New England Fisheries

To Rebuild Cod, We Must Stop Overfishing

Image via NOAA.

The Gulf of Maine is warming faster than 99 percent of the global ocean. The Gulf of Maine cod population has plummeted to historic lows. Are the two connected? A new article in Nature says no.

Comparing the North Sea cod recovery to the continued decline of Gulf of Maine cod (two stocks that were originally on the same downward trajectory), Keith Brander from the Technical University of Denmark argues that the difference in current stock conditions is due to fishing pressure, not climate change.

This position is in contrast to a widely cited 2015 article published in Science by Pershing et al, which argued that warming water temperatures have directly impacted Gulf of Maine cod stock size.

Even though the Gulf of Maine is rapidly warming, Brander says that both cod populations have experienced high temperatures. But while the Gulf of Maine cod population continues to struggle, the North Sea cod population is thriving. In fact its spawning stock biomass has reached a 35-year high. Brander argues that the North Sea cod recovery is the result of reduced fishing mortality since 1999. Over the same time period, however, fishing mortality of Gulf of Maine cod continues to be above a sustainable level, sometimes as much as three times higher.

Brander’s argument is simple: sustained high levels of fishing will decrease population size and sustained low levels of fishing will help population size increase.

Unfortunately, fishery management decisions in New England are heavily influenced by industry, and the climate change argument has become a distraction from solving the real problem that’s facing Gulf of Maine cod – overfishing. As Brander says, “Concern has been expressed that if climate change is viewed as an overwhelming factor causing decline in the Gulf of Maine cod stock then the case for enforcing a recovery strategy, by reducing fishing mortality, may be weakened.”

Let’s be clear, though, climate change does matter, and fishery managers should pay attention to its impacts on fisheries (as Pershing et al argued in 2015). Warming water temperatures are leading to population shifts, changes in growth and reproduction, and new predator-prey relationships. These impacts are just more reasons why we need to manage fisheries holistically and think about each stock as part of the larger ocean ecosystem.

It’s past time, however, that fishery managers in New England take a page out of the North Sea’s book. If Gulf of Maine cod – a stock that has been overfished for decades – are ever going to rebuild, a low level of fishing mortality must be sustained. We must stop overfishing.


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