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The present study aims to evaluate the bioavailability of Hg and Se in blacktip shark, Asian tiger shrimp and squid tube samples after three culinary treatments: boiling, frying and sauteing. Cooked and uncooked samples were evaluated for each seafood species with and without addition of spices (salt, lemon juice and garlic). After each culinary treatment, the seafood samples were freeze-dried, ground and stored for further analysis. The following parameters were evaluated and optimized: sample mass, sample size, cooking time and temperature. The determination of total concentration of Hg and Se was carried out by ICP-MS/MS. In order to minimize the memory effects for Hg, an integrated sample introduction system (ISIS) coupled with ICP-MS/MS was used employing water, 5% HNO3 and 5 mg L−1 Au for the washing steps. No significant losses of Se in the seafood were observed after culinary treatments with and without spices. For Hg, losses for blacktip shark and Asian tiger shrimp were observed after boiling, frying and sauteing procedures (14 to 33%) with and without spices. Blacktip shark showed the highest Hg concentration, about 245% higher than the maximum level recommended by the official health organizations. The Se/Hg molar ratio was also determined in all samples and blacktip shark showed a Se/Hg molar ratio

Information on how shark populations respond to fishing mortality ( F ) is critical to developing successful management and conservation strategies. However, data on catch, fishing effort and species abundance are often lacking for shark populations – preventing stock assessments from being conducted. Static demographic models circumvent this issue as they only require life history parameters. Age-structured Leslie Matrix models were developed and applied for silvertip shark Carcharhinus albimarginatus and common blacktip shark Carcharhinus limbatus sampled from heavily fished populations in the Indo-Pacific. Stochasticity was introduced to these models by varying vital rates though Monte Carlo simulations. Varying levels of F were introduced to the analyses to determine how both species respond to fishing pressure. Management scenarios were further developed to determine strategies that could facilitate sustainable harvesting. The demographic estimates demonstrated that without fishing both species would have increasing populations ( λ = 1.06 yr −1 for C. albimarginatus and 1.05 yr −1 for C. limbatus ) until density dependent effects occur. However, both populations would decline when low levels of F (>0.1 yr −1 ) were applied to all age-classes. The matrix elasticities revealed that changes to fertility elements had little effect on λ, while changes in juvenile survival led to the largest changes. However, age-at-first-capture analysis suggests protecting the juvenile life stage of both species would be an ineffective management strategy as both species mature at old ages. An age-at-last-capture analysis suggests these species could be harvested while maintaining increasing populations through a gauntlet fishery. This required F to be restrained to individuals C. limbatus and C. albimarginatus, respectively, until density dependent effects begin to manifest. However, this strategy depends on the ability to successfully protect all other age-classes from fishing – a strategy that may not be pragmatic in developing nations where little regulation occurs.

The ability of predators to modulate prey capture in response to the size, location, and behavior of prey is critical to successful feeding on a variety of prey types. Modulating in response to changes in sensory information may be critical to successful foraging in a variety of environments. Three shark species with different feeding morphologies and behaviors were filmed using high-speed videography while capturing live prey: the ram-feeding blacktip shark, the ram-biting bonnethead, and the suction-feeding nurse shark. Sharks were examined intact and after sensory information was blocked (olfaction, vision, mechanoreception, and electroreception, alone and in combination), to elucidate the contribution of the senses to the kinematics of prey capture. In response to sensory deprivation, the blacktip shark demonstrated the greatest amount of modulation, followed by the nurse shark. In the absence of olfaction, blacktip sharks open the jaws slowly, suggestive of less motivation. Without lateral line cues, blacktip sharks capture prey from greater horizontal angles using increased ram. When visual cues are absent, blacktip sharks elevate the head earlier and to a greater degree, allowing them to overcome imprecise position of the prey relative to the mouth, and capture prey using decreased ram, while suction remains unchanged. When visual cues are absent, nurse sharks open the mouth wider, extend the labial cartilages further, and increase suction while simultaneously decreasing ram. Unlike some bony fish, neither species switches feeding modalities (i.e. from ram to suction or vice versa). Bonnetheads failed to open the mouth when electrosensory cues were blocked, but otherwise little to no modulation was found in this species. These results suggest that prey capture may be less plastic in elasmobranchs than in bony fishes, possibly due to anatomical differences, and that the ability to modulate feeding kinematics in response to available sensory information varies by species, rather than by feeding modality.

The blacktip shark (Carcharhinus limbatus) is a placental shark that uses coastal nursery areas in the Galapagos Marine Reserve, where juveniles live during their early life stages. To better understand the feeding behavior of early juvenile blacktip sharks, we conducted stable isotope analysis on 57 samples from three coastal nurseries around the archipelago. We evaluated the intraspecific variation in trophic shifts of four size classes (

The status of five species of commercially exploited sharks within the Great Barrier Reef Marine Park (GBRMP) and south-east Queensland was assessed using a data-limited approach. Annual harvest rate, U , estimated empirically from tagging between 2011 and 2013, was compared with an analytically-derived proxy for optimal equilibrium harvest rate, U MSY Lim . Median estimates of U for three principal retained species, Australian blacktip shark, Carcharhinus tilstoni , spot-tail shark, Carcharhinus sorrah , and spinner shark, Carcharhinus brevipinna , were 0.10, 0.06 and 0.07 year −1 , respectively. Median U for two retained, non-target species, pigeye shark, Carcharhinus amboinensis and Australian sharpnose shark, Rhizoprionodon taylori , were 0.27 and 0.01 year −1 , respectively. For all species except the Australian blacktip the median ratio of U/U MSY Lim was U MSY Lim was low (0.04–0.07 year −1 ) and that U/U MSY Lim was likely to be >1. Harvest of the Australian blacktip shark above U MSY could place this species at a greater risk of localised depletion in parts of the GBRMP. Results of the study indicated that much higher catches, and presumably higher U , during the early 2000s were likely unsustainable. The unexpectedly high level of U on the pigeye shark indicated that output-based management controls may not have been effective in reducing harvest levels on all species, particularly those caught incidentally by other fishing sectors including the recreational sector.

The use of turtle excluder devices (TEDs) has resulted in fewer elasmobranchs (i.e. sharks and rays) caught in tropical penaeid-trawl fisheries. However, very few studies in the primary literature have quantified the effects of various TED design aspects affecting the escape of elasmobranchs. Data collected by observers on board commercial trawlers operating in Australia’s northern prawn fishery (NPF) during 2001 were re-examined to quantify the effect of TEDs on catches of various elasmobranchs. During this sampling, a total of 6204 elasmobranchs were caught from 1440 net trawls. The 34 species identified, from 15 families and four taxonomic orders, were dominated by small carcharhinids (n = 2160, median total length = 75 cm) and dasyatids (n = 2030, median disc width = 24 cm). The TEDs assessed significantly reduced the numbers of large elasmobranchs caught: increasing fish size was found to result in higher escape for all taxonomic orders. Further, top-shooter TEDs increased the escape of Carcharhiniformes, while bottom-shooter TEDs facilitated greater escape of Myliobatiformes. Grid orientation had no effect on the escape of Orectolobiformes or Rhinopristiformes. Decreasing bar space was found to increase the escape of only one species, the Australian blacktip shark (Carcharhinus tilstoni). The TEDs facilitated the escape of several species of conservation interest including the globally endangered scalloped hammerhead (Sphyrna lewini) and zebra shark (Stegostoma fasciatum). However, the rostrum of the narrow sawfish (Anoxypristis cuspidata) inhibited the escape of this globally important species. Fishery-specific research is required to determine the appropriate TED bar spaces that reduce catches of elasmobranchs while minimising the loss of commercially important species.

Globally, many gillnet fisheries have excessive discards which can comprise charismatic megafauna threatened with extinction, including numerous elasmobranchs. Very few discarded elasmobranch species have been assessed for their associated fates. Here we describe the immediate mortality of several threatened species discarded from gillnets deployed off eastern Australia to target key carcharhinids and white sharks, Carcharodon carcharias (within an objective of protecting bathers) and causal factors for abundant elasmobranchs. In total, 420 animals comprising at least 22 species were gillnetted with a total immediate mortality of 49 % and group-specific estimates of 100 % for dolphins (n = 8), 100 % for teleosts (n = 16), 86 % for sharks (n = 75), 45 % for turtles (n = 20) and 36 % for rays (n = 301). Among elasmobranchs, species that were obligate ram-ventilating (e.g. great hammerhead, Sphyrna mokarran and common blacktip shark, Carcharhinus limbatus) had greater mortality (>95 %) than those species with spiracles, and likely capable of some stationary respiration (e.g. whitespotted guitar fish, Rhynchobatus australiae, whitespotted eagle ray, Aetobatus ocellatus, Australian cownose ray, Rhinoptera neglecta and to a lesser extent, pygmy devilray, Mobula kuhlii cf. eregoodootenkee) (16–74 % mortality). Mortalities among Australian cownose rays increased across longer soaks. The effect of soak time was further assessed to determine an optimal to maintain gillnet efficiency for target sharks, but minimise the absolute mortality of abundant rays and was estimated at up to three or four fishing nights (72–96 h). Other potential operational modifications, including using light and better retroactive deterrents to reduce turtle and dolphin bycatches and mortality, warrant investigation.

Kuwait’s waters are one of only two locations where the smoothtooth blacktip shark Carcharhinus leiodon is known to occur. Concentrations of 11 trace elements were analysed in five juvenile and two adult specimens of this coastal predator. Concentrations of lead in muscle increased with length, whilst manganese concentration decreased. Arsenic concentrations in muscle were among the highest reported in elasmobranchs, and the concentration in the liver increased significantly in relation to length. In comparison to published literature, concentrations of manganese (liver), lead (muscle) and iron (muscle and liver) were high. Mercury concentrations in the muscle exceeded European Food Safety Authority limits and were among the highest reported in any elasmobranch. Concentrations of selenium, which may inhibit mercury toxicity, were also high. These results and previous studies indicate that potentially hazardous levels of mercury and other contaminants may occur in sharks in this region, adding further stressors to these vulnerable populations.

Elasmobranchs can bioaccumulate considerable amounts of persistent organic pollutants (POPs) and utilize several reproductive strategies thereby influencing maternal transfer of contaminants. This study provides preliminary data on the POP transfer from pregnant females to offspring of three species (Atlantic stingrays, bonnethead, blacktip sharks) with different reproduction modes (aplacental, placental viviparity). Polychlorinated biphenyl (PCB) levels were generally higher than any other POPs. Stingrays and blacktip shark embryos contained the lowest POP concentrations while bonnetheads and the blacktip adult female had the highest concentrations. Results suggest that POPs are more readily transferred from the mother to the embryo compared to what is transferred to ova in stingrays. Statistically significant differences in levels of selected POPs were found between embryos from the left and right uterus within the same litter as well as between female and male embryos within the same litter for bonnetheads, but not for the blacktip sharks. (C) 2015 Elsevier Ltd. All rights reserved.

Inhibition of angiotensin converting enzyme (ACE), human LDL cholesterol and DNA oxidation by hydrolysates from blacktip shark gelatin prepared using papaya latex enzyme with different degrees of hydrolysis (DH of 10, 20, 30 and 40%) were evaluated. ACE-inhibitory activity of hydrolysate increased as the DH increased ( P −1 inhibited LDL cholesterol oxidation by 8.32–39.21%. Additionally, gelatin hydrolysate with DH of 40% effectively inhibited hydroxyl and peroxyl radical-induced DNA scission. Therefore, gelatin hydrolysate from blacktip shark skin with DH of 40% could serve as a potential source of functional food ingredient for health promotion.

Antioxidant activities of gelatin hydrolysates from blacktip shark skin prepared using papaya latex enzyme with different degrees of hydrolysis (DHs: 10%, 20%, 30% and 40%) were evaluated. All antioxidant activity indices of hydrolysates increased with increasing DH (P0.05). When gelatin hydrolysate with 40%DH was determined for its pH and thermal stability, ORAC and chelating activity remained constant or slightly increased in a wide pH range (1-9) and during heating (100°C) for 240min. It was also stable in simulated gastrointestinal tract model system. Moreover, gelatin hydrolysate at a level of 500 and 1000ppm could inhibit lipid oxidation in both β-carotene linoleate and cooked comminuted pork model systems. Therefore, gelatin hydrolysate from blacktip shark skin (40%DH) can potentially be used as an alternative source of natural antioxidants.

Acid soluble collagen (ASC) and pepsin soluble collagen (PSC) from the cartilages of brownbanded bamboo shark (BBS; Chiloscyllium punctatum ) and blacktip shark (BTS; Carcharhinus limbatus ) were isolated and characterized. ASC and PSC extracted from BBS cartilage showed the yields of 1.27 and 9.59 g/100 g (Based on dry weight), respectively, while yields of ASC and PSC from BTS cartilage were 1.04 and 10.30 g/100 g (based on dry weight), respectively. All collagens had protein as a major constituent with the trace amount of ash and fat. They contained glycine as the major amino acid with high contents of alanine, proline and hydroxyproline. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoretic patterns and subunit compositions, all collagens more likely comprised 2 types of collagen, type I and II, and contained α- and β-chains as the major components. Peptide maps of those collagens from both species digested by V8-protease and lysyl endopeptidase were different and were completely different from those of type I collagen from calf skin. Thermal transition temperature of ASC from those collagens (36.28–36.73 °C) was slightly higher than their corresponding PSC (34.56–35.98 °C). From zeta potential analysis, isoelectric points (pI) of collagen from the cartilages of BBS and BTS were estimated to be from 6.53 to 7.03 and from 6.96 to 7.26, respectively. Fourier transform infrared (FTIR) spectra of both ASC and PSC were quite similar, suggesting that pepsin hydrolysis did not affect the secondary structure of collagen, especially triple-helical structure.

Gelatins from the skins of brownbanded bamboo shark (BBS; Chiloscyllium punctatum) and blacktip shark (BTS; Carcharhinus limbatus) were extracted using the distilled water at different temperatures (45, 60 and 75 °C) and times (6 and 12 h). Yields of gelatin from the skins of BBS and BTS were 19.06–22.81% and 21.17–24.76% (based on wet weight), respectively. Gelatins from both species extracted at 45 °C for 6 h exhibited the highest bloom strength (206–214 g), which was higher than that of commercial bovine bone gelatin (197 g) (p

The increasing demand for shark fins in Asia, and the publicity resulting from finning and discarding live sharks, has generated concern regarding the sustainability of the world's shark populations. These concerns can be attributed to the shark's life history, which is characterized by a pattern of slow growth, late maturity, few offspring, and long life, making populations vulnerable to overexploitation. Once overexploited, shark stocks will be slow to recover due to these constraints. Despite an increase in consumption and trade of shark fins and other shark products, and the vulnerability of shark populations once overexploited, little effort has been expended to understand the biology and economics of sharks and shark fisheries until recently. This study adds to the understanding of linkages between shark product markets, specifically shark fins, and the biology of shark populations by explicitly incorporating multi-attribute market information into bioeconomic modeling. Results from conjoint analysis of the Hong Kong dried, processed end-user markets is incorporated into a blacktip shark (Carcharhinus limbatus) cohort model to estimate the optimal harvest size and age that maximize economic value. Results show that optimal harvest sizes and ages for all mortality and discount factor scenarios are greater than the maturation sizes and ages for both male and female blacktip. Policy implications for this study are also discussed.

Cartilaginous fish of the Gulf of Mexico may help to meet the ever increasing consumer demand for seafood products that are low in fat and enriched in the n -3 polyunsaturated fatty acids reputed to have significant health benefits. Two shark species, Atlantic sharpnose shark ( Rhizoprionodon terraenovae ) and blacktip shark ( Carcharhinus limbatus ), and two ray species, Atlantic stingray ( Dasyatis sabina ) and southern stingray ( Menticirrhus americanus ), were collected from nearcoastal waters in the northeastern Gulf of Mexico and analyzed for fatty acids and proximates. Fat content is very low in these fish, ranging only from 0.45 to 0.62%, which is similar to reports on cartilaginous fish from colder and also more tropical waters. The major n -3 fatty acid in all four species is docosahexaenoic acid with total n -3 fatty acids accounting for 20–33% of the total fatty acids of these fish. The n -3 fatty acid content is somewhat less than that reported in cold water sharks, rays, and skates and more than that reported in cartilaginous fish in tropical waters. Cholesterol content ranges from 16 to 69 mg/100 g.