If you talk to New England commercial fishermen long enough, sooner or later, you¹ll hear their opinion on dogfish. Rarely is it flattering. Distributed from Labrador to Florida, dogfish, known by the scientific name Squalus acantias, migrate northward to the Gulf of Maine and Georges Bank in summer.
When this happens, they come in droves — and with big appetites.
Schooling in swirls of fins and teeth, dogfish, many fishermen believe, gobble thousands of metric tons of herring and other baitfish and, they fear, juvenile cod, haddock and flounder as well.
Some say the dogfish schools have been so thick as to clog trawl gear and gillnets, making fishing in parts of July, August and on their return trips in parts of the fall fruitless.
Yet according to government scientists, the relative biomass of mature female dogfish is considerably below its maximum sustainable yield. Part of the concern is that Squalus bear live young, producing on average only six pups a year. Thus, under the Sustainable Fisheries Act, the stock is considered “overfished” and entitled to all the rights and privileges therein.
Currently dogfish are managed jointly by the Mid-Atlantic and New England Fishery Management Councils as a single stock in the northwest Atlantic.
What accounts for such a discrepancy between what fishermen are seeing in their nets and what scientists are seeing in stock assessments? With this context as a backdrop, Capt. Joe Jurek of the
F/V Mystique Lady of Andover, Mass. partnered with Dr. Paul Tsang, a biologist at the University of New Hampshire, Walter Bubley, a grad student at UNH and Dr. James Sulikowsky, a scientist at the University of Florida at Gainesville on a study that will investigate basic dogfish life history and biology using sophisticated satellite tagging technology. The research could have important implications for fishermen in Maine, many of whom believe that ineffective dogfish management has unnecessarily contributed to decreased landings and economic hardship.
“I’ve watched the numbers of dogfish climb over the years. When they’re around you simply can’t get away from them. They eat commercially valuable species before they reach maturity and keep us away from fish we’d otherwise be landing. It’s a perfect example of a management rule that doesn’t help fish or fishermen, and contributes to a mistrust of management in general,” said Mattie Thompson, a lobsterman and gillnetter from Monhegan.
Two fundamental scientific questions hang over dogfish management in New England: First, should dogfish in the Gulf of Maine be considered part of the northwest Atlantic stock? Second, what areas of the Gulf of Maine represent essential habitats for the species?
Recent tagging efforts on dogfish in the Carolinas and Canada suggest there are at least two independent stocks. But the information that can be gleaned from the simple plastic tags used in the studies is limited.
“Conventional tags really only tell you a couple things: where the fish was tagged and where the fish was captured,” said Bubley. “What happens between point A and point B is anyone’s guess.” Another limitation is that as many as 95 percent of tags in conventional studies are never recovered.
For highly migratory species like dogfish that may travel thousands of miles, satellite tags offer a means to study real-time movement patterns and to see how fish utilize the environment. And because the tags pop up after a preset time they have a much higher rate of return.
Such tags have proven very useful in studying several marine species, such as a 1997 New England Aquarium project that affixed tags to 20 tuna in the region¹s coastal waters. The tags were programmed to transmit information about the fish’s location and water temperature to a satellite at fixed intervals and sent to the researchers by email.
The initial findings from this study demonstrated the presence of adult bluefin tuna in the mid-Atlantic region during their presumed spawning period and challenged one of the main assumptions underlying current management policies: western Atlantic bluefin tuna spawn exclusively in the Gulf of Mexico.
“Central to any successful fishery management plan is the availability of accurate, detailed and updated life history information on the species. If this approach proves successful in our pilot effort, then satellite tags may be used to determine whether or not there is a unit stock of spiny dogfish in the Gulf of Maine, and to locate areas in the Gulf of Maine that represent essential fish habitats for this species,” said Bubley. “This is the first step in identifying the health of the stocks as seperate. It is possible that what we find changes our outlook on the numbers and lead to a total allowable catch that fishermen can actually make some money on.”
The study begins this July, when Squalus typically return to the western Gulf of Maine.
Mike Crocker is the editor of Collaborations, a report on research conducted between scientists and fishermen and the Gulf of Maine and Georges Bank. For a free subscription email mike@namanet.org.