We assessed the ecological uniqueness of fish and crustaceans in traditional fishing grounds from a tropical shallow marine ecosystem, where bycatch is historically high. Trimestral trawling was carried out between November 2009 and August 2010 in nine sites along 80 km of coastline in South Brazil. We investigated the local (LCBD) and species contribution to beta diversity (SCBD) using beta regression models, disentangling the influence of environmental (water, sediment characteristics) and biotic (S, abundance, diversity, dominance) parameters over LCBD; and species occurrence, total and mean local abundance association with SCBD. The shallow marine areas presented high beta diversity of fish and crustacean. We identified two ecological unique sites for fishes that occurred in colder sites, while the only unique site identified for crustaceans occurred, where crustacean species richness was lower. The ecological unique sites for both taxa were those with lower species richness and abundance, with distinct assemblages’ composition, although the location of the unique sites differed between taxa. Species contribution to beta diversity was mostly driven by species with intermediary–high distribution on the region with high variability in occurrence and abundance. High biodiversity is the general rule when assessing bycatch species, and the singularity of the species composition in the unique sites stems from the occurrence of rare species, which increases the size of the species pool.

我们评估了热带浅海生态系统传统渔场中鱼类和甲壳类动物的生态独特性，该生态系统兼捕历史最高。2009 年 11 月至 2010 年 8 月期间，在巴西南部 80 公里海岸线沿线的 9 个地点进行了三期拖网。我们使用β回归模型研究了本地（LCBD）和物种对β多样性（SCBD）的贡献，解开了环境（水，沉积物特征）和生物（S，丰度，多样性，优势）参数对LCBD的影响；和物种发生、总和平均局部丰度与 SCBD 的关联。浅海区鱼类和甲壳类生物多样性较高。我们确定了两个发生在较冷地点的鱼类生态独特地点，而唯一发现甲壳类动物的独特地点发生在甲壳类动物物种丰富度较低的地方。两个类群的生态独特位点都是物种丰富度和丰度较低的那些，具有不同的组合组成，尽管独特位点的位置在不同类群之间有所不同。物种对 β 多样性的贡献主要是由在该地区具有中等高度分布的物种驱动的，该地区的发生率和丰度具有高度可变性。高生物多样性是评估兼捕物种的一般规律，独特地点物种组成的奇异性源于稀有物种的出现，从而增加了物种库的规模。具有不同组合的组成，尽管独特地点的位置在分类群之间有所不同。物种对 β 多样性的贡献主要是由在该地区具有中等高度分布的物种驱动的，该地区的发生率和丰度具有高度可变性。高生物多样性是评估兼捕物种的一般规律，独特地点物种组成的奇异性源于稀有物种的出现，从而增加了物种库的规模。具有不同组合的组成，尽管独特地点的位置在分类群之间有所不同。物种对 β 多样性的贡献主要是由在该地区具有中等高度分布的物种驱动的，该地区的发生率和丰度具有高度可变性。高生物多样性是评估兼捕物种的一般规律，独特地点物种组成的奇异性源于稀有物种的出现，从而增加了物种库的规模。