Sea Grant experiment shows promise for pair-trawling for tuna


Drawn to the sea, they travel in pairs, are partial to moonless nights and considered all but illicit. But don't get the wrong idea-these couples are fishing boats trawling for tuna on the southern side of Georges Bank, at the edge of the continental shelf. In an experiment sponsored by the MIT Sea Grant Program and approved by the National Marine Fishery Services (NMFS), a small group of New England fishermen are hauling in bigeye, yellow fin and albacore tuna by a method not yet approved for this fishery. The fishermen hope that the data from this experiment will convince the NMFS to revise its regulations to authorize commercial pair trawling for tuna.

On the East Coast, traditional commercial tuna fishing methods include long-lining and gill netting, both of which involve bycatch levels that concern fishermen and environmentalists alike. [Bycatch is the capture of unwanted species or undersize members of the species sought.] The problem with long-lining, in which miles of line with hooks and bait are set out at sea, is that sharks and other game fish are also caught. And gill nets, which are long panels of webbing that catch fish by entanglement, can also capture marine mammals, turtles and diving seabirds. Fishermen participating in the MIT experiment hope to show that bycatch is less of a problem with pair trawling than with these other techniques.

According to MIT Sea Grant fisheries engineer Clifford Goudey, who is coordinating the experiment, pair trawling is effective with tuna because these fast-swimming fish must be caught with large nets. And because of their speed, tuna would tend to scatter with a boat operating directly above them. With pair trawling, each vessel pulls on one side of a net. By carefully coordinating the speed of their boats, the distance between boats and the length of tow wires, fishermen can precisely control the net's position.

Captain John Riemer, whose boat is part of the experiment, believes that the catch from this experiment could convince the NMFS to reconsider its position on appropriate gear for tuna fishing.

"In my opinion, pair trawling is much cleaner than other methods," he said. "We think it's efficient and conservation-minded, and you land a good product." Capt. Riemer formerly pair-trawled for codfish, a practice that was outlawed earlier this year.

Pair-trawling for tuna provides boats with an alternative to goundfishing for cod, haddock and yellowtail flounder. Once staples for the New England fishing community, those stocks are now severely depleted.

In order to monitor the experiment, NMFS observers are accompanying fishermen on most of their trips. Fishermen from the 10 boats also provide Mr. Goudey with details of their activities. In addition to data about the kinds and numbers of fish caught, participants keep careful records of the towing geometry, the net's depth, environmental conditions and other factors that influence the performance of the gear. All this information should aid in optimizing the method for catching tuna, while reducing or eliminating the take of undersized or prohibited species.

Mr. Goudey points out that no method of fishing can be 100 percent free of bycatch. However, he says that through the use of specific setting and hauling techniques, and an emphasis on individual vessel accountability, "we have seen remarkably low levels of incidental takes." The experiment concluded at the end of December, after which the vessels returned to other, more traditional fisheries.

A version of this article appeared in MIT Tech Talk on January 25, 1995.


Topics: Oceanography and ocean engineering

Back to the top