Shark-like batoids in Pacific fisheries: prevalence and conservation concerns

Shark-like batoids are a group of elasmobranchs with a body form similar to that of sharks (i.e. elongate body, well developed caudal and dorsal fins, and head, gill and mouth morphology similar to that of skates and sting rays). Despite a poor understanding of their biology, ecology and resilience to fishing, shark-like batoids are known to have been heavily exploited throughout the Indo-Pacific. Between 2007 and 2009, we recorded the occurrence of shark-like batoid species in the inshore gillnet fishery of Queensland (Australia) across 2 habitat types. Glaucostegus typus and Anoxypristis cuspidata were most frequently caught in intertidal habitats, whereas Rhynchobatus spp. dominated the catch in inshore coastal habitats. Comparison of gillnet catches to research longline sampling showed that not all size classes of shark-like batoids are captured by the gillnet fishery. Given that home-range size and habitat use by elasmobanchs can change between ontogenetic stages and species, vulnerability to fisheries may vary depending on overlap of preferred habitats and fishing activity and whether each size class is susceptible to the gear. Gillnets are highly selective for certain sizes classes; therefore, knowledge of which sizes and thus which life-history stages are susceptible is necessary to effectively regulate the use of this type of fishing gear. Understanding the occurrence and availability of shark-like batoid species to fishing activities and their contribution as bycatch/by-products in fisheries is critical to management and conservation of these species