Vulnerability assessment of elasmobranch species to fisheries in coastal Kenya: implications for conservation and management policies

Ecological risk assessment (ERA) of species to fisheries is useful for making informed management decisions especially in data-scarce situations based on species relative vulnerabilities to fisheries. Understanding the vulnerability of species to fishing gears is important for targeted management measures especially for species known to have delicate life-history strategies such as the elasmobranchs. As part of a National Plan of Action for Sharks (NPOA-sharks) initiative, a three-day workshop was organized (in April 2022) involving various experts and stakeholders to analyze relative vulnerability risks of shark and ray species to fishing gears in Kenya’s Exclusive Economic Zone (EEZ). The workshop applied a Productivity and Susceptibility Analysis (PSA) approach to estimate relative vulnerability of species to the fishing gears. A total of 30-shark and 29-ray species were used for analysis of relative vulnerability to artisanal fishing gears, prawn trawlers, and industrial pelagic longline fishery within Kenya’s EEZ. Overall, results showed high species vulnerability to the prawn trawl fishery (35% for rays and, 65% for sharks and shark-like rays) and to the industrial longlines (100% for rays and, 46% for sharks and shark-like rays). There were variable but lower vulnerability ranges for species in the artisanal fishery gears. Thirty species, grouped as a High Vulnerability Species Assemblage (HVSA), were assessed to have High Relative Vulnerabilities to the gears calling for their targeted management strategies. Of the HVSA group, five species; Sphryna lewini, Pseudoginglymostoma brevicaudatum, Rhina ancyclostoma, Rhynchobatus djiddensis, Rhynchobatus laevi are classified as Critically Endangered (CR), while another five; Carcharhinus plumbeus, Mobula birostris, Mobula eregoodoo, Stegostoma tigrinum, Rhinoptera jayakari are Endangered (EN) according to the IUCN Red List assessment (www.iucnredlist.org, release 2022-1). The results suggest that a lower fishing-pressure threshold is required to predispose the prawn trawl bycatch species to High Vulnerabilities. Lastly, over 50% of the species evaluated as being of High Vulnerability also fell under the IUCN Threatened Category. A validation approach has been used to reduce uncertainty around PSA, however, the tool will require continuous updating to include more species and improve on its sensitivity. A precautionary Shark and Ray Management Plan (SRMP) that takes into account the outputs of the PSA is recommended for the management and conservation of the elasmobranch stocks within the framework of a NPOA-Sharks for Kenya.