Bicolor damselfish Stegastes partitus (Poey 1986) has been used as a model for studies of the population structure of reef species as an aid for the designing and monitoring of marine protected areas. Studies using allozymes have shown gene flow between populations, but it has been suggested that the lack of structuring could be a consequence of the insensitivity of these markers. We used 11 polymorphic microsatellite loci to evaluate the genetic connectivity of 299 bicolor damselfish from four representative areas of the Colombian coast in the South Caribbean (Santa Marta, Rosario Islands, Capurganá, and San Andrés Island). Genotyping was made using detection by fluorescence of multiple alleles. Genetic differentiation among geographic populations and different oceanographic scenarios was analyzed using the statistic Φ ST and analysis of molecular variance. The correlation between genetic and geographic distance was explored using the Mantel test. All loci were polymorphic, and showed a high number of alleles per locus and heterozygosity deficit with a consequent departure from Hardy-Weinberg equilibrium. We found evidence of gene flow between the geographic and oceanographic populations examined and a lack of correlation between the genetic and geographic distances. The information obtained can be used by the agencies responsible for the design and conservation of marine protected areas and as reference in the monitoring of the genetic diversity and structure of the population under study.

Species of the family Lutjanidae constitute an important fishery resource in tropical marine areas worldwide and are intensely exploited because of their excellent commercial value and quality. In Colombia, the lane snapper Lutjanus synagris is considered vulnerable to overfishing due to its biological characteristics, habitat deterioration, and historical decrease in catch rates in regions where it used to comprise the highest percentage of the landings. In order to generate more biological information needed to make effective fishery management decisions and policies, the genetic structure of L. synagris was analyzed in three areas of the Colombian Caribbean (Santa Marta, Rosario Islands, and Capurganá) using microsatellite-type molecular markers. Fourteen primers reported for two phylogenetically close species (Rhomboplites aurorubens and Lutjanus campechanus) were analyzed, eight of which were polymorphic and informative for the species under study. All loci were found to depart from Hardy-Weinberg equilibrium due to marked heterozygote deficiency in all the populations studied. Both the analysis of molecular variance (total population ΦST = 0.006, P = 0.022) and spatial analysis of molecular variance showed a slight statistically significant population structure (best FCT = 0.003, ΦST = 0.007, P = 0.0001) that separated the Capurganá population from those of the other areas with no evidence of isolation by distance (Mantel test Rxy = 0.023, P = 0.057). The results suggest that the life history of the species and the regional oceanographic conditions play an important role in determining the genetic structure and the existence of two different genetic stocks that should be managed according to their population structure.