Field identification guide to Western Australian Sharks and Shark-like Rays
Sharks and their relatives (the skates, rays and chimeras) are a highly diverse group of fish that evolved over 400 million years ago. These fish (collectively called Chondrichthyes) are characterised by a cartilaginous skeleton; multiple gill openings; skin covered with modified teeth instead of scales and external male reproductive organs. Over 160 species of sharks are known to inhabit Australian seas, although new species continue to be discovered. Sharks have been so evolutionarily successful that they inhabit all aquatic habitats: from freshwater rivers and lakes to ocean depths of thousands of metres.
As ‘apex predators’, many shark species occupy the very top level of the food chain and thereby play an essential role in maintaining the health of the marine environment. As well as their environmental importance, sharks provide a valuable resource for both the fishing and tourism industries, and chemical compounds derived from shark products are being examined for their potential pharmaceutical uses, particularly for cancer and arthritis treatments.
Despite their significance, sharks are a poorly understood group which urgently require further scientific study. As a first step, this guide is intended to improve the standard of identification and shark-catch reporting in Western Australia’s widespread and varied fisheries. The information that we hope you will be able to provide is crucial in ensuring that these species survive into the future.
Section 1 provides a guide to each family of sharks and 3 families of shark-like rays. These have been included because of their biological and ecological similarity to sharks. This section is ordered according to each family’s usual habitat: deep water, open-ocean, coastal waters near the seafloor and coastal waters on the seafloor.
However, because most sharks are highly mobile, members of each family may in fact occur in any of these habitats. Each family description also provides a colour-coded list of the most common or otherwise significant species within that family. The colour-coding corresponds to the coloured ranges in the map. (e.g. the green range on the map refers to the green species in the list). Species lists are not provided for families which contain numerous species or where species are too similar to distinguish easily.
Section 2 provides a more detailed species-level guide to the whaler sharks (family Carcharhinidae), which are of particular interest because they are commonly caught by a wide variety of Western Australian fisheries. Features which are highlighted in red are key identifying features that can be used quickly and reliably to distinguish a particular species or family. A diagram and glossary of technical terms are provided on pages v and vi. All lengths referred to in this guide are approximate total lengths.