One in Two Fin Whales Already Entangled

Entanglements involving fin whales or blue whales reported to Fisheries and Oceans Canada or to the Quebec Marine Mammal Emergency Response Network are rare. The majority of incidents take place far from the eyes of fishermen. How is fishery bycatch measured, then?

Usually, entanglement rates are estimated from scars found on the animals. However, entanglements frequently occur at the tail or mouth, two body parts that fin and blue whales do not often show when they are at the surface. For these species, photos used for photo-identification are taken of the flank and the dorsal fin, areas that are unlikely to show any traces of entanglement.

By studying photos that show the peduncle, i.e. the area between the dorsal fin and the tail, the proportions of animals with entanglement scars changed dramatically: 80% for fin whales had 60% for blue whales.

The thing about these figures is that fin and blue whales seldom show their peduncle. It is therefore possible that injured whales might have to arch their back more to dive and therefore show more of their peduncle, which would result in a higher percentage.

It was therefore necessary to cross-check the data. Using drones, researcher Christian Ramp and his team filmed the body parts of fin whales that remain underwater and that historically had gone “under the radar”. Aerial images revealed that about one in two fin whales have scars from an entanglement.

“Changing the perspective by a few degrees showed us a totally different portrait of the threats that represent entanglements,” points out Ramp. By using a larger sample size and including marks present on carcasses, the researcher hopes to achieve a more accurate assessment of this threat. Either way, it was clear that it had been underestimated.

While whales can die after getting themselves ensnared in fishing ropes, traps or nets, they can also free themselves or be untangled by rescue teams. However, just because a whale is no longer dragging fishing gear does not mean it is not still paying the price for its mishap: injuries, infections, fractures, pain, energy loss due to difficulty swimming, increased stress, etc.

There is no evidence that the decline was caused mainly, or even at all, by entanglement, but this seems highly plausible given the impact of entanglement on other populations like right whales. It is possible that a whale that is entangled or has just been disentangled is not able to reproduce, for instance,” says Ramp.

“We don’t know where the humpback whales that visit the Gulf of St. Lawrence are getting entangled. Is it during migration? When they arrive in the Gulf? Our humpbacks overlap with different fisheries and at different moments. They really are urban whales. We have to understand better where and when these whales get entangled to prevent the threats,” explains Ramp.

“This paper was the easiest to write in my career; everything was clear, visible. But I think it might be the one that will have the biggest impact in conservation,” he notes. Currently, major efforts are being made by the Government of Canada and the fishing industry to reduce the risks of entanglement for the endangered North Atlantic right whale. Closing a fishing area when right whales are present could make entanglements less likely. Will we see similar measures for other species?

The solution may also lie in modified fishing gear. Numerous companies and organizations are endeavouring to make crabbing less dangerous for right whales (and other species). One of the innovations is to keep the ropes retracted until the owner comes to harvest his or her catch. The first prototypes were tested last summer. “One might think that bycatch and entanglement is a problem that only concerns fishermen. But as citizens, we can also have an impact… ask at the fish market to get snow crab from ropeless fishing gear or with a sustainable certification/label. It will increase the speed of changes.

And fewer whales will get caught.