FISHERY CHARACTERISTICS AND POPULATION GENETIC STRUCTURE OF LETHRINUS LENTJAN IN SELECTED FISHING AREAS ALONG THE KENYA COAST

Abstract

The species Lethrinus lentjan (pink-ear emperor) is commercially important and primarily distributed in the western region of the Indo-Pacific Ocean. This species contributes a significant portion of the artisanal landings, making it one of the dominant species along the Kenya coast. This species is, however, reported to be overexploited. Data on L. lentjan for the stock status of its artisanal fishery and genetic diversity is still inadequate along the coast of Kenya. Therefore, the study’s focus was to evaluate the recent stock status as well as population genetic differentiation for this species in selected fishing areas along the coast of Kenya to provide management recommendations. Monthly shore-based catch assessments for fisheries and biological data were collected for 11 months (October 2020 to September 2021). Fin clips for genetic analysis were obtained from the caudal fin and stored in 100% ethanol prior to DNA extraction. The CTAB approach was used for genomic DNA extraction using ethanol-preserved samples. These samples were inspected for purity and quantity and stored at -20oC before sequencing. Polymerase chain reaction (PCR) and sequencing of the CO1 gene were performed using universal primers for marine fishes. A total of 22 lethrinid species were recorded over the study period. Msambweni had the highest lethrinid artisanal landings, accounting for more than 69%, while L. lentjan contributed 25% of the total landings. Female individuals of L. lentjan were more abundant than males, with an overall sex ratio 1:1.53, and this differed significantly from the expected ratio of 1:1. Lethrinus lentjan recorded a negative allometric growth with an asymptotic length (L∞) and growth coefficient (K) of 51 cm and 0.46y-1 , respectively. The mortality coefficients Z, M, and F were 2.07, 0.963, and 1.10, respectively, with an exploitation rate of 0.53. The recorded E value of 0.53, in this study, was slightly higher than the optimum exploitation rate E = 0.5, indicating this species was slightly overexploited. The absence of genetic differentiation between sites indicates L. lentjan comes from a single genetic population, and the management strategy of this fishery needs to be interpreted carefully along the Kenya coast.