Effects of the shrimp trawling fisheries on the reproductive activity of fish: a study case in southern Brazil.

Abstract

The consequences of changing in closed seasons of small scale shrimp in Southern Brazil trawling on the breeding activity of fish bycatch species were investigated from samples collected from October 2005 to March 2007. From the 72 species recognized, 21% were Sciaenidae. Trawling caught mainly immature fish, and individuals of 22 species were found at this condition only. Other 32 species presented mature individuals, nine of them showing also spawned or ripe individuals. Reproductive Activity Index has indicated that in trawling Pellona harroweri and Stellifer sp are found in a very intense breeding activity, and that Isopisthus parvipinnis, Paralonchurus brasiliensis, Stellifer brasiliensis, S. stellifer and Symphurus tesselatus are found in intense breeding activity. Spring 2005, Summer 2006 and Summer 2007 were periods with species in a very intense reproductive activity. Summer 2007, having succeeded the closed season of spring 2006, has showed just one more species in breeding activity than summer 2006, a year when trawling was closed in autumn. In view of this, it is proposed that this change in the closed season for trawling did not affected the reproducitive activity of the fish assemblage as a whole.