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Patterns of genetic variation reflect interactions among microevolutionary forces that vary in strength with changing demography. Here, patterns of variation within and among samples of the mouthbrooding gafftopsail catfish (Bagre marinus, Family Ariidae) captured in the U.S. Atlantic and throughout the Gulf of Mexico were analyzed using genomics to generate neutral and non‐neutral SNP data sets. Because genomic resources are lacking for ariids, linkage disequilibrium network analysis was used to examine patterns of putatively adaptive variation. Finally, historical demographic parameters were estimated from site frequency spectra. The results show four differentiated groups, corresponding to the (1) U.S. Atlantic, and the (2) northeastern, (3) northwestern, and (4) southern Gulf of Mexico. The non‐neutral data presented two contrasting signals of structure, one due to increases in diversity moving west to east and north to south, and another to increased heterozygosity in the Atlantic. Demographic analysis suggested that recently reduced long‐term effective population size in the Atlantic is likely an important driver of patterns of genetic variation and is consistent with a known reduction in population size potentially due to an epizootic. Overall, patterns of genetic variation resemble that of other fishes that use the same estuarine habitats as nurseries, regardless of the presence/absence of a larval phase, supporting the idea that adult/juvenile behavior and habitat are important predictors of contemporary patterns of genetic structure. Gafftopsail catfish show high levels of genetic structuring across their distribution in the U.S., Atlantic and Gulf of Mexico. Non‐neutral data present two contrasting signals of structure and historical demography is likely an important driver of patterns of neutral and non‐neutral genetic variation. Results of this study are similar to what is seen in other fishes that use the same estuarine habitats as nurseries, but gafftopsail catfish lack a larval phase, supporting the idea that adult/juvenile behavior and habitat use are important predictors of contemporary patterns of genetic structure. [ABSTRACT FROM AUTHOR]

Understanding how interactions among microevolutionary forces generate genetic population structure of exploited species is vital to the implementation of management policies that facilitate persistence. Philopatry displayed by many coastal shark species can impact gene flow and facilitate selection, and has direct implications for the spatial scales of management. Here, genetic structure of the blacktip shark (Carcharhinus limbatus) was examined using a mixed‐marker approach employing mitochondrial control region sequences and 4339 SNP‐containing loci generated using ddRAD‐Seq. Genetic variation was assessed among young‐of‐the‐year sampled in 11 sites in waters of the United States in the western North Atlantic Ocean, including the Gulf of Mexico. Spatial and environmental analyses detected 68 nuclear loci putatively under selection, enabling separate assessments of neutral and adaptive genetic structure. Both mitochondrial and neutral SNP data indicated three genetically distinct units—the Atlantic, eastern Gulf, and western Gulf—that align with regional stocks and suggest regional philopatry by males and females. Heterogeneity at loci putatively under selection, associated with temperature and salinity, was observed among sites within Gulf units, suggesting local adaptation. Furthermore, five pairs of siblings were identified in the same site across timescales corresponding with female reproductive cycles. This indicates that females re‐used a site for parturition, which has the potential to facilitate the sorting of adaptive variation among neighbouring sites. The results demonstrate differential impacts of microevolutionary forces at varying spatial scales and highlight the importance of conserving essential habitats to maintain sources of adaptive variation that may buffer species against environmental change. [ABSTRACT FROM AUTHOR]

The age, growth, and maturity of bonnetheads, Sphyrna tiburo, inhabiting estuarine and coastal waters of the U.S. Gulf of Mexico (GOM) were investigated. Based on results of a concurrent population genetics study, two populations were examined, the eastern GOM and western GOM. Vertebrae were collected and aged from 1081 females and 811 males ranging in size 261–1060 mm and 227–898 mm fork length (FL), respectively. The von Bertalanffy growth model provided the best fit to length-at-age data. Eastern GOM von Bertalanffy parameters (length parameters in mm FL) were L∞ = 844, k = 0.23, to = -1.99, and Lo = 310 for females and L∞ = 680, k = 0.39, to = -1.44, and Lo = 294 for males. Western GOM von Bertalanffy parameters were L∞ = 1005, k = 0.20, to = -1.81, and Lo = 298 for females and L∞ = 807, k = 0.30, to = -1.44, and Lo = 285 for males. Maximum observed age was similar between populations with an overall maximum of 17.1 years for females, and 12.1 years for males. Length and age at 50% maturity for the eastern GOM was 661.5 mm and 4.9 years for females, and 564.1 mm and 3.5 years for males and for the western GOM 772.7 mm and 5.3 years for females, and 644.9 mm and 4.4 years for males. Bonnetheads in the eastern GOM generally grow faster and to smaller asymptotic lengths than those from the western GOM; however, longevity is similar between the two populations. [ABSTRACT FROM AUTHOR]

Red snapper, Lutjanus campechanus , supports one of the more important fisheries in marine waters of the United States. Consequently, it has been the focus of intensive fisheries research for more than 20 years. Here, we present a genomic analysis of population structure that uses a landscape genetics approach to characterize patterns of variation in adult red snapper in the Gulf of Mexico (GOM) alongside a synoptic view of decades of stock-structure research. The results support Atlantic and GOM stocks and indicate weak heterogeneity within the GOM. Furthermore, redundancy analysis using Moran Eigenvector Maps based on physical distance, larval dispersal probability, and adult dispersal probability reveal heterogeneity on various spatial scales, with adult movement explaining a larger component of variation than spatial position or larval dispersal. Results of this study support the idea that red snapper in the GOM display metapopulation structure, but also suggest a potential genetic discontinuity along the West Florida Shelf not previously described. The approach of using landscape genomics and dispersal data (larval and/or adult) to better understand metapopulation dynamics is promising for not only red snapper, but also for other marine species that occupy a diversity of habitats and are seemingly distributed continuously. [ABSTRACT FROM AUTHOR]

Cutting-edge DNA methylation-based epigenetic aging techniques were applied to Gulf of Mexico northern red snapper (Lutjanus campechanus; n = 10; 1–26 years old) and red grouper (Epinephelus morio; n = 10; 2–14 years old). Bisulfite-converted restriction site-associated DNA sequencing was used to identify CpG sites (cytosines followed by guanines) that exhibit age-correlated DNA methylation, and species-specific epigenetic clocks developed from hundreds of CpG sites in each species showed strong agreement between predicted and otolith-derived age (r2 > 0.99 for both species). Results suggest epigenetic age estimation could provide an accurate and efficient approach to mass-aging fishes in a non-invasive manner. [ABSTRACT FROM AUTHOR]