Reproductive biology of the planehead filefish Stephanolepis hispidus (Pisces: Monacanthidae), in the Canary Islands area

Abstract

The reproductive biology of the planehead filefish, Stephanolepis hispidus, in the waters of the Canary Islands area was studied. The study was conducted with a sample of 906 specimens from 8.9 to 25.9 cm in total length (TL) that were caught in fish traps from February 1998 to August 1999. Females predominated in the catches, and the sex ratio of 1.0:1.4 significantly deviated from the theoretical 1:1 distribution. This ratio varied when calculated by the length classes and by the season. Based on the monthly evolution of the Gonadosomatic Index (GSI) and the proportion of mature individuals, the spawning season occurred between May and October, with a peak in July and August for both sexes. This species accumulates energy reserves in the liver to be spent during the maturation of the gonads and spawning. The mean size at sexual maturity (L50) was 13.9 cm TL in females and 14.9 cm TL in males. The fecundity of S. hispidus fluctuated between 14,071 and 91,323 (mean = 55,239 ± 19,079), and the relative fecundity oscillated between 460 and 1,238 oocytes/g of eviscerated weight (mean = 904 ± 206). The diameter of the oocytes was 0.47 mm (SD = 0.10). The described reproductive characteristics provide options to fishery managers including regulations for spatial and temporal fishing closures to protect the breeding fish during spawning and the selectivity of fishing gears. Thus, it is proposed that fishing be limited to water depths greater than 30 m and that the minimum legal length of fish be established at 18 cm TL.