With its mild flavour and dense, flaky, white flesh, Cod has been a popular staple of the New England Fishery. However, it has been declining in the recent decades. Regardless of repeated attempts of rebuilding the stock, assessments suggest that the species has not recovered. Cod in the Gulf of Maine can be divided into two genetically-distinct groups and according to a new study, understanding the unique behavior and life cycles of these two groups may be the key to creating a better management strategy.
Micah Dean is a doctoral student at the Marine Science Center of the Northeastern University. He led the study and is of the belief that these subpopulations are dramatically different from one another, and the mix of these subpopulations change over space, season, and time. This sort of complexity needs to be accounted for. Incorporating the differences between these two groups into population models could improve management decisions. Those decisions are vital for the survival and recovery of the fishery.
Dean and his colleagues wanted to know if ignoring any differences between the subpopulations could lead to flawed management decisions. They found that they could tell the difference between spring-spawning cod and winter-spawning cod using a small structure inside the fish’s head, called an otolith. Otoliths help cod with orientation and direction in the water. Winter cods have a full year of growth before their first ring, while spring cods have only six months. Over 1,600 otoliths were examined.
Though several important differences were found, one result was particularly surprising. The oldest, largest fish in the population seemed to be spring cod, which spent more of their time in areas of the Gulf of Maine that were closed for fishing. Old, large fish are usually considered the most important to protect in a population. However, the majority of the young fish caught in recent years were winter cod.
“Gulf of Maine cod doesn’t have a great track record—the stock has been overfished for decades and hasn’t responded well to the management actions that we’ve put in place. I’m really hopeful that this will uncover some pieces that were missing when we were managing and assessing the stock in the past”, concluded Dean.
Shahjadi Jemim Rahman
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