José F Domínguez-Contreras
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Adrian Munguia-Vega
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Bertha P Ceballos-Vázquez
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Marcial Arellano-Martínez
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Francisco J García-Rodríguez
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The fishery for octopus in Northwest Mexico has increased to over 2,000 tons annually, but to date the specific composition of the catch has been ignored. With at least three main species with varying life histories targeted by artisanal fisheries in the region, lack of information about the distribution of each species and metapopulation size and structure could impede effective fisheries management to avoid overexploitation. Here we tested if different life histories in three species of octopus help to predict observed patterns of genetic diversity, population dynamics, structure and connectivity that could be relevant to the sustainable management of the fishery. We sequenced two mitochondrial genes and genotyped seven nuclear microsatellite loci to identify the distribution of each species in 20 locations from the Gulf of California and the Pacific coast of the Baja California peninsula. We tested four a priori hypothesis derived from population genetic theory based on differences in the fecundity and dispersal potential for each species. We found that the species with low fecundity and without a planktonic larval stage (Octopus bimaculoides) had lower average effective population size and genetic diversity, but higher levels of kinship, population structure, and richness of private alleles, suggesting limited dispersal and high local recruitment. In contrast, two species with higher fecundity and planktonic larvae (O. bimaculatus, O. hubbsorum) showed higher effective population size and genetic diversity, and overall lower kinship and population structure, supporting higher levels of gene flow over a larger geographical scale. Even among the latter, there were differences in the calculated parameters possibly associated with increased connectivity in the species with the longest planktonic larval duration (O. bimaculatus). We consider that O. bimaculoides could be more susceptible to over exploitation of small, isolated populations that could have longer recovery times, and suggest that management should take place within each local population. For the two species with pelagic larvae, management should consider metapopulation structure over larger geographic scales and the directionality and magnitude of larval dispersal between localities driven by ocean currents. The distribution of each species and variations in their reproductive timing should also be considered when establishing marine reserves or seasonal fishing closures.
Comparison of the population structure of Streptococcus uberis mastitis isolates from Austrian small-scale dairy farms and a Slovakian large-scale farm
