ASPECTOS BIOECOLÓGICOS DE Macrobrachium amazonicum (HELLER,1862) A JUSANTE DO RESERVATÓRIO DA HIDRELÉTRICA DE TUCURUÍ –PARÁ

Abstract

This paper reports some bioecological aspects of Macrobrachium amazonicum(Heller, 1862) caught downstream the dam of Tucuruí power plant, Pará State.The samples were taken at Cametá county in the period from June, 2004 to May,2005. At the Cepnor/Ibama Carcinology laboratory the specimens were identified,sorted out by sex, measured and the morphologic and physiologic maturities ascertained. The pertinent performed analyses were: reproductive period,gonadosomatic index and length at first sexual maturity. The species occurred inall the samplings, even so it was more abundant during the rainy season. Thefemales were more abundant in a proportion of 1.2:1.0. The months with higherpercentages of females were October (85.9 %) and December (83.7 %), both onthe less rainy season, and January (67.9 %) on the rainy season. The highestnumber of immature females occurred in the less rainy season (August) and inJune (rainy season); females in maturation were more frequent in June and July;mature females were more abundant in May and August; and spent females inJanuary and October. The gonadosomatic mean index monthly variation indicatesApril and October as the period of major reproductive activity (rainy season). Theaverage length at first sexual maturity was 4.75 cm in total length. Key words: Macrobrachium amazonicum, ecological aspects, sex-ratio, length atfirst sexual maturity, reproductive season, Tucuruí power plant.