Marine animal rescuers are trialling different ways of freeing whales stuck in fishing gear off the West Australian coast in response to changing trends.
The latest annual report from the Department of Biodiversity, Conservation and Attractions (DBCA) said an increasing trend of entangled whales becoming tethered to the sea floor had prompted a change to disentanglement strategies.
DBCA Swan region marine and river park coordinator Melissa Evans said freeing a whale was challenging at the best of times and even more so when it was tangled near the ocean floor.
"In the past, we had predominantly free-swimming entangled animals, so they would have ropes either wrapped around their bodies or their tails, but they were still moving," she said.
"What we've found in the past few years is that we're getting more and more of those animals that are actually tethered to gear that is attached to the sea floor.
"It's not necessarily an increasing number of entangled whales overall, but what we are seeing is the type of entanglement has changed over time."
Ms Evans said the ocean mammals were being caught in different types of fishing gear.
"If there's a loop or a loose line in any of that gear, the whales can sort of swim through it and then they'll find that they can often get up to the surface to breathe, but they can't swim away because generally their tails are entangled to the sea floor," she said.
DBCA has been trialling different grappling tools and cutting equipment that would sink down to reach entanglements deep in the water.
"It's new, and it's only really been trialled last year and this year. We've had mixed success with it so far," Ms Evans said.
The DBCA reported 23 animal entanglements in the past year, most of which were humpback whales but also included one vulnerable leatherback turtle.
Eleven whales were not seen again after their initial report, which meant they were not able to be freed.
The DBCA succeeded in untangling five animals including the leatherback turtle.
Rock lobster gear was involved in many of the whale entanglements until modifications were introduced in 2014 that eliminated surface rope, shortened rope lengths, and reduced the number of pots in the water during whale migration.
Research by a team at the University of Western Australia indicated that these changes reduced entanglement in rock lobster fishing gear by at least 25 per cent.
Western Rock Lobster Council chief executive officer Matt Taylor said the changes had been so successful that last year there was only one confirmed entanglement in their gear.
"Which is quite remarkable when we have up to 30,000 pots in the water," he said.
"It's something that we take very seriously, it's part of our social license, we understand that and we're doing what we can, not just for our fishery but for the WA seafood industry to make sure we're minimising interactions with the increasing number of migrating whales along our coast."
In the state's north west, the Pilbara Ports Authority reported one whale entangled in a fishing net in Port Hedland during this year's whale migration.
It coordinated a response that resulted in the whale being freed from the net.
In the past three months, the authority has also reported three dead humpback whales in Port Hedland.
