WA SHARKS, SHARK FISHERIES AND SAFETY TIPS
Sharks are a highly diverse group of fishes which have evolved to inhabit all marine habitats, from the surfline to the depths of oceanic trenches. More than 160 species of sharks are found in Australia and new species are still being discovered. The largest fish on earth is the whale shark, Rhincodon typus, which grows to over 12 metres in length and feeds exclusively by sieving plankton from the water as it swims. The smallest species of shark is the pygmy shark, Euprotomicrus bispinatus, a tiny dogfish, which only grows to about 25 centimetres. One of the most common species of sharks in metropolitan Metres waters is the Port Jackson shark, Heterodontus portusjacksoni, which is a small shark that feeds mainly on shellfish. Other common species include wobbegongs (family Orectolobidae), which lie motionless on the seabed waiting for their fish prey to swim past; small whaler sharks (family Carcharhinidae), gummy and whiskery sharks, which eat small fish, squid and octopus. Several species of shark are caught commercially in Western Australia, including the gummy shark, whiskery shark, dusky shark (bronzie) and sandbar shark (thickskin). Commercial shark fishing targets the smaller species and juvenile whaler sharks. Shark is mainly sold through fish and chip shops although is becoming increasingly popular as a table fish. In recent years, the value of shark fins, a delicacy in Asia, has increased dramatically. This has led to increased targeting of sharks purely for the value of their fins, but legislation passed in October 2000 now prevents fishers from catching sharks only for their fins in Western Australian waters.
1
Shark catches in these fisheries for the 2001/2002 season were as follows: JASDGDLF: 842 tonnes WCDGDLF: 310 tonnes
Great White Shark
WANCSF + JANSF: 456 tonnes Despite their ‘man-eating’ reputation, most sharks are entirely harmless to humans, preferring a diet of fish and invertebrates. As ‘apex predators’, which occupy the very top level of the food chain, sharks play an essential role in maintaining the health of the marine environment and are deserving of our respect. As well as their environmental importance, sharks are a valuable resource for both the fishing and tourism industries. Of more than 160 known species of Australian sharks, only three are accepted as posing a significant risk to human safety. Most wild animals will bite when they feel threatened; sharks are no exception. No matter how big or small, all sharks are capable of biting and should be left alone. The three most dangerous species are the great white shark (also known as the white pointer or white shark), Carcharodon carcharias; the tiger shark, Galeocerdo cuvier; and the bull shark (also known locally as the Swan River whaler), Carcharhinus leucas. Whaler sharks, wobbegongs and hammerheads, while usually timid, have also bitten humans (although rarely fatally), and should be avoided. The great white is the largest predatory shark in the world, reaching about 6 metres in length when fully grown.
Whaler Shark Wobbegong
Port Jackson
2 3 4 5
Figure 1 Shark Sizes
Owing to their relatively low reproductive rates (the number of pups produced per year), and the length of time taken to reach sexual maturity, fished shark stocks require careful management if they are to be sustained. The shark fishery in Western Australia is managed as four separate zones, as shown in figure 2.
123˚45'E JANSF
WANCSF 114˚12'E
Closed to Shark Fishing 26˚9'S
JANSF
Joint Authority Northern Shark Fishery
JASDGDLF Joint Authority Southern
Demersal Gillnet & Demersal Longline Fishery
WANCSF WCDGDLF
WA North Coast Shark Fishery Gillnet & Demersal Longline Fishery
WCDGDLF West Coast Demersal
33˚S
JASDGDLF Zone 1
JASDGDLF Zone 2
128˚E
116˚30'E
Figure 2 Shark Fishery map
WA SHARKS, SHARK FISHERIES AND SAFETY TIPS
The diet of young great whites consists almost entirely of fish. Bigger white sharks have a generally broader diet, comprising of large fish, other sharks and rays, seals, dolphins and occasionally whales. Great white sharks may occasionally scavenge sick and dead whales as they pass on their annual migration. The great white is a widespread but scarce species, which occurs in most temperate waters of the world. The southern coast of Australia is recognised as being one of the last areas of relatively high white shark abundance, although numbers have been reduced through game fishing and accidental commercial catches. The lower west, and particularly the south coast of Western Australia, are considered part of the species’ normal range. Little is known about the biology of this species, largely because it is scarce and the cost of research is extremely high. Scientists do know that great white sharks take a long time to reach sexual maturity and give birth to very few offspring when they do reproduce. This biology makes the species highly susceptible to over-exploitation, and due to anecdotal evidence indicating a decline in their numbers, the Commonwealth and State Governments have protected white sharks in almost all Australian waters. The grey nurse shark, a relatively harmless but easily overfished coastal species, and the whale shark are also protected throughout Australian waters. stings and lightning strikes that are killed by sharks. People can reduce the risk of encountering sharks while in the water by following a few simple tips. • Swim between the flags at patrolled beaches. • Avoid time in/on the water around dusk and dawn – when most fish are feeding and sharks are likely to be active. • Avoid areas where there are large schools of fish, or among seals or sea lions close to rookeries. • Avoid areas where animal, human or fish waste enter the water. • Avoid deep-water channels or drop-offs nearby. • Do not remain in the water with bleeding wounds. • If spearing fish, don’t carry dead or bleeding fish attached to you, and remove all speared fish from the water as quickly as possible. • If you see a shark, leave the water as quickly and calmly as possible. Avoid excessive splashing or noise. These measures are not a guarantee that you will never encounter a shark, but they will help reduce the risk. The only way to avoid all risk is to stay out of the water.
Gummy Shark Wobbegong
• Never handle a shark’s head or mouth even after it has been landed, as involuntary muscle spasms often result in biting actions and injuries to fishers. • Never feed or berley large sharks while boat fishing, as this may train them to nudge other boats looking for a free feed. Further Reading Edmonds, C. (1989). Dangerous Marine Creatures. Reed Books, Sydney. State of the Fisheries Report 1998/1999. Fisheries Western Australia (annual publication).
Whiskery Shark
SAFETY TIPS – FISHING AND HANDLING
• If you hook a large shark or one you don’t want to keep, it is better to cut the line, as close as possible to the hook, after you have brought it close to the boat. • Be extremely careful when dealing with wobbegongs, as they can turn full circle and bite if you are holding them by the tail.
3rd floor The Atrium 168 St George’s Tce, Perth WA 6000 Ph (08) 9482 7333 Fax (08) 9482 7389 Website: www.fish.wa.gov.au Email: headoffice@fish.wa.gov.au
SAFETY TIPS – WATER ACTIVITIES
The risk of shark attack is extremely low. On average, there is less than one fatal shark attack at Australian beaches per year. Worldwide, more people die each year from bee
NOV 2003
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