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Ecosystem/Bras d'Or Lake
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The Green Crab: Bothersome Bio-invader
Call it the “supercrab”: it can pry open oyster shells, dig up clams buried in the sand and devour up to 36 mussels a day. It feeds voraciously on bivalves, shellfish and other crabs, and tolerates a wide range of environmental conditions. It has already been blamed for the demise of the soft-shelled clam industry in the northeastern United States and is being implicated in the decline of shore crab along the Pacific Coast.
Now the green crab, native to Europe, has made its way into the inland Bras d’Or Lakes. The species grows quickly in the warmer water temperatures of the Lakes, and biologists fear that this bio-invader has the potential to disturb the Bras d’Or’s ecological balance. The Lakes’ oyster aquaculture industry, also under assault from the MSX parasite, is particularly threatened. Physically shielding small bivalves from the crabs may solve the problem: studies show that green crabs do not prey on oysters more than 60 millimetres in length or mussels of more than 45 millimetres.

The Great Bras d’Or’s Arctic Connection

Although the Great Bras d’Or Channel, the Lakes’ main opening to the sea, is considered to be an extension of the southern Gulf of St. Lawrence, its waters contain a surprising number of Arctic and sub-arctic species. Fauna profiles of the Channel have revealed that a significant portion of the waterway’s aquatic life dates back to the end of the last ice age, when Cape Breton Island was depressed and flooded with sub-Arctic waters. While about 35% of the waterway’s species are typical of those found in the Gulf of St. Lawrence, 50% are of Arctic or Arctic-boreal origin. Scientists have concluded that these “relict” species, surviving outside their normal range, have become isolated from their parent populations by the narrow, shallow channels of the little Bras d’Or Channel and St. Peter’s Inlet. Their presence in the Great Bras d’Or Channel demonstrates both the versatility of the inlet and the adaptability of the Arctic species.
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