Peter M. Kyne

Extinction risk and conservation of the world’s sharks and rays

The rapid expansion of human activities threatens ocean-wide biodiversity. Numerous marine animal populations have declined, yet it remains unclear whether these trends are symptomatic of a chronic accumulation of global marine extinction risk. We present the first systematic analysis of threat for a globally distributed lineage of 1,041 chondrichthyan fishes—sharks, rays, and chimaeras. We estimate that one-quarter are threatened according to IUCN Red List criteria due to overfishing (targeted and incidental). Large-bodied, shallow-water species are at greatest risk and five out of the seven most threatened families are rays. Overall chondrichthyan extinction risk is substantially higher than for most other vertebrates, and only one-third of species are considered safe. Population depletion has occurred throughout the world’s ice-free waters, but is particularly prevalent in the Indo-Pacific Biodiversity Triangle and Mediterranean Sea. Improved management of fisheries and trade is urgently needed to avoid extinctions and promote population recovery. DOI: http://dx.doi.org/10.7554/eLife.00590.001

Limited potential to recover from overfishing raises concerns for deep-sea sharks, rays and chimaeras

As global fishing effort increasingly expands into deeper water, concerns exist over the ability of deep-sea fishes to sustain fisheries. There is however little quantitative evidence to support these concerns for the deep-sea cartilaginous fishes (Chondrichthyes: sharks, rays and chimaeras). This paper compiled available life history data for this group to analyse their ability to rebound from population declines relative to continental shelf and pelagic species. Deep-sea cartilaginous fishes have rates of population increase that are on average less than half those of shelf and pelagic species, and include the lowest levels observed to date. Population doubling times indicate that once a stock has been depleted, it will take decades, and potentially centuries, before it will recover. Furthermore, population recovery rates decrease with increasing depth, suggesting species that occur deepest are those most vulnerable to fishing. These results provide the first assessment of the productivity of deep-sea chondrichthyans, highlighting that precautionary management of developing deep-sea fisheries is essential if stocks and biodiversity are to be maintained.

The status of chondrichthyan conservation in the Indo-Australasian region

The status of chondrichthyan (sharks, batoids and chimaeras) conservation in the Indo-Australasian region is examined, and issues relevant to the conservation of this fauna at the subregional level [Australia, Indonesia (excluding West Papua), New Guinea (West Papua and Papua New Guinea), New Caledonia and New Zealand] are discussed. According to the 2009 IUCN Red List of Threatened Species, c. 21% of Indo-Australasian chondrichthyans are classified as threatened (critically endangered, endangered and vulnerable) and c. 40% are of conservation concern (threatened and near threatened). The proportion of threatened species is highest in New Guinea (c. 39%) and Indonesia (c. 35%) and least in New Zealand (c. 11%). In New Guinea, three quarters of the species are of conservation concern; in Indonesia, nearly two thirds are of conservation concern. Within the region, the proportion of threatened batoids (c. 29%) is higher than threatened sharks (c. 17%), while there are no threatened chimaeras. Conservation status is discussed at the order (for sharks), suborder (for batoids) and family level. Issues relating to the conservation status of chondrichthyans vary greatly between each subregion, but they mostly relate to targeted or incidental capture in fisheries. A handful of sharks and batoids are protected within Australian waters, while one species is protected in New Zealand. Both Australia and New Zealand have developed National Plans of Action for the Conservation and Management of Sharks (NPOA-Sharks), but these are lacking elsewhere. Development and implementation of NPOA-Sharks are a priority in order to drive the conservation of the regional fauna. Sustainable fisheries management (including by-catch), confronting the challenge of illegal, unreported and unregulated fishing, species protection where appropriate and marine protected areas (MPA) are all likely to prove vital in ensuring the long-term conservation of Indo-Australasian sharks, batoids and chimaeras.

Ecological risk assessment and its application to elasmobranch conservation and management.

Ecological risk assessments (ERAs) are employed to quantify and predict the vulnerability of a particular species, stock or population to a specific stressor, e.g. pollution, harvesting, climate change, by-catch. Data generated from ERAs are used to identify and prioritize species for implementation of effective conservation and management strategies. At this time, ERAs are of particular importance to elasmobranchs, given the ecological importance and documented global population declines of some elasmobranch species. Here, ERAs as a tool for elasmobranch conservation and management are reviewed and a theoretical roadmap provided for future studies. To achieve these goals, a brief history of ERAs and approaches used within them (in the context of elasmobranchs) are given, and a comprehensive review conducted of all ERA studies associated with elasmobranchs published between 1998 and 2011. The hazards assessed, species evaluated and methodological approaches taken are recorded. Chronological and geographical patterns suggest that this tool has grown in popularity as a commercial fishery management instrument, while also signalling a recent precautionary approach to elasmobranch management in commercial fisheries globally. The analysis demonstrates that the predominant parameters incorporated in previous ERAs are largely based on life-history characteristics, and sharks have received the majority of attention; batoids (including skates) have received less attention. Recreational fishing and habitat degradation are discussed as hazards which warrant future investigation through ERA. Lastly, suggestions are made for incorporating descriptive ecological data to aid in the continued development and evolution of this management tool as it applies to future elasmobranch conservation.

Diet of the eastern shovelnose ray, Aptychotrema rostrata (Shaw & Nodder, 1794), from Moreton Bay, Queensland, Australia

The diet of the eastern shovelnose ray, Aptychotrema rostrata, in Moreton Bay, south-eastern Queensland was investigated through stomach content analysis. Two major, two minor and four uncommon prey groups were identified. The diet of A. rostrata was dominated by decapod crustaceans. The Index of Relative Importance indicated that penaeid prawns and carid shrimps were the most important prey groups consumed, representing 51.84% and 26.32% of the diet respectively. Brachyuran crabs (12.84%) and teleost fishes (8.86%) were minor dietary components, while stomatopods, amphipods, isopods and squid constitute uncommon prey groups. Minor ontogenetic differences in diet were recognized, with carids significantly more important in juveniles than in adults, and penaeids, brachyurans and teleosts slightly more important in adults. The predatory activity of A. rostrata on the benthic fauna, together with its relative abundance, suggests it may have an important role in the trophic structure of Moreton Bay.

Reproductive biology of the eastern shovelnose ray, Aptychotrema rostrata (Shaw & Nodder, 1794), from Moreton Bay, Queensland, Australia

The eastern shovelnose ray, Aptychotrema rostrata (Rhinobatidae), is an endemic batoid common to the east coast of Australia. The reproductive cycle was studied in Moreton Bay, south-eastern Queensland, over a 14-month period. Aptychotrema rostrata is an aplacental yolksac viviparous species with an annual, seasonal reproductive cycle in Moreton Bay. Females mature at 54-66 cm total length, and males at 60-68 cm total length. Gravid females were observed during September-November and parturition occurred in November-December. Vitellogenesis does not proceed in parallel with gestation. Ovulation and copulation probably occur during July-September, resulting in a gestational period of 3-5 months. Uterine fecundity ranges from 4 to 18, with a significant positive relationship between uterine fecundity and maternal body length. In mature males, a peak in the proportion of mature spermatocysts in the testes was observed in July, whereas gonadosomatic index peaked in April.

Mitogenomics of the Speartooth Shark challenges ten years of control region sequencing

BackgroundMitochondrial DNA markers have long been used to identify population boundaries and are now a standard tool in conservation biology. In elasmobranchs, evolutionary rates of mitochondrial genes are low and variation between distinct populations can be hard to detect with commonly used control region sequencing or other single gene approaches. In this study we sequenced the whole mitogenome of 93 Critically Endangered Speartooth Shark Glyphis glyphis from the last three river drainages they inhabit in northern Australia.ResultsGenetic diversity was extremely low (π =0.00019) but sufficient to demonstrate the existence of barriers to gene flow among river drainages (AMOVA ΦST =0.28283, P <0.00001). Surprisingly, the comparison with single gene sub-datasets revealed that ND5 and 12S were the only ones carrying enough information to detect similar levels of genetic structure. The control region exhibited only one mutation, which was not sufficient to detect any structure among river drainages.ConclusionsThis study strongly supports the use of single river drainages as discrete management units for the conservation of G. glyphis. Furthermore when genetic diversity is low, as is often the case in elasmobranchs, our results demonstrate a clear advantage of using the whole mitogenome to inform population structure compared to single gene approaches. More specifically, this study questions the extensive use of the control region as the preferential marker for elasmobranch population genetic studies and whole mitogenome sequencing will probably uncover a large amount of cryptic population structure in future studies.

Freshwater sharks and rays.

Lucifora et all introduce the biology of elasmobranchs —sharks and rays — living in freshwater.

Round scallops and square meshes: a comparison of four codend types on the catch rates of target species and by-catch in the Queensland (Australia) saucer scallop (Amusium balloti) trawl fishery

Concern over the amount of by-catch from benthic trawl fisheries and research into the problem have increased in recent years. The present paper demonstrated that by-catch rates in the Queensland (Australia) saucer scallop (Amusium balloti) trawl fishery can be reduced by 77% (by weight) using nets fitted with a turtle excluder device (TED) and a square-mesh codend, compared with a standard diamond-mesh codend with no TED. This large reduction was achieved with no significant effect on the legal size scallop catch rate and 39% fewer undersize scallops were caught. In total, 382 taxa were recorded in the by-catch, which was dominated by sponges, portunid crabs, small demersal and benthic fish (e.g. leatherjackets, stingerfish, bearded ghouls, nemipterids, longspine emperors, lizard fish, triggerfish, flounders and rabbitfish), elasmobranchs (e.g. mainly rays) and invertebrates (e.g. sea stars, sea urchins, sea cucumbers and bivalve molluscs). Extremely high reductions in catch rate (i.e. ≥85%) were demonstrated for several by-catch species owing to the square-mesh codend. Square-mesh codends show potential as a means of greatly reducing by-catch and lowering the incidental capture and mortality of undersize scallops and Moreton Bay bugs (Thenus australiensis) in this fishery.

Rediscovery of the Threatened River Sharks, Glyphis garricki and G. glyphis, in Papua New Guinea

Recent surveys of the shark and ray catches of artisanal fishers in the Western Province of Papua New Guinea (PNG) resulted in the rediscovery of the threatened river sharks, Glyphis garricki and Glyphis glyphis. These represent the first records of both species in PNG since the 1960s and 1970s and highlight the lack of studies of shark biodiversity in PNG. Two individuals of G. garricki and three individuals of G. glyphis were recorded from coastal marine waters of the Daru region of PNG in October and November 2014. The two G. garricki specimens were small individuals estimated to be 100–105 cm and ~113 cm total length (TL). The three G. glyphis specimens were all mature, one a pregnant female and two adult males. These are the first adults of G. glyphis recorded to date providing a more accurate maximum size for this species, i.e. ~260 cm TL. A single pup which was released from the pregnant female G. glyphis, was estimated to be ~65 cm TL. Anecdotal information from the fishers of pregnant females of G. glyphis containing 6 or 7 pups provides the first estimate of litter size for this species. The jaws of the pregnant female G. glyphis were retained and a detailed description of the dentition is provided, since adult dentition has not been previously documented for this species. Genetic analyses confirmed the two species cluster well within samples from these species collected in northern Australia.