Two stories on cod in North American have appeared this week. In an article entitled Northern Cod Comeback, George Rose describes the changes in the abundance of this stock in the last 30+ years. The collapse of the northern cod fishery in Canada and the subsequent moratorium was the poster child for fisheries failure in the 1990s, and the failure to rebuild for almost 20 years a source of much mystery. The collapse was ascribed to a perfect storm of overfishing combined with unfavorable, colder temperatures and the collapse of the main prey species, capelin. But what was once one of the largest fish stocks in the world is coming back, with large spawning aggregations and large old fish reappearing. Water temperatures have warmed and the capelin stock has rebuilt.
Another paper appeared this week on cod in the Gulf of Maine with quite a different story. This stock is in terrible shape, again due to a combination of overfishing and temperature. However, in this case it is still too warm for the cod. Gulf of Maine cod are at the southern end of cod’s range in the U.S. and Northern cod at the northern end, so warmer years are good for Northern cod, but bad for Gulf of Maine cod.
The lesson from both of these papers is that rebuilding the stocks to historical levels depends both on fisheries management reducing harvest to sustainable levels and on the return of favorable environmental conditions.
