Growth and Survival Rates of Exploited Coral Reef Fishes in Kenyan Marine Parks Derived From Tagging and Length-Frequency Data

Abstract

Growth increments were obtained from 157 recaptured fishes and yielded estimates of absolute growth rates (cm day-1) for 11 species and growth parameters (K, L[infinity] for 7 species. A total of 3,916 exploited coral reef fishes were tagged within Malindi and Watamu National Marine Parks, Kenya, in 2001 and 2002. Growth rates ranged over an order of magnitude among species. Of the dominant commercial species, the whitespotted rabbitfish, Siganus sutor, had both the highest absolute growth rate (21.9[plus or minus]14.6 cm yr-1) and growth coefficient (K = 1.2 yr-1), whereas emperors (Lethrinus spp.) had somewhat lower rates (overall mean 10.95[plus or minus]3.65 cm yr-1; maximum for L. nebulosus, 4.6[plus or minus]7.3 cm yr-1 ; K = 0.92 yr-1). In contrast, the orangestriped triggerfish, Balistapus undulatus, had an average annual growth rate of only 2.0[plus or minus]1.9 cm. Growth coefficient (K) estimated for S. sutor and the sky emperor, Lethrinus mahsena, using length-frequency analysis (LFA) indicated a lower growth rate (K=0.54 yr-1) for S. sutor than derived from tagging, but for L. mahsena the LFA-derived growth rate (K=0.64 yr-1) was comparable to the K derived from tagging (0.57/year). Growth rates estimated here for most, but not all species (L. mahsena in particular) were similar to those reported from other coral reef regions. Annual survival rates (S) derived from length-converted catch-curves were higher for S. sutor (0.145) than for L. mahsena (0.029), whereas, natural annual mortality rates (M) were comparable for the species (S. sutor, 1.12; L. mahsena, 1.25).