Distribution and abundance of South‐west Atlantic anchovy spawners (Engraulis anchoita) in relation to oceanographic processes in the southern Brazilian shelf

Abstract

The reproductive environment of the South‐west Atlantic anchovy, Engraulis anchoita, in the southern Brazilian coast was investigated using maritime weather reports from the US National Climatic Center. These reports were summarized to yield seasonal distributions of sea surface temperature, wind stress and Ekman transport for 2‐month segments of the seasonal cycle. The vertical oceanographic structure and dynamics were studied using temperature and salinity data collected from oceanographic cruises. The seasonal distribution and biomass of South‐west Atlantic anchovy spawners were estimated by acoustic surveys. Anchoita spawns intensively off southern Brazil during winter and early spring when the Ekman transport is directed onshore, and the combined effects of freshwater run‐off and the flow of cold water near the bottom result in a strong vertical stability over the continental shelf. During this season, primary production peaks due to nutrient input from Sub‐Antarctic waters and freshwater run‐off. These conditions would avoid dispersal of eggs and larvae offshore and favour the production and maintenance of fine‐scale food particle aggregations required for successful first feeding of newly hatched larvae. In summer, the conditions are almost reversed and anchoita spawners are virtually absent from the area. Thus, the spawning strategy of anchoita in southern Brazil seems to be tuned in a way to optimize larval retention, minimize exposure to turbulent mixing and take advantage of enhanced plankton productivity.

Zooplankton and ichthyoplankton distribution on the southern Brazilian shelf: an overview

“…Eddies and frontal processes are regarded as important mechanisms for retention and concentration of zooplankton and fish larvae towards the shelf (Lima and Castello, 1995). However, there is still very little knowledge about transport processes along the shelf break in this region.…”

“…Larval fish diversity increases towards the shelf break (~200 km from the coast) where high-salinity Tropical Waters (TW) from the Brazil Current (BC) dominate. The importance of water column stability, larval transport and retention, as well as enrichment processes for selecting the reproductive habitat of Engraulis anchoita was discussed by Lima and Castello (1995).…”

Long-term variation in the ichthyofauna of Flamengo Cove, Ubatuba, São Paulo

“…In terms of the number of individuals, we noticed that nearly 71% of the total number of individuals was sampled in spring, although the biomasses of both seasons are nearly 50% of the total weight. This shows that there are more individuals relatively smaller in spring than in autumn, which may indicate a possible reproductive season for at least some of the species (e.g., Araújo & Santos, 1999;Bernardes & Dias, 2000;Robert & Chaves, 2001;Castello & Castello, 2003;Godefroid et al, 2004;Lima & Castello, 2007;Bruno & Muelbert, 2009). As for the biomass, approximately 71% of the total weight was sampled in 1990 although the number of individuals did not differ much between the two years.…”

Uma Estratégia Para O Monitoramento Da Anchoita (Engraulis Anchoita, Engraulididae, Pisces): O Último Estoque De Pequeno Peixe Pelágico Capaz De Sustentar Uma Pesca Comercial De Média Escala Em Águas Brasileiras

“…Uma análise crítica foi realizada quanto a metodologia de obtenção de dados de todos os cruzeiros voltados à estimativas de abundância de anchoita na região sul do Brasil, que incluem quatro campanhas da série AREPE, entre 1980 e 1990 e três da série ECOPEL (Lima & Castello, 1995) . As setas indicam o sentido da navegação.…”

“…Durante o inverno, uma fração do estoque migra de águas argentinas e uruguaias para o Brasil, onde há condições favoráveis de desova e alimentação, voltando para águas costeiras e intermediárias argentinas no fim da primavera, pico da estação reprodutiva (Lima & Castello, 1995). Considera-se a estação de pico reprodutivo da espécie na região sul brasileira, correspondente aos meses de inverno, como a época mais adequada a levantamentos acústicos de abundância.…”