Fisheries Depredation by Killer and Sperm Whales, Behavioural Insights, Behavioural Solutions
Fisheries Depredation by Killer and Sperm Whales, Behavioural Insights, Behavioural Solutions
October 2-5, 2006 Pender Island, BC Hosted by the Vancouver Aquarium

 

Principal Findings and Advice

Below is a quick summary of the key findings of the meeting:

1) The problem of depredation (the raiding of fishing gear) by killer whales and sperm whales is growing around the world. This increase likely reflects a) diminishing natural food supplies for these species, and b) the transmission of depredation behaviours between whales by social learning. Hook and line fisheries are most affected, whereas depredation of net fisheries by these species is very rare.

2) Depredation is much easier to prevent or control before it becomes an entrenched behaviour. It is very difficult to control the behaviour of whales that have become dependent on depredation.

3) Depredation by killer and sperm whales is not widespread in BC yet, but appears to be increasing and could become a serious problem in several years. At present, the fishers most affected are commercial salmon trollers and sport fishers targeting chinook and coho salmon.

4) Depredation is a severe problem in Alaska. In the Alaskan panhandle, sperm whales depredating the valuable sablefish (black cod) fishery are the main problem. Along the NW coast of Alaska and the Aleutian Island chain, the main problem is killer whales that raid sablefish and halibut fishers. In the southern ocean, the lucrative toothfish (Chilean sea bass) fishery is seriously affected, whereas in the tropics, various species of tuna are taken.

5) The principle problem posed by depredating whales to fishers is the loss of catch. Gear damage is relatively minor and rare, and the whales do no appear to pose a danger to fishers.

6) As well as causing serious problems to fishermen, depredation harms whale populations in at least two ways. First, efforts to deter depredating whales can cause injury. Second, dependence on depredation can cause whales to lose natural behaviours, harming their populations in the long run.

7) Various research projects are being initiated to look for ways to reduce or prevent depredation. Most promising among these are acoustic devices and modifications to fishing gear, particularly the conversion of hook and line gear to pots and traps. Research will be conducted collaboratively with both fishers and researchers.

8) Because no "quick fix" solution exists at present, the best immediate advice for fishermen is a strict "do not reward" policy. Long-line fishers should drop their gear and troll fishers should remove theirs from the water when whales approach; both should only resume fishing when whales have left the area.


Vancouver Aquarium
Whale Image Montage