ASSESSING THE IMPACTS OF BEACH SEINES ON THE POPULATION STRUCTURE OF Leptoscarus vaigiensis QUOY AND GAIMARD, 1824 AND Siganus sutor VALENCIENNES, 1835 IN SOUTH COAST KENYA

Abstract

The small-scale fishery in Kenya is an important source of food and livelihood for the coastal fishing communities. The fishery is characterized by multi-species, multi-gear, open access, and poor management. This has resulted in increased pressure due to increased fishing effort augmented by the use of destructive fishing gear, threatening the sustainability of these fishery resources. This study assessed the impact of beach seines on the population structure of the shoemaker spinefoot rabbitfish Siganus sutor and the marbled parrotfish Leptoscarus vaigiensis in the fisheries of the Majoreni seascape in south coast Kenya. The Siganus sutor and L. vaigiensis are among the most common commercial fish species of the small-scale fisheries of the Kenya coast. The study was conducted through monthly shore-based catch assessments during February through August in 2015, covering both the northeast monsoon (NEM) season (February, March and April) and the southeast monsoon (SEM) season (July and August). A sub-sample of 186.5 kg, (35.6%) of the landed fish was sampled out of a total catch of 524.35 kg (64.4%) composing of 67 species belonging to 22 families. The two species, Siganus sutor and L. vaigiensis collectively made up 33.8% of all fish species sampled by weight. Analysis estimated the overall daily catch rate at 1.51± 0.15 kg/fisher/day over the study period. Further analysis showed distinct separation of catches by months (nMDS), while ANOSIM showed significant differences in species composition between months (r = 0.170; p<0.05). The daily catch rate per fisher differed between months but was not significantly different (1-way ANOVA: df = 4; f = 2.007; p = 0.109). The total length sizes at sexual maturity (L50) were determined as 22.8 cm for S. sutor and 14.5 cm for L. vaigeinsis. Both species showed differences in the proportion of mature individuals during the survey months. Siganus sutor showed immature individual's sizes ranged between <15 to <20 cm and mature individual's sizes from <20 to over 30 cm while L. vaigiensis