Di Tullio Juliana Couto, Gandra Tiago B R, Zerbini Alexandre N, Secchi Eduardo R
Laboratório de Ecologia e Conservação da Megafauna Marinha (ECOMEGA), Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, Rio Grande do Sul, Brasil.
Laboratório de Geotecnologias e Meio Ambiente (GEOMA), Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Sul (IFRS), Rio Grande, Rio Grande do Sul, Brasil.
PLoS One. 2016 May 31;11(5):e0155841. doi: 10.1371/journal.pone.0155841. eCollection 2016.
Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer continental shelf (150m) and slope (1500m) off southeastern and southern Brazil (23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings. The overall number of species was similar between the two areas, though it was higher in the spring in the south area. Five species were dominant and diversity varied more seasonally than spatially. ANOVA and kernel analyses showed that overall cetacean densities were higher in spring compared to autumn. Physeter macrocephalus, the most frequent species, concentrated throughout the south area at depths over 1000m in both seasons. Despite the overlapped occurrence at a broader scale, small delphinids presented latitudinal and in-offshore gradients as well as seasonal variation in distribution patterns, which could indicate habitat partitioning between some species. Delphinus delphis was only recorded in the south and its density decreased in areas where the presence of Stenella frontalis increased, mainly beyond the 250m isobath. Densities of S. longirostris and S. attenuata increased in lower latitudes and beyond the shelf break. The large delphinids Tursiops truncatus and Globicephala melas formed mixed groups in many occasions and were observed along the study area around depths of 500m. Grampus griseus was twice as frequent in the south area and densities increased in waters deeper than 600m. As expected, densities of both small and large migratory whales were higher during spring, over the continental slope, in the southeast area. The results presented here provided strong evidence on the importance of the outer continental shelf and slope to a diverse community of cetaceans occurring in the subtropical Southwestern Atlantic.
通过2009年至2014年春秋两季在巴西东南部和南部（约南纬23°至约南纬34°）外大陆架（约150米）和陆坡（1500米）进行的8次海上调查，研究了鲸类多样性和分布的时空模式。根据海洋学特征，将调查区域分为东南部和南部地区。在503次目击记录中观察到了21个物种。两个区域的物种总数相似，尽管南部地区春季的物种数更多。有5个物种占主导地位，多样性的季节变化大于空间变化。方差分析和核分析表明，与秋季相比，春季鲸类的总体密度更高。最常见的物种抹香鲸在两个季节都集中在南部地区1000米以上的深度。尽管在更广泛的尺度上存在重叠出现的情况，但小型海豚科动物呈现出纬度和离岸梯度以及分布模式的季节性变化，这可能表明一些物种之间存在栖息地划分。条纹原海豚仅在南部被记录到，其密度在长吻飞旋原海豚出现的区域有所下降，主要在250米等深线以外。长吻飞旋原海豚和热带点斑原海豚的密度在较低纬度和陆架断裂带以外增加。大型海豚科动物宽吻海豚和领航鲸在很多情况下形成混合群体，并在研究区域深度约500米处被观察到。灰海豚在南部地区的出现频率是其他地区的两倍，其密度在600米以上的水域增加。正如预期的那样，小型和大型洄游鲸类的密度在春季、大陆坡以及东南部地区更高。此处呈现的结果有力地证明了外大陆架和陆坡对西南大西洋亚热带地区鲸类多样化群落的重要性。
