, larvae of coastal species with pelagic eggs (Mugillidae and Sparidae) were numerically dominant at the front itself, while inshore of the front, larvae of coastal species with benthic eggs (Gobiesocidae and Gobiidae) were more abundant. Offshore catches mainly comprised Engraulidae (pelagic species with pelagic eggs) larvae, which were generally restricted to the bottom, where current velocities were onshore on each occasion. On the occasion when fast (>100cm/s) currents prevailed, however, accumulation of the larvae of coastal species occurred offshore of the front, and larvae were mixed throughout the water column. Thus, larval occurrence at these coastal frontal systems was strongly affected by the degree of mixing by currents, which on most occasions resulted in onshore retention. The results underline the importance of frontal systems in determining the nearshore distributions of fish larvae, particularly by retaining coastal fish species in the inshore region. The environmental variability observed at these frontal systems has potential implications for larval connectivity of fish populations.

中文翻译:

沿海地区幼体鱼类组合结构及环境变化的影响

在沿海地区,海洋特征(例如前缘)可能会对幼体鱼的丰度和分布产生重大影响。我们通过在四个单独的浪潮潮汐时刻联合收集了南非南部沿海近岸水域的物理(ADCP和CTD)和生物(幼虫)数据,研究了锋面对幼虫鱼组合的影响。观察到鱼幼虫在主要与内部波相关的前沿聚集,与近岸相比,其近岸和内的幼体密度更高。在每种情况下,带有浮游卵的沿海物种(Mugillidae和Sparidae)的幼虫在数量上占优势,而在沿海近岸,带有底栖卵的沿海物种(Gobiesocidae和Gobiidae)的幼虫数量更多。离岸捕捞物主要包括En科(带浮游卵的浮游物种)幼虫,通常被限制在底部,每次都在岸上以目前的速度。然而,在快速(> 100cm / s)的水流泛滥之际,沿海物种的幼虫在前缘附近发生了积聚,并且幼虫在整个水柱中混合。因此,在这些沿海额叶系统中幼虫的发生受到洋流混合程度的强烈影响,在大多数情况下,这导致陆上滞留。结果强调了额叶系统在确定鱼类幼体近岸分布中的重要性,特别是通过将沿海鱼类保留在近海区域中。
更新日期:2021-05-10
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