Idade e crescimento do cascudo preto Rhinelepis aspera (Siluriformes, Loricariidae) no rio Paranapanema, bacia do rio Paraná

Abstract

Age and growth were estimated from counts of hyaline zones in the vertebrae of the armoured catfish Rhinelepis aspera. The annual cycle of the hyaline zones formation was determined by monthly variation of the length of specimens with the same number of hyaline zones and by the monthly frequency of marginal rings. The method to infer age was validated for age groups ranging from 3 to 9 years by these procedures. Data indicate that hyaline zones are formed essentially during April-May. The oldest fish examined was estimated to be 10 years old. The growth curve in Von Bertalanffy's growth equations was: males : Lt = 64,6 [1 - e-0,124.(t + 0,86)] females : Lt = 74,5 [1 - e-0,102.(t + 0,85)] The length-weight relation of males and females was different and has been described by the equations: males: Wt = 0,0153 . Lt2,986 (n = 689) females: Wt = 0,0137 . Lt3,018 (n=632) males + females: Wt = 0,0151 . Lt3,007 (n = 1.321) The estimated weights of male and female asymptotic measurements were 3894.1 g and 6105.0 g respectively. The reduced number of older specimens used in the adjustment of the growth curve may have produced a higher asymptotic measurement.