Grand Banks Cod Stocks Rebound After Thirty Years

The great news is that the Grand Banks Cod fishery is certainly recovering, or more correctly it is returning to its natural balance.  I suspect that another decade will see a full restoration including the reemergence of the larger fish.

As one reads through this article, one sees that the lessons learned are remarkable and important.  One must mange the whole biome and very carefully pick one spots to harvest stocks so as not to place downward pressure on any particular stock.

The reality is that the biome produces a huge surplus that can be easily harvested every year provided we maintain the correct balance.  That means harvesting a wide range of species to the appropriate level.  I think we understand this now and I think that the fishing lobby is sufficiently chastened to actually work closely to ensure that this is what happens.

What this means is that after thirty years of rest, we can now look forward to rebuilding a healthy and vibrant fishery over the next twenty years that will be an example to the world on how to properly do it.  At least we now have a chance to get it right and know some of our limits a little better.

East Coast cod stocks slowly returning to normal – scientists

Published Friday July 29th, 2011

By MARGARET MUNRO

Postmedia News

http://dailygleaner.canadaeast.com/cityregion/article/1427538

Canada's fabled East Coast fishery, which was feared to be gone forever, is showing "very positive" signs of recovery, according to scientists.

There are now so many cod, haddock, pollock and other benthic fish (also known as groundfish) in the waters of the Scotian Shelf off Nova Scotia that their total biomass has "attained levels approaching those observed during the pre-collapse period," a team led by Kenneth Frank at the federal Bedford Institute of Oceanography in Nova Scotia, reported Thursday in the journal Nature.

Atlantic cod and redfish have reached levels not seen since the early 1990s and haddock is at an unprecedented high, the scientists said.

The study is sure to ignite debate over lifting the fishing moratorium, but the researchers said the recovery still has a long way to go.

While there are lots of fish, they tend to be much smaller than they used to be, said co-author Brian Petrie, also of the Bedford Institute.

Five-year-old cod are 60 per cent the size they were before fish stocks collapsed in the 1990s, and haddock are 40 per cent of their pre-collapse size at the same age.

It isn't known why the fish are so small, Petrie said, but one of the prevailing theories is that overfishing killed off the big fish leaving behind fish that could slip through the nets and were genetically predisposed to be small.

Those small fish were left to rebuild the stocks.

The scientists said another surprise in the "unfolding drama" on the Scotian Shelf is that haddock is the dominant species, while cod is in the No. 2 spot.

It's an open question whether the species makeup will ever return to the way it was before, they said, but overall, the changes in recent years are "very, very positive," Petrie said in an interview.

"The answer to the critical question of whether or not such profound changes in the dynamics of large marine ecosystems are reversible seems to be 'Yes'," the team reported.

Petrie, Frank and their colleagues spent years charting the changes on the Scotian Shelf that accompanied the demise of the East Coast cod stocks in the early 1990s.

In 2005, they reported that it was an open question whether the fish stocks would ever return.

For centuries, cod was the most abundant predator fish in the East Coast marine ecosystem and supported a thriving fishing industry.

The stocks, which were still plentiful in the early 1980s, crashed a few years later, and a moratorium was placed on cod fishing in 1993.

Fish managers and fishing communities hoped the cod would bounce back if nets were kept out of the water for a few years.

The scientists said it has taken far longer than expected because the decimation of cod stocks had a domino effect that radically restructured the marine food web - the first time such a "trophic cascade" had been documented in an open-ocean ecosystem.

Petrie said the recovery was seriously hampered by small fish such as herring, capelin and sandlance that flourished on the Scotian Shelf in the absence of bigger predatory fish such as cod.

"They just exploded," Petrie said, noting how the biomass of small fish at one point in the 1990s reached 900 per cent of the pre-collapse biomass.

The small fish inflicted serious damage on the remaining cod and other benthic fish by swallowing their larvae and young in a phenomenon known as predator-prey reversal.

Petrie likened it to a deer eating wolf pups.

The populations of small fish eventually crashed because they had overgrazed their food supply, and this allowed more of the young cod, haddock and other predatory fish to survive.

Petrie sidestepped the question of when the ecosystem will be healthy enough for fishing to resume, calling it "very loaded" and saying it will be up to fish managers and politicians to decide.

"One is hopeful that things could be better managed in future," he said, noting that much has been learned by studying the demise of Canada's cod, which used to support one of the world's great fisheries.

"One of the important lessons is that you have to manage ecosystems," Petrie said, "not single species."