What are the main local drivers determining richness and fishery yields in tropical coastal fish assemblages?

ABSTRACT Seasonal ecological effects caused by temperature and photoperiod are typically considered minimal in the tropics. Nevertheless, annual climate cycles may still influence the distribution and abundance of tropical species. Here, we investigate whether seasonal patterns of precipitation and wind speed influence the structure of coastal fish assemblages and fishing yields in northeast Brazil. Research trips were conducted during the rainy and dry seasons using commercial boats and gear to sample the fish community. Diversity was analyzed using abundance Whittaker curves, diversity profiles and the Shannon index. Principal Component Analysis (PCA) was used to analyze associations between the abundance of species and various environmental variables related to seasonality. A total of 2,373 fish were collected, representing 73 species from 34 families - 20 of which were classified as both frequent and abundant. Species richness was greater and more equitable during the rainy season than the dry season - driven by changes in the precipitation rather than to wind speed. Species diversity profiles were slightly greater during the rainy season than the dry season, but this difference was not statistically significant. Using PCA was identified three groups of species: the first associated with wind speed, the second with precipitation, and the third with a wide range of sampling environments. This latter group was the largest and most ecologically heterogeneous. We conclude that tropical coastal fish assemblages are largely influenced by local variables, and seasonally mediated by annual changes related to precipitation intensity and wind speed, which in turn influences fishery yields.

摘要：通常认为，温度与光周期（photoperiod）引发的季节性生态效应在热带地区微乎其微。尽管如此，年度气候周期仍可能影响热带物种的分布与种群丰度。本研究旨在探究巴西东北部沿海的降水与风速季节性模式是否会影响沿岸鱼类群落（fish assemblages）结构与渔业产量。本研究在雨季与旱季期间，借助商用渔船及配套捕捞装备开展实地采样，以调查鱼类群落组成。研究采用物种丰度惠特克曲线（Whittaker curves）、多样性剖面与香农指数（Shannon index）分析群落多样性，并通过主成分分析（Principal Component Analysis，PCA）解析物种丰度与各类季节性相关环境变量间的关联。本次研究共采集鱼类样本2373尾，隶属于34科73种，其中20种兼具较高出现频率与种群丰度。雨季的物种丰富度显著高于旱季，且物种分布更为均匀，该差异主要由降水变化而非风速变化驱动。雨季的物种多样性剖面值略高于旱季，但该差异未达到统计学显著性水平。通过主成分分析，本研究共识别出三类物种类群：第一类与风速相关，第二类与降水相关，第三类对应广泛的采样环境；第三类类群规模最大且生态异质性最高。本研究结论表明，热带沿岸鱼类群落在很大程度上受局地变量影响，并通过与降水强度及风速相关的年度周期变化呈现季节性调控效应，进而对渔业产量产生影响。