A tangled web: global review of fishing interactions with rhino rays

Abstract

Rhino rays (Order Rhinopristiformes) are one of the most threatened vertebrate groups. Despite overfishing being recognised as the greatest threat to this group, a comprehensive assessment of the fisheries and types of fishing gear that rhino rays interact with is lacking. We reviewed published and grey literature (n = 116 references) to evaluate interactions between rhino rays and fisheries, determine gear types most responsible for their capture, and species for which most interactions occur by region. Interactions (n = 420) were reported from 37 of 88 range states, for 52 of 68 known species. Combined, 59% of the literature reported interactions from trawlers and gillnets. Wedgefishes (Rhinidae) were the most reported family (29%) and bowmouth guitarfish (Rhina ancylostomus) the most reported species (9.5%). Asia accounted for half of interactions (n = 211), with 67% of the literature from unspecified gear (e.g., mixed landings), masking gear-specific interactions. Data quality was variable, with the highest resolution in countries with lower species diversity and where species are least imperiled (e.g., Australia). Discard mortality and physiological effects of capture are poorly known with data available for 25% of species (almost exclusively from Australia and the Americas). While additional data are urgently required to quantify the true extent of rhino ray catch globally, reducing fisheries mortality is a priority and key to address declining populations. Recommendations include prioritizing spatial management in critical habitats (e.g., nursery areas), expansion in the use of proven bycatch reduction devices, encouraging safe release and handling, and addressing drivers of retention and trade.