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UNE Professor Presents Significant Dogfish Findings

Tom Porter
/
MPBN
Dr. James Sulikowsi of the University of New England.

New research by a Maine-based marine biologist could have big implications for fisheries management in the Gulf of Maine.

The study, authored by University of New England professor James Sulikowski, suggests that a voracious predator known as spiny dogfish may be far more prevalent in the Gulf of Maine than originally thought, and could be more of a threat to other species.

Sulikowski used satellite tagging technology to track the movement of some 40 dogfish, from the Gulf of Maine down to the mid-Atlantic, something that had never been done before.

He says conventional wisdom is that dogfish in East Coast waters move around in one huge population, in packs of 10,000 or more.

"The old paradigm on their moving patterns was that essentially they would spend the summers and fall up here in the Gulf of Maine and then travel like snowbirds down to North Carolina and then back up here in the spring, and so that was old paradigm, sort of this big long packlike movement of these moving on the bottom," Sulikowski says.

But satellite tagging data indicate there are two distinct sets of dogfish — one in the Gulf of Maine, and one in the mid-Atlantic, off North Carolina — and they don't tend to mix. And Sulikowsi says this means spiny dogfish are a year-round presence in New England waters, devouring other fish right through the winter months. The study also finds that population estimates could be underinflated. That's because dogfish do not only dwell at the bottom of the ocean, as widely believed.

Sulikowski's research shows them moving vertically, up and down the water column, which means current trawler surveys may not be giving the whole picture.

"There could be more dogfish out there, and that's what we think is going on," he says. "You see these increases in population because a large portion are being missed."

Sulikowski says it's also important to bear in mind just how destructive dogfish can be. They're hardy, opportunistic and they move around in very large numbers.

"Imagine a pack of 10,000 dogfish coming down into an ecosystem," he says. "What do you do if you're a fish there? Either you leave, you find another place to stay, or you are outdated or even eaten.

"These are very powerful fish," he says. "They can chase down anything else and bite it, and eat it."

Mike Breton is a commercial fisherman from southern Maine with more than 30 years in the industry. He says the latest research on dogfish reinforces his own observations — that dogfish are more prevalent than official data suggest. Even after they were declared overfished in the late 90s by regulators, Breton says he witnessed dogfish in large numbers — especially when fishing for tuna.

"When we fish for tuna fish, we use live bait, or a chunk of bait, put that bait anywhere from 80 feet down in the water column, down to 200 feet, and over last several years our baits have been taken by the dogfish, so it was almost impossible to fish for tunas with that method," he says.

Dogfish are keen predators of groundfish, such as cod and haddock, and this has implications for fisheries policy, says Sulikowsi, because it means factors other than overfishing could help explain the decline in groundfish numbers.

But Sean Mahoney of the Conservation Law Foundation says overfishing is still the main culprit when it comes to falling stocks, and he says it's essential that protected areas remained closed to fishing.

Mahoney acknowledges that factors such as dogfish predation and climate change are affecting groundfish such as cod, but, he says, "All of those just exacerbate a problem created by overfishing, and the bottom line is that we just don't have enough cod and dogfish are definitely adding pressure on that."

Last year catch limits for Gulf of Maine cod were cut by nearly 80 percent. And just last week the the National Oceanic and Atmospheric Administration, or NOAA, released numbers indicating that cod stocks worsened last year, despite drastic quota cuts. Mahoney says encouraging fishermen to catch more dogfish would be a good idea — but there's one key factor working against that: lack of demand.

"It would be great if we could find more markets for dogfish because there's lots of them, but so far we've been challenged by lack of an effective marketing strategy by the states," he says.

UNE's professor Sulikowski agrees. Annual quotas for dogfish have increased by about 300 percent in the last few years, but could easily go even higher. In addition to being good to eat, Sulikowsi says dogfish can be used both as fertilizer and bait.

"The resource is there and it's available, so now it's up to us as scientists, working with NOAA and other management agencies, to build an infrastructre so we can sell the dogfish," he says.

He says that could help New England's struggling commercial fishing industry.

Sulikowski's study was published in the Public Library of Science. NOAA, which helped fund it, says the findings will be considered during the next full stock assessment.

1152575.mp3
Tom Porter interviews James Sulikowski.