Tasmanian fishermen learn the wisdom of listening to killer whales

July 1, 2018

When the crew on board Will Mure’s fishing boat Diana spot the fin of a killer whale, it’s not a photo opportunity.

It’s a day ruined.

Killer whales or orcas are adept at pinching fish off long lines, leaving fishermen out of pocket.

Mures Tasmania director Will Mure said the whales had been taking fish off his and his late father George’s lines for the past 40 years.

“They will at times take all of your catch, and sometimes that will be in excess of a tonne of fish,” he said.

“So you’ll have a pod of killer whales of maybe half a dozen that will just take the whole lot, so it is devastating.

“They essentially dive down the line we’re hauling off the bottom … and all you end up with is a bit of the lips of the fish and that’s it.”

He said orcas were extremely clever.

“They can recognise the individual noises of the boat,” he said.

“They’ll come directly to our boat and there will be other boats around and they’ll leave them alone, so they’re very smart animals.”

He said the killer whales were fussy about which fish they would take.

“When we go for blue eye — which we have traditionally always caught for the last 30-40 years — that’s where they appear and they love blue eye.”

Blue eye is a high-value fish.

“If they’re taking a tonne of fish, you’re talking in excess of $10,000 of product that they take in a day and the crew get paid as a percentage of the catch, so they’re obviously very unhappy with it as well because they don’t get any pay either,” Mr Mure said.

“They also love tuna. There was a very good tuna fishery in Tasmania some time ago, but they were so persistent with the tuna fishermen that eventually that fishery has actually moved to other parts of Australia now.”

Trying to outmanoeuvre the orcas

When the Diana returns to Tasmanian waters later this year to catch blue eye, Mr Mure has a trick up his sleeve to outsmart the animals.

“It’s not actually a new method. I don’t know why we haven’t thought about it before but there’s a hydrophone product which is actually a listening device,” he said.

“You put it into the water and you actually hear if the killer whales are in the vicinity. We’re in the process of purchasing one of those.”

But he said it was not a silver bullet.

“So we’ll hear them, and say ‘right, we can’t fish here today’, and spend a day steaming to the fish somewhere else.”

Ben Sellers, a PhD student with the Institute of Marine and Antarctic Studies, is looking at the diet and range of killer whales in Australian waters, using biochemical techniques and satellite tagging.

He has spent some time on board the Diana, and observed killer whales taking fish off long lines.

“They’ll miraculously appear just as the lines are being hauled. They are very clever animals.”

Mr Sellers said using a listening device and moving away from the orcas was a good way for the fishing industry to deal with the problem, as it breaks the cycle of animals connecting the fishing boats with a free feed.

“The more they move away from the animals, or stop the animals depredating just by changing fishing grounds, the less association there is, and the less conditioning there will be for the whales to associate boats with fish.”

He said a lot of work had been done trying to come up with an underwater acoustic deterrent, which emits sounds the killer whales want to avoid.

“They’re making developments for the North Pacific fisheries where depredation is a real issue, where killer whales take the halibut from fishermen around Alaska.

“In the Southern Ocean with the Patagonian toothfish fishery, the French have a real problem there with the killer whales, and you have actual pods specialising in taking the fish off the boats,” Mr Sellers said.

He said so far, acoustic deterrents had not worked.

That means, for now, a listening device and avoiding fishing grounds where the killer whales are waiting for a free feed, is the best bet for fishermen wanting to keep their catch.

Source: ABC Net.au

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