Genetic Composition of Largemouth Bass in Puerto Rico Reservoirs

Abstract

AbstractThe Largemouth Bass Micropterus salmoides includes two recognized subspecies, the Northern Largemouth Bass (NLMB; M. salmoides salmoides) and the Florida Largemouth Bass (FLMB; M. salmoides floridanus), which can hybridize to produce introgressed Largemouth Bass (ILMB; NLMB × FLMB). Largemouth Bass were introduced into Puerto Rico by using source populations from unknown origins (1915), a natural intergrade zone (1946 and 1947; ILMB), and peninsular Florida (1957; FLMB). All subsequent supplemental stocking efforts used broodstock collected from reservoirs in Puerto Rico with an effort to preferentially propagate non‐introgressed FLMB. Here, we document contemporary FLMB‐specific alleles and genotypes, changes in allele frequencies over the last decade, and differences in size structure between genotypes of the FLMB and its hybrids (ILMB) in Puerto Rico. Among 12 island reservoirs, FLMB alleles were prevalent at rates similar to estimates from a decade earlier, and the proportion of FLMB alleles (0.77–0.85) was less than that of the hatchery broodstock. No NLMB genotypes were resolved, and the proportion of FLMB genotypes ranged from 0.03 to 0.64. Length frequency distributions differed between the FLMB and ILMB types (Kolmogorov D‐statistic = 0.172, P = 0.026), with FLMB observed more frequently in larger size‐classes. Given their greater sizes and potentially greater longevity, we suggest that FLMB should be used exclusively for future stocking efforts in Puerto Rico.Received January 25, 2017; accepted July 3, 2017 Published online October 11, 2017