Older fishermen remember when herring spawned all along the coast of Maine. Dense schools crowded the shore, filling the weirs used to trap herring and mackerel. Dories full of seine twine lay ready to shut off the coves when the fish swam in on moonless nights. Whales and seals sometimes found themselves on the wrong side of the twine, but they were usually set free unharmed. In the mornings, diesel-powered sardine carriers, long sleek boats, pumped the herring aboard and took them to local canneries or bait dealers.
Things changed in the 1980s, when purse seiners took over the fishery. The big boats caught herring further offshore over more months of the year. Purse seiners hunted the fish and circled the schools with long deep nets that could be closed on bottom, and then drawn in like a lasso. They, too, caught other species, or herring unfit for market, but often the unintended bycatch could be released alive. Seals were sometimes observed jumping out over the floats that held the top of the net on the surface.
In the late 1990s, the fishery changed again, with the advent of mid-water trawlers designed to harvest what was believed to be a record-setting biomass of herring on Georges Bank. Mid-water nets could be towed by a single boat, known simply as a mid-water trawler, or by two boats, known as pair trawlers. They are very different gear types, said Kohl Kanwit, a biologist with Maines Department of Marine Resources (DMR). A mid-water boat uses doors to spread the net and is limited in how high in the water column it can tow its gear. The pair trawlers can tow anywhere, right up to the surface.
While purse seiners remained limited to night fishing, when the herring rise off bottom, the mid-water boats could target herring close to the bottom, and they have become the most lethal means of catching herring yet invented. They have proven lethal to bycatch as well, not much that enters the net survives, and virtually no chance exists to release any unintended catch alive.
The Canadian Perspective
Canadas Department of Fisheries and Oceans (DFO) looked at mid-water trawling for herring in the early 80s and abandoned the idea. But when U.S. mid-water boats started targeting a shared herring resource on Georges Bank, however, the Canadians got back in the game. We have issued three mid-water permits for Georges Bank only, said Greg Peacock, the DFOs executive director of federal and provincial relations. According to Peacock, a yearlong study with full observer coverage paid for by the boats showed a .2 percent bycatch of groundfish. We didnt think it would cause problems on Georges, said Peacock. And we needed to be consistent with the U.S effort.
Nonetheless, Peacock expressed concern about the other impacts of mid-water gear. I think the primary gear should be purse seine, he said. Things evolve, weve gone from weirs to purse seines, but even the purse seines are passive, to a certain extent. They have to wait for the fish to come up. Mid-water trawling is hunting, and thats different; it tends to be a hungry application. Its a costly way to fish and it needs volume. Weve found that leads to a decline in coastal fisheries.
Kohl Kanwit points out that the U.S. and Canada have very different needs. Canadas is mostly a food fishery, she said, and ours is mostly a bait fishery. Thats why mid-water trawling evolved here. It can supply large quantities of bait when theyre needed.
But large gaps of knowledge exist regarding the impact of mid-water gear on herring and other species that feed on them, such as whales, tuna, and cod. Weve done a literature study on that, said Kanwit. But it was inconclusive.
Allocation battles between those who want to preserve historic fisheries or keep the herring in the water to feed rebounding wild stocks, and those who need to feed a growing high-volume fishery, are looming on the horizon. In order to make wise decisions, getting a handle on the true costs and benefits of mid-water trawling becomes increasingly critical.