Images: The first image shows, via the United Nations’ Fisheries and Aquaculture Department, a tuna longline. A yellowfin tuna is caught on a weak hook in the second image. Larger species are excluded, because the hooks “straighten when a large fish, such as bluefin tuna, is hooked, releasing it but holding on to smaller fish.” The image is via Mike Carde. Via NOAA, some weak hooks, at various stages of bending, are shown in the third image. The fourth image, via izik on Flickr, illustrates some longline hooks from an Alaskan fishery.

In a fishery, which can mean many things, fishers target certain species for personal consumption or for market. However, sometimes, fishers catch other species in addition to the species that they’re targeting. These non-target species are known as bycatch, and even though bycatch might be illegal to keep, to consume, to target, or to market, bycatch may still be incidentally caught in some fisheries.

Therefore, if the fisher doesn’t have a permit to keep certain species or if the species is illegal to keep, it’s simply wastefully discarded overboard. Bycatch isn’t wasted, however, if a fisheries observer is onboard to scientifically sample the species or if the fishers keep the specimen to turnover to scientists for research. As a result, bycatch can yield valuable data about a species and its interaction with commercial fishing gear.

Nonetheless, bycatch is a serious problem in some fisheries — particularly in some commercial fisheries, where the ecological footprint can be significant. Bycatch might include other species of fish, undersized or juvenile target species, marine mammals, sea turtles, sea birds, or invertebrates. Fisheries with little or no bycatch and minimal impact to the environment are often called clean fisheries. For example, “environmental seafood guides produced by Audubon and the Monterey Bay Aquarium have cited the Albacore troll fishery as an example of a clean fishery with little bycatch or impact on the environment.”

Due to being incidentally caught, some species, in particular, are at risk. For example, populations of endangered species, valuable species, or species that are easily caught as bycatch in certain fisheries suffer from illegal fishing or from fisheries that are inefficient or dirty. However, fisheries research can result in improvements that mitigate or even eliminate bycatch of certain species (thus making the fishery cleaner), so cooperative research is important in ensuring continued seafood production and in making fisheries more sustainable.

Big, fat female fish, which have a higher fecundity, and therefore are important to sustaining certain fish stocks or populations, are vulnerable as bycatch in some fisheries. The loss of important breeding individuals is devastating to certain fish stocks or to certain populations of fish species. One such fishery, which is problematic for incidentally removing important breeding individuals, is the surface-longline fishery. However, conservationists, fishery managers, and scientists are working to improve the fishery by tweaking fishing gear or utilizing bycatch reduction devices. Starting May 5, 2011, for example, “NOAA’s Fisheries Service will require commercial fishermen who fish for yellowfin tuna, swordfish and other species with longlines in the Gulf of Mexico to use a new type of hook, called a weak hook, designed to reduce the incidental catch of Atlantic bluefin tuna.” More via NOAA:

Directed fishing for bluefin tuna in the Gulf has been prohibited since the early 1980s, however bluefin are caught incidentally by longline fishermen who target other species. The Gulf of Mexico is the only known spawning area for the western stock of Atlantic bluefin tuna, a historically overfished species. Many bluefin die from the stress endured in this incidental capture in warm water even if fishermen release them.

“NOAA worked with longline fishermen from the Gulf to test the weak hook carefully over the last three years,” said Eric Schwaab, assistant NOAA administrator for NOAA’s Fisheries Service. “Our cooperative scientific research with fishermen is showing that this new technology can protect bluefin tuna in the Gulf while still allowing fishermen to target yellowfin tuna and swordfish.”

The weak hook is a circular hook constructed of thin gauge wire, and is designed to straighten when a large fish, such as bluefin tuna, is hooked, releasing it but holding on to smaller fish. The average size of bluefin tuna landed in the Gulf of Mexico longline fishery is 485 pounds, while the average for yellowfin tuna is about 86 pounds.

Yellowfin tuna and swordfish are valuable commercial fisheries in the Gulf of Mexico, supporting fishing jobs on approximately 50 vessels as well as jobs on shore. The two species bring longline fishermen annual dockside earnings of $7 million. Research showed that the weak hook could result in some reductions in target catch while some longline fishermen have reported weak hooks did not hurt their businesses.

“During our tests, we used regular hooks for half our hooks and half were the new weak hooks,” said Capt. Mike Carden, a longline fisherman from Panama City, Fla. who took part in the cooperative research. “We were so happy with the weak hooks we quit using the heavy hooks. The weak hook releases fish we don’t want to catch. Because it’s smaller and lighter, we catch more yellowfin tuna on the weak hook. There’s several of us who have gone to the weak hook.”

And from Dot Earth:

Federal fisheries officials, after field studies and public debate, have issued a new rule requiring commercial fishing boats deploying long lines of fish hooks in the Gulf of Mexico to use “weak hooks” that hold smaller, abundant species like yellowfin tuna but, in theory, will allow  depleted Atlantic bluefin tuna and other rare large species to escape. Here’s background in a news release from the National Oceanic and Atmospheric Administration.

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The agency release included a supporting comment from a captain of one of the 50 or so commercial longline vessels in the fishery:

“During our tests, we used regular hooks for half our hooks and half were the new weak hooks,” said Capt. Mike Carden, a longline fisherman from Panama City, Fla., who took part in the cooperative research. “We were so happy with the weak hooks we quit using the heavy hooks. The weak hook releases fish we don’t want to catch. Because it’s smaller and lighter, we catch more yellowfin tuna on the weak hook. There’s several of us who have gone to the weak hook.”

The Pew Environmental Trusts, which has been tracking the issue closely, gave a very mixed review to the move. Here’s a statement e-mailed to me by Dave Bard, a spokesman, followed by a video the group has produced on bluefin and the gulf:

Pew is pleased that the National Marine Fisheries Service (NMFS) has recognized the major bycatch problem with bluefin tuna in the Gulf of Mexico, the fish’s only known spawning area in the western Atlantic Ocean. The agency has issued a short-term solution requiring the use of “weak” hooks starting May 5, 2011. Pew is also pleased that NMFS has left the door open to consider long-term solutions including time and area closures. But, a year-round prohibition on surface longlines is the only way to provide effective long-term protection for bluefin tuna and other rare and beautiful species in the Gulf. This prohibition would still allow fishermen in the Gulf to catch swordfish and yellowfin tuna; they would just be required to use more selective alternatives to wasteful surface longlines.

Here’s the video report:

You can continue reading more about this story at Dot Earth.

Online Resources:

1. New Fishing Hooks Protect Bluefin Tuna in Gulf of Mexico But Allow Catch of Yellowfin Tuna and Swordfish
2. Longline Gear Innovation
3. Industrial Tuna Longlining
4. WWF’s International Smart Gear Competition
5. Stop Surface Longlining in the Gulf of Mexico
6. Northeast Cooperative Fisheries Research
7. Seafood Watch Program: A Consumer’s Guide to Sustainable Seafood