Inter-estuarine and temporal patterns of the fish assemblage of subtropical subestuaries along the Río de la Plata coast (Uruguay)

ABSTRACT Fish assemblages in subestuaries have been poorly studied worldwide. In order to evaluate the inter-estuarine and temporal variability of the ichthyofauna of subestuaries along the Uruguayan coast of the Río de la Plata (RdlP), the Pando, Solís Chico and Solís Grande systems were sampled between 2011 and 2013. Fish biomass, abundance, species richness and diversity indices were analysed, defining fish assemblages characterised by a few species and great abundance. Estuarine resident and freshwater species represented 55.5% of the fish assemblage according to estuarine use guilds. Species occurrence was similar in the three subestuaries, but the relative abundances differed among them. The analysed community parameters showed a decreasing trend from west to east along the Uruguayan coast. Highest diversity and fish abundance were recorded in the Pando system located in the proximities of an important spawning area in the inner RdlP estuary. In the Solís Grande subestuary occurred the lowest species richness and fish abundance. The Solís Chico was characterised as a transitional subsystem. All three subestuaries showed an increase in species richness and abundance during high temperature periods, probably related to the life cycle of the species sharing habitats between the RdlP and the coastal subestuaries. This study constitutes the first step in assessing the fish assemblage patterns in coastal ecosystems of the RdlP and an approach about the ecological role of the subestuaries in the southwest Atlantic Ocean.摘要：全球范围内对亚河口（subestuary）鱼类群落的研究均较为匮乏。为评估拉普拉塔河（Río de la Plata, RdlP）乌拉圭沿岸亚河口鱼类区系（ichthyofauna）的河口间与时间变异性，研究团队于2011至2013年间对潘多（Pando）、小索利斯（Solís Chico）与大索利斯（Solís Grande）三个系统开展了采样工作。研究分析了鱼类生物量、丰度、物种丰富度与多样性指数，结果显示该区域鱼类群落以少数物种占绝对优势、整体丰度较高为特征。依据河口利用功能群划分，河口定居种与淡水种占该鱼类群落总物种数的55.5%。三个亚河口的物种出现频率较为相似，但各站点的物种相对丰度存在显著差异。所分析的群落参数沿乌拉圭海岸呈现自西向东递减的趋势。位于拉普拉塔河内湾重要产卵场邻近区域的潘多系统，其鱼类多样性与丰度均为最高。大索利斯亚河口的物种丰富度与鱼类丰度均为最低。小索利斯亚河口则属于过渡性亚系统。三个亚河口在高温时段的物种丰富度与丰度均有所提升，这可能与共享拉普拉塔河与沿岸亚河口生境的物种的生命周期密切相关。本研究为评估拉普拉塔河沿岸生态系统的鱼类群落格局迈出了第一步，同时也为探究西南大西洋沿岸亚河口的生态功能提供了研究基础。