Ecological risks of demersal fishing on deepwater chondrichthyan populations in the Southern Indian and South Pacific Oceans

Abstract

Risks to deepwater chondrichthyans (sharks, rays, and chimaeras) from fishing are poorly understood, particularly in areas beyond national jurisdiction. We adapted productivity–susceptibility analysis (PSA) and sustainability assessment for fishing effects (SAFE) to assess the vulnerability of 173 deepwater chondrichthyans to various demersal fishing gears in the Southern Indian and South Pacific Oceans. Several species were categorized as being at high or extreme vulnerability, including some deepwater shark species in the Southern Indian Ocean that are reported to be commercially targeted. There was good concurrence between PSA and SAFE results for species categorized as being at high or extreme vulnerability by the SAFE, but as expected there was an overall greater number assessed to be as higher vulnerability using PSA due to its precautionary nature. Our results indicate probable misclassifications in the PSA relative vulnerability rankings, highlighting the value of applying more quantitative tools, such as SAFE, when adequate data are available. Our findings indicate that better catch, effort, and biological information are needed to inform the assessment and management of deepwater chondrichthyans. If targeted fishing of deepwater shark species continues in the Southern Indian Ocean, improved assessments and estimates of sustainable yields are urgently required to mitigate the risk of overexploitation.

Seamounts, plateaus and governance issues in the southwestern Indian Ocean, with emphasis on fisheries management and marine conservation, using the Walters Shoal as a case study for implementing a protection framework

“…Deep-water demersal sharks (living below 200 m depth) are another matter of concern, as a by-catch of demersal trawl, mid-water trawl, demersal longline and demersal gillnet gears. These sharks have a very low fecundity and have been rated as extremely vulnerable by ecological risk assessment analyses (Lucena-Frédou et al, 2017;Georgeson et al, 2019). In the SWIO, 112 species of such chondrichthyan species have been reported to interact with the deep-sea gears (Ebert 2013(Ebert , 2014.…”

Novel use of pop-up satellite archival telemetry in sawsharks: insights into the movement of the common sawshark Pristiophorus cirratus (Pristiophoridae)

“…Montpellier, CNRS, IFREMER, IRD, Sète, France. 3 School of Environmental and Life Sciences, University of Newcastle, Ourimbah, NSW, 2258 Australia. 4 Sydney Institute of Marine Science, Mosman, NSW, 2088 Australia * Author for correspondence, Email: Patrick-john.burke@hdr.mq.edu.au…”

“…Organisms in the deep-sea biome present various environmental challenges for study even with the most technologically advanced equipment (1). Despite a lack of biological information for many deep-sea inhabitants, habitat within the deep-sea biome are increasingly targeted for harvest by expanding sheries (2,3). Deep-sea sharks (species that predominantly occur below 200 meters) remain one of the more poorly understood group of elasmobranchs but continue to be regularly caught in sheries (4,5).…”

Novel use of pop-up satellite archival telemetry in sawsharks: insights into the movement of the common sawshark Pristiophorus cirratus (Pristiophoridae)

“…Organisms in the deep-sea biome present various environmental challenges for study even with the most technologically advanced equipment (1). Despite a lack of biological information for many deep-sea inhabitants, habitat within the deep-sea biome are increasingly targeted for harvest by expanding sheries (2,3). Deep-sea sharks (species that predominantly occur below 200 meters) remain one of the more poorly understood group of elasmobranchs but are regularly caught in sheries (4,5).…”