Selective catching of "tambiú” Astyanax bimaculatus Linnaeus, 1758 [Characiformes, Characidae], by employing monofilament gill-nets, in Ibitinga Reservoir, Tietê River, São Paulo State, Brazil

Abstract

The mean selectivity curve of gill-nets employed to cach "tambiú", Astyanax bimaculatus, in Ibitinga Reservoir, Tietê River, São Paulo State, Brazil, was determined according to Gulland (1969). The observed results are:

c* (L) = e ^{- 0.5207 (L-1.3478 m)2}

Where:

c* (L) = relative frequency of retention

L = total length of the fish (cm)

m = internal perimeter of the mesh (cm)

The interval of selection for different mesh sizes (m) is given by:

L_m = mean L - 1.15 (cm)  and  L_M = mean L + 1.15 (cm).

The following relationships were also determined:

- Total weight / total length of body: W = 0.0184 L ^2.9685, where W = total weight of body (g) and L = total length of the fish (cm)

- Fish perimeter (l) / mean fish total length relationship: l = 0.8299 L (cm)

- Total lengths (and body weights) / internaI perimeter of meshes

Since the females body length at the first sexual maturation is known (L_pm = 8.43 cm) in the reservoir, gill -nets with internaI perimeter major than 6.3 cm are recommended.