Adelaide researchers believe that sex in the water in South Australia's upper Spencer Gulf could boost tourism. Sex among cuttlefish, that is.

And the South Australian public is being asked to spy on the cuttlefish – for the benefit of science.

“The breeding habits of the Giant Australian Cuttlefish are important to South Australia's ecotourism industry, which is why we're calling for the public's help in locating large numbers of cuttlefish (groups of more than 10) over the next few months,” says Dr Bronwyn Gillanders from the University of Adelaide's School of Earth & Environmental Sciences.

Dr Gillanders and Dr Steve Donnellan (Evolutionary Biology Unit, SA Museum) are leading a team of researchers that aims to learn more about the population structure and movements of cuttlefish. This is critical to the sustainable management of the species and the design of a marine protected area in the upper Spencer Gulf.

Cuttlefish are a significant part of ecotourism at Whyalla because of their “crazy” mating behaviour. They congregate in dense numbers and in shallow depths, providing a spectacle for divers and snorklers.

Among their range of unusual sexual antics is “sneaky sex”, where the physically smaller males, who can't compete with larger males, “cross-dress”. The smaller males change body colour and trick the stronger males into thinking they're females. When the strong males are not looking, the smaller males change colour again and quickly mate with the females.

This can be exciting viewing for tourists, but the cephalopod species (including cuttlefish, squid and octopus) are an important resource for fishing, and their reputation as a delicacy in restaurants has led to the demise of many species.

“Preventing long-term harm to the Giant Australian Cuttlefish population is a major concern,” Dr Gillanders says. “We aim to protect the marine ecology, while at the same time provide unique benefits to the fishing and ecotourism industries, and South Australia's economy.”

To better understand the Giant Australian Cuttlefish's breeding locations and population, South Australian divers and fishermen – especially those outside the upper Spencer Gulf – are urged to keep a look out for mating cuttlefish and areas where they are found in large numbers.

“The public's efforts will be vitally important in providing information about where cuttlefish are laying eggs, especially in areas outside the upper Spencer Gulf,” Dr Gillanders says.

“Although cuttlefish's sexual antics are a wonderful display to divers and snorklers, the fact is that the cuttlefish will die soon after they've laid their eggs.

“This gives us a window of only two or three months from now – following on from their mating season – to gather as much information as we can from willing members of the community.”