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Nematodes belonging to the genus Anisakis are important parasites due to their abundance in seafood and health impacts on humans. In the present study Anisakis larvae were found in a number of uncommon hosts including the Grey petrel, Procellaria cinerea , the Little penguin, Eudyptula minor , Blue-lipped sea krait, Laticauda laticaudata and Spinner shark, Carcharhinus brevipinna . Morphological examination showed nematodes in these animals are Anisakis larval type I. Genetic characterisation suggested that the larva from one Grey petrel was Anisakis berlandi, whereas the other larvae from the second Grey petrel and from the little penguin were Anisakis pegreffii. A number of larvae found in Blue-lipped sea krait and Spinner shark were identified as Anisakis typica . This is the first report of infective stage of Anisakis larvae parasitising hosts other than teleost fish. Understanding of the extent of infection and the pathogenicity of anisakid nematodes in hosts found in the present study is important in the conservation studies and management plans of these hosts. [ABSTRACT FROM AUTHOR]

The removal of large predatory sharks from the world's oceans poses profound threats to marine community structure and species conservation. Effective management of exploited shark stocks requires a sound understanding of the life histories of target species. Here we provide the first assessment of age and growth for Carcharhinus brevipinna in Australian waters, and for C. obscurus and C. plumbeus in eastern Australian waters, based on interpretations of vertebral growth bands. In doing so, we provide arguably among the most robust growth parameters to date for the abovementioned taxa on the bases of genetic validation and sample size and distribution, but acknowledge equally a range of limitations—most notably those associated with vertebral ageing and our lack of age validation. Comparatively, the three species displayed both contrasts and consistencies in their growth characteristics off Australia's southeast coast. For all three sharks, rates of growth were greatest in the years immediately after birth, males grew more rapidly than females in the juvenile phase, and females were observed to grow larger, live longer and were generally larger at any given age. Longevity and all modelled growth parameters (L∞, k and L0), however, differed among the three species, and appeared to challenge the findings for conspecific populations in other parts of the world. The validity of these latter comparisons is, however, compromised by a range of confounding factors. Nevertheless, we provide the least conservative k estimates for C. obscurus and C. plumbeus of those previously reported, and extend maximum age estimates for C. brevipinna. In this way, our results have important implications for the assessment of natural mortality, productivity, and hence resilience to stock depletion, in these species in southeastern Australian waters. [ABSTRACT FROM PUBLISHER]

Micro-computed tomography (microCT) produced 3D reconstructions of shark Carcharhinus brevipinna vertebrae that could be virtually sectioned along any desired plane, and upon which growth bands were readily visible. When compared to manual sectioning, it proved to be a valid and repeatable means of ageing and offers several distinct advantages over other ageing methods. [ABSTRACT FROM AUTHOR]

In the north-west Atlantic Ocean, stock assessments conducted for some commercially harvested coastal sharks indicate declines from 64 to 80% with respect to virgin population levels. While the status of commercially important species is available, abundance trend information for other coastal shark species in the north-west Atlantic Ocean are unavailable. Using a generalized linear modelling (GLM) approach, a relative abundance index was derived from 1994 to 2009 using observer data collected in a commercial bottom longline fishery. Trends in abundance and average size were estimated for bull shark Carcharhinus leucas, spinner shark Carcharhinus brevipinna, tiger shark Galeocerdo cuvier and lemon shark Negaprion brevirostris. Increases in relative abundance for all shark species ranged from 14% for C. brevipinna, 12% for C. leucas, 6% for N. brevirostris and 3% for G. cuvier. There was no significant change in the size at capture over the time period considered for all species. While the status of shark populations should not be based exclusively on abundance trend information, but ultimately on stock assessment models, results from this study provide some cause for optimism on the status of these coastal shark species. [ABSTRACT FROM AUTHOR]

Our understanding of the ecological role of larger elasmobranchs is limited by a lack of information on their spatial and seasonal abundance. Analysis of 14 years of gill-net catch data in south-eastern Queensland, Australia, revealed that the species composition of large sharks and other elasmobranchs significantly differed among beaches and seasons. Spinner sharks (Carcharhinus brevipinna) and hammerhead sharks (Sphyrna spp.) comprised nearly half the catch of all elasmobranchs. Although the distribution of these sharks overlapped, spatial variation existed in their abundance. Spinner sharks characterised the catch at Sunshine Coast beaches, whereas the catch at Gold Coast beaches was dominated by hammerhead sharks. Seasonal differences in elasmobranch community structure were also apparent, driven largely by a lower abundance of many species during the winter and the predominance of species such as spinner sharks and hammerheads in spring and summer. The present study provides the first quantitative data for numerous species of Carcharhiniformes in south-eastern Queensland and demonstrates that analysis of catch-rate data can improve our understanding of how larger sharks partition resources. [ABSTRACT FROM AUTHOR]

Shark liver oils are rich in polyunsaturated fatty acids, especially the n3 moieties. Data on the liver fatty acids of sharks from African waters, however, are limited. Liver samples from sharks from the western Indian Ocean off the east coast of South Africa and those from the Atlantic Ocean and Gulf of Mexico were examined. This study reports on the fatty acids found in the total lipid fractions from the livers of two shark species found in these regions, the spinner Carcharhinus brevipinna and blacktip Carcharhinus limbatus. Greater amounts of total lipids were found in sharks from the Indian Ocean than in those from the Atlantic Ocean (spinner 0.431 g g-1 vs 0.324 g g-1, p = 0.004; blacktip 0.426 g g-1 vs 0.261 g g-1, p = 0.004). The individual fatty acids in the same animals showed reduced amounts of saturates (spinner 26.22% vs 30.68%, p = 0.013; blacktip 28.94% vs 35.14%, p = 0.007) and slightly increased n3 polyunsaturates (spinner 33.67% vs 22.89%, p = 0.001; blacktip 24.77% vs 18.68%, p = 0.025). Generally, the geographical location rather than the shark species was most important in determining the proportions of hepatic lipids. [ABSTRACT FROM AUTHOR]

Abstract: Stable isotopes (δ 15N and δ 13C) are being widely applied in ecological research but there has been a call for ecologists to determine species- and tissue-specific diet discrimination factors (∆13C and ∆15N) for their study animals. For large sharks stable isotopes may provide an important tool to elucidate aspects of their ecological roles in marine systems, but laboratory based controlled feeding experiments are impractical. By utilizing commercial aquaria, we estimated ∆15N and ∆13C of muscle, liver, vertebral cartilage and a number of organs of three large sand tiger (Carcharias taurus) and one large lemon shark (Negaprion brevirostris) under a controlled feeding regime. For all sharks mean±SD for ∆15N and ∆13C in lipid extracted muscle using lipid extracted prey data were 2.29‰±0.22 and 0.90‰±0.33, respectively. The use of non-lipid extracted muscle and prey resulted in very similar ∆15N and ∆13C values but mixing of lipid and non-lipid extracted data produced variable estimates. Values of ∆15N and ∆13C in lipid extracted liver and prey were 1.50‰±0.54 and 0.22‰±1.18, respectively. Non-lipid extracted diet discrimination factors in liver were highly influenced by lipid content and studies that examine stable isotopes in shark liver, and likely any high lipid tissue, should strive to remove lipid effects through standardising C:N ratios, prior to isotope analysis. Mean vertebral cartilage ∆15N and ∆13C values were 1.45‰±0.61 and 3.75‰±0.44, respectively. Organ ∆15N and ∆13C values were more variable among individual sharks but heart tissue was consistently enriched by ~1–2.5‰. Minimal variability in muscle and liver δ 15N and δ 13C sampled at different intervals along the length of individual sharks and between liver lobes suggests that stable isotope values are consistent within tissues of individual animals. To our knowledge, these are the first reported diet–tissue discrimination factors for large sharks under semi-controlled conditions, and are lower than those reported for teleost fish. [Copyright &y& Elsevier]

1. Life-history theory predicts that organisms will provide an optimal level of parental investment for offspring survival balanced against the effects on their own survival and future reproductive potential. 2. Optimal resource allocation models also predict an increase in reproductive output with age as expected future reproductive effort decreases. To date, maternal investment in sharks has received limited attention. 3. We found that neonatal dusky sharks ( Carcharhinus obscurus) are not independent from maternal resource allocation at the point of parturition but instead are provisioned with energy reserves in the form of an enlarged liver that constitutes approximately 20% of total body mass. 4. Analysis of long-term archived data sets showed that a large proportion of this enlarged liver is utilized during the first weeks or months of life suggesting that the reported weight loss of newborn sharks signifies a natural orientation process and is not necessarily related to prey abundance and/or indicative of high mortality rates. 5. Interrogation of near-term pup mass in two carcharhinids, the dusky and spinner shark ( Carcharhinus brevipinna), further revealed an increase in reproductive output with maternal size, with evidence for a moderate decline in the largest mothers. 6. For the dusky shark, there was a trade-off between increasing litter size and near-term pup mass in support of optimal offspring size theory. 7. For both the dusky and spinner shark, there was a linear increase in near-term pup mass with month, which may indicate variable parturition strategies and/or that carcharhinids are able to adjust the length of the gestation period. 8. The identification of optimal size-specific reproductive output has direct implications for improving the reproductive potential of exploited shark populations and for structuring future management strategies. [ABSTRACT FROM AUTHOR]

The age and growth dynamics of the spinner shark (Carcharhinus brevipinna) in the northwest Atlantic Ocean off the southeast United States and in the Gulf of Mexico were examined and four growth models were used to examine variation in the ability to fit size-at-age data. The von Bertalanffy growth model, an alternative equation of the von Bertalanffy growth model with a size-at-birth intercept, the Gompertz growth model, and a logistic model were fitted to sex-specific observed size-at-age data. Considering the statistical criteria (e.g., lowest mean square error [MSE], high coefficient-of-determination, and greatest level of significance) we desired for this study, the logistic model provided the best overall fit to the size-at-age data, whereas the von Bertalanffy growth model gave the worst. For "biological validity," the von Bertalanffy model for female sharks provided estimates similar to those reported in other studies. However, the von Bertalanffy model was deemed inappropriate for describing the growth of male spinner sharks because estimates of theoretical maximum size (L∞) indicated a size much larger than that observed in the field. However, the growth coefficient (k=0.14/yr) from the Gompertz model provided an estimate most similar to that reported for other large coastal species. The analysis of growth for spinner shark in the present study demonstrates the importance of fitting alternative models when standard models fit the data poorly or when growth estimates do not appear to be realistic. [ABSTRACT FROM AUTHOR]

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-Cysand tRNA-Ser2) to 75 bp (tRNA-Leu1) in length. Only the tRNA-Ser2could 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%). [ABSTRACT FROM PUBLISHER]

Background:Quantifying genetic diversity and metapopulation structure provides insights into the evolutionary history of a species and helps develop appropriate management strategies. We provide the first assessment of genetic structure in spinner sharks (Carcharhinus brevipinna), a large cosmopolitan carcharhinid, sampled from eastern and northern Australia and South Africa. Methods and Findings:Sequencing of the mitochondrial DNA NADH dehydrogenase subunit 4 gene for 430 individuals revealed 37 haplotypes and moderately high haplotype diversity (h = 0.6770 ±0.025). While two metrics of genetic divergence (ΦST and FST) revealed somewhat different results, subdivision was detected between South Africa and all Australian locations (pairwise ΦST, range 0.02717–0.03508, p values ≤ 0.0013; pairwise FST South Africa vs New South Wales = 0.04056, p = 0.0008). Evidence for fine-scale genetic structuring was also detected along Australia’s east coast (pairwise ΦST = 0.01328, p < 0.015), and between south-eastern and northern locations (pairwise ΦST = 0.00669, p < 0.04). Conclusions:The Indian Ocean represents a robust barrier to contemporary gene flow in C. brevipinna between Australia and South Africa. Gene flow also appears restricted along a continuous continental margin in this species, with data tentatively suggesting the delineation of two management units within Australian waters. Further sampling, however, is required for a more robust evaluation of the latter finding. Evidence indicates that all sampled populations were shaped by a substantial demographic expansion event, with the resultant high genetic diversity being cause for optimism when considering conservation of this commercially-targeted species in the southern Indo-Pacific. [ABSTRACT FROM AUTHOR]