Depredation

Depredation causes economic loss for fishermen, places increased pressure on fish stocks, and can lead to injury or mortality for whales.

The Problem

The principle problem posed by depredating whales to fishers is the loss of catch, costing potentially tens of thousands of dollars a day. One fisherman in Tasmania estimates that he loses about $ 7,700 US per day when killer whales target his boat. Near the Crozet Islands, the Patagonian toothfish fishery loses nearly $ 5 million a year to killer whale and sperm whale depredation (Roche et al 2007).

Species at Risk

In areas where depredation behaviors emerge, whales are at greater risk of vessel strike, entanglement, conflict with fishermen, and altered foraging strategies. In B.C. most depredation events on sport fishing gear appear to be by members of the northern resident (fish-eating) killer whale population – a threatened species protected under the Species-at-Risk Act. Sperm whales, the other notable whale engaging in depredation in BC Waters,  are a protected species under the Species-at-Risk Act.

The Solution

Preventing depredation events before it can become widespread in an area is key. Two handouts were created after the 2018 workshop to provide information and outline best practices for recreational and sport fishermen, and commercial fishermen. Download the guides below.

 

Depredation causes economic loss for fishermen, places increased pressure on fish stocks, and can lead to injury or mortality for whales.

Depredation (removal of fish caught on fishing lines) by toothed whales is a widespread problem in many oceans around the world. Negative impacts of depredation include economic losses to fishermen, increased pressure on fish stocks, and injury or mortality to whales.

Anecdotes regarding incidents of depredation by Killer whales ( Orcinus orca ) and Sperm Whales ( Physeter microcephalus ) are relatively common along the coast of British Columbia among halibut, black cod, and salmon fishermen, and appear to be increasing. Hook and line fisheries appear to be the most frequently targeted, although fisheries using pots or trawl gear can contribute to the problem by discarding offal and releasing bycatch in the presence of whales. Cetaceans are highly intelligent and social, and once learned, these behaviors are very difficult to extinguish and may spread to other members of a population. While the issue may not be large here in British Columbia (yet), prevention is key to ensuring fisheries are not significantly impacted and collaboration can help to prevent expansion. Preventing depredation events before it can become widespread in an area is key. Two handouts were created after a workshop in 2018 to provide information and outline best practices for recreational and sports fishermen, and commercial fishermen. Tap the images below to download a copy.

The Problem
The principle problem posed by depredating whales to fishers is the loss of catch, costing potentially tens of thousands of dollars a day. One fisherman in Tasmania estimates that he loses about $ 7,700 US per day when killer whales target his boat. Near the Crozet Islands, the Patagonian toothfish fishery loses nearly $ 5 million a year to killer whale and sperm whale depredation (Roche et al 2007).

Gear damage, by comparison, has been relatively minor and rare, and the whales do not appear to pose a danger to fishers. In BC there are increasing reports of fish snatched from lines, especially from sport fishermen. Depredation by killer and sperm whales is not widespread in BC yet, but appears to be increasing, and could become a serious problem in the coming years.

At present, the fisheries most affected are commercial salmon trollers and sport fishers targeting chinook and coho salmon. Several incidences of depredation are reported each year, but likely many events go unreported. Anyone who experiences a depredation event by whales or dolphins should  report it  so that scientists and managers may learn more about when and where this problem is occurring.

Species at Risk
Whales are at greater risk of vessel strike, entanglement, conflict with fishermen, and altered foraging strategies. Both killer whales and sperm whales are the most often noted to engage in depredation in B.C. waters, and are both protected species under the Species-at-Risk Act.
The Solution

 In 2006, an International Depredation Symposium was hosted by the cetacean research department at the Vancouver Aquarium. This initial symposium developed guidelines for fishermen and fisheries managers affected by killer whale and sperm whale depredation. In February 2018, Ocean Wise’s Marine Mammal Research Program held follow-up workshop which brought together fishers, managers, and scientists to continue this discussion of whale depredation, and develop a clear direction forward for British Columbia. As a result of the workshop, Pacific Halibut Commission logbooks will be used to formally record depredation events in BC. This data will be used to develop a baseline of the issue in BC, and will track geographic and temporal patterns of depredation along the entire west coast . Preventing depredation events before it can become widespread in an area is key. Two handouts were created after the 2018 workshop to provide information and outline best practices for recreational and sport fishermen, and commercial fishermen. Click the images below to download a copy.

Depredation handout for Recreational/Sports Fishermen

Depredation handout for Commercial Fishermen

What can you do to help?

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Take Care When You Fish

Take care and be aware of where and how you fish when whales are present or nearby.  When whales are present, leave the area and fish where they are absent, and never throw chum or offal in the water when whales are near, or reported to be in the area.

Report and Record Marine Mammal Depredation

Record depredation events in your logbook and report them to the Fisheries and Oceans Canada confidential reporting email:

[email protected]

Whale Depredation: Sneaking an easy Snack

Written by: Karina Dracott Research Biologist at Ocean Wise Marine Mammal Conservation Research Program Two new resources were developed this year by Ocean Wise for fishermen to address the issues of whale depredation. If a marine mammal has ever stolen your fish, you...