Isolation and Characterization of Polymorphic Microsatellite Markers from a Globally Distributed Marine Apex Predator, the Tiger Shark (Galeocerdo cuvier)

High levels of fishing have resulted in declines among many of the oceans top predators, including the globally distributed tiger shark (Galeocerdo cuvier). Overexploitation of this species has led to declines in parts of its distribution, which may have important ecological consequences given the tiger shark’s trophic position as a large bodied, generalist predator. To assess the population genetics of this species, an enrichment protocol was used to isolate a suite of nine di- and tetra-nucleotide microsatellite loci within the tiger shark, which were subsequently characterized using genomic DNA derived from 40 individuals sampled from Hawaiian waters. The number of alleles per locus ranged from 3 to 23, and the average expected heterozygosities across loci ranged from 0.30 to 0.93. Analyses suggested a low frequency of null alleles across markers, and all loci conformed to both Hardy–Weinberg and linkage equilibrium at P \u3e 0.01

Development and Characterization of 11 Novel Microsatellite Loci for the Roundscale Spearfish Tetrapturus georgii and Their Cross-Species Amplification Among Other Istiophorid Species

Eleven novel polymorphic microsatellite loci were developed and characterized for the recently validated roundscale spearfish Tetrapturus georgii. Characterization of these markers, based on 35 roundscale spearfish from the western North Atlantic, revealed two to 21 alleles per locus with an average expected heterozygosity (HE) of 0·09–0·94, and all loci conformed to Hardy–Weinberg expectations. Cross-amplification of these 11 loci against all other eight known istiophorid species indicates promising prospects for the utility of these markers for istiophorids in general

Deep-Diving and Diel Changes in Vertical Habitat Use by Caribbean Reef Sharks Carcharhinus perezi

Longline sampling (83 sets) supplemented with 6 pop-off archival transmitting (PAT) tag deployments were used to characterize vertical habitat use by Caribbean reef sharks Carcharhinus perezi at Glover\u27s Reef atoll, Belize. Longline catch-per-unit-effort (CPUE) in 2 shallow reef habitats (lagoon \u3c18 m depth, fore-reef \u3c40 m depth) underwent significant nocturnal increases for sharks larger than 110 cm total length (TL), but not for smaller sharks. Nocturnal CPUE of small sharks appeared to increase in the lagoon and decrease on the fore-reef, suggestive of movements to avoid larger conspecifics. PAT tag deployments (7 to 20 d) indicate that large C. perezi generally increased the amount of time they spent in the upper 40 m of the water column during the night, and inhabited much greater depths and tolerated lower temperatures than previously described. The wide vertical (0 to 356 m) and temperature range (31 to 12.4°C) documented for this top-predator reveals ecological coupling of deep and shallow reef habitats and has implications for Marine Protected Area (MPA) design

Development and Characterization of Thirteen Microsatellite Markers for the Longbill Spearfish (Tetrapturus pfluegeri)

The longbill spearfish (Tetrapturus pfluegeri; Istiophoridae) is an epipelagic billfish species broadly distributed in the Atlantic Ocean and exploited by multinational fisheries. No data exist on the population structure or genetic diversity of this apex predator, despite a strong need for this information to inform international conservation and management efforts. Thirteen microsatellite loci, comprising mostly tri- and tetra-nucleotide repeats, were isolated and characterized for this species by genotyping individuals (n = 29–42) obtained from western North and South Atlantic fisheries. The average number of alleles ranged from 3 to 16 and the expected heterozygosity ranged from 0.35 to 0.86. This suite of markers provides the first population genetic nuclear resources for the longbill spearfish, allowing initiation of studies for assessing the population structure and demography of this poorly understood species

Virgin Birth in a Hammerhead Shark

Parthenogenesis has been documented in all major jawed vertebrate lineages except mammals and cartilaginous fishes (class Chondrichthyes: sharks, batoids and chimeras). Reports of captive female sharks giving birth despite being held in the extended absence of males have generally been ascribed to prior matings coupled with long-term sperm storage by the females. Here, we provide the first genetic evidence for chondrichthyan parthenogenesis, involving a hammerhead shark (Sphyrna tiburo). This finding also broadens the known occurrence of a specific type of asexual development (automictic parthenogenesis) among vertebrates, extending recently raised concerns about the potential negative effect of this type of facultative parthenogenesis on the genetic diversity of threatened vertebrate species

Three complete mitochondrial genomes of shortfin mako sharks, Isurus oxyrinchus, from the Atlantic and Pacific Oceans

We present complete mitogenome sequences of three shortfin mako sharks (Isurus oxyrinchus) sampled from the western Pacific, and eastern and western Atlantic oceans. Mitogenome sequence lengths ranged between 16,699 bp and 16,702 bp, and all three mitogenomes contained one non-coding control region, two rRNA genes, 22 tRNA genes, and 13 protein-coding genes. Comparative assessment of five mitogenomes from globally distributed shortfin makos (the current three and two previously published mitogenomes) yielded 98.4% identity, with the protein-coding genes ATP8, ATP6, and ND5 as the most variable regions (sequence identities of 96.4%, 96.5%, and 97.6%, respectively). These mitogenome sequences contribute resources for assessing the genetic population dynamics of this endangered oceanic apex predator

Comparative Population Genetics and Evolutionary History of Two Commonly Misidentified Billfishes of Management and Conservation Concern

Background: Misidentifications between exploited species may lead to inaccuracies in population assessments, with potentially irreversible conservation ramifications if overexploitation of either species is occurring. A notable showcase is provided by the realization that the roundscale spearfish (Tetrapturus georgii), a recently validated species, has been historically misidentified as the morphologically very similar and severely overfished white marlin (Kajikia albida) (IUCN listing: Vulnerable). In effect, no information exists on the population status and evolutionary history of the enigmatic roundscale spearfish, a large, highly vagile and broadly distributed pelagic species. We provide the first population genetic evaluation of the roundscale spearfish, utilizing nuclear microsatellite and mitochondrial DNA sequence markers. Furthermore, we re-evaluated existing white marlin mitochondrial genetic data and present our findings in a comparative context to the roundscale spearfish. Results: Microsatellite and mitochondrial (control region) DNA markers provided mixed evidence for roundscale spearfish population differentiation between the western north and south Atlantic regions, depending on marker-statistical analysis combination used. Mitochondrial DNA analyses provided strong signals of historical population growth for both white marlin and roundscale spearfish, but higher genetic diversity and effective female population size (1.5-1.9X) for white marlin. Conclusions: The equivocal indications of roundscale spearfish population structure, combined with a smaller effective female population size compared to the white marlin, already a species of concern, suggests that a species-specific and precautionary management strategy recognizing two management units is prudent for this newly validated billfish

Contrasting Patterns of Population Structure and Dispersal for the Giant Barrel Sponge (Xestospongia muta) within the Florida Reef Tract and Caribbean

Sponges are one of the dominant fauna on Florida and Caribbean reefs, with species diversity often exceeding that of scleractinian corals. Despite their importance as structural components and habitat providers on reefs, their dispersal dynamics are little understood. We utilized eight microsatellite markers to study the population structure and migration patterns of the giant barrel sponge (Xestospongia muta), a widespread species throughout Florida and the Caribbean. Bayesian multilocus genotype analyses clustered 157 samples from the Bahamas, Honduras, and the US Virgin Islands into three distinct groups. 159 samples from nine locations within 284 km of the Florida reef tract (Key Largo to the Dry Tortugas) formed a fourth group. Population structure among the four groups was high (FST = 0.155; P = 0.001), with no recent migration among the groups. In contrast, high levels of migration were detected within the Florida reef tract. Reefs in the Upper Keys (Long Key) appear to be sources of larvae to reefs in the north (Key Largo) and also to reefs in the south (Key West and the Dry Tortugas). This pattern of migration closely matches current pathways within the South Florida recirculation system, suggesting that currents play an important role in dispersing X. muta larvae within the Florida reef tract. Although there was an overall lack of isolation by distance among the four groups, a significant correlation between genetic and geographic distance was found among the Florida sampling sites indicating that mating within the reef tract is not random. Asexual reproduction appears not to be the cause as only 1.3% of individuals in Florida shared the same genotype (1.6% overall). Rather, limited larval dispersal along the reef tract and among Caribbean locations has probably led to inbreeding within reefs, explaining the significant deficit in heterozygosity detected (FIS = 0.219; P = 0.001)

Circle Hooks in Commercial, Recreational, and Artisanal Fisheries: Research Status and Needs for Improved Conservation and Management

The intent of convening the International Symposium on Circle Hooks in Research, Management, and Conservation was to yield a contemporary, science-based assessment of the management and conservation utility of circle hooks in commercial, recreational, and artisanal fisheries around the globe. The symposium objective was to provide a forum for individuals, organizations, and agencies to share relevant research results and perspectives. Based on the presentations, an examination of the literature, and the collective experience and knowledge of the authors, we provide a brief overview of the current status of circle hook research along with a list of research needs, with a particular focus on science that has the potential to inform managers and stakeholders. Progress was made on the definition of a “true circle hook.” There was strong recognition that circle hooks represent just one of the tools available to managers for reducing bycatch and release mortality. Also defined was the need for an integrative approach that considers strategies that complement the use of circle hooks. Some of the research needs identified include a greater emphasis on human dimension studies to identify those factors that may impede adoption of circle hook technology by stakeholders and comparative studies of circle hook performance relative to mouth morphology, dentition, and feeding behavior. While the literature on effective use of circle hooks is growing, there remains a number of unanswered questions that will require study before circle hooks are more widely adopted for conservation and management of aquatic living resources