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by Madeleine Hall-Arber
CAMBRIDGE, MA - It may seem an impossible challenge, something like looking for the proverbial needle in a haystack, but codfish are being tagged and recovered. And the early returns from three tagging projects are proving that motivated fishermen can provide extremely valuable information to the scientific understanding of the make-up and movement of cod stocks.
The concept is simple: ask a fisherman to measure a cod, tag it, record where and when he released it; and then, when the fish is recaptured and the tag retrieved, compare the same information.
By graphing and measuring many returns of fish tagged in many different places, scientists can develop a picture of a cod stock movements, distribution, and rate of growth over time. Any supplementary information fishermen can take the time to record adds value to the observations.
Today, when the sustainability of fishing and fishing communities depends on effective management, scientists and fishermen believe it is critically important to understand the size of fish stocks in terms of time and space.
Michael Morin shows one of the cod tagged aboard Jim Ford's Lisa Ann last May as part of the UNH tagging project, as described on page 12B. UNH Tagging Project photo.
Area closures, mixing
Area closures are used by both Canada and the Northeast region of the US as part of their management strategies to reduce effort and rebuild stocks.
In some cases, where these closed areas are placed is determined based on data collected in the 1930s, '40s and '50s. Yet global climate change, impacts of fishing, and/or even genetic changes in the fish stocks may have altered fish behavior since those days.
In addition, the use of rolling closures as an effort-reduction tool demands a precise understanding of what and how much is being protected in order for managers to tally their benefits.
Scientists and fishermen know there is some mixing between the stocks, but not enough to warrant the supposition that Gulf of Maine and Georges Bank cod are all one stock.
So the real question is "how much mixing?"
For Gulf of Maine cod, which has been declared seriously overfished, strict quotas have been imposed that limit US fishermen to retaining 400 pounds of Gulf of Maine cod per day-at-sea.
Yet, the stocks of Georges Bank cod - generally defined as cod caught south of the 42° line - are considered to be in much better shape and fishermen working there are allowed to land as much as 2,000 pounds per day.
If tagging studies demonstrate a significant degree of mixing, the fishermen who target Georges Bank cod would likely face sudden and potentially harsh restrictions.
The potential implications of cod migration and distribution elevates the demand for accurate and credible research.
Many fishermen believe the strict management regime has already led to increases in the number of cod, often in inshore areas where cod has been absent for a human generation or two.
However, the traditional National Marine Fisheries Service trawl surveys used in stock assessments have not yet supported fishermen's observations.
The resulting distrust of each other's observations and methods is widely acknowledged as undermining efforts to design compromises and effective management.
So, scientists and fishermen have been making a serious effort to develop collaborative research that will benefit from both fishermen's experience and scientific methodology.
Cooperative research
There are currently three major cod-tagging programs going on in the Gulf of Maine. All three projects are successful collaborations among commercial fishermen and scientists from the University of New Hampshire (UNH), the University of Massachusetts Dartmouth's School of Marine Science and Technology (SMAST), and the Canadian Department of Fisheries and Oceans (DFO).
Additionally, a cod-tagging task force has recommended formally linking, coordinating, and extending the individual cod-tagging projects to the whole Gulf of Maine.
