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While dorsal-ventrally compressed chondrichthyans are among the most imperiled fishes in the world, there is still limited knowledge of the biology of many of these species, even in well-studied ocean basins. In the western North Atlantic Ocean, the population structure of the Atlantic angel shark (Squatina dumeril) is not fully understood; therefore, the portioning of genetic variation was assessed among individuals caught along the east coast of the United States (Atlantic) and on the northern Gulf of Mexico (Gulf) using reduced representation genomics and mitochondrial sequencing. Three distinct groups were delineated with nuclear data, the Atlantic, the eastern Gulf, and the western Gulf, along boundaries described by previous research. Mitochondrial data only resolved two groups, with the western Gulf separated from the eastern Gulf and Atlantic combined. Demographic modeling suggested that the Atlantic population separated from a single Gulf population which subsequently split into eastern and western populations. Additionally, there was evidence that adjacent populations experienced gene flow after splitting, which may explain the incongruence between results based on nuclear and mtCR data. Correlations between environmental variables and allele frequencies at 873 loci indicated potential local adaptation. Therefore, the preservation of all three groups is necessary for the conservation of long-term adaptive variation important for species persistence. [ABSTRACT FROM AUTHOR]

Globally, many pond turtles (Family Emydidae) are of conservation concern due to contracting ranges, increasingly fragmented habitats, and declining populations. One of these turtles, the diamondback terrapin (Malaclemys terrapin), is of concern within the United States, but surveying potential estuarine habitat for the presence of the species requires high levels of time and effort. Here a species-specific, probe-based qPCR assay for identifying terrapin DNA from environmental DNA (eDNA) is described. To expand the utility of this tool, the assay was designed to allow for potential detection of at least 19 other pond turtles taxa and the utility was tested by designing a second species-specific probe for red-eared slider (Trachemys scripta elegans) with a different fluorophore, which can be used simultaneously with the terrapin probe to detect either species. Probes were found to be species-specific and effective at detecting low levels of DNA for the target species, the diamondback terrapin (10 fg/µL) and the red-eared slider (100 fg/µL) in laboratory conditions. The assay also showed species-specific detection in environmental samples taken from field locations where one species or the other were known to reside. Through citizen science approaches, this assay could be used for discovering novel terrapin habitats, monitoring invasive red-eared slider populations or surveying other emydids, with species-specific probes, at a fraction of the cost of traditional surveys. [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]

The Rio Grande drainage of the southwestern United States and Mexico has undergone intense anthropogenic alteration by water diversions, extraction and associated habitat changes. These alterations have disproportionately impacted the pelagic broadcast spawning guild of minnows (pelagophils). Several Rio Grande endemic pelagophils, including the co-occurring Rio Grande Shiner (Notropis jemezanus) and Speckled Chub (Macrhybopsis aestivalis), have experienced dramatic recent range-wide declines yet have slipped under the radar of conservation efforts. The status of N. jemezanus and M. aestivalis in the Rio Grande and Pecos River was evaluated and standing genetic variation was characterized. Genetic evidence indicates that populations of both species found in the Rio Grande and Pecos River are genetically distinct. Additionally, 159 outlier loci were identified in M. aestivalis suggesting possible local adaptation in the Rio Grande and Pecos River populations. Though range-wide genetic data are limited, N. jemezanus populations in both rivers harbor considerable genetic diversity. Mitochondrial data from both taxa are consistent with a history of secondary contact between formerly isolated populations with deeply divergent haplotypes found within the Rio Grande and Pecos River populations of N. jemezanus and within the Rio Grande population of M. aestivalis. Extensive survey efforts in the lower Rio Grande and its tributaries in Texas document significant range contraction and near extirpation of N. jemezanus from this part of the basin; highlighting the need for immediate action to protect the species. [ABSTRACT FROM AUTHOR]

Species-specific monitoring through large shark fin market surveys has been a valuable data source to estimate global catches and international shark fin trade dynamics. Hong Kong and Guangzhou, mainland China, are the largest shark fin markets and consumption centers in the world. We used molecular identification protocols on randomly collected processed fin trimmings (n = 2000) and non-parametric species estimators to investigate the species composition of the Guangzhou retail market and compare the species diversity between the Guangzhou and Hong Kong shark fin retail markets. Species diversity was similar between both trade hubs with a small subset of species dominating the composition. The blue shark (Prionace glauca) was the most common species overall followed by the CITES-listed silky shark (Carcharhinus falciformis), scalloped hammerhead shark (Sphyrna lewini), smooth hammerhead shark (S. zygaena) and shortfin mako shark (Isurus oxyrinchus). Our results support previous indications of high connectivity between the shark fin markets of Hong Kong and mainland China and suggest that systematic studies of other fin trade hubs within Mainland China and stronger law-enforcement protocols and capacity building are needed. [ABSTRACT FROM AUTHOR]