The influence of population structure and reproductive aspects of the genus Stellifer (Oken, 1817) on the abundance of species on the southern Brazilian coast

Abstract

The differences between abundance and the relationship with aspects of population and reproductive Stellifer rastrifer, Stellifer stellifer and Stellifer brasiliensis were analysed. Data were collected monthly trawl directed for capture of seabob shrimp in Armação do Itapocoroy, an important fishing area on the southern Brazilian coast. The chi-square test showed that the population of S. rastrifer presented values of capture significantly higher than others in all evaluated periods. The frequency distribution of total length curves combined with records of the size at first maturity (L 50 ) showed that S. rastrifer is a species with a majority of the adults effectively participating in the reproductive period. The frequency of occurrence of individuals in reproduction monthly examined together with changes in the gonadosomatic index (GSI) and the reproductive activity index indicated that spring was the main breeding season for the three species. However, it was observed that the reproductive period of S. rastrifer was more pronounced and more extensive than that of its congeners, apparently providing it with ecological advantages and enabling a more effective population balance given the pressure exerted by fishing in the study area.Keywords: fish reproduction, gonadosomatic index, reproductive activity index, population dynamics, bycatch, species coexist.A influência da estrutura populacional e dos aspectos reprodutivos na abundância de espécies do gênero Stellifer (Oken, 1817) no litoral sul brasileiro ResumoAs diferenças nas abundâncias numéricas e a relação dessas com os aspectos reprodutivos e populacionais de Stellifer rastrifer, Stellifer stellifer e Stellifer brasiliensis foram analisadas. Os dados foram coletados em arrastos mensais destinados à captura do camarão sete-barbas em Armação do Itapocoroy, uma importante área pesqueira do litoral sul brasileiro. O teste de qui-quadrado demonstrou que a população de S. rastrifer apresentou valores de captura significantemente superiores que as demais em todos os períodos avaliados. A distribuição em classe de tamanho sobreposta ao valor de primeira maturação sexual (L 50 ) evidenciou que S. rastrifer foi a espécie com a maior proporção de indivíduos capturados considerados adultos, ou seja, que efetivamente participam do evento reprodutivo. A frequência de ocorrência mensal dos estádios de maturação sexual analisada conjuntamente com as variações do índice gonadossomático e do índice de atividade reprodutiva indicaram que a principal estação reprodutiva para as três espécies foi a primavera, Entretanto, observou-se que o período reprodutivo de S. rastrifer foi mais acentuado e mais extenso do que o de suas congenéricas, aparentando lhe fornecer vantagens ecológicas e possibilitando um equilíbrio populacional mais eficaz frente à pressão exercida pela pesca na área de estudo.Palavras-chave: reprodução de peixes, índice gonadossomático, índice de atividade reprodutiva, dinâmica de populações, fauna acompanhante, coexistência de espécies.

Reproductive biology of Cetengraulis edentulus (Cuvier, 1829), the major fishery resource in Guanabara Bay, Brazil

“…Condition factor (K) is another descriptor widely used in studies on reproductive biology of fishes, predicting that individuals with higher K values are in better physiological conditions (Rodrigues-Filho et al, 2011). In our study, C. edentulus of higher K values were recorded immediately before the periods of greatest reproductive activity, indicating that those individuals store reserves to withstand future losses of energy during gonad maturation.…”

“…In addition to those descriptors, Dei Tos et al (2002) used the index of reproductive activity (IRA), a method that 820 combines the proportion of reproducing individuals and values of gonadosomatic index to evaluate the reproductive activity for the whole fish assemblage or single populations. Although the IRA has been broadly applied for fresh water fish assemblages (Dias et al, 2005;Bailly et al, 2008;Braga et al, 2008), few studies used this index to describe reproductive activity of marine fish (Souza & Chaves, 2007;Rodrigues-Filho et al, 2011).…”

Feeding habits of the congeneric species Stellifer rastrifer and Stellifer brasiliensis (Acanthopterygii: Sciaenidae) co-occurring in the coast of the state of Santa Catarina, Brazil

“…A similar length distribution for the congener species Stellifer stellifer was found by Almeida and Branco (2002), in Penha, a county in Santa Catarina Satate, located only a few miles from Porto Belo, when in the fall of 1997 64.5% of the sample were represented by individuals shorter than 8 cm. A larger number of sampled juveniles was also found by Rodrigues-Filho et al (2011) in the same area. This can be explained by the low selectivity in bottom trawls used in shrimp fisheries (Coelho et al, 1985(Coelho et al, , 1987Paiva Filho, 1990, 1995), and therefore very subtle variations in the values of Kr for the two species throughout the year, leads us to disregard any significant seasonal variation in the feeding composition, so that these variations would not be a result of food shortages or changes of abiotic factors, but reflect the changing age structure of the population, since it is influenced by the entry of new individuals periodically, whether small or bigger (youth and adults).…”

“…These species occur in abundance in the studied area, as discussed by Rodrigues-Filho (2011), where the overlapping of the reproductive period was observed. In this case, the values of relative condition factor indicated that Stellifer brasiliensis more effectively leverages food resources than S. rastrifer.…”

Influence of the flood pulse on the reproduction of Tocantinsia piresi (Miranda Ribeiro) and Auchenipterus nuchalis (Spix & Agassiz) (Auchenipteridae) of the middle Xingu River, Brazil

“…In A. nuchalis, females matured at larger sizes than males, a pattern found in other auchenpterids (Freitas et al, 2011;Santos et al, 2013) as well as many other tropical fishes (Barbieri et al, 2004;Nunes et al, 2004;Gomiero et al, 2007;Rodrigues-Filho et al, 2011;Prudente et al, 2015). In this case, size differences between males and females at first maturity may be related to reproductive competition, with males investing in early maturation in order to be ready to reproduce as soon as possible, ensuring the perpetuation of their genes.…”