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Fisheries management is essential to guarantee sustainable capture of target species and avoid undesirable declines of incidentally captured species. A key challenge is halting and reversing declines of shark and ray species, and specifically assessing the degree to which management is sufficient to avoid declines in relatively data‐poor fisheries. While ecological risk analyses focus on intrinsic 'productivity' and extrinsic 'susceptibility', one would ideally consider the influence of 'fisheries management'. Currently, there is no single management evaluation that can be applied to a combination of fishery types at the scale of individual country or Regional Fisheries Management Organizations (RFMOs). Here, we outline a management‐risk (M‐Risk) framework for sharks, rays and chimaeras used to evaluate species' risk of overfishing resulting from ineffective management. We illustrate our approach with application to one country (Ecuador) and RFMO (Inter‐American Tropical Tuna Commission) and illustrate the variation in scores among species. We found that while both management units assessed had similar overall scores, the scores for individual attributes varied. Ecuador scored higher in reporting‐related attributes, while the IATTC scored higher in attributes related to data collection and use. We evaluated whether the management of individual species was sufficient for their relative sensitivity by combining the management‐risk score for each species with their intrinsic sensitivity to determine a final M‐Risk score. This framework can be applied to determine which species face the greatest risk of overfishing and be used by fisheries managers to identify effective management policies by replicating regulations from countries with lower risk scores. [ABSTRACT FROM AUTHOR]

One‐third of all elasmobranch species currently known to occur in Papua New Guinea are taken as bycatch in the Gulf of Papua trawl fishery. An ecological risk assessment was conducted on the 16 species of sharks and 23 species of rays caught by the fishery.Eight species were classified to be at low risk, 28 species were at medium risk while three species – Rhynchobatus palpebratus (eyebrow wedgefish), Carcharhinus coatesi (Australian blackspot shark) and Maculabatis astra (blackspotted whipray), all endemic to New Guinea and northern Australia – faced the highest level of risk from the fishery at current fishing levels.There is potential for more vessels to enter the fishery in future, which is likely to elevate the risk for a greater proportion of elasmobranch species. Ongoing monitoring of bycatch levels, supported by biological and ecological studies on frequently caught species, is required to assess and manage risk in the future.The development and use of trawl excluder devices or bycatch reduction devices in this fishery have the potential to reduce bycatch levels and reduce risk levels. [ABSTRACT FROM AUTHOR]

The eastern shovelnose ray (Aptychotrema rostrata) is a medium-sized coastal batoid endemic to the eastern coast of Australia. It is the most common elasmobranch incidentally caught in the Queensland east coast otter trawl fishery, Australia's largest penaeid-trawl fishery. Despite this, age and growth studies on this species are lacking. The present study estimated the growth parameters and age-at-maturity for A. rostrata on the basis of sampling conducted in southern Queensland, Australia. This study showed that A. rostrata exhibits slow growth and late maturity, which are common life-history strategies among elasmobranchs. Length-at-age data were analysed within a Bayesian framework and the von Bertalanffy growth function (VBGF) best described these data. The growth parameters were estimated as L 0 = 193 mm TL, k = 0.08 year–1 and L ∞ = 924 mm TL. Age-at-maturity was found to be 13.3 years and 10.0 years for females and males respectively. The under-sampling of larger, older individuals was overcome by using informative priors, reducing bias in the growth and maturity estimates. As such, the results can be used to derive estimates of natural mortality for this species. The eastern shovelnose ray is a coastal batoid endemic to the eastern coast of Australia, commonly caught as by-catch in Queensland's prawn trawl fishery. Growth and age-at-maturity for A. rostrata were assessed and this species exhibits slow growth and late maturity, which are common life-history strategies among elasmobranchs. Females attain a larger size and mature later than do males. [ABSTRACT FROM AUTHOR]

Small-bodied coastal sharks are often caught as by-catch in fishing operations. Life-history information for these sharks is needed to ascertain the level at which these populations are potentially affected by fishing. This study determined the age, growth and maturity of Carcharhinus coatesi captured by prawn trawlers in the Gulf of Papua. Using vertebral aging and an information-theoretic multimodel approach, the von Bertalanffy growth model fit the data best; parameters were L0 = 40.6 cm ± 0.8, L∞ = 74.8 cm ± 2.1, k = 0.33 year−1 ± 0.06. Length-at-maturity analysis indicated that males reach maturity at L50 = 66.3 cm (CI: 63.8, 71.4) and L95 = 71.6 (CI: 64.6, 74.2) cm while females matured at L50 = 71.4 cm (CI: 61.5, 72.01) and L95 = 72.5 cm (CI: 62.7, 74.0). Age-at-maturity estimates showed that both males (A50 = 5.1 years (CI: 4.6, 7.1), A95 = 6.4 years (CI: 5.1, 7.2)) and females (A50 = 5.3 years (CI: 3.5, 8.7), A95 = 7.4 years (CI: 3.6, 8.8)) reach maturity at about the same age. This study addresses the need for specific life-history information for a data-deficient species in a region that has remained relatively under-researched but in need of ongoing improvements to fisheries management. This study addresses the need for region-specific life-history data to improve fisheries management. The Australian blackspot shark is commonly caught as by-catch in the Gulf of Papua prawn trawl fishery. We found that this shark species is relatively fast growing and reaches maturity at approximately five years of age in this region of Papua New Guinea. [ABSTRACT FROM AUTHOR]

Growth and maturity of the silvertip shark Carcharhinus albimarginatus from Papua New Guinea were estimated to form the basis of future population assessments. Samples were collected from commercial longline vessels targeting sharks in the Bismarck and Solomon Seas. A total of 48 C. albimarginatus-28 males (95-219 cm total length, TL) and 20 females (116-250 cm TL)-provided data for the analyses. Employing back-calculation techniques accounted for missing juvenile length classes and supplemented the sample size. A multi-model framework incorporating the Akaike information criterion was used to estimate growth parameters. The von Bertalanffy growth function (VBGF) provided the best-fit growth estimates. Parameter estimates were L = 72.1 cm TL, k = 0.04 yr and L = 311.3 cm TL for males; and L = 70.8 cm TL, k = 0.02 yr and L = 497.9 cm TL for females. The biologically implausible L occurred for females as their growth did not asymptote; a typical trait of large shark species. The maximum age estimated from vertebral analysis was 18 yr for both sexes, while the calculated longevity from the VBGF parameters was 27.4 yr for males and 32.2 yr for females. Males matured at 174.7 cm TL and 10.5 yr old, while females matured at 208.9 cm TL and 14.8 yr old. [ABSTRACT FROM AUTHOR]

Coastal sharks face increasing pressure from anthropogenic impacts and environmental change. Estimated population declines in some species have created uncertainty about the effectiveness of existing management approaches. In particular, there are scarce data on the benefits of marine protected areas (MPAs) for sharks, including whether they can be used to conserve multiple sympatric species comprising diverse life histories and habitat use patterns., This study used fishery-independent longline and gill-net surveys to investigate the effects of sub-bay-sized MPAs ( c. 100-300 km2) on the abundance and community structure of tropical coastal sharks. In addition, tag-recapture data from fishery-dependent and fishery-independent sources were used to investigate the movements of individuals across MPA boundaries., Species composition varied significantly between management zones, and overall shark abundance on longlines was higher inside MPAs., Length-frequency distributions of blacktip ( Carcharhinus tilstoni/Carcharhinus limbatus) and pigeye ( Carcharhinus amboinensis) sharks inside MPAs included a greater proportion of sharks larger than c. 800 mm compared with those in open zones, although results varied between gear types for pigeye sharks., Tagging and recapture locations indicated repeated and potentially long-term use of MPAs by individuals of some species., Although the potential benefits of MPAs were not equal for all species, coastal MPAs may increase the survival of young sharks to maturity, or shelter parts of breeding stocks, and therefore do not necessarily need to be large to provide benefits., Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Increased oceanic uptake of atmospheric carbon dioxide (CO2) is a threat to marine organisms and ecosystems. Among the most dramatic consequences predicted to date are behavioural impairments in marine fish which appear to be caused by the interference of elevated CO2 with a key neurotransmitter receptor in the brain. In this study, we tested the effects of elevated CO2 on the foraging and shelter-seeking behaviours of the reef-dwelling epaulette shark, Hemiscyllium ocellatum. Juvenile sharks were exposed for 30 d to control CO2 (400 µatm) and two elevated CO2 treatments (615 and 910 µatm), consistent with medium- and high-end projections for ocean pCO2 by 2100. Contrary to the effects observed in teleosts and in some other sharks, behaviour of the epaulette shark was unaffected by elevated CO2. A potential explanation is the remarkable adaptation of H. ocellatum to low environmental oxygen conditions (hypoxia) and diel fluctuations in CO2 encountered in their shallow reef habitat. This ability translates into behavioural tolerance of near-future ocean acidification, suggesting that behavioural tolerance and subsequent adaptation to projected future CO2 levels might be possible in some other fish, if adaptation can keep pace with the rate of rising CO2 levels. [ABSTRACT FROM AUTHOR]

Understanding the extent of movements and space use of animals is necessary to identify vital habitats and better conserve and manage vulnerable species. We used acoustic telemetry to examine movement patterns and habitat use of juvenile mangrove whiprays (Himantura granulata) in an intertidal bay at Orpheus Island, Australia. Thirteen juveniles were acoustically monitored between March and December 2012, and in July 2012, four active tracks were completed. The majority of the acoustically monitored rays remained within the intertidal bay for the entire monitoring period. Tidal changes caused rays to move from the inner-bay mangrove (high tide) habitat to coral reef in the outer bay (low tide). Actively tracked rays moved in a directed way during running tides, remaining in shallow water. During periods of high and low tide, when rays refuged in mangrove or reef habitats, movement was limited and sinuosity was high. In mangrove areas, rays were most commonly observed refuging under or close to mangrove roots, and rarely in open sand areas. Refuging behaviour in mangrove and reef habitats suggested that predation risk may be the predominant factor influencing the movement of small rays. The continuous use of intertidal habitats demonstrates their importance to Himantura granulata. Understanding the movements and space use of animals is necessary to identify vital habitats and better manage vulnerable species. We used acoustic telemetry to examine movement patterns of juvenile Himantura granulata in an intertidal bay. The majority of rays remained within the intertidal bay for the entire monitoring period, demonstrating the importance of intertidal habitats to H. granulata. Rays exhibited refuging behaviour in mangrove and reef habitats, suggesting that predation risk may be a principal factor influencing the movement of small rays. [ABSTRACT FROM AUTHOR]

Effective conservation and management of shark populations is complicated by our limited understanding of their spatial ecology. For example, there are scarce data on diversity in community structure and nursery function across broader geographic scales (e.g. across multiple inshore systems) and the implications of this diversity for shark populations. Accordingly, fishery-independent surveys were undertaken to investigate shark communities along ~400 km of the tropical eastern coast of Australia (18.1-20.6°S, 146.0-148.8°E). A variety of shark species were encountered, with 19 species of Carcharhiniformes contributing 99.2% of the total shark catch. Of the 1806 sharks captured, 567 were immature, including 336 young-of-the-year individuals. Immature sharks from 18 species were present; however, interspecific variation in the proportions of life-history stages was apparent. Multivariate analyses identified significant spatial heterogeneity in immature-shark communities. Results also highlighted the importance of tropical coastal habitats for numerous shark species, and indicated community-wide spatial structuring of sharks on the basis of body size rather than life-history stage. In addition to building on traditional shark-nursery paradigms, these results demonstrated that data on nursery function from restricted areas may not accurately portray patterns occurring over broader geographic scales, and this diversity may provide population-level benefits for sharks. Fishery-independent surveys were undertaken to investigate shark communities along ~400 km of the tropical eastern coast of Australia. Multivariate analyses identified significant spatial heterogeneity in immature-shark communities. Results demonstrated that data on nursery function from restricted areas may not accurately portray patterns occurring over broader geographic scales, and this diversity may provide population-level benefits for sharks. [ABSTRACT FROM AUTHOR]

Determining the recovery potential of endangered species is an important component for developing strategies necessary to return populations to healthy levels. Many species of endangered marine animals have been regarded as having low productivity and therefore, an inherent inability to rapidly recover from severe depletion., An age-structured Leslie matrix model was constructed for the US population of smalltooth sawfish, Pristis pectinata, to determine their ability to recover under scenarios using different life history inputs and the effects of bycatch mortality and catastrophes., Population growth was highest ( λ=1.237 yr-1) when age-at-maturity was 7 yr and decreased to 1.150 yr-1 when age-at-maturity was 11 yr., Despite a high level of variability throughout the model runs, in the absence of fishing mortality or climate catastrophic effects the population grew at a relatively rapid rate approaching carrying capacity in 40 or 50 yr when the initial population was 600 or 2250 females, respectively. Population projections under various levels of fishing mortality resulted in extinction when mortality was highest, initial population size was small, and age-at-maturity was 11 yr. Scenarios testing the potential effects of extreme cold exposure showed little difference to those scenarios testing the effects of fishing mortality., Using the optimistic estimates of population size, lower age-at-maturity and the lower level of fisheries-related mortality, smalltooth sawfish in US waters appear to have the ability to recover within the foreseeable future. Effective management and recovery of this species can only be achieved by keeping fishing-related mortality low., Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The smalltooth sawfish ( Pristis pectinata) is one of seven critically endangered sawfishes worldwide that little is known about beyond their presence in estuaries and rivers primarily during early life history. Movements of 24 juvenile P. pectinata (<3 years old) were monitored over more than 2 years using acoustic tags and an array of 33 acoustic receivers. The receivers were distributed in both main-stem river habitats, which are known to be used by this species, and non-main-stem habitats (i.e., natural mangrove-lined creeks, seminatural creeks, seawall-lined canals) of the highly altered, flow-managed tidal Caloosahatchee River, Florida to determine (1) the extent of non-main-stem habitat use and (2) responses to freshwater inflow-related changes by P. pectinata. Twenty P. pectinata used non-main-stem habitats, and 11 used these habitats more than 10 % of the time, which has implications for management within the federally protected nursery area. The daily activity space of P. pectinata was 0.7 km of river distance, which is similar to that of other demersal ray species. There was little evidence that P. pectinata left the river and returned; they remained in the nursery under a wide range of environmental conditions. The distribution of all P. pectinata combined was significantly related to 90-day lagged salinity; sawfish moved upriver as salinity increased. Salinity patterns within the river had a greater effect on the distribution (mean river position) of <1-year-old P. pectinata (90-day lagged salinity) than on that of older individuals (120-day lagged salinity). These results provide further evidence of the importance of this system as a nursery and provide specific habitat use patterns that will be useful in the development of management strategies for sawfishes and their habitats. [ABSTRACT FROM AUTHOR]

Sawfish (family Pristidae) are among the most critically endangered marine fish in the world, yet very little is known about how genetic bottlenecks, genetic drift, and inbreeding depression may be affecting these elasmobranchs. In the US Atlantic, the smalltooth sawfish (Pristis pectinata) has declined to 1–5% of its abundance in the 1900s, and its core distribution has contracted to southwest Florida. We used 8 polymorphic microsatellite markers to show that this remnant population still exhibits high genetic diversity in terms of average allelic richness (18.23), average alleles per locus (18.75, standard deviation [SD] 6.6) and observed heterozygosity (0.43–0.98). Inbreeding is rare (mean individual internal relatedness = −0.02, SD 0.14; FIS = −0.011, 95% confidence interval [CI] = −0.039 to 0.011), even though the estimated effective population size (Ne) is modest (250–350, 95% CI = 142–955). Simulations suggest that the remnant smalltooth sawfish population will probably retain >90% of its current genetic diversity over the next century even at the lower estimate of Ne. There is no evidence of a genetic bottleneck accompanying last century’s demographic bottleneck, and we discuss hypotheses that could explain this. We also discuss features of elasmobranch life history and population biology that could make them less vulnerable than other large marine vertebrates to genetic change associated with reduced population size. [ABSTRACT FROM PUBLISHER]

The article presents a study on the abiotic affinities of juvenile sawfish (Pristis pectinata) in Charlotte Harbor estuarine system in Florida. The study used gill nets and seines to capture and release the 137 juvenile sawfish in the nursery. It mentions that habitat suitability curves, logistic regression, and electivity indices were applied in plotting the locations of the captured sawfish. Results show the affinities of sawfish including its avoidance to water less than one meter deep.

Small-scale and artisanal fisheries for sharks exist in most inshore, tropical regions of the world. Although often important in terms of food security, their low value and inherent complexity provides an imposing hurdle to sustainable management. An observer survey of a small-scale commercial gill-net fishery operating within the Great Barrier Reef World Heritage area revealed at least 38 species of elasmobranch were present in the catch. Of the total elasmobranch catch, 95% was 25 species of Carcharhiniformes from the families Carcharhinidae, Hemigaleidae and Sphyrnidae. Individual species were captured in a variety of ways by the fishery, often with strongly biased sex ratios and in a variety of life stages (e.g. neonates, juveniles, adult). Despite this, the main carcharhiniform taxa captured could be qualitatively categorised into four groups based on similar catch characteristics, body size and similarities in life history: small coastal (<1000mm); medium coastal (1000-2000mm); large coastal/semi-pelagic (>2000mm); and hammerheads. Such groupings can potentially be useful for simplifying management of complex multispecies fisheries. The idiosyncrasies of elasmobranch populations and how fisheries interact with them provide a challenge for management but, if properly understood, potentially offer underutilised options for designing management strategies. [ABSTRACT FROM AUTHOR]

Mangrove habitats can serve as nursery areas for sharks and rays. Such environments can be thermally dynamic and extreme; yet, the physiological and behavioural mechanisms sharks and rays use to exploit such habitats are understudied. This study aimed to define the thermal niche of juvenile mangrove whiprays, Urogymnus granulatus. First, temperature tolerance limits were determined via the critical thermal maximum (CT Max) and minimum (CT Min) of mangrove whiprays at summer acclimation temperatures (28 °C), which were 17.5 °C and 39.9 °C, respectively. Then, maximum and routine oxygen uptake rates (Ṁ O 2max and Ṁ O 2routine , respectively), post-exercise oxygen debt, and recovery were estimated at current (28 °C) and heatwave (32 °C) temperatures, revealing moderate temperature sensitivities (i.e., Q 10) of 2.4 (Ṁ O 2max) and 1.6 (Ṁ O 2routine), but opposing effects on post-exercise oxygen uptake. Finally, body temperatures (T b) of mangrove whiprays were recorded using external temperature loggers, and environmental temperatures (T e) were recorded using stationary temperature loggers moored in three habitat zones (mangrove, reef flat, and reef crest). As expected, environmental temperatures varied between sites depending on depth. Individual mangrove whiprays presented significantly lower T b relative to T e during the hottest times of the day. Electivity analysis showed tagged individuals selected temperatures from 24.0 to 37.0 °C in habitats that ranged from 21.1 to 43.5 °C. These data demonstrate that mangrove whiprays employ thermotaxic behaviours and a thermally insensitive aerobic metabolism to thrive in thermally dynamic and extreme habitats. Tropical nursery areas may, therefore, offer important thermal refugia for young rays. However, these tropical nursery areas could become threatened by mangrove and coral habitat loss, and climate change. • Mangrove whiprays have high heat tolerance but poor cold tolerance relative to rays. • Mangrove whiprays have low thermal sensitivity of oxygen uptake rates. • Mangrove whiprays showed signs of thermotaxic behaviour. • Mangrove whiprays showed positive electivity above and below body temperatures. • Mangrove habitats may act as thermal refugia for young sharks and rays. [ABSTRACT FROM AUTHOR]

Ciguatoxins (CTXs) produced by benthic Gambierdiscus dinoflagellates, readily biotransform and bioaccumulate in food chains ultimately bioconcentrating in high-order, carnivorous marine species. Certain shark species, often feeding at, or near the top of the food-chain have the ability to bioaccumulate a suite of toxins, from both anthropogenic and algal sources. As such, these apex predators are likely sinks for CTXs. This assumption, in conjunction with anecdotal knowledge of poisoning incidents, several non-specific feeding trials whereby various terrestrial animals were fed suspect fish flesh, and a single incident in Madagascar in 1994, have resulted in the widespread acceptance that sharks may accumulate CTXs. This prompted a study to investigate original claims within the literature, as well as investigate CTX bioaccumulation in the muscle and liver of 22 individual sharks from nine species, across four locations along the east coast of Australia. Utilizing an updated ciguatoxin extraction method with HPLC-MS/MS, we were unable to detect P-CTX-1, P-CTX-2 or P-CTX-3, the three primary CTX congeners, in muscle or liver samples. We propose four theories to address this finding: (1) to date, methods have been optimized for teleost species and may not be appropriate for elasmobranchs, or the CTXs may be below the limit of detection; (2) CTX may be biotransformed into elasmobranch-specific congeners as a result of unique metabolic properties; (3) 22 individuals may be an inadequate sample size given the rare occurrence of high-order ciguatoxic organisms and potential for CTX depuration; and (4) the ephemeral nature and inconsistent toxin profiles of Gambierdiscus blooms may have undermined our classifications of certain areas as CTX hotspots. These results, in combination with the lack of clarity within the literature, suggest that ciguatoxin bioaccumulation in sharks remains elusive, and warrants further investigation to determine the dynamics of toxin production, accumulation and transformation throughout the entire food-web. [ABSTRACT FROM AUTHOR]

Increased oceanic uptake of atmospheric carbon dioxide (CO2) is a threat to marine organisms and ecosystems. Among the most dramatic consequences predicted to date are behavioural impairments in marine fish which appear to be caused by the interference of elevated CO2 with a key neurotransmitter receptor in the brain. In this study, we tested the effects of elevated CO2 on the foraging and shelter-seeking behaviours of the reef-dwelling epaulette shark, Hemiscyllium ocellatum. Juvenile sharks were exposed for 30 d to control CO2 (400 µatm) and two elevated CO2 treatments (615 and 910 µatm), consistent with medium- and high-end projections for ocean pCO2 by 2100. Contrary to the effects observed in teleosts and in some other sharks, behaviour of the epaulette shark was unaffected by elevated CO2. A potential explanation is the remarkable adaptation of H. ocellatum to low environmental oxygen conditions (hypoxia) and diel fluctuations in CO2 encountered in their shallow reef habitat. This ability translates into behavioural tolerance of near-future ocean acidification, suggesting that behavioural tolerance and subsequent adaptation to projected future CO2 levels might be possible in some other fish, if adaptation can keep pace with the rate of rising CO2 levels. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]