Abstract
Marine-protected areas (MPAs) have the potential to enhance fisheries through transport of larvae or by a net emigration of adult and juvenile fish to adjacent fished areas. A network of appropriately located MPAs will have the potential to reseed fished areas and other MPAs. Connectivity studies are therefore important to assess the effectiveness of a network of MPAs and to determine the spatial scale necessary for spillover effects. The principal aim of this study was to determine the potential for Kenyan MPAs to reseed adjacent fishing zones by evaluating the levels of genetic differentiation of populations of Lethrinus mahsena, a commercially important fish, along a continuum of protected and nonprotected sites. Fish samples were collected from MPAs (Mombasa and Kisite Mpunguti Marine Parks) and the fished reserves adjacent to the two MPAs. Total length and weight of the fish from the sites and fin clips from one of the pectoral fins were collected and preserved in 90% ethanol. Genomic profiles for each sample were obtained through genotyping by sequencing using diversity array technology markers. Results from population structure, diversity, and admixture analyses indicated very low genetic differentiation (F ST = 0.00184, P > 0.05) and low population substructure between samples obtained from the study locations implying a free exchange of fish across protected and nonprotected sites. There was a high gene flow and multidirectional migration rate among the sampling sites. Inbreeding was moderately high (F IS = 0.15, P < 0.05) in the marine parks, indicating high relatedness and probably limited mating options for the species due to small population size or spatial restriction. The lack of genetic differentiation between protected areas and open fishing grounds is indicative of genetic connectivity for the sky emperor. This reinforces the significance of maintaining protected areas to serve as breeding and spawning grounds of fish without adversely affecting the livelihoods of communities that depend on the various fisheries linked to MPAs.
Highlights
Establishment of marine-protected areas (MPAs) has been one of the most popular approaches used to protect oceans from anthropogenic threats (Steffen et al, 2007)
The Mantel test further confirmed that genetic differentiation was caused by geographical distance (Bird et al, 2011), as the distance between Bamburi and Shimoni was furthest among the sites
Low genetic differentiation is probably caused by high levels of genetic connectivity of L. mahsena in the study locations
Summary
Establishment of marine-protected areas (MPAs) has been one of the most popular approaches used to protect oceans from anthropogenic threats (Steffen et al, 2007). MPAs have been advocated worldwide as a powerful tool for conservation and management of fisheries and marine ecosystems (Pujolar et al, 2013). Genetic connectivity considerations and likely influence of physical and biotic factors play an important role in the design of MPAs (Palumbi, 2003). These areas are developed based on the assumption that they will act as sources of recruits and that there will be sufficient dispersal among them to maintain connectivity (Palumbi, 2003; Shanks et al, 2003). There is a general paucity of empirical data underpinning connectivity within and among MPAs worldwide (Botsford et al, 2001; Palumbi, 2003)
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