Gulf Of Maine Cod Do Better After Release Than Thought

For some time, studying where fish in the Gulf of Maine go after they’ve been caught has used outdated methods. These include relying on data like measurements of length and weight and then turning those into estimates of the number of fish that survive being caught and released.

Since those methods haven’t always been the most accurate and because a direct measurement of where fish go after they’re released had never been done before, researchers from the New England Aquarium, along with others, recently embarked on a study into the issue.

The idea is to help fishing managers get a better handle on what happens when cod, haddock and cusk get thrown from a fisherman’s line back into the sea. The first round of the research, on the Gulf of Maine cod, found that 9 percent to 21 percent of the fish died, less than the 30 percent estimate regulators had been using before.

That data could help change quotas for recreational fishermen, who must abide by strict limits on some species. Scientists involved in the work say that their findings are much more precise than the conservative estimates of the past.

Before the effort, there was a real lack of data on groundfish in the recreational sector, scientists say. One of the complicating factors was accounting for the large numbers of small fish that get thrown back. Other studies in the past had also used gear like cages or tanks, which don’t adequately capture the movements of fish like other methods can.

For the recent research project, researchers used acoustic tags to track the movement of the fish after they were released to determine if they were alive or dead. The work on cod is finished, while data on haddock is still being analyzed. Work on cusk will continue until 2017.

Juvenile Atlantic cod. (Credit: Hans Hillewaert / Creative Commons 4.0)

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. They also 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.

More than 700 cod were caught and 130 were fitted with specialized tags, which cost $600 a piece. Each receiver with buoy cost $1,700. For the study on haddock, more than 2,400 fish were caught and 157 tagged.

Scientists say that the data have already been helpful to fisheries managers. Data on cod helped regulators decide to keep the recreational haddock fishery open in 2015. Cod, in the midst of a steep decline off of New England, are frequently taken as bycatch by haddock fishermen, and their high rate of survival after discard eases some concern that they frequently die when thrown back.

Having this sort of information is important, researchers say, because it makes decision making easier, enabling managers to protect and utilize what they should.

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 is funding the cusk study.


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A wholly owned subsidiary of Fondriest Environmental, FishSens Technology designs and manufactures products in a state-of-the-art marine instrumentation and fabrication shop near Dayton, Ohio