Reproductive biology of Brazilian mackerel, Somberomorus brasiliensis (Osteichthyes:Scombridae), off Rio Grande do Norte State

Abstract

The Spanish mackerel,  Scomberomorus brasiliensis , is a marine species of commercial importance, which inhabits a  major part of the coastal waters of Brazil, except for the extreme north and south. The objective of the present study was to  determine its reproductive biology in the coastal waters of Rio Grande do Norte. Fish samples were collected on a monthly  basis, during August, 2003 to July, 2004. The  fish were measured, weighed, dissected and the gonads were removed,  weighed and examined for the sex and for estimating such variables as mean size at  fi rst sexual maturity, gonadossomatic  index, fecundity, type of spawning and breeding season. The results indicate that the females of S. brasiliensis attained  gonad maturity at 280 mm and males at 345 mm of total length. The gonadossomatic index (GSI) ranged from 1.18 to  13.54 in females and from 1.10 to 4.66 in males. The absolute and relative fecundities were estimated as 871,523 oocytes  and 952 oocytes per gram of  fish weight. The relative frequency distribution of the oocyte diameter sizes indicates that  Brazilian mackerel is a total spawner. Breeding of this species occurred all year round, with a peak coinciding with  the month of December. The use of small-meshed nets accounts for the capture of immature  fishes, which impairs the  recruitment process of this species.