These rays have a body that looks like a shark’s body, but their head is flattened and their paired gills are located on the underside of the head, so their English common names – wedgefish, guitarfish or shovelnose ray, depending on which family they belong to – are apt. Local fishermen refer to these shark-like rays as ‘sharks’, and collectively call all shark-like rays yu kemejan (ikan yu or simply yu is Bahasa Malaysia for ‘shark’).
The rays have a worldwide distribution in tropical and subtropical seas, and a few species even inhabit intertidal and freshwater habitats. In Sabah’s inshore coastal waters the families Rhinidae, Rhinobatidae and Glaucostegidae have been recorded, but none has so far been reported in fresh water.
Most of the shark-like batoids or rays have a benthic or demersal habitat, spending their time feeding on invertebrates and small fishes close to the sea bottom. When not feeding, they rest on the sea floor rather than burrow into its mud or sand, which unfortunately makes them highly susceptible to being caught in demersal trawl nets, a common fishing gear used in the commercial fishing industry of this country.
Taking a yu kemejan as by-catch is a bonus for local fishers, as the large fins and snout (which is also traded as shark fin) can fetch a high price in the shark-fin trade, and the meat of this ray is considered to be of a high quality.
My preliminary analyses comparing Sabah’s shark and ray landings based on fish market surveys in 1996–1997 and 2016–2018 indicate a shift in the abundance of the shark-like batoids, which used to dominate the ray species being landed.
A simple key to the three shark-like ray families recorded from Sabah has been developed:
2a. Anterior cranium and base of rostral shaft dark and very sharply demarcated from rest of snout; nostrils long and narrow, with anterior nasal opening rectangular – family Glaucostegidae (Giant guitarfishes)
2b. Anterior cranium and base of rostral shaft much paler and diffuse, not sharply demarcated from rest of snout; nostrils not greatly elongated, anterior nasal opening circular to oval – family Rhinobatidae (Guitarfishes)
Read more on how sharks are still skinned for fins in Sabah in this news article.
Saving sharks in Sabah
In Sabah, Malaysia access to the ocean is easy for researchers – and fishers. The area is also home to at least 95 species of sharks and rays. Mabel will visit local fish markets to discover important information about these animals and how they are being exploited.