With cod at historically low population levels and commercial fishermen limited to landings that are just a fraction of what they once were, the recreational catch is now believed to account for as much as one-third of total landings of Gulf of Maine cod.
But recreational landings data was considerably poorer than the commercial data, which made it hard to estimate their true impact on the population or know the effectiveness of regulatory measures.
Solving the cod crisis will take a lot of research. Now, scientists are no longer restricted to their lab. As a recent study shows, creative thinking and technology can turn the ocean into a lab, and the results can be more precise and minimize the regulatory impact on fishermen.
A key missing piece in the puzzle was information on how many fish died after they were released by anglers. Until recently, regulators assumed that 100 percent of those fish died. But that could lead to an overestimate of the population size, and overly strict regulations to bring reduce that amount of mortality. Researchers started collecting better biological data on the cod being caught by recreational anglers in 2005. By 2012, a panel reviewed the information they had along with scientific literature and arrived at a consensus that 30 percent of cod released by anglers died. But there was concern that there were no directed studies, in the U.S. or internationally to truth-test the estimate. It became one of the top priorities for the next Gulf of Maine stock assessment. “There was a paucity of data in the recreational sector on all the groundfish (cod, haddock and flounders),” said John Mandleman, a research scientist at New England Aquarium. “In the Gulf of Maine you have to account for a lot of small fish that are being thrown back.”
Back in 2013, Mandelman was part of a team of scientists from New England Aquarium, the University of Massachusetts, University of New England and Massachusetts Division of Marine Fisheries that performed a survey by putting acoustic tags that send out a signal unique to each fish on cod caught and released by recreational fishermen off Gloucester. They used a submerged field of receivers laid out by Division of Marine Fisheries researchers to study spawning cod. The area was chosen because it is a cod spawning area, meaning cod would stick around for months at a time.
While other survivor studies had used cages or tanks to study what happens to fish after they were released, scientists believed that didn’t account for the effects of predators that might more easily capture fish whose mobility was compromised by the exertion or damage of being snared by a hook.
In effect, the field of receivers was like a big cage without walls that allowed the fish to swim naturally in familiar surroundings while their tags told scientists where they were, how deep and fast they were swimming, and other behavioral clues.
The researchers used charter boats operating out of Gloucester and their clients as a part of the project. They didn’t just concentrate on the fish, however, but looked at who is catching them. They wanted to know what effect handling the fish had on survivability: how long it took to land the fish, how experienced the person pulling the hook was in preventing additional injury and how baited hooks or the use of jigs and lures affected whether a fish lived or died.
Over 700 cod were caught and 130 were fitted with specialized tags, which cost $600 a piece. Each receiver with buoy cost $1,700. A second study was done last year on haddock in which over 2,400 fish were caught and 157 tagged. The data is still being evaluated from that survey and the team will be conducting a study of cusk, another codlike North Atlantic fish, this year. The New England Fishery Management Council funded the cod study with a $247,000 grant. The Council awarded a $147,000 grant to go with a National Marine Fisheries Service Kennedy Saltonstall grant of $112,000 for the haddock study and a Kennedy Saltonstall grant of $226,000 for the cusk study.
What they found was that the experience of the fisherman, the gear and environmental conditions makes a difference in cod surviving after release.
“You’re more likely to meet your maker if you’re being caught by a kid on a jig, on a warm summer day,” Mandelman said.
The result of the cod study was a reduction in the mortality estimates for recreational fishing from 30 percent to 15 percent. National Marine Fisheries Service scientists and analysts checked the new study and compared it to a European study that estimated an 11 to 12 percent mortality rate among catch-and-release cod. “There was a pretty strong feeling these were scientifically valid (studies),” said Michael Palmer, a research fishery biologist with in Woods Hole. The new mortality study was considered strong and rigorous enough that the lower estimate was used in crafting new regulations even before it had been peer reviewed and published. With fewer fish now believed to die when they are thrown back by anglers, fishermen could catch more and still stay within the quota. That led to proposed regulations that will allow fishermen to land one cod per day this year, as opposed to none, and increase haddock landings from five fish to 15. “When we get studies that are better, that are done on the water and get into handling practices and discards … the better served we are in the management process,” said Jonathan Peros, fishery analyst for the New England Fishery Management Council. — Follow Doug Fraser on Twitter: @dougfrasercct
Due to a reporter's error, a couple of paragraphs in this story have been updated with clarified information.