Warming of the Gulf of Maine

The Gulf of Maine certainly tracks us closely.

For at least some thousands of years before the Europeans invaded a few hundred years ago, the ecosystem of the Gulf of Maine was dominated by finfish, particularly cod and haddock. They kept crab and lobster numbers under control, sea urchins were abundant and kept macroalgae from flourishing, resulting in extensive expanses of crustose coralline algae, impervious to sea urchin grazing.

Cold water sweeps counter-clockwise around the Gulf of Maine (oceandata.gmn.org)

Cold water sweeps counter-clockwise around the Gulf of Maine (oceandata.gmn.org)

Though the finfish were mostly fished out by the 1980s, tight regulations, including the moratorium on cod fishing that began in the early 1990s, have not resulted in their recovery.

Then in the late 1980s a boom-and-bust virtually unregulated sea urchin fishery occurred, feeding the yen of the Japanese for high quality sea urchin gonads. That fishery peaked in 1993, and by the end of the decade few sea urchins were left in the Gulf.

Green sea urchins once were hugely abundant in the Gulf of Maine, but now few are left (allposters.com)

Green sea urchins once were hugely abundant in the Gulf of Maine, but now few are left (allposters.com)

As a result of all of this, the top predator finfish were fished out, the single dominant herbivore, the sea urchin, was fished out, and the ecosystem flipped to a new and apparently stable state, lacking both the fish and the sea urchins. Instead macroalgae, especially kelp and Irish moss Chondrus crispus grow everywhere. The macroalgae provide excellent nurseries and cover for crabs, dominated by one species, the Jonah Crab, Cancer borealis, and excellent cover for juvenile lobsters as well.

Attempts to reseed sea urchins have failed because Jonah crabs surged in and ate them all. Crabs and lobsters are now the top predators, and are likely to remain so until finfish return.

And now the Gulf community is experiencing the warmest temperatures on record.

The lobster glut continues, and this summer lobster shell-disease has been noticed in a very small number of lobsters in the southern Gulf of Maine. This is a bacterial infection that disfigures the lobster’s carapace – it doesn’t effect meat quality, but it sure can make a boiled lobster on your plate look very unappetizing. The shell-disease is common in lobster populations in southern New England, with 20-30% of the animals infected, and predictions are that as the Gulf warms the disease will spread north.

The lobster shell-disease has arrived in the southern Gulf of Maine (newenglandboating.com)

The lobster shell-disease has arrived in the southern Gulf of Maine (newenglandboating.com)

Another sign of the warming of the Gulf involves the small and sweet Northern shrimp, Panadalus borealis, which live in the northern colder seas of the world in both the North Atlantic and the North Pacific. The Gulf of Maine has been as far south it has lived on the on the American coast, where it has been caught nearshore in mid-winter for decades.

The shrimp fishery has actually been tightly regulated – we don’t mess up every fishery through ignorance and overfishing. But last winter, though the total available quota was considerably decreased, the fishing fleet could not even catch the amount that had been allocated. The shrimp are very temperature sensitive, and they have shifted north, out of the Gulf.

What’s ahead for the Gulf? Colder water species like cod and northern shrimp will continue to respond to the warmer water by moving north. Crabs and lobsters will continue to flourish as sea urchins fail to re-establish themselves. The shell-disease of lobsters will move north through the Gulf. Other players of no economic value in the ecosystem, like starfish and sand dollars, will retreat further away from the shore into deeper, colder water. Macroalgae will will continue to flourish.

Nostalgia for the stable community that once was is wasted energy. The various species around us in the Gulf of Maine will die, depart, invade, and perhaps even adapt in response to never-ending resource exploitation and now climate warming.

We have learned to expect the unexpected. Of course this is true everywhere else as well. We just are documenting it more closely in the Gulf of Maine.

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