Biology subjects

Kyne, P. M.

Publications and source records attributed to Kyne, P. M..

3 recordsLinked to original sources

bioRxiv2022

Extremely low sample size allows age and growth estimation in a rare and threatened shark

Understanding life history parameters is key to assessing biological productivity, extinction risk, and informing the management of exploited fish populations. Age-and-growth analyses in chondrichthyan fishes (sharks, rays, and ghost sharks) is primarily undertaken through counting band pairs laid down in vertebrae. For rare, threatened, and protected species such as river sharks (family Carcharhinidae; genus Glyphis) of northern Australia, obtaining sufficient samples of vertebrae may not be possible. Here we use a very sample size, selective size-class sampling, and back-calculation techniques to provide age and growth data on the Speartooth Shark Glyphis glyphis from which comprehensive sampling is not possible. Ten individuals were sampled from the Adelaide River, Northern Territory, Australia. Length-at-age models were applied to the observed and back-calculated data with the sexes combined due to the small sample size and growth estimated using a multi-model framework. Band pair counts produced age estimates of 0-11 years. Most model parameter estimates for length-at-birth (L0) and asymptotic length (L{infty}) were biologically plausible. The model averaged parameters for the observed data were [Formula] total length (TL) and [Formula] TL, and for back-calculated data were [Formula] TL and [Formula] TL. Overall, the parameter standard errors and model residual standard errors were lower for the back-calculated data due to the addition of interpolated data. Analysed samples were restricted to juveniles and sub-adults as adult G. glyphis have not been encountered in the Northern Territory. The ageing results suggest an age-at-maturity of >12 years for this species. The lack of mature individuals in the sample means that this analysis should be considered as a partial growth curve with length-at-age estimates that are valid over the available age range. The results presented here provide the first age and growth estimation for river sharks.

zoology↗

bioRxiv2022

Extinction risk, reconstructed catches, and management of chondrichthyan fishes in the Western Central Atlantic Ocean

Chondrichthyan fishes are among the most threatened vertebrates on the planet because many species have slow life histories that are outpaced by intense fishing. The Western Central Atlantic Ocean, which includes the greater Caribbean, is a hotspot of chondrichthyan biodiversity and abundance, but is historically characterized by extensive shark and ray fisheries and a lack of sufficient data for effective management and conservation. To inform future research and management decisions, we analyzed patterns in chondrichthyan extinction risk, reconstructed catches, and regulations in this region. We summarized the extinction risk of 180 sharks, rays, and chimaeras using contemporary IUCN Red List assessments and found that over one-third (35.6%) were assessed as Vulnerable, Endangered, or Critically Endangered largely due to fishing. Reconstructed catches from 1950 to 2016 reached their peak in 1992, then declined by 40.2% through the end of the series. The United States, Venezuela, and Mexico were responsible for most catches and hosted large proportions of the regional distributions of threatened species; these countries therefore held the greatest responsibility for chondrichthyan management. The abundance and resolution of fisheries landings data were poor in much of the region, and national-level regulations varied widely across jurisdictions. Deepwater fisheries represent an emerging threat, although many deepwater chondrichthyans currently find refuge beyond the depths of most fisheries. Regional collaboration as well as effective and enforceable management informed by more complete fisheries data, particularly from small-scale fisheries, are required to protect and recover threatened species and ensure sustainable fisheries.

ecology↗

bioRxiv2019

The thin edge of the wedge: extremely high extinction risk in wedgefishes and giant guitarfishes

O_LIThe process of understanding the rapid global decline of sawfishes (Pristidae) has revealed great concern for their relatives, the wedgefishes (Rhinidae) and giant guitarfishes (Glaucostegidae), not least because all three families are targeted for their high-value and internationally-traded white fins.\nC_LIO_LIThe objective of this study was to assess the extinction risk of all 10 wedgefishes and 6 giant guitarfishes by applying the International Union for Conservation of Nature (IUCN) Red List Categories and Criteria, and to summarise their biogeography and habitat, life history, exploitation, use and trade, and population status.\nC_LIO_LIWedgefishes and giant guitarfishes have overtaken sawfishes as the most imperilled marine fish families globally, with all but one of the 16 species facing an extremely high risk of extinction due to a combination of traits - limited biological productivity, presence in shallow waters overlapping with some of the most intense and increasing coastal fisheries in the world, and over-exploitation in target and bycatch fisheries driven by the need for animal protein and food security in coastal communities and trade in meat and high-value fins.\nC_LIO_LITwo species with very restricted ranges, the Clown Wedgefish (Rhynchobatus cooki) of the Indo-Malay Archipelago and the False Shark Ray (Rhynchorhina mauritaniensis) of Mauritania may be very close to extinction.\nC_LIO_LIOnly the Eyebrow Wedgefish (Rhynchobatus palpebratus) is not assessed as Critically Endangered, due to it occurring primarily in Australia where fishing pressure is low, and some management measures are in place. Australia represents a lifeboat for the three wedgefish and one giant guitarfish species occurring there.\nC_LIO_LITo conserve populations and permit recovery, a suite of measures will be required which will need to include species protection, spatial management, bycatch mitigation, and harvest and international trade management, all of which will be dependent on effective enforcement.\nC_LI

ecology↗