Biologia reprodutiva de Rhinelepis aspera Spix & Agassiz,1829 (Osteichthyes,Loricariidae) no submédio São Francisco,Petrolina-PE

Abstract

Aiming to investigate the population and reproductive biology of the “black scale fish” Rhinelepis aspera Spix & Agassiz, 1829, studies have been carried through in a section of the Submiddle São Francisco River Valley , next to the city of Petrolina-PE, located 09º 09' of South Latitude and 40º 22" West of Longitud. Two hundred forty eight specimens were catched by net and mesh (meshes from 8 to 14 cm) in the period of February of 2005 to January of 2006. For each individual was determined sex, total length (Tl-cm), total weight (Tw-g) and gonadal weight (Gw-g). The morfometric description was effected to characterize them macroscopically, defining the GSI (Gonadossomatic Index). Microscopic characterizations had been made to describe the histological aspects of the ovaries and the testicles. The stages of gonadal development were described and a scale of maturity was established (1 - rest, 2 - initial maturation, 3 – mature or advanced maturation and 4 - disposed or spawned) in function of the histological characteristics. During the period collect there was a slight predominance of females (56,4%). The females were more numerous in the classes of bigger lengths and had reached the length of the first maturation (L50) about 41 cm. Themales had reached the length of the first maturation (L50) about 41,5 cm. From 50,5 cm all individuals, males and females, are apt to participate in the reproductive process (L100). It was obtained for all the population of R. aspera the value of angular coefficient (q ≅ 3. 0), as to the relation total weight/ total length, the growth is an isometric type. The GSI presented greater values in the months of February and December 2005 for females and in the months of April 2005 and January 2006 for males.