Incidental catch, or "by-catch," refers to unintended or unwanted animals caught by the fishing industry. It is estimated that by-catch-related mortality is causing population declines in 13 out of the 44 species of marine mammals that are suffering high death rates from human activities. Commercial fishers use a number of techniques for ensnaring animals, from setting miles of line and baited hooks (called longlines) to catch animals such as sharks, swordfish, and tuna, to using large nets to catch schools of fish. These large nets are towed underwater by what are called trawlers. A trawler is a fishing vessel designed for the purpose of operating a trawl, a type of fishing net that is dragged along the bottom of the sea (or sometimes just above the bottom at a specified depth).

UNEARTHING THE OCEAN FLOOR
A single pass of a trawl removes up to 20% of the seafloor fauna and flora - legally. And the fisheries with the highest levels of by-catch are shrimp fisheries: 80%-90% of a catch may consist of marine species other than the shrimp being targeted. 80%-90% of the animals caught in these nets that are targeting shrimp and prawns are actually non-target animals – they’re by-catch.

Shrimp are bottom-dwellers, which is why trawling nets are used to – remove them from the ocean. Since even jumbo shrimp are really small, the nets used to catch the shrimp are very fine, which means these nets scoop up all the animals – all the life – found on the ocean’s floor. According to a 2003 U.S. News and World Report article on fishing and its detrimental affects on the oceans of the world, every pound of shrimp that’s caught results in the killing of ten pounds of other marine life. According to the Worldwide Fund for Nature, in the Gulf of Thailand it can be 14 pounds of by-catch per pound of shrimp.

Now, a lot of the dead by-catch is made up of tiny animals that people don’t have emotional attachments to; that is, they may not be as cute as baby seals or dolphins, but they contribute to the oceans’ biodiversity and they have a right to be there – to live.

The other thing to consider is that the dredging along the ocean floor also breaks up coral and the habitats of bottom-dwellers. And because the same areas are dredged again and again, it’s not like these habitats and inhabitants have time to recover before being destroyed again. Fish populations, communities, and ecosystems are being destroyed so humans can eat shrimp cocktail.

The animals termed as by-catch are often discarded back into the ocean already dead or dying. Many are half-alive and die slow, unnecessary deaths. Trawl nets in general, and shrimp trawls in particular where the discard may be 90% of the catch, have been identified as sources of mortality for many species of concern, including endangered animals and cetaceans, such as whales, dolphins and porpoises. Sea turtles, already endangered, have been killed by the thousands in shrimp trawl nets.

It's hard to get exact number, but another way to put this is that anywhere between 6.8 million and 27 million tons of fish could be being discarded each year. We may be looking at the one fish on our plate or the 5 shrimp in our seafood salad, but countless numbers of animals were dredged up and killed for the individuals we see on our own plates.

CETACEANS (WHALES, DOLPHINS, PORPOISES)
I've been focusing primarily about the by-catch caused by trawling nets and shrimp nets, but there are other commercial fishing methods that also result in by-catch. Nets tend to kill cetaceans (dolphins, porpoises and whales), and longline fishing kills birds, for instance. As for the first group, an estimated 300,000 cetaceans (whales, dolphins and porpoises) die as by-catch each year, because they are unable to escape when caught in nets. We may not think cod fish are particularly cute, but most people get pretty emotional about whales, dolphins, and porpoises. If we don’t consider the cod, perhaps we can consider the animals for whom we do have sympathy.

SHARKS - THE TRUE VICTIMS IN THE HUMAN-FISH RELATIONSHIP
In the case of the shark by-catch in the tuna industry, "data for Pacific longline tuna fisheries are limited, but available data indicate that shark catches are often as high as tuna catches and more than 50 species of sharks and fish are captured as by-catch in West Pacific tuna longline fisheries." (Incidentally, in defense of sharks, it has been estimated that a staggering 100 million sharks are caught every year, have their dorsal fins cut off - to serve in soup, and are thrown back into the ocean to die a slow death.

SEABIRDS - MANY ON THE BRINK OF EXTINCTION
As I mentioned earlier, seabirds are also inevitable "by-catch" victims, as they dive for the bait planted on long fishing lines, swallow the bait along with the hook, and are pulled under the water where they drown. Around 100,000 albatrosses are killed by longline fisheries every year, particularly where tuna are fished, and because of this, many species are facing extinction. This is very prevalent in the waters off Chile, where sea bass is aggressively hunted by boats towing fifty-mile longlines.

According to the Pew Oceans Commission, Patagonian toothfish long-liners killed around 265,000 seabirds between 1996 and 1999; in the northwestern Hawaiian Islands, where the total breeding population of the black-footed albatross is 120,000 birds, annual fishing-related mortalities of 1,000 and 2,000 birds are significant; and longline fisheries in the U.S., including the Pacific cod fishery kills some 9,400 to 20,200 seabirds every year.

In subsequent posts, I'll address the dolphins, sea turtles, seals, and other marine mammals who are also written off as "collateral damage." Look forward to more on the un-sustainability of farm-raising fish, on the evidence of fish intelligence, and much more related to our pursuit of gustatory pleasure. Check out my previous post for the reasons to obtain Omega-3 fatty acids from plant sources rather than fish (hint: the fish obtain these fats from plant sources, too!)

Humans have no nutritional requirement for the flesh or secretions of other animals. Like the non-human animals we eat, we can go straight to the source - to the plants - for all the nutrients we need to survive and thrive.