For the first time in 15 years, the acoustic alarms attached to shark nets off Queensland's coastline are changing pitch. A five-week trial has begun in waters off Noosa Heads, where authorities hope new, higher-frequency "pingers" will do a better job of warning whales away from the nets — right as the southern migration hits full swing, with about 50,000 humpbacks passing along Australia's east coast each year.

The trial is a collaboration between the University of Queensland, the state government and alarm supplier Future Oceans. Shark control program operations coordinator Sam Fary said only about "0.02 per cent" of the whales would interact with the nets — but there was always room for improvement. "This is a higher frequency, something that we haven't used before … this is world-leading research in this space," he said.

James Turner from Future Oceans, whose devices already hang on nets and drum lines, said the pingers send a sound into the water that whales and dolphins are understood to hear. "They acoustically illuminate things like fishing nets and drum lines … whales are actually moving away from whatever the gear the pingers are attached to," he said. The new pitch came out of University of Queensland testing: "The University of Queensland did some trials and decided that one of the frequencies was going to be even better than the frequency that the government's been using for the past 15 years in the pingers." Separate alarms on the same nets are tuned to deter dolphins.

For the length of the trial, UQ researchers will be stationed at Noosa Heads for 10 hours a day, putting the alarms to the test with binoculars rather than microphones. "We're watching the shark nets and observing any whales that track close to them," researcher Riona McNamara said. "People are really inquisitive about what we're doing and yeah, perfect position to watch the nets and the whales migrating through."

Not everyone is convinced the answer is a better ping. Olaf Meynecke, chief executive of conservation organisation Humpbacks and High-rises, which monitors whale movements, said previous studies had not shown similar pingers to be a sufficient deterrent — and pointed to roughly 60 entanglements along the east coast each year, a number he said could be higher due to inaccurate reporting. "These shark nets have clearly proven to be lethal for a lot of non-target species, and their effectiveness [in deterring sharks] is questionable," Dr Meynecke said. "If we take out the shark nets during the whale season, we won't have any entanglements of whales. It's simple as that." A whale became entangled in the nets off Noosa Heads itself in August 2022.

The state government is holding its line on the nets. Primary Industries Minister Tony Perrett said the trial reflected the government's commitment to swimmer safety. "Queensland's shark control program plays an important role in protecting beachgoers, and we are always looking at ways we can improve the program with contemporary technology and science," he said. The Shark Control Program exists to reduce the risk of shark bites in Queensland coastal waters, and last year the government announced a multi-million-dollar expansion described as the biggest investment in the program's history.

The nets will be monitored throughout the trial to gauge the effect on migratory whales, with the hope of cutting the number entangled each year. And the acoustics may not stop at deterrence: Turner said the technology was constantly evolving, and researchers hope to eventually decode what the whales are saying back. "Researchers think that they can start to break down the sequences and the signals whales are using," he said. "And if we learn what are deterrent signals or an alert signal to them, then we can replicate those."