Crescimento e estado de explotação do Salminus brasiliensis (Cuvier, 1816) (Characiformes: Characidae) na Bacia do Alto Paraguai

Abstract

Measure growth parameters has been an important tool in assessing the dynamics of populations, providing support for the management of stock assessment. Populations are characterized by individual differences, so estimates of long-term population dynamics can be affected by factors of intra-population variation, which highlights the importance of understanding the nature of the variation in growth between individuals of a population. Among the calcified structures used to estimate growth of teleost, the most suitable is the otolith, which grows by successive deposition and increments, forming an important register in life story of fish. In the basin of the Upper Paraguay, Salminus brasiliensis is one of the most attractive species for sport and commercial fishing, and yet, has suffered greatly reducing their populations. This paper examines the somatic growth of S. brasiliensis at different scales and assess fish stocks. Sampling was carried out in the main tributaries of the Upper Paraguay River Basin. With the reading of growth rings was estimated that the captured individuals had zero to seven years old. For backcalculation fish size in earlier ages was used to capture biological intercept method. By indirect analysis of the marginal increase was found ring of the formation period in the period of the dry season (June and July). To assess the growth parameters, the data were adjusted for age and length growth model was used von Bertallanffy. To estimate the growth parameters in individual and spatial scale was used mixed model using the maximum likelihood method. The first model estimated growth parameters at the individual scale (L∞ = 894 mm; k = 0.19; t0 = -2.06). The second model estimated the same parameters, but in spatial scale (L∞ = 895.94 mm; k = 0.20; t0 = -1.71). The third model estimated the parameters on an individual basis, considering the effect of growth between males and females (L∞ = 753 mm;k= 0.31; t0 = -1.45). All models were compared using the Akaike Information Criterion (AIC) and the first model had the best fit to the length at age data (model 1 = 2762.5; model 2 = 3207.7; model 3 = 3177.5). Thus, it was found that there are only changes in growth on an individual basis and the use of statistical models that consider the individual variation was found to be good tool to represent the biology of the species. The yield per recruit analysis and the current status of exploitation show that has not reached the maximum sustainable yield, which indicates that the stock of S. brasiliensis is not overexploited.