By-catch & Entanglement
When marine mammals get entangled in fishing gear, nets and trawls, or get hooked on longlines, they drown. As they are not the target of the fishery, this is called by-catch or incidental catch. Although it is called incidental, by-catch is largely foreseeable as it mainly happens in specific types of gear, with gillnets being the number one killer. Entanglement can also happen in “ghost gear” or nets that have been lost or discarded at sea.
Entanglement is a problem mainly for large whales, such as humpback whales or right whales, and seals. These can get by-caught in seine nets, or stuck in discarded fishing gear or marine debris, which can make it impossible for the animal to feed, it may slow them down or make them use more energy to swim. With humpback whales becoming more and more common in the coastal regions of Iceland, Greenland, and Norway, it is expected that entanglement will be an increasing problem.
References
[1] Read, A.J., Drinker, P., & Northridge, S. (2006). Bycatch of Marine Mammals in U.S. and Global Fisheries. Conservation Biology, 20: 163-169. https://doi.org/10.1111/j.1523-1739.2006.00338.x
[2] International Whaling Commission. Conservation and Management – Entanglement of large whales. https://iwc.int/management-and-conservation/entanglement
[3] ASCOBANS. (2020, September 4). Bycatch – Still a Major Cause of Small Cetacean Mortality. https://www.ascobans.org/en/news/bycatch-%E2%80%93-still-major-cause-small-cetacean-mortality
[4] NAMMCO. By-catch, entanglement and ship strike. https://nammco.no/by-catch-entanglement-and-ship-strike
Did you know that....
- Global annual by-catch is estimated to be half a million marine mammals, but is largely underreported [1]
- It is estimated that worldwide more than 300,000 marine mammals die from entanglement each year [2]
- In the North East Atlantic, Baltic, Irish and North Seas by-catch is recognised as the single-largest cause of mortality for small cetaceans [3]
- In NAMMCO member Countries, by-catch is likely mostly impacting harbour porpoises, grey seals, and harbour seals [4]
Discuss
Since by-catch is largely foreseeable, can it really be called incidental catches?























































































































