Whales follow deep sea trawlers – but only when they’re fishing for halibut, reveals new research.
Eric Cantona infamously stated: “When seagulls follow the trawler, it’s because they think sardines will be thrown into the sea.”
Now some of the world’s largest mammals – sperm and northern bottlenose whales – have been seen regularly swimming behind the nets of trawlers in the western North Atlantic to feed on escaping fish.
But the whales were only spotted when the catch was Greenland halibut, not redfish or thorny skate.
Researchers “frequently” observed sperm and northern bottlenose whales following a trawler off the coast of Newfoundland to feed on fish escaping from the net as it was hauled in.
Dr. Usua Oyarbide tracked whale encounters over 50 days while onboard the trawler as a North Atlantic Fisheries Organization observer.
Sperm whales were seen in 129 encounters and northern bottlenose whales in 86 encounters directly interacting with the ship in areas where the trawler was fishing for Greenland halibut.
Dr. Oyarbide said: “The whales weren’t observed when the trawler was fishing redfish, thorny skate or any other fish species the trawler took, suggesting halibut was the fish of choice for both species.
“The longest sighting of a sperm whale – one hour and 20 minutes of continuous observation – occurred while the trawling net was being towed across the ocean bed to catch fish.
“In general, during towing, sperm whales – but not northern bottlenose whales – were often seen swimming parallel to the ship and surfacing or breaching.
While other studies of Greenland halibut fisheries have described sperm and northern bottlenose whales feeding primarily on offal and discards, Dr. Oyarbide said that was not observed on this specific vessel, where both whale species primarily fed on live halibut escaping from the net during hauling.
The research team said it suggests that differences in fishing practices across regions or over time may change whale behavior when associating with ships.
Dr. Oyarbide, of the University of the Basque Country in Spain, added: “Our research provides new insights into the behaviour of sperm and northern bottlenose whales around a commercial fishing vessel targeting Greenland halibut.”
She said more research on interactions between whales and fisheries are needed to assess the implications and possible risks – such as entanglement in nets – for whales.
Produced in association with SWNS Talker
