Whitespotted wedgefish

1/3/2018

The first wedgefish for #WedgefishWednesday on The Fins United Initiative is Rhynchobatus australiae. You may know it by a variety of common names, such as the whitespotted wedgefish, the bottlenose wedgefish, the white-spotted guitarfish, fiddler, giant guitarfish, sand shark, shovelnose shark, white-spotted shovelnose ray, whitespot ray, and the list goes on. For our sake, we’ll refer to Rhynchobatus australiae as the whitespotted wedgefish.

This may be because their distribution is quite large. Found in the Western Pacific Ocean, they can be observed in the Gulf of Thailand all the way to the Philippines and down to Queensland, Australia. In the past, the whitespotted wedgefish has been referred to as Rhynchobatus djiddensis, which is in the Western Indian Ocean (their range is debated due to species confusion). The Whitespotted Guitarfish is also confused with the Smoothnose Wedgefish, Rhynchobatus laevis, which also calls Australian waters home and has recently been described. More research needs to be done since there are substantial similarities and variations among individuals.

If a shark and a ray were to end up smashed together in a freak genetic accident, the end result would probably be what a wedgefish looks like. This animal is like a really flat shark. The whitespotted wedgefish is a grey-brown colour with a creamy underbelly, and its dorsal side is covered in white spots (hence the common name). Like sharks, they have two dorsal fins (which are impressive in size on the whitespotted wedgefish).

In the respective range, the whitespotted wedgefish is observed in shallow waters, occurring on soft, sandy (or muddy) bottoms near reefs. Here, they feed on a plethora of invertebrates, shellfish, and crustaceans (like crabs). Little is known about the biology of this wedgefish, but scientists do know it is viparous with yolk-sac (also known as aplacental viviparous) thanks to research done by Dulvy and Reynolds in 1997.

The IUCN has assessed these animals as Vulnerable (VU) due to Rhynchobatus australiae being caught by artisanal and commercial fisheries as a target species and as bycatch. The flesh of the whitespotted wedgefish is sold in Asia for human consumption and their fins can fetch a pretty big sum, too. While they can be caught as bycatch, the introduction of turtle exclusion devices (TEDS) in fishing nets may help these animals escape.

what new #finfact did you learn about this animal?

glossary

Artisanal fishery: There is, as yet, no universally-accepted definition; the term is used interchangeably with ‘small scale fishery.’ In general, artisanal fishing will be family-based, employing small or no boats and simple and/or traditional methods.
Bycatch: The part of a fishery’s catch that is made up of non-target species.
Commercial fishery: The activity of catching fish and other seafood for profit.
Crustaceans: Group of animals with a hard exoskeleton, jointed legs and segmented body.
Invertebrates: Animals with no backbone (i.e. crustaceans, jellyfish, corals, sea anemones).
IUCN: International Union for Conservation of Nature.
Shellfish: The term for invertebrate animals with an exoskeleton such as molluscs, crustaceans, and echinoderms.
TEDs: A turtle excluder device (TED) is a specialized device that allows a captured sea turtle to escape when caught in a fisherman's net.
Viviparous with yolk-sac: Also known as aplacental viviparous and previously known as ovoviviparous/ovoviviparity; it is the production of eggs that are fertilised and hatch inside the female shark but the embryos lack a placental connection to the oviduct or uterus and so do not feed off the mother.