Rodrigues-Filho, J.L.; Branco, J.O.; Monteiro, H.S.; Verani, J.R., and Barreiros, J.P., 2015. Seasonality of ichthyofauna bycatch in shrimp trawls from different depth strata in the southern Brazilian coast.
Changes in the species composition and ecological descriptors of fish assemblages in terms of abiotic factors such as depth, temperature, salinity, and granulometry were analyzed. Monthly trawls, from October 2003 to September 2004 (30 minutes each) were analyzed in two areas covering an important shrimp fishing site of the Brazilian coast. Results using bifactorial analysis of variance revealed a seasonal variation of environmental variables (p < 0.05), and granulometry analyses showed that the composition of the fishing grounds was similar—mostly sand. A total of 12,613 fish were collected: 7880 in area I and 4733 in area II. The highest values of capture in numerical abundance (catch per unit effort) occurred during winter. Fifty taxa were caught in area I, and 53 taxa were caught in area II. Both values are considered high when compared to previous studies conducted in nearby areas. Sciaenidae was the most speciose family in all samples and in both areas were dominant in number of species (37 species in area I and 42 species in area II). Cynoscion striatus was the most abundant and dominant species in both areas. Estimates of ecological descriptors, such as richness, diversity, and evenness, showed that the ichthyofauna structure was strongly influenced by climatic factors, and all values were more pronounced during fall and winter. The permutational multivariate analysis of variance demonstrated that ichthyofauna species composition differs among seasons. The Student's t test applied a posteriori showed that the community composition differed (significantly) in the following comparisons: spring vs. fall (p < 0.05) and winter vs. summer (p < 0.05). According to similarity percentage analysis, changes in the community structure were mainly correlated with species classified as abundant, which occurred unevenly during the different periods. Our results show that the fish community is influenced by seasonal variations such as salinity and temperature but not by depth or sand grain sizes.
As alterações na composição específica e nos descritores ecológicos das assembleias de peixes em função dos fatores abióticos, tais como profundidade, temperatura, salinidade e granulometria, foram analisadas no presente trabalho. Arrastos mensais de trinta minutos de duração foram realizados em duas áreas com diferentes profundidades em um importante ponto de pesca camaroeira do litoral sul brasileiro. Paralelamente, registrou—se os valores de temperatura e salinidade da água, bem como foi amostrado o tipo de substrato dos fundos de pesca. A aplicação do teste t de Student demonstrou variação sazonal dessas variáveis ambientais no estudo (p < 0,05) e a análise granulométrica demonstrou que a composição dos fundos de pesca foi bastante similar, sendo composta principalmente por areia. No total foram capturados 12.613 exemplares, sendo 7.880 na área I e 4.733 na área II. Os maiores valores de captura (CPUE) ocorreram no inverno. Foram capturados 50 táxons na área I e 53 na área II, um alto valor quando comparado com estudos pretéritos em localidades próximas. A família dos sciaenideos foi a mais representativa nas coletas, predominando em ambas as áreas espécies incidentais (37 na área I e 42 na área II). Cynoscion striatus foi a espécie mais abundante e predominante em ambas as áreas. As estimativas dos descritores ecológicos, tais como a riqueza, a diversidade e equitabilidade, evidenciaram que a estrutura da ictiofauna foi fortemente influenciada pelo fator tempo e que os valores mais acentuados ocorreram no outono e inverno. A aplic
