Influence of Size, Age, and Spawning Season on Sex Change in Black Sea Bass

Abstract

AbstractA tagging study was conducted off the New Jersey coast to study sex change in Black Sea Bass Centropristis striata as a function of size, age, and spawning season. Throughout 2011–2013, 3,670 fish were measured and 1,498 were tagged from research, charter, and commercial fishing vessels. Of the tagged fish, 437 were recaptured. Size at 50% probability of sex change was 355 mm TL; the proportion of female fish in sexual transition increased with body size from 0.5% at 175–225 mm to 15.7% at 375–425 mm and increased with age from 0.6% at 3 years old to 18.2% at 6 years old. Relatively few females (8 of 107) changed sex during the spawning season, but a larger proportion (8 of 22 females) transitioned between spawning seasons. The proportion of females with transitional gonads was lowest at the start of the spawning season in June (0.2%), slowly increased over the summer, and sharply peaked just after the spawning season in October (9.5%). In addition, a high proportion of young mature fish were male (40% at age 2), which may indicate the presence of primary males. This is the first tagging study to estimate sex change as a function of size, age, and season in a protogynous hermaphroditic fish species. Use of tagging avoids potential problems that are associated with inferring sex change rates from sex ratios based on catch data.