pelagic thresher

8/24/2018

We've mentioned before on The Fins United Initiative that there are three thresher sharks. A fourth species (currently unrecognized) may exist, currently known from one specimen’s muscle samples. We're excited to introduce you to one of these zorro-like marine animals today! It goes by a number of common names such as Fox Shark, Smalltooth Thresher Shark, Whiptail Shark or just plain Thresher Shark... but we will refer to it as the Pelagic Thresher Shark.

From our General: Thresher Sharks blog post:
One of the more recognised sharks thanks to their whip-like tail. Just as deadly as Zorro’s sword, they instead use the elongated upper lobe of their caudal (tail) fin to herd, stun, and ultimately kill their prey (which includes small fish, squids, octopi and sometimes seabirds).

Now in this general blog post, we mentioned that thresher sharks have the super power of endothermic capabilities. HOWEVER, the pelagic thresher shark (Alopias pelagicus) is unable to control its body temperature and is a true cold-blooded fish. They are slow to grow and reproduce, giving live birth to a pair of large pups. This is problematic as they are caught by commercial shark fisheries and as bycatch by other fisheries.

Populations worldwide are declining, and little protection exists. This pale grey/blue shark has a white underbelly, big eyes, and that signature long, scythe-like tail. They can whip that tail and stun a number of fish, allowing this shark to quickly gobble them up with little effort. It is the smallest of the three recognised species of thresher shark, reaching a total of 3.65 m total (TL). The IUCN has assessed them as Vulnerable (VU).

WHAT DID YOU LEARN ABOUT THIS ANIMAL?

GLOSSARY

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.
Endemic: Native to a specific region or environment and not occurring naturally anywhere else.
Gestation: The period in which a fetus develops, beginning with fertilization and ends at birth.
IUCN: International Union for Conservation of Nature.
Pup: Give birth to baby sharks, skates, rays or chimaeras (pups).
Pups: Baby sharks, skates, rays, or chimaeras.
Trawl fisheries: Fisheries that pull a fishing net through the water behind one or more boats.
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.