Idade, crescimento e mortalidade natural da arraia-cururu (Potamotrygon wallacei) do médio Rio Negro

Abstract

The study of growth parameters in elasmobranch is of great importance, mainly due to intrinsic characteristics such as slow growth, late maturation and low reproductive potential. While much of elasmobranch exhibit these characteristics, some species of marine rays show fast growth rate when compared to large sharks. The Potamotrygonidae stingrays family are the only fully adapted to the freshwater environment. Some species are legally exploited for ornamental fish; however, the management of the reference points of these species has no biological connotation and are strongly biased by the demand. Our objective was to estimate the growth rate and mortality of stingray cururu (Potamotrygon wallacei) in the Middle Rio Negro region. To estimate growth curve parameters, we realize growth bands count. To increase the number of data, the original data was retrocalculated to adjust the von Bertalanffy curve. The estimated parameters were used to estimate the natural mortality rate by Jensen and Pauly methods. The growth rate (K) was estimated at 0.26 y -1 , maximum theoretical size estimated 19.8 cm, the time when the size of the ray is zero (t0) is estimated at -1.4 years and size at birth estimated at 9.6 cm. Longevity was estimated between 7 years and 13 years and four months by Ricker and Fabens methods. Estimated mortality by two methods was 0.75 yr -1 and 0.42 yr -1 . The size exploited by ornamental fish (14 cm) represents individuals two years, accounting for the few survivors who went through the high mortality rate of the first two years. The exploitation of the cohort for one year indicates a catch limit of up to 12 cm, covering fishing in the age range of most natural mortality, minimizing the effect of fishing.