Estudo da ocorrência e reprodução do surubim (Pseudoplatystoma coruscans, Agassiz 1829) no Lago de Sobradinho, Remanso-BA

Abstract

Aiming to contribute to the knowledge of the occurrence and reproductive biology of surubim pintado (Pseudoplatystoma coruscans), studies on the production and reproductive aspects were made in areas I and II in the Lake of Sobradinho – Remanso – BA, located 09º40'15" South Latitude and 42º04'26" Greenwich Longitude. The occurrence was verified by the control of unloading in the port of Remanso, the samples proceeded from fish captured with fishing with mesh varying from 6 to 25 cm and hook, in the period from January 2004 to December 2005. For occurrence study a form was used defining: place of capture and unloading, dates, fishing resources, the sample amount of surubim and other species. It was captured non eviscerated surubim specimens in the period between January 2004 and January to February 2005 for reproductive studies, based in biometric descriptions and histological analyses of the gonads. The morfometric description was effected to macroscopically characterize them defining the GSI (Somatic Gonad Index). Microscopic characterizations were made to describe the histological aspects of ovaries and testicles. The stages of gonad development were described and it was established a maturity scale (1 rest, 2 initial maturation, 3 advanced maturation and 4 spawned or spermatic) according to histological characteristics. The frequencies of males and females had been defined by classes of length and weight. The parameters observed during the experiment were: pH, temperature, clearance and rainfall rates. The total monthly production fished was 38,203 kg, in which the surubim in all the period of captures represented 18 % of all the catches. The captured specimen total of surubim for the reproductive study was 230, being 129 females and 101 males. Females were registered in all capture period, the males had been absent only in January 2005. Males and females were registered in rest between the months of March and July. Females were found in the stages 2 and 3 ofmaturation in September and spawned in January 2004 and January and February 2005. Males in these same stages were also captured in January, September and October of 2004. The peak of spawned females occurred in the months of January 2004 and January and February of 2005, and the spermatic males were registered in the months of January and September of 2004 and February of 2005. The sexual proportion was 1.27 female to 1 male. The biggest captured male reached 90 cm, and the smallest 42 cm of total length. The biggest female presented 135 cm and the smallest 45 cm. The greatest body weight registered was of a spawned female weighing 21.7 kg and the smallest in a in rest female with 0.4 kg. The biggest female in advanced maturation presented 109 cm and the smallest 88 cm. The smallest spawned female with 72 cm. The biggest male in advanced maturation with 75 cm and the smallest 62.5 cm. In spite of predatory fishing, the dam, the destruction of the ciliar bush, the pollution, the not respecting the defense period, the lake of Sobradinho still continues with great fishing production, thanks to the structure of the areas with food production that guarantees the reproduction and shelters that protect fries and young fish, so assuring the permanence of a lot of species, including the surubim.