Bycatch, Accidental and Unintended Catch
Bycatch is a fish or other marine species that is caught unintentionally while catching certain target species. It can either be a different species, the wrong sex, or an undersized or juvenile individual of the target species. Why is it such an issue? Current commercial fishing methods such as longline, purse seine, and bottom trawling are indiscriminate in what they catch and therefore produce a massive amount of unintended catch such as sharks, turtles, marine mammals, and unwanted fish.
In longline fisheries as much as 40% is wasted; on shrimp trawlers, as much as 80-90% of the catch gets thrown back overboard! Millions of tons of marine life wasted.
As many as 50 million sharks are caught on longlines set for other fish, a number that could be drastically lower if it wasn’t for the incentive to get the extra cash for fins. Sharks used to be cut loose, and every released shark had a high chance of survival.
Global bycatch may amount to 40% of the world’s catch, totaling 63 billion pounds per year. Less than 20% of existing fisheries management plans include incentives for fishermen to minimize bycatch.
Federal fisheries managers continue to authorize shrimp trawlers in the Gulf of Mexico to kill more than 50,000 sea turtles each year (that’s 150 per day!).
According to some estimates, global bycatch may amount to 40% of the world’s catch, totaling 63 billion pounds per year.
It's estimated that around 100,000 albatrosses are killed every year by longline and trawl fisheries around the world, where they are hooked and drowned, or struck by trawler cables and dragged under the water.
For more bycatch numbers, click here.
BYCATCH IS NOT ALWAYS ACCIDENTAL
Mitigation methods exist, but they are not used because they may be more time-consuming, more expensive, or simply not desired because there is no incentive to avoid “bycatch”. It may even be desired, as is often the case with sharks.
Long line fishers know where to go and how to fish in order to avoid sharks. They have the option to choose gear that lets sharks break lose and they can make the effort to release them. Many animals would survive and recover.
Last but not least, think about what you eat. Generally speaking, that means eat less or smaller portions of fish, eat low on the food chain (sardines, not tuna) and eat locally, sustainably harvested (i.e. pole caught) seafood. Better yet, find a good replacement (veggies, nuts, seeds) that give you the protein and Omega-3 you need, without the toxins you get from fish these days. To read more about overfishing, fisheries subsidies and the farming of fish, check out this blog and article by Coty Perry in our Oceans Knowledge Base.
BYCATCH STATISTICS
Not all fisheries in the U.S. were included in these reports, and not all data was able to be collected so these are likely underestimates. Below is a summary for US.
Benaka et al. 2019:
In 2015, 54% of the U.S. bycatch from fisheries in the monitoring process came from only 4 fisheries.
Fisheries included in this US National Bycatch Report caught approximately 6538.20 million pounds of fish (including sharks) and discarded approximately 814.53 million pounds of fish (including sharks). So, approximately 12.46% of what was landed was discarded.
Roughly 3006 marine mammals bycaught.
Roughly 1779 sea turtles bycaught.
Roughly 9575 seabirds bycaught.
Bonfil 1994:
Around 50% of the global taking of sharks from the ocean occurs from bycatch in high seas pelagic longline fisheries.
Generally, most fisheries data obtained regarding elasmobranch bycatch don’t provide species-level data. Instead, mass/weight of elasmobranchs caught is obtained and estimated.
Global estimates are likely underestimates, as much bycatch data is not reported at all, data on bycatch can't really be taken from all countries/fisheries.
United States Specifics
Benaka et al. 2019: U.S. National Bycatch Report (U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service (NOAA)):
This report, published by NOAA’s National Marine Fisheries Service, examines, “bycatch occurring across major fisheries managed under the Magnuson-Stevens Fishery Conservation and Management Act (MSA)” (pg. 5).
In this report, they define bycatch as, “discarded catch of any living marine resource plus unobserved mortality due to a direct encounter with fishing gear,” which they state is a more inclusive definition of the word/phenomenon because they wanted to expand to other interactions with mammals, birds, as well as fish.
Please note that the numbers in this list are only from the fisheries that were assessed in this particular research. There are other fisheries out there so there is likely more bycatch than described here.
2015, United States:
Overall, fisheries included in this monitoring caught approximately 6538.20 million pounds of fish (including sharks) and discarded approximately 814.53 million pounds of fish (including sharks). So, approximately 12.46% of what was landed was discarded.
Marine mammal bycatch:
Greater Atlantic and Alaska regions - 2,361 marine mammals.
Southeast Region - Approximately 221 individual marine mammals, including the dolphin, pilot whale, and sperm whale.
Alaska Region - Approximately 66 individuals including the stellar sea lion, harbor porpoise, and Dall’s porpoise.
West Coast - No exact numbers provided for all fisheries studied.
Common dolphins and California sea lions comprised a large amount of the bycatch that did occur.
One fishery reported 20 marine mammals bycaught, with more than half of these being Steller and California sea lions.
Another fishery in 2015 also bycaught 15 California sea lions.
Pacific islands region - Approximately 53 individuals from reports.
Sea turtle bycatch:
Southeast Region - 1,632 individuals.
Alaska Region - None observed.
West Coast - Low to no sea turtles estimated to be bycaught.
Pacific islands region - Approximately 147 sea turtles.
Seabird bycatch:
19 fisheries, and 6 fishery groups from the Greater Atlantic region - 2,572 seabirds.
Southeast - 33 seabirds (of fisheries monitored here).
Alaska region - 5,919 seabirds (estimate of fisheries monitored in this region).
Longline fisheries accounted for 88% of seabird bycatch.
West Coast - Approximately 270 individuals reported.
Pacific islands region - Approximately 781 seabirds.
Murray et al. 2018, United States:
Estimates of sea turtle bycatch between 2012-2016 from sink gillnet gear, where 87% of sea turtle bycatch occurred from trips where spiny dogfish, skates, or monkfish were targets for landing.
The Greater Atlantic Region estimated approximately 989 sea turtles, of which there were 781 mortalities (loggerhead, Kemp’s ridley, leatherback, and unidentified sea turtles).