Those transfers included parasites, which cause rashes, and the Asian clam, which altered the entire food web in San Francisco Bay.

运送来的生物包括爆发繁殖的寄生生物，还有威胁整个旧金山港食物网的亚洲蛤。

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More recently, the federal government, along with Delaware and New Jersey, tried to improve the wild-shellfish habitat by dropping millions of clam shells into the bay, which helps oysters mature by giving the larvae something to attach to.

WSJ: Planting Seeds for a Better Oyster Harvest