Reproductive biology of pacu Piaractus mesopotamicus (Holmberg, 1887) (Teleostei: Characidae) in the Cuiabá River Basin, Mato Grosso, Brazil

Abstract

The purpose of this study was to analyze the reproductive strategy and life-history traits involved in the reproductive processes of P. mesopotamicus in two regions of the Cuiabá River basin, the first of these encompassing its headwaters (Cuiabazinho River -Rosário Oeste) and the other the flood area of the Cuiabá River (Porto Cercado -Poconé). A total of 391 individuals were sampled monthly from August 2006 to July 2007, 159 from the headwaters and 232 from the flood area. The size structure indicated that the females in the headwaters attain longer lengths than the males, while no differences in length were found in the flood area. Females predominated in the headwaters, while males outnumbered females in the flood area. The reproductive period in the headwaters extended from October to March, but was restricted to October and November in the flood area. Feeding activity showed significant differences in both sexes between the stages of gonadal maturation, with the highest values recorded in stages of gonadal inactivity. The length at first maturity was 34.89 cm and the length at which all specimens were ready for reproduction was 44 cm at both sampling sites. The spawning type was total and fecundity was positively correlated to the size of the female.O presente estudo teve como objetivo analisar a estratégia reprodutiva e os traços de história de vida relacionados aos processos reprodutivos de P. mesopotamicus em duas regiões da bacia do rio Cuiabá: uma que representa a região das cabeceiras (rio Cuiabazinho -Rosário Oeste) e outra que abrange a área de inundação do rio Cuiabá (Porto Cercado -Poconé). Indivíduos foram amostrados, mensalmente, no período de agosto de 2006 a julho de 2007. Foram amostrados 391 indivíduos, sendo 159 de ambiente de cabeceira e 232 de área alagada. A estrutura de tamanho mostrou que em ambiente de cabeceira as fêmeas atingem comprimentos maiores que os machos, enquanto que em área alagada não houve diferença nos comprimentos. Ocorreu predomínio de fêmeas em ambiente de cabeceira, e de machos em área alagada. O período reprodutivo para o ambiente de cabeceira estendeu-se de outubro a março e para a área alagada foi restrito a outubro e novembro. A atividade alimentar apresentou diferenças significativas para ambos os sexos entre os estádios de maturação gonadal com os maiores valores encontrados em estádios de inatividade gonadal. O comprimento de primeira maturação foi de 34,89 cm e o comprimento em que todos estão aptos a reproduzirem foi de 44 cm para ambos os locais. O tipo de desova é total e a fecundidade foi positivamente relacionada ao tamanho da fêmea.

Effects of re-stripping on the seminal characteristics of pacu ( Piaractus mesopotamicus ) during the breeding season

“…This result can be explained, at least partially, by differences in each particular spawning season. Spawning is affected by abiotic parameters, such as temperature, photoperiod, and pluviosity (Costa and Mateus, 2009;Oliveira et al, 2010;Dala-Corte and Fialho, 2014;Giora et al, 2014), which can influence the spermatogenic process (Rurangwa et al, 2004).…”

Individual, spatial and inter-sex variation in somatic growth: a study of Piaractus mesopotamicus (Characiformes: Serrasalmidae), a long-distance freshwater Neotropical migratory fish

“…Frequency of growth marks formation in otoliths, based on the marginal increment method (MI) indicated two band-forming periods; linked to the reduction in P. mesopotamicus growth rate, it is likely that the first band is formed during the late the ebb and early dry season, about a year after hatching of the cohort (Costa, Mateus, 2009). The results of this study confirm that cyclical process (dry season and wet) occur in tropical wetland environments with distinct seasonal variation, and that these have direct impacts on fish life cycles (Pérez, Fabré, 2009).…”

“…Individuals then keep increasing until the second year and then reduce the rate of body growth. This slowdown in body growth increase rate is probably associated with the onset of gonadal maturation that occurs when total length reaches around 35 cm (Costa, Mateus, 2009), which was the average length of two-year old individuals.…”

“…The difference in body length between males and females is related to variation in growth parameters (Morita et al, 2015). From the adaptive point of view, this variation allows greater fecundity per unit biomass, since larger females can produce more eggs (Costa, Mateus, 2009), or the production of larger eggs with greater food reserves and thus the promotion of enhanced larval survival rates (Stearns, 1976;Araújo, Haimovici, 2000).…”

“…Gonads were removed, and histological analysis was performed to identify the sex. For a detailed description of gonad processing the sex identification in P. mesopotamicus, see Costa, Mateus (2009).…”