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Understanding the spatial scale of demographic connectivity in marine reef fishes dispersing pelagic larvae is a challenging task because of the technical difficulties associated with tagging and monitoring the movements of progeny at early life stages. Several studies highlighted a strong importance of local retention with levels of dispersal of ecological significance restricted to short distances. To date little information is available in species where pelagic dispersal lasts for long periods of time. In this work, population structure and connectivity were studied in the grey triggerfish, Balistes capriscus. Grey triggerfish larvae and juveniles remain associated with floating Sargassum sp. beds for an estimated period of 4-7 months before settling on benthic habitats where they remain sedentary as adults. Analysis of genetic variation among populations along the continental shelf of the northern Gulf of Mexico and U.S. east coast, encompassing over 3,100 km of coastline, revealed homogeneous allele frequencies and a weak isolation-by-distance pattern. Moment and maximum-likelihood estimates of dispersal parameters both indicated occurrence of large neighbourhoods with estimates of the dispersal distribution parameter σ of 914 and 780 km, respectively. Simulated distributions of dispersal distances using several distribution functions all featured substantial fractions of long-distance dispersal events with the 90% percentiles of travel distance prior to settlement averaging 1,809 km. These results suggest a high dependency of local recruitment on the output of nonlocal spawning stocks located hundreds of kilometres away and a reduced role of local retention in this species. [ABSTRACT FROM AUTHOR]

Population-genetic structure and average long-term effective size of yellowtail snapper, Ocyurus chrysurus (Bloch), sampled offshore from the Florida Keys and four localities in the US Caribbean, were investigated using nuclear-encoded microsatellites and a fragment of the mitochondrially encoded ND-4 gene. Analysis of spatial genetic variation revealed occurrence of up to four groupings (stocks) of yellowtail snapper: one in the Florida Keys, one along the west coast of Puerto Rico, one that includes the east coast of Puerto Rico and St. Thomas and one offshore of St. Croix. The observed genetic differences among localities are not strong, and additional sampling to examine whether the observed patterns of population structure are temporally stable is warranted. Levels of genetic variability and estimates of average, long-term effective size ( Ne) indicate that yellowtail snapper at all five localities have, at present, sufficient genetic variation to maintain long-term integrity and sustainability. [ABSTRACT FROM AUTHOR]

Parentage analysis, employing five hypervariable microsatellite markers, was used to follow spawning patterns of red drum Sciaenops ocellatus broodfish in two spawning tanks through most of a calendar year in a marine fish hatchery dedicated to stock enhancement. Five of six dams and all four sires spawned at least once during the year. Variation in dam and sire spawning incidence and in number of progeny produced per dam and per sire translated into reduced genetic effective size ( Ne) per spawn by 40·6% in one tank and 50·8% in the other. [ABSTRACT FROM AUTHOR]

Genetic diversity, population structure, average long-term effective population size (Ne), and average long-term genetic migration rate of red drum Sciaenops ocellatus in each of four Texas bays were assessed using variation in 13 nuclear-encoded microsatellites among samples from the 2004 and 2005 cohorts. No significant differences in genetic diversity were detected among bays. Levels of gene diversity of red drum in each bay were equal to or greater than estimates reported for microsatellites in red drum sampled previously from two of the four bays and from other bays in the southeastern USA, including some that had not yet been supplemented with hatchery-raised fish. Tests of the homogeneity of allele and genotype distributions (including analysis of molecular variance) among the four bays were nonsignificant. Estimates of the migration rate (m) between bays ranged from 0.08% to 0.15%, with the average long-term number of migrants (calculated as Ne x m) between bays estimated to range from 1.04 to 2.37 fish/generation. Estimates of average long-term Ne in the four bays ranged from 1,302 to 1,581 fish and collectively were well within the range hypothesized to support sustained, long-term persistence. The estimates of Ne also were, on average, five to six times higher than comparable estimates reported for the 1986-1989 red drum cohorts sampled from seven bays across the northern Gulf of Mexico. Adjustment of long-term Ne in each of the four bays relative to bay-specific spatial parameters revealed a positive relationship with red drum abundance as measured by catch-per-unit-effort statistics compiled by the Texas Parks and Wildlife Department between 1982 and 2005. The observed high levels of genetic diversity, estimates of average long-term Ne, and increased N over the past 15-20 years are consistent with the hypothesis that the Texas Parks and Wildlife Department's stock enhancement program has not genetically compromised the resident red drum subpopulations in the four bays. [ABSTRACT FROM AUTHOR]

Lane snappers ( Lutjanus synagris), sampled from eight localities in the northern Gulf of Mexico (Gulf) and one locality along the Atlantic coast of Florida, were assayed for allelic variation at 14 nuclear-encoded microsatellites and for sequence variation in a 590 base-pair fragment of the mitochondrially encoded ND-4 gene (mtDNA). Significant heterogeneity among the nine localities in both microsatellite allele and genotype distributions and mtDNA haplotype distributions was indicated by exact tests and by analysis of molecular variance (AMOVA). Exact tests between pairs of localities and spatial analysis of molecular variance (SAMOVA) for both microsatellites and mtDNA revealed two genetically distinct groups: a Western Group that included six localities from the northwestern and northcentral Gulf and an Eastern Group that included three localities, one from the west coast of Florida, one from the Florida Keys, and one from the east (Atlantic) coast of Florida. The between-groups component of molecular variance was significant for both microsatellites ( ΦCT = 0.016, P = 0.009) and mtDNA ( ΦCT = 0.208, P = 0.010). Exact tests between pairs of localities within each group and spatial autocorrelation analysis did not reveal genetic heterogeneity or an isolation-by-distance effect among localities within either group. MtDNA haplotype diversity was significantly less ( P < 0.0001) in the Western Group than in the Eastern Group; microsatellite allelic richness and gene diversity also were significantly less in the Western Group ( P = 0.015 and 0.013, respectively). The difference in genetic variability between the two groups may reflect reduced effective population size in the Western Group and/or asymmetric rates of genetic migration. The relative difference in variability between the two groups was substantially greater in mtDNA and may reflect one or more mtDNA selective sweeps; tests of neutrality of the mtDNA data were consistent with this possibility. Bayesian analysis of genetic demography indicated that both groups have experienced a historical decline in effective population size, with the decline being greater in the Western Group. Maximum-likelihood analysis of microsatellite data indicated significant asymmetry in average, long-term migration rates between the two groups, with roughly twofold greater migration from the Western Group to the Eastern Group. The difference in mtDNA variability and the order-of-magnitude difference in genetic divergence between mtDNA and microsatellites may reflect different demographic events affecting mtDNA disproportionately and/or a sexual and/or spatial bias in gene flow and dispersal. The spatial discontinuity among lane snappers in the region corresponds to a known zone of vicariance in other marine species. The evidence of two genetically distinct groupings (stocks) has implications for management of lane snapper resources in the northern Gulf. [ABSTRACT FROM AUTHOR]

Multiplexed microsatellite markers were evaluated as genetic tags for red drum ( Sciaenops ocellatus) juveniles used in stock enhancement. Offspring were generated from spawns of nine sets of five broodfish (three dams and two sires) in individual brood tanks. Intensive sampling, by trawling, at 2, 7, 8, 10 and 11 days after release of ∼192 500 hatchery-raised fingerlings resulted in recovery of a total of 310 fingerlings. All parents and recovered offspring were genotyped for variation at 30 microsatellites combined for simultaneous assay in six multiplex panels. An optimal combination employing three of the six multiplex panels allowed unambiguous parentage assignment of all recovered offspring. Only 21 of 52 possible dam x sire combinations were represented among recovered offspring. The founder equivalent ( fe) of the recovered offspring was 8.7 vs the expected fe of 36.0 (95% CI = 33.3–38.4) if reproductive success was randomly distributed among breeders. The significantly lower founder equivalent translated into reduced genetic diversity among the recovered offspring and may reflect differing contributions of individual broodfish to spawning events, differing productivity among brood tanks, and/or variable survival of families during early larval and/or juvenile stages. [ABSTRACT FROM AUTHOR]

The stock enhancement program for red drum Sciaenops ocellatus in Texas annually releases from 25 to 30 million fingerlings into Texas bays and estuaries and represents one of the largest such programs for marine fishes worldwide. We used 16 nuclear-encoded microsatellites and a 370-base-pair fragment of the mitochondrial DNA (mtDNA) D-loop to assign red drum sampled from two bays along the Texas coast to either hatchery or wild origin. A total of 30 hatchery-released fish were identified among 321 red drum belonging to three year-classes sampled from Galveston Bay, while a total of 11 hatchery-released fish were identified among 970 red drum belonging to four year-classes sampled from Aransas Bay. Allelic richness (microsatellites) was significantly lower among hatchery-released fish than among hatchery broodfish and wild fish. Similarly, the expected number of mtDNA haplotypes in hatchery-released fish (based on simulation analysis) was significantly lower than that expected in a random sample of both brood and wild fish. The contribution of brood dams, sires, and dam x sire combinations to the hatchery-released fish was nonrandom, as was the distribution of hatchery-released and wild fish with respect to sampling stations (localities) within each bay. The possibility of a Ryman-Laikre effect is discussed. [ABSTRACT FROM AUTHOR]

We examined allelic variation at 22 nuclear-encoded markers (21 microsatellites and one anonymous locus) and mitochondrial (mt)DNA in two geographical samples of the endangered cyprinid fish Notropis mekistocholas (Cape Fear shiner). Genetic diversity was relatively high in comparison to other endangered vertebrates, and there was no evidence of small population effects despite the low abundance reported for the species. Significant heterogeneity (following Bonferroni correction) in allele distribution at three microsatellites and in haplotype distribution in mtDNA was detected between the two localities. This heterogeneity may be due to reduced gene flow caused by a dam built in the early 1900s. Bayesian coalescent analysis of microsatellite variation indicated that effective population size of Cape Fear shiners has declined in recent times (11–25 435 years ago, with highest posterior probabilities between 126 and 2007 years ago) by one-two orders of magnitude, consistent with the observed decline in abundance of the species. A decline in effective size was not indicated by analysis of mtDNA, where sequence polymorphism appeared to carry the signature of an older expansion phase that dated to the Pleistocene (∼12 700 > 1 million years ago). Cape Fear shiners thus appear to have undergone an expansion phase following a glacial cycle but to have declined significantly in more recent times. These results suggest that rapidly evolving markers such as microsatellites may constitute a suitable tool when inferring recent demographic dynamics of populations. [ABSTRACT FROM AUTHOR]

Twenty-five microsatellites from Atlantic bluefin tuna ( Thunnus thynnus thynnus) were characterized. All 25 microsatellites were polymorphic; the number of alleles among up to 56 individuals surveyed ranged from two to 23. Atlantic bluefin tuna are highly exploited and major questions remain as to stock structure and abundance in the eastern and western North Atlantic. The microsatellites will be useful in testing stock-structure hypotheses and in generating estimates of effective population size. The polymerase chain reaction primer sets developed also amplified identifiable alleles in three other species of genus Thunnus: T. albacares (yellowfin tuna), T. alalunga (albacore tuna) and T. obesus (bigeye tuna). [ABSTRACT FROM AUTHOR]

We isolated 11 microsatellites from the Pacific sardine Sardinops sagax sagax. The number of alleles and HE among 30 individuals from a single population ranged from four to 24 and from 0.606 to 0.959, respectively. Pacific sardines are a vital economic resource in the northeastern Pacific Ocean, but insufficiently polymorphic loci have limited inferences about its stock structure and genetic variation. The level of variability of these new markers will prove useful in testing hypotheses on the stock-structure and long-term genetic integrity of the species. [ABSTRACT FROM AUTHOR]