Phenotypic divergence in reproductive traits of the marbled parrotfish, Leptoscarus vaigiensis (Quoy and Gaimard, 1824), among reefs of varying protection levels in Kenya

Abstract

Phenotypic divergence in the reproductive traits of the marbled parrotfish (Leptoscarus vaigiensis) was studied among six reef sites exposed to varying levels of fishing pressure in coastal Kenya from May 2011 to April 2012. Baited fish traps were used to capture fish within two no-take marine parks (Malindi and Watamu) and their adjacent reserves that allow regulated fishing. Fish samples from two non-protected reefs (Kanamai and Vipingo) were obtained from fishers. Reproductive attributes (fecundity, oocyte size and length at first maturity) of the species were determined and compared between sites. Results showed significant differences in fecundity between sites (F = 3.742, P = 0.004) with higher mean (± SD) fecundity for fish in the parks (110,128 ± 75,492) and reserves (145,570 ± 88,873) compared to those in non-protected sites (76,250 ± 55,337). Further, Multidimensional Scaling (MDS) analysis using fecundity estimates clustered sites based on their protection levels. Fish in non-protected sites have equivalent to higher fecundities at smaller sizes relative to larger fishes from protected sites. A comparison of length at first maturity (L₅₀) between sites indicated that females from non-protected sites matured at lower lengths (11.2 cm, 11.1-11.4 cm, 95% CI) compared to those from park (16.7 cm, 15.7-17.3 cm, 95% CI) and reserve (16.8 cm, 16.6-17.1 cm, 95% CI) sites. Overall, the results indicated some level of phenotypic divergence between sites, which is likely to be an adaptive strategy for enhancing resilience to fishing pressure and helping to sustain local populations. The real causes of this divergence cannot be partitioned between fishing mortality, genetic variability or habitat- induced variations. Nonetheless, the data provides a basis for future studies on the causal factors for the observed divergence in life-history traits of the species between reefs.