The following article first appeared in Trumpet Call, newsletter of the Alliance for America, and is reproduced with the author's permission.

A Tuna Tale: Managing a Fishery to Increase Positives, Reduce Negatives

By Teresa Platt

April 1996

(At the time of writing, the author was co-director of the San Diego-based Fishermen's Coalition. In 1998, she left to become executive director of Fur Commission USA.)

WHETHER ON LAND OR ON SEA, animals are present in all food harvesting operations. A farmer looking through the fields before harvesting his crop sees rabbits, opossums, mice, rats, birds, foxes, skunks and snakes. These animals flee as the combines come through the fields but there is accidental and unavoidable mortality.

The ocean is no different. As farmers of the sea, fishermen use various equipment designed to harvest specific fish. Non-targeted animals flee or are released unharmed. However, there is accidental and unavoidable mortality of non-target species.

A challenge for every fisherman is to design and use equipment and methods which selectively catch the target fish the fisherman wants while minimizing non-targeted "bycatch" (unwanted catch) and discards (rejects returned to the sea) where our discards become something else's lunch.

The Basics

If you were to design a program to reduce the bycatch in a fishery, you would want to answer a few basic questions:

  • How many affected animals are there in this fishery?
  • How much does their population increase every year naturally (births less natural mortality or "net reproductive rate")?
  • How many animals are people killing accidentally every year?
  • Is this number so high that it is negatively effecting the animal populations?
  • Can we reduce the number of animals accidentally killed without putting fishermen out of business?
  • Can we reduce the numbers of animals accidentally killed without substituting gear and equipment that will have a different or greater negative impact on the ocean's inhabitants?

A Case Study

Over the last thirty years, one area of the world has received a great amount of attention due to an unwanted bycatch of dolphins during fishing operations. The eastern tropical Pacific (ETP) yellowfin tuna fishery, an 8 million square mile area stretching from California to Chile and out to Hawaii, is the traditional fishing grounds for the U.S. tuna fleet and eight to nine other countries. This multi-country fleet has operated under the conservation programs of the Inter-American Tropical Tuna Commission (IATTC) since 1949. Because of the presence of this conservation program, this fishery boasts one of the world's most comprehensive marine databases. In terms of science, this is a wonderful accomplishment. But this can be negative in that anyone can take numbers and generate hysteria.

Putting It In Perspective

So let's put the numbers in perspective. The eastern Pacific is the half of the Pacific Ocean that abuts the west coast of North America, Central and South America. Within this area is the yellowfin tuna fishery in the eastern tropical Pacific Ocean (ETP).

  • The ETP yellowfin tuna fishery covers over 8 million square miles of ocean, an area almost three times the size of the United States.
  • The ETP produces about 800 million pounds of skipjack and yellowfin tuna (lightmeat tuna) per year, about 20 to 25% of the world's canned tuna supply.
  • The ETP is the world's largest yellowfin tuna fishery and produces about 30% of the world's yellowfin tuna, a delicious and prolific fish which lives to about five years and can grow to weigh 400 pounds.
  • The ETP is home to approximately 10 million dolphins which are commonly found swimming in association with large yellowfin tuna. The ETP is also home to many other whales and dolphins not generally found swimming in association with dolphins. It is also home to uncounted other fish, sharks, billfish, rays and turtles.
  • The fishermen use a seine net in this fishery to encircle the tuna like a fence. Seine, like the river in France, is French for a "net which hangs."
  • The bottom of the seine is "pursed" so the catch cannot escape. Like in a drawstring purse, cables close the bottom of the net, so the nets are called "purse seines" and the boats which use them are called purse seiners.
  • The fishermen maneuver the net to carefully release any dolphins unharmed before putting the fish on board.
  • The fishermen encircle and release over a million dolphins a year in this fishery.
  • Because the area is so large and the dolphins so numerous, if the U.S. Marine Mammal Protection Act were applied equally to this international fishery, an allowance for accidental kills of approximately 55,000 dolphins annually in this fishery would be considered biologically insignificant.
  • The estimates of dolphins accidentally killed in this fishery has varied over the last thirty years from guesstimates of hundreds of thousands annually to estimates of tens of thousands to counts by on-board observers of approximately 4,000 in recent years, or 0.04% of the abundance of the dolphins found in this fishery. This is completely sustainable and a fraction of what is allowed U.S. fishermen fishing domestically within the 200-mile limit of the United States.
  • Additionally, protections by stock of dolphins are in place, ensuring that takes remain below 0.2 percent of any stock of dolphins. This allowance is scheduled to decrease to 0.1 percent of each stock of dolphins in the near future.

Education Plus Commitment Equals Stunning Results

Educating the fishermen on the correct gear and how to use it has resulted in one of the cleanest, most efficient fisheries in the world. Fishing for tuna swimming in association with dolphins results in discards of less than 0.1 percent of the catch. Marine mammal mortality is a fraction of what is experienced in many other fisheries and it is recognized that substitution of other gear would result in higher dolphin mortality. In addition, concentrating the fishing on the mature and large yellowfin tuna keeps the fishery healthy and avoids overfishing the resource.

Avoiding all dolphin interaction ("dolphin safe" as currently defined) forces the fishermen to fish on small yellowfin which scientists estimate will reduce the production of yellowfin tuna by 30 to 60 percent.

Additionally, focusing the fishing on smaller tunas which do not generally swim with dolphins, results in unacceptably high discards of as much as 30 percent of the catch. These discards include many other fish, billfish, sharks and sea turtles. "Dolphin safe" needs to be redefined as a gold star for perfect performance by the fishermen in releasing dolphins unharmed. This definition encourages fishermen to continue improving their performance at releasing the involved dolphins unharmed while catching very clean schools of very large yellowfin. This redefinition lets the fishermen earn a living while keeping the fishery healthy.

Simply put, marine mammals are present in all the world's oceans and therefore all the world's fisheries. An allowance for interaction and some mortality allows fishermen to earn a living and supply the world with a food product. If we are to continue to make progress in addressing environmental issues, we need to base our fisheries policies on fact, not fantasy, and support rational, scientifically based conservation programs in every ocean of the world.

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