Australasian Science: Australia's authority on science since 1938

Shark Declines Can Lead to Fish with Smaller Eyes and Tails

The full text of this article can be purchased from Informit.

An analysis of two neighbouring coral reef systems off the coast of north-west Australia have linked body shape changes in fish with declining shark numbers due to overfishing.

The Rowley Shoals and the Scott Reefs are each comprised of multiple ring-shaped reefs and are identical biologically and physically in all but one way: the coral reefs in Rowley Shoals are protected from fishing, while the coral reefs in the Scott Reefs have been subjected to commercial shark fishing for more than a century.

Targeted shark fishing has intensified in the region in recent decades to fuel the demand of shark fin soup. As a result, shark populations have been decimated at the Scott Reefs but remain healthy at the Rowley Shoals.

The research team collected 611 fish from seven species across multiple sites within the Rowley Shoals and the Scott Reefs. They then took photographs of each fish and digitally analysed photographs, measuring body length, body width, eye area and tail area of each fish.

At Scott Reefs the researchers found the eyes of fishes that are normally prey for sharks were on average up to 46% smaller compared with the same-sized fish of the same species on reefs at the Rowley Shoals. The same pattern was seen for fish tail sizes, with tails being up to 40% smaller at the Scott Reefs compared with the Rowley Shoals.

Dr Shanta Barley...

The full text of this article can be purchased from Informit.