Crab Wars

Introduction of foreign species to an ecosystem is usually very dangerous. The new species often has fewer predators and can disrupt the balance of resources, endangering the survival of native species. This was the case with the European crab when it came to New England by ship in the 1800s and spread throughout the southeast United States and eastern Canada.

Where one foreign species is dangerous, two can be catastrophic. In Hawaii multiple invading birds drove into extinction the plants they fed on, and native bird species that relied on them. So when the Asian crab landed in New England in the 1980s, environmental biologists kept close watch. What they observed was not the ecological carnage they expected however. The two crab species actually did far more harm to one another than to their environment. The two crabs have different diets, the European eats soft shelled clams (the same diet of the native crabs) while the Asian eats algae. They favor the same habitats however. Asian crabs were seen displacing many European crabs from their homes in rock caves which in turn reduced the time they could spend feeding. When the crabs were unable to grow to the sizes they were used to without the competition, they became more likely to fall to predation.

In the past a method of dealing with dangerous invading species has been introducing a natural predator of the invading species to keep it under control. This technique has a major drawback however, in that the predator is another invading species that can cause disruption. This crab study has demonstrated that it may be better to try to introduce a species that competes with the invader for food or habitats, rather than direct predation, so that both species can hinder each other in order to keep the overall impact on the ecosystem smaller.

Posted by Jon Hicks (6)