Getting seafood to the dining table comes at an expense to endangered species that too often perish in the nets and hooks set to capture the fish and shellfish we eat. The collateral mortality of non-target marine animals in fishing is referred to as “bycatch,” and is one of the principal threats to marine biodiversity worldwide.

Why Does Bycatch Occur?

Much of the fishing industry is very specific about what species it targets for capture. Unfortunately, other animals become hooked or trapped either when attracted to the bait or target catch, or when simply unable to avoid capture or entanglement in fishing gear. One of the most widely publicized examples of bycatch was in the 1970s, when many learned about dolphins killed in tuna purse seine nets in the Pacific. It is only one example of a widespread problem occurring in all fisheries, in all seas, and that spares no group of animals from delicate corals to massive whales.

How Serious Is Bycatch?

Many would argue that even though the unintentional loss of marine life is tragic, bycatch is an acceptable consequence to supplying the world with wild-caught seafood. However, when the scale of mortality reaches many thousands it threatens the very survival of species and the environments in which they form an integral part. Every year across the globe, at least 7.3 million tons of marine life is caught incidentally by fishing. In some fisheries the percentage of bycatch far outweighs the amount of target catch. For example, for every shrimp caught by nets dragged behind boats (or trawls) in the Gulf of Mexico, over four times its weight is made up of bycatch.

If the problem is ignored, the result too often is depletion or extinction of endangered animals. In 2007 the world learned that the baiji, a freshwater porpoise found only in China’s Yangtze river, finally succumbed to decades of incidental hooking among other causes of mortality, and is now believed to be effectively extinct. In the Northwest Atlantic, Canada and the USA are working to ensure that the North Atlantic right whale, now numbering fewer than individuals, does not suffer the same fate from fatal entanglements in fishing lines. These are not rare examples, but part of a systemic problem occurring worldwide.

What Can Be Done About It?

The good news is that there are solutions to the threat that bycatch poses to endangered species. One approach is to reduce fishing or direct it away from hotspots of conflict between fishing operations and non-target animals. There are also fishing technologies and methods that keep the fishing industry active but that reduce bycatch to levels at which it no longer poses a threat to the survival of non-target species. The challenge is to identify the most practical solutions in collaboration with the fishing industry.