Growth, size structure and spawning potential of sharks and rays in Kenyan inshore and industrial longline fisheries

Effective management of elasmobranch populations requires robust estimates of growth, mortality, and reproductive potential, particularly in data-poor artisanal and industrial fisheries.

We analysed growth, size structure and spawning potential of dominant shark and ray species exploited by Kenya’s inshore (artisanal and prawn trawl) and industrial longline fisheries using Von Bertalanffy Growth Function (VBGF), ELEFAN and Length-Based Spawning Potential Ratio (LBSPR) approaches on data collected between 2016–2025, including combined 2018–2021 series, to assess life-history parameters and current exploitation levels.

Our results reveal a concerning trend of severe overexploitation across multiple species. Inshore and coastal stocks, including Holohalaelurus lineatus, Sphyrna lewini, Pliotrema warreni, and Raja clavata, are at critical risk of collapse, with SPR values approaching 0% and dominant juvenile cohorts exceeding 90% of the sample. In contrast, large-pelagic species targeted by industrial longline fisheries showed varied statuses; while the Blue shark (Prionace glauca) appears to maintain a sustainable status (SPR = 41%), the Silky shark (Carcharhinus falciformis) and Oceanic whitetip (Carcharhinus longimanus) are severely overfished (SPR = 9% and 7%, respectively).

These findings emphasize the urgent need for species-specific management interventions, increased protection for juvenile habitats, and stricter catch regulations to mitigate the risk of local extinction for highly vulnerable species.