The objective of this study was to optimize the methodology for spectrophotometric determination of sperm concentration in Atlantic croaker Micropogonias undulatus L. milt and to estimate its potential for short-term cold-storage. The spectrophotometric determination of sperm concentration was evaluated using milt samples from six males serially diluted in Hank's balanced salt solution at 200 mOsm kg À1 (HBSS). The predictive power of regression models between sperm concentration and absorbance was determined from 200 to 500 nm and found to be highest within the visible spectrum despite a peak of milt absorbance at 288 nm. Absorbance reading at 400 nm was selected for further analysis to maximize the absorbance of the sample hence the sensitivity of the method while minimizing the impact of potential sample contamination with blood. The standard-curve of correlation between sperm absorbance at 400 nm and concentration was validated and held an accuracy ranging between À7.40% and +4.56% across males. Total sperm motility duration and the proportion of motile spermatozoa were significantly higher in milt samples diluted 1:3 in HBSS than in the undiluted control during up to 30 h of cold-storage.The methodologies investigated in this study can be applied to optimize sperm usage and achieve predictable artificial fertilization protocols in Atlantic croaker.

Gray triggerfish Balistes capriscus is a reef fish exploited by recreational and commercial fisheries in the southeastern United States. Recent stock assessments indicated that the species is overfished, and a rebuilding plan is in progress. The U.S. fishery is currently managed as a single stock owing to the absence of reliable information on stock structure. We sequenced a 617‐base‐pair fragment of the ND4 mitochondrial gene in a total of 150 specimens from five localities (South Texas, Louisiana, West Florida, southeastern Florida, and South Carolina) encompassing the exploited range of the species in the USA. Analysis of molecular variance, spatial analysis of molecular variance, and spatial autocorrelation analysis did not reveal significant spatial heterogeneity in haplotype distributions within the studied range. Significant departure from neutrality was inferred from neutrality tests and may reflect the signature of a rapid population expansion following the recent glacial epochs, an inference that was supported by the results of Bayesian coalescent analysis. While the present results are consistent with management of the species as a single stock, development of additional genetic markers is needed to increase the resolution in genetic analyses and evaluate fine‐scale genetic stock structure in the region.Received January 10, 2011; accepted May 5, 2011

No abstract

The blackfin tuna, Thunnus atlanticus, is a small tropical tuna exploited by recreational and commercial fisheries in various parts of its range. Information on stock structure is needed to develop management plans for this species but is currently lacking. In this work, 470 blackfin tuna from nine geographic populations were assayed at 13 homologous microsatellite markers to provide a first assessment of stock structure across the species range. The overall divergence among locality samples was very low (overall FST = 0.0004) indicating high connectivity of blackfin tuna across their range. No clear grouping of localities in differentiated units was inferred but structuring followed a weak isolation by distance pattern (r = 0.16, P = 0.032). Pairwise exact tests and spatial analysis of molecular variance suggested divergence of the sample collected offshore Baía Formosa (Brazil) possibly reflecting reproductive isolation of Brazilian populations from those in the Caribbean region and further north. Further study of the status of Brazilian populations and the transition between this region and the Caribbean is warranted. Cryptic subdivision within the Northern Hemisphere part of the range is possible and should be evaluated using increased marker density and a more comprehensive geographic coverage.

Abstract-Twenty homologous microsatellite markers, or simple sequence repeats (SSRs), were developed for blackfin tuna (Thunnus atlanticus) through the use of a direct Seq-to-SSR approach. The number of alleles per locus ranged between 5 and 26, and the expected heterozygosity ranged between 0.640 and 0.969. Three loci displayed significant departure from Hardy-Weinberg equilibrium expectations, likely reflecting occurrence of null alleles. Another locus showed consecutive alleles that differed by one base pair only. Consequently, this locus may be prone to elevated rates of scoring errors. The remaining 16 loci will be valuable for studies in conservation genetics of blackfin tuna.