Over-hunting sharks is detrimental for fish at every level of the food chain, West Australian scientists have found.
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The study by marine biologists from The University of Western Australia and the Australian Institute of Marine Science concluded sharks influence the number, kind and size of fish on coral reefs and should be protected from overfishing.
Fish schools at the protected Rowley Shoals on WA's northwest coast were compared to fish at nearby Scott Reef, where Indonesian shark hunters have legally reduced the animals' population.
Shanta Barley from UWA said the results suggested having fewer sharks in coral reefs changed fish communities at every level, rather than a series of knock- down effects from the top of the food web.
"This is worrying because fish at the bottom of the food web may maintain reef health by eating algae," Dr Barley said.
The research team found fewer large shark species may lead to greater numbers of smaller shark species, such as the white tip reef shark, which was 570 per cent more abundant and had 190 per cent more biomass at Scott Reef relative to Rowley Shoals.
On the reefs where sharks were fished, their small to medium sized prey were 200 per cent more common compared to the marine reserve, as were a range of plant- eating fish that sit at the bottom of the food web.
"There is debate around whether predators are the 'guardians' of biodiversity or whether they actually reduce diversity by 'eating' species to local extinction but our research suggests the former," Dr Barley said.
- AAP
