Shark Carcharhinus Research Articles

Longevity of Atlantic Sharpnose Sharks Rhizoprionodon terraenovae and Blacknose Sharks Carcharhinus acronotus in the western North Atlantic Ocean based on tag-recapture data and direct age estimates

Longevity of Rhizoprionodon terraenovae and Carcharhinus acronotus in the western North Atlantic Ocean was examined using direct age estimates from vertebral sections and tag-recapture data. Time-at-liberty ranged from 7.7-14.0 years (mean =10.1) for R. terraenovae and 10.9-12.8 years (mean =11.9) for C. acronotus. Maximum estimated longevity was determined to be 19.8 years through tag-recapture data and 18.5 years from direct age estimates for R. terraenovae and 22.8 years through tag-recapture data and 20.5 years through direct age estimates for C. acronotus. These longevity estimates represent a large increase over previous estimates and may have significant effects on analyses that depend on longevity including lifetime fecundity, mortality rates, demographic analyses and stock assessments.

Mechanical challenges to freshwater residency in sharks and rays.

Major transitions between marine and freshwater habitats are relatively infrequent, primarily as a result of major physiological and ecological challenges. Few species of cartilaginous fish have evolved to occupy freshwater habitats. Current thought suggests that the metabolic physiology of sharks has remained a barrier to the diversification of this taxon in freshwater ecosystems. Here, we demonstrate that the physical properties of water provide an additional constraint for this species-rich group to occupy freshwater systems. Using hydromechanical modeling, we show that occurrence in fresh water results in a two- to three-fold increase in negative buoyancy for sharks and rays. This carries the energetic cost of lift production and results in increased buoyancy-dependent mechanical power requirements for swimming and increased optimal swim speeds. The primary source of buoyancy, the lipid-rich liver, offers only limited compensation for increased negative buoyancy as a result of decreasing water density; maintaining the same submerged weight would involve increasing the liver volume by very large amounts: 3- to 4-fold in scenarios where liver density is also reduced to currently observed minimal levels and 8-fold without any changes in liver density. The first data on body density from two species of elasmobranch occurring in freshwater (the bull shark Carcharhinus leucas, Müller and Henle 1839, and the largetooth sawfish Pristis pristis, Linnaeus 1758) support this hypothesis, showing similar liver sizes as marine forms but lower liver densities, but the greatest negative buoyancies of any elasmobranch studied to date. Our data suggest that the mechanical challenges associated with buoyancy control may have hampered the invasion of freshwater habitats in elasmobranchs, highlighting an additional key factor that may govern the predisposition of marine organisms to successfully establish in freshwater habitats.

Development of microsatellite markers for globally distributed populations of the threatened silky shark, Carcharhinus falciformis

Eighteen microsatellite loci were developed for the silky shark Carcharhinus falciformis and screened across a total of 53 individuals from the western Atlantic Ocean, Eastern Tropical Pacific Ocean, and Red Sea. The number of alleles per locus ranged from 3 to 19, observed heterozygosity ranged from 0.158 to 0.917, and the probability of identity values ranged from 0.010 to 0.460. Though believed to be one of the most abundant species of large sharks, C. falciformis were recently listed as “near threatened” globally and “vulnerable” in the Eastern Tropical Pacific by the IUCN, due to reductions in catch rates from both target and non-target fisheries (Dulvy et al. in Aquat Conserv 18:459–482, 2008). Very little information exists about the population structure and genetic diversity of C. falciformis around the world. These new loci will provide effective tools for examining the sustainability of this declining species.

Complete mitochondrial genome of the Pigeye Shark Carcharhinus amboinensis (Carcharhiniformes: Carcharhinidae)

In this manuscript we describe the first complete mitochondrial sequence for the Data Deficient Pigeye Shark Carcharhinus amboinensis. The mitogenome is 16,704 bp long and consists of 1 control region, 2 rRNA genes, 22 tRNA genes and 13 protein-coding genes with an overall base composition of 31.6% A, 24.9% C, 13.1% G and 30.4% T. The gene arrangement pattern and transcriptional direction were typical for a vertebrate species. The tRNA-Ser2 lacks the dihydrouridine arm and forms a simple loop, therefore it cannot be folded into the typical cloverleaf secondary structures like other tRNAs.

Annellida, Hirudinea, Piscicolidae, Stibarobdella macrothela (Schmarda, 1861): First report for northeastern Brazil

This is the first report of Stibarobdella macrothela , a parasitic marine leech, for Ceara (Northeastern Brazil), the second report for Brazil, and the first report for the genus Stibarobdella in Northeastern Brazil. Two specimens separated from the host shark Carcharhinus sp. were identified in the invertebrate collection at LIMCe (Laboratorio de Invertebrados Marinhos do Ceara, Universidade Federal do Ceara). This record shows that the distribution of the S. macrothela is continuous in the Western Atlantic Ocean. Here, a brief description of the morphology and a new distributional map of the species is presented.

The complete mitochondrial genome of the spinner shark Carcharhinus brevipinna

The mitochondrial genome of the spinner shark (Carcharhinus brevipinna) was determined in this study. It was 16,706 bp in length with the typical genomic organization and gene order as most vertebrates. Whole nucleotide base composition was 31.3% A, 25.3% C, 13.2% G and 30.1% T. Among the protein-coding genes, there are three overlapping reading-frames on the same strand, while one of it on the opposite strand. Two start codons (ATG and GTG) and three stop codons (AGG, TAG and TAA/T) were used in 13 protein-coding genes. The 22 tRNA ranged from 67 (tRNA-Cys and tRNA-Ser2) to 75 bp (tRNA-Leu1) in length. Only the tRNA-Ser2 could not fold into the typical clover-leaf structure, which lost the dihydrouridine (DHU) arm and replaced by a simple loop. The control region was 1064 bp in length and showed a higher AT content (66.8%) than the average value of whole mitogenome (61.4%).

Isolation and characterization of 20 microsatellite markers from Carcharhinus leucas (bull shark) and cross-amplification in Galeocerdo cuvier (tiger shark), Carcharhinus obscurus (dusky shark) and Carcharhinus plumbeus (sandbar shark)

With the development of genetics methods, it becomes possible to study the population structure and some aspects of the reproductive behaviour of endangered sharks. Here we describe the isolation of 20 polymorphic microsatellite markers in the bull shark Carcharhinus leucas (Carcharhinidae) and their characteristics. Two to 10 alleles per locus were detected. Observed and expected heterozygosities ranged from 0.00 to 0.78 and from 0.05 to 0.80, respectively. Four markers showed deviations from Hardy–Weinberg equilibrium; among them, three showed presence of null alleles. No linkage disequilibrium was detected among any of the loci. Moreover, four, 11 and 19 of these 20 markers successfully cross-amplified in the tiger shark Galeocerdo cuvier, the sandbar shark Carcharhinus plumbeus and the dusky shark Carcharhinus obscurus, respectively.

Longevity of Atlantic Sharpnose Sharks Rhizoprionodon terraenovae and Blacknose Sharks Carcharhinus acronotus in the western North Atlantic Ocean based on tag-recapture data and direct age estimates.

Longevity of Rhizoprionodon terraenovae and Carcharhinus acronotus in the western North Atlantic Ocean was examined using direct age estimates from vertebral sections and tag-recapture data. Time-at-liberty ranged from 7.7-12.1 years (mean =9.2) for R. terraenovae and 10.9-12.8 years (mean =11.9) for C. acronotus. Maximum estimated longevity was determined to be 19.8 years through tag-recapture data and 18.5 years from direct age estimates for R. terraenovae and 22.8 years through tag-recapture data and 20.5 years through direct age estimates for C. acronotus. These longevity estimates represent a large increase over previous estimates and may have significant effects on analyses that depend on longevity including lifetime fecundity, mortality rates, demographic analyses and stock assessments.

Complete mitochondrial genome of the blacktip reef shark Carcharhinus melanopterus (Carcharhiniformes: Carcharhinidae)

The complete mitochondrial genome of the blacktip reef shark Carcharhinus melanopterus is determined for the first time in this study. The gene composition and order in the mitogenome of C. melanopterus is identical to most vertebrates. The overall base composition is 31.3% A, 25.3% C, 13.3% G and 30.1% T. There are 29 bp overlaps and 21 bp short intergenic spaces in the mitogenome. Two start codons and three stop codons were found in protein-coding genes. The dihydrouridine arm of tRNA-Ser2 was replaced by a simple loop and the other tRNAs could be folded into the typical cloverleaf structure. The termination associated sequence (TAS) and the conserved sequence blocks (CSB1-3) are found in the control region.

Distribution and dynamic habitat use of young bull sharks Carcharhinus leucas in a highly stratified northern Gulf of Mexico estuary.

Understanding how animals alter habitat use in response to changing abiotic conditions is important for effective conservation management. For bull sharks (Carcharhinus leucas), habitat use has been widely examined in the eastern and western Gulf of Mexico; however, knowledge of their movements and the factors influencing them is lacking for populations in the more temperate north-central Gulf of Mexico. To examine how changes in hydrographic conditions affected the presence of young bull sharks in Mobile Bay, Alabama, thirty-five sharks were fitted with internal acoustic transmitters and monitored with an acoustic monitoring array consisting of thirty-three receivers between June 2009 and December 2010. Tagged sharks ranged in size from 60 to 114 cm fork length and were detected between the upper and lower portions of Mobile Bay. Despite a variety of freshwater sources associated with this highly productive estuary, sharks were most consistently detected at the largest input to the system – the Mobile and Tensaw Rivers. Our findings suggest a combination of hydrographic factors interact to influence the distribution of juvenile bull sharks in Mobile Bay. The factors affecting the probability of detecting at least one bull shark varied both temporally (2009 vs 2010) and spatially (upper vs lower bay). Electivity analysis demonstrated that bull sharks showed highest affinity for warm water (29–32°C), moderate salinities (10–11 psu) and normoxic waters (5–7 mg/l), although these patterns were not consistent between regions or across years. We suggest future studies coupling telemetry and hydrographic variables should, when possible, consider the interactions of multiple environmental parameters when defining the dynamic factors explaining the spatial distribution of coastal sharks.

Age and Growth of the Bull Shark in the Western North Atlantic Ocean

AbstractAge and growth estimates for the Bull Shark Carcharhinus leucas were derived from 121 vertebral centra collected from Bull Sharks (59.1–223.5cm FL) between 1966 and 2010 in the western North Atlantic Ocean. Size at birth was confirmed with an additional 20 embryos (44.2–54.4cm FL). The maximum age based on vertebral band pair counts was 25 (184cm FL) and 27 (196cm FL) years for males and females, respectively. The logistic and Gompertz growth models fitted the size‐at‐age data best for males and females, respectively. Based on previously published estimates of length at maturity, males mature at 15–17years (176–185cm FL) and females at 15years (189cm FL). Bull Sharks in the western North Atlantic Ocean and the Gulf of Mexico have similar growth rates and reach similar sizes at age.

Complete mitogenome of the Graceful Shark Carcharhinus amblyrhynchoides (Carcharhiniformes: Carcharhinidae)

In this manuscript we describe the first complete mitochondrial sequence for the Near Threatened Graceful Shark Carcharhinus amblyrhynchoides. It is 16,705 bp in length, consists of two rRNA genes, 22 tRNA genes, 13 protein-coding genes and one control region with the typical gene arrangement pattern and translate orientation in vertebrates. The overall base composition is 31.4% A, 25.1% C, 13.2% G and 30.3% T. The shortest tRNA-Ser2 cannot fold into a clover-leaf secondary structure due to the lack of the dihydrouridine arm.

Mitochondrial genome of the spot-tail shark Carcharhinus sorrah (Carcharhiniformes: Carcharhinidae)

In this article, we first presented the complete mitogenome of the spot-tail shark Carcharhinus sorrah, which is a medium-sized shark distributed in the tropical Indo-Pacific and is currently listed as “Near Threatened” on the International Union for Conservation of Nature (IUCN) Red List. The complete mitogenome of C. sorrah is 16,707 bp in length and contains typical 37 genes and one control region. The overall base composition is 31.4% A, 25.8% C, 13.2% G and 29.6% T. The control region is 1066 bp in length with the highest A + T content (66.8%) and lowest G content (13.2%).

Long-Term Changes in Species Composition and Relative Abundances of Sharks at a Provisioning Site

Diving with sharks, often in combination with food baiting/provisioning, has become an important product of today’s recreational dive industry. Whereas the effects baiting/provisioning has on the behaviour and abundance of individual shark species are starting to become known, there is an almost complete lack of equivalent data from multi-species shark diving sites. In this study, changes in species composition and relative abundances were determined at the Shark Reef Marine Reserve, a multi-species shark feeding site in Fiji. Using direct observation sampling methods, eight species of sharks (bull shark Carcharhinus leucas, grey reef shark Carcharhinus amblyrhynchos, whitetip reef shark Triaenodon obesus, blacktip reef shark Carcharhinus melanopterus, tawny nurse shark Nebrius ferrugineus, silvertip shark Carcharhinus albimarginatus, sicklefin lemon shark Negaprion acutidens, and tiger shark Galeocerdo cuvier) displayed inter-annual site fidelity between 2003 and 2012. Encounter rates and/or relative abundances of some species changed over time, overall resulting in more individuals (mostly C. leucas) of fewer species being encountered on average on shark feeding dives at the end of the study period. Differences in shark community composition between the years 2004–2006 and 2007–2012 were evident, mostly because N. ferrugineus, C. albimarginatus and N. acutidens were much more abundant in 2004–2006 and very rare in the period of 2007–2012. Two explanations are offered for the observed changes in relative abundances over time, namely inter-specific interactions and operator-specific feeding protocols. Both, possibly in combination, are suggested to be important determinants of species composition and encounter rates, and relative abundances at this shark provisioning site in Fiji. This study, which includes the most species from a spatially confined shark provisioning site to date, suggests that long-term provisioning may result in competitive exclusion among shark species.

Complete mitochondrial genome of the blacknose shark Carcharhinus acronotus (Elasmobranchii: Carcharhinidae)

The complete mitochondrial genome of the blacknose shark Carcharhinus acronotus has been determined in this work. It has a length of 16,719 bp and consisted of 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and 1 control region. The gene composition and genome organization was similar to other vertebrates. This study represents part of an ongoing effort to obtain mitochondrial genome sequences for chondrichthyan species in order to better estimate their phylogenetic relationships.

Mitochondrial genome of the bull shark Carcharhinus leucas (Carcharhiniformes: Carcharhinidae)

The bull shark Carcharhinus leucas is a large elasmobranch species widespread in tropical and warm oceans, rivers and lakes. We first determine the complete mitogenome of C. leucas in this article. It is 16,704 bp in length, consists 37 genes and one control region with the typical gene order in vertebrates. The ND6 gene used the rare AGG as stop codon. The 22 tRNA genes ranged from 67 to 75 bp. The tRNA-Ser2 lacks the dihydrouridine arm and cannot form the typical cloverleaf structure. The control region is 1066 bp in length with high A + T and low G contents.

Feeding Ecology of the Sandbar Shark in South Carolina Estuaries Revealed through δ13C and δ15N Stable Isotope Analysis

AbstractStable isotope ratios of carbon and nitrogen (δ13C and δ15N) from muscle samples were used to examine the feeding ecology of a heavily exploited shark species, the Sandbar Shark Carcharhinus plumbeus. Two hundred and sixty two Sandbar Sharks were sampled in five South Carolina estuaries. There were no significant differences in average δ13C or δ15N signatures between estuaries, between sampling years, or between male and female Sandbar Sharks, suggesting that these variables do not affect diet. A potential ontogenetic diet shift between young‐of‐year and juvenile Sandbar Sharks in South Carolina, similar to a shift previously described in Virginia and Hawaii populations, is suggested by significant differences in average δ13C and average δ15N signatures between these age‐classes. Results confirm that Sandbar Sharks in South Carolina are generalist predators and that juvenile Sandbar Sharks have a wider diet breadth than young‐of‐year sharks, a pattern common in elasmobranchs. Sandbar Shark diet in South Carolina is similar to that found in previous stomach content analysis studies. This study also demonstrates that nonlethal sampling methods can be applied to sharks to obtain diet and trophic information, including the detection of ontogenetic shifts in diet.Received September 17, 2013; accepted April 1, 2014

New biological data on the rare, threatened shark Carcharhinus leiodon (Carcharhinidae) from the Persian Gulf and Arabian Sea

New biological data relevant to the conservation of the rare and threatened shark Carcharhinus leiodon are presented, based on specimens sampled in fish markets in Kuwait, the UAE and Yemen. The maximum size of this species is extended to 1648 mm total length (TL); females are mature by at least 1312 mm TL and demonstrate placental viviparity with litters of 4–6 embryos. In the north-western Persian Gulf there is evidence that parturition occurs in spring when embryos are ~350–515 mm TL, with at least some neonate individuals probably remaining in the area through the summer. Further records of C. leiodon from the western Arabian Sea indicate that adults are present in this region throughout the year. Landings of C. leiodon apparently caught in the eastern Persian Gulf may extend the highly fragmented known distribution of this species. Contrary to an earlier study, the first detailed examination of dissected adult C. leiodon jaws revealed that fine serrations are present on upper teeth, and characters are provided to separate the dentition and jaws of C. leiodon from congeners. The stomach of an adult C. leiodon contained bentho-demersal fish, and an individual with fin abnormalities is noted.

A review of the Oceanographic Research Institute's Cooperative Fish Tagging Project: 27 years down the line

The Oceanographic Research Institute's (ORI) Cooperative Fish Tagging Project was initiated in 1984 and is one of the most enduring and successful environmental projects of its kind in South Africa. By the end of 2011, 5 130 anglers had joined the project, of whom 3 457 had tagged one or more fish. In the project's 27-year history (1984–2011), over 251 900 fish from 368 different species have been tagged and released, of which approximately 13 192 (5.2%) have been recaptured. The five most commonly tagged species to date are galjoen Dichistius capensis, dusky kob Argyrosomus japonicus, dusky shark Carcharhinus obscurus, garrick/leervis Lichia amia and spotted grunter Pomadasys commersonnii. Information from the Tagging Project has been extensively used in numerous research projects, scientific publications, popular articles and postgraduate theses. The results generated by this project have also contributed to policy development and decision-making on linefish management in South Africa. Furthermore, the project has had a positive impact on improving angler awareness and knowledge about linefish resources. The concept of tag and release has partly been responsible for changing the ethics of the recreational fishing community, many of whom now release their catch, thereby contributing to a more sustainable fishing future. This paper critically assesses the contribution that the ORI Tagging Project has made as a conservation achievement in general and to linefish management in particular, and reflects on future directions for the project.

Historical demography and genetic differentiation inferred from the mitochondrial DNA of the silky shark (Carcharhinus falciformis) in the Pacific Ocean

The population genetic structure of the silky shark Carcharhinus falciformis in the Pacific Ocean was studied by analyzing 14 haplotypes identified by sequencing a 732bp fragment of the mitochondrial DNA control region from 353 silky sharks. The mean haplotype (0.48±0.03) and nucleotide diversity (0.0009±0.00008) of the silky shark population were lower than in other shark species. The AMOVA analysis comparing Western and Eastern Pacific regions showed a low, but significant, level of variance associated with differences between groups (ΦCT=0.0199, P=0.008). Here, we present the first population genetic study of the silky shark in the Pacific and provide evidence of the existence of distinct Eastern and Western Pacific populations. Despite the significance found on the population subdivision level, it was not possible to definitively reject the hypothesis of panmixia due to the small differences registered as a result of the low levels of mtDNA genetic variation. The population history of C. falciformis was examined using neutrality tests, mismatch distributions and coalescence analyses based on Bayesian approximations. The results were consistent with a population expansion occurring approximately 12,000–40,000 years ago. The results from IMa showed that the time of divergence was approximately 170,161 years ago, and that in terms of coalescence, the migration that supported the population expansion occurred from west to east across the Pacific. Similarly, the effective population size estimates were consistent with a reduction in the silky shark populations when compared to the ancestral levels. Based on our results and on the population exploitation levels, we suggest evaluating the adoption of a two-stock management strategy to sustain the long-term use of this resource.