Population biology of Stellifer rastrifer, S. brasiliensis and S. stellifer in Caraguatatuba Bay, northern coast of São Paulo, Brazil

Abstract

Ecosystems may reflect environmental changes in many respects, from the debilitation of individuals to alterations in community composition. Equally, population parameters may provide reliable indications of environmental changes. Members of the sciaenid fish genus Stellifer are usually very abundant where they occur, often with two or more species living in sympatry. Here, the population dynamics of three Stellifer species from southeastern Brazil were assessed. Sampling was carried out in shallow marine areas of Caraguatatuba Bay, from August 2003 to October 2004. The species evaluated were Stellifer rastrifer (n=3183), S. brasiliensis (n=357) and S. stellifer (n=116). The area under greater continental influence tended to support more, but smaller individuals. Size variations over time were similar among species and negatively correlated with Krel, which showed smooth fluctuations. The general length-frequency distribution was concentrated between 6.0 and 9.0 cm, and the great majority of females did not present mature gonads during the sampling period. The findings support the existence of a stratification by size for these species, indicating that the area is essential for the development of younger fish. Failure to consider these characteristics for the management of similar areas may have serious implications for these environments.<br>Os ecossistemas podem refletir mudanças ambientais em muitos aspectos, desde o enfraquecimento dos indivíduos até alterações na composição da comunidade. Do mesmo modo, os parâmetros populacionais podem fornecer indicações confiáveis de mudanças ambientais. Sciaenídeos do gênero Stellifer são peixes geralmente muito abundantes e em suas populações é frequente a ocorrência de duas ou mais espécies simpátricas. No presente trabalho, a dinâmica populacional de três espécies de Stellifer do sudeste do Brasil foi avaliada. A amostragem ocorreu em águas rasas das zonas marinhas da Baía de Caraguatatuba, de agosto de 2003 a outubro de 2004. As espécies avaliadas foram Stellifer rastrifer (n = 3.183), S. brasiliensis (n = 357) e S. stellifer (n = 116). Os resultados mostraram que a área sob maior influência continental tende a suportar um número maior de indivíduos menores. Variações de tamanho ao longo do tempo foram semelhantes entre as espécies e negativamente correlacionadas com o Krel, que apresentou flutuações suaves. De modo geral a distribuição de freqüência de comprimento ficou concentrada entre 6,0 e 9,0 cm e para a grande maioria das fêmeas as gônadas se apresentaram imaturas durante o período avaliado. Os resultados suportam a existência de estratificação populacional por tamanho dentro destas espécies, indicando que a área é apropriada para o desenvolvimento de juvenis. A desconsideração de tais características pode acarretar sérias implicações para a gestão dessas áreas

Seasonality, Dietary Overlap and the Role of Taxonomic Resolution in the Study of the Diet of Three Congeneric Fishes from a Tropical Bay

“…Since the three congenerics showed very similar size ranges and means, and it is also known that they behave very similarly concerning population biology in the study area [28], these results do not reflect ontogenetic shifts. These differences could be due to different periods of foraging activity, a common strategy for resource partitioning [2], [5].…”

The barred grunt Conodon nobilis (Perciformes: Haemulidae) in shallow areas of a tropical bight: spatial and temporal distribution, body growth and diet

“…From this point on, both the traditional approach (best goodness-of-fit value, considering oscillation modification of the VBGM, as proposed by Pauly and Gaschutz 1979) and a visual one (which took into account biological features of the species and the particularities of the area) were performed. For the former, we used the ELEFAN I routine of the FISAT package.…”

Novel structure in sciaenid fish skulls indicates continuous production of the cephalic neuromast cupula

“…For this purpose, two months, April and September 2004, considered of key importance due to the local pattern of population dynamics14, were chosen for ALCB size assessments. For these periods, the same individuals assessed for ALCB abundance had their ALCBs measured, i.e., 60 individuals for each month, homogeneously distributed across a length range.…”