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The presence of cryptic species can hinder effective conservation planning and implementation, as has been the case for speciose groups of freshwater fishes that are difficult to differentiate due to conserved morphologies. The West Texas shiner Notropis megalops and the Texas shiner Notropis amabilis are a cryptic pair of leuciscids (minnows) that co‐occur in spring‐fed tributaries of the Rio Grande in Texas and Mexico. Both N. megalops and N. amabilis are listed as Species of Greatest Conservation Need by the Texas Parks and Wildlife Department. Notropis amabilis is widespread and listed as apparently secure by Texas Parks and Wildlife Department whereas N. megalops has a very limited distribution and has not been ranked by Texas Parks and Wildlife Department because of data deficiency. Morphological differences between these species have been described; however, proper identification in situ remains problematic. Furthermore, given their range of overlap there is potential for hybridization, and limited genetic data have been collected comparing the species. Therefore, reduced representation genomic and mitochondrial sequencing data were used to reassess the distinctness of the species, screen for hybridization, and characterize their relative frequencies throughout their range of overlap. Genomic analyses recovered two distinct genetic groups corresponding to the species (F'CT = 0.89) with no evidence of admixture or introgression. The species were found to co‐occur at three sampling locations, two in the Devils River and one in the Pecos, but not in equal frequencies. Overall, these results provide data and tools for further research on N. megalops needed for accurate conservation policies and management practices. [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). Bisulfiteconverted 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 [r.sup.2] > 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. Des methodes epigenetiques de pointe de determination de l'age reposant sur la methylation de l'ADN ont ete appliquees au vivaneau campeche (Lutjanus campechanus; n = 10; 1-26 ans) et au merou rouge (Epinephelus morio; n = 10; 2-14 ans). Le sequencage avec conversion au bisulfite d'ADN associe a des sites de restriction a ete utilise pour cerner des sites CpG (cytosines suivies de guanines) qui presentent une methylation de l'ADN correlee a l'age, et des horloges epigenetiques propres a l'espece developpees a partir de centaines de sites CpG de chaque espece ont revele de fortes concordances entre les ages predits et les ages obtenus par analyse d'otolites [r.sup.2] > 0,99 pour les deux especes). Les resultats donnent a penser que l'estimation epigenetique de l'age pourrait constituer une approche non invasive exacte et efficiente de determination des ages de quantites massives de poissons., Introduction Age data are fundamental to determining life history parameters (e.g., age-at-length, age-at-maturity, age-related fecundity) and are thus critical for fisheries assessment and management, particularly when age-structured stock assessment models [...]

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]

The silky shark is the second most common shark in Southeast Asia's dried fin markets and is managed in the Atlantic Ocean by the International Commission for the Conservation of Atlantic Tuna (ICCAT) and by three Indo‐Pacific regional fisheries management organizations (RMFOs). The International Commission for the Conservation of Atlantic Tuna reports ∼ 7% of global silky landings but there is a moratorium on the export of their fins. During a 4‐year period (2014–2017) we used genetic differentiation observed between Atlantic and Indo‐Pacific silky sharks to assess the contribution of Atlantic individuals to fins randomly obtained in the two largest shark fin markets in the world, Hong Kong and Guangzhou, China (N = 604). We did not detect any Atlantic fins in either market despite robust sampling effort with an estimated Indo‐Pacific contribution of 99.8% to these markets. These findings indicate that supply chains for silky shark fins in Hong Kong and Guangzhou primarily originate in the Indo‐Pacific and are mainly under the purview of three Regional Fisheries Management Organizations. Our results are consistent with the possibility that ICCAT parties have achieved high compliance with the ban on silky sharks. We suggest research and monitoring improvements that could enhance our understanding of the global trade of silky sharks and enable better fisheries management. [ABSTRACT FROM AUTHOR]

The white shark, Carcharodon carcharias, is both one of the largest apex predators in the world and among the most heavily protected marine fish. Population genetic diversity is in part shaped by recent demographic history and can thus provide information complementary to more traditional population assessments, which are difficult to obtain for white sharks and have at times been controversial. Here, we use the mitochondrial control region and 14 nuclear-encoded microsatellite loci to assess white shark genetic diversity in 2 regions: the Northwest Atlantic (NWA, N = 35) and southern Africa (SA, N = 131). We find that these 2 regions harbor genetically distinct white shark populations (ΦST = 0.10, P < 0.00001; microsatellite FST = 0.1057, P < 0.021). M-ratios were low and indicative of a genetic bottleneck in the NWA (M-ratio = 0.71, P < 0.004) but not SA (M-ratio = 0.85, P = 0.39). This is consistent with other evidence showing a steep population decline occurring in the mid to late 20th century in the NWA, whereas the SA population appears to have been relatively stable. Estimates of effective population size ranged from 22.6 to 66.3 (NWA) and 188 to 1998.3 (SA) and evidence of inbreeding was found (primarily in NWA). Overall, our findings indicate that white population dynamics within NWA and SA are determined more by intrinsic reproduction than immigration and there is genetic evidence of a population decline in the NWA, further justifying the strong domestic protective measures that have been taken for this species in this region. Our study also highlights how assessment of genetic diversity can complement other sources of information to better understand the status of threatened marine fish populations. [ABSTRACT FROM AUTHOR]