Length-weight relationships and biological aspects for 34 fish species from trÊs irmÃos reservoir, lower tietÊ river basin, SP – Brazil

Abstract

The length-weight relationship of fish species is widely used in fisheries monitoring programs and it is an important tool for proposing stock management measures. The objective of this study was to estimate the growth parameters of 34 species belonging to the fish community captured by experimental fishery in the Três Irmãos reservoir, Tietê river. The biological and ecological characteristics of these species are also presented in order to understand the profile of the present fish community. The fish were collected during ten experimental fishing seasons between October/2015 and February/2018, with quarterly frequency using four types of fishing gear. All fish captured were identified and the total length-TL (cm), standard length-SL (cm) and total weight-TW (g) were measured. The length-weight relationship was established using the linear regression TW vs SL (log-transformed): Log (TW) = log (a) + b log (SL), where a is the regression curve intercept (coefficient related to body shape) and b is the coefficient of regression (exponent indicating the type of growth). A total of 7,319 individuals was identified, comprising five orders: Characiformes (7 Families), Siluriformes (5 Families), Perciformes (1 Family), Cichliformes (1 Family) and Cyprinodontiformes (1 Family). The most abundant species were Plagioscion squamosissimus (N=1,513), Geophagus sveni (N=1,160), Serrasalmus maculatus (N=1,049) and Metynnis maculatus (pacu-CD) (N=974), all of them being target species for professional artisanal fishing, with the exception of pacu-CD, which is discarded since it has no commercial interest. From the whole set of analyzes 15 species (44.1%) have positive allometric growth type (3.15< b <3.59), 14 (41.2%) isometric (2.98< b < 3.08), and 5 (14.7%) negative allometric growth (2.7 < b < 2.90). Among the species studied nine reached a maximum length above that of the FishBase: Cichla piquiti (TL= 55.4 cm), Crenicichla haroldoi (SL= 21.5 cm), C. jaguarensis (SL= 23.5 cm), Cyphocharaxnagelii (TL= 22.9 cm), Hypostomus ancistroides (TL= 28.5 cm), Metynnis maculatus (TL= 19.5 cm), Piaractus mesopotamicus (SL= 60.0 cm), Roeboides descalvadensis (SL= 11.3 cm) and Schizodon borellii (TL= 40.0 cm).