A: There are many ways animals can be introduced into new habitats. Ships coming from faraway places can carry organisms that have attached to their hulls or that they’ve carried in their ballast waters. Ballast water is ocean water taken up by an empty ship to help maintain the correct balance and buoyancy in the ocean. This water is then released when the ship takes on cargo or additional weight.
Unhappy aquarium owners who dump the contents of their aquaria into a local lake, river or even the ocean to set their pets free can introduce new species too. For instance, there’s a species of algae that has clogged beaches in the Mediterranean. Now it is showing up in California after being introduced here that very way. Even fish that are raised in farms, like salmon or trout, may escape into the wild.
Animals invading the habitats of others are an increasing problem. Usually an invasive species can take over in a brand-new place because it has the ability to adapt quickly and easily to a new environment. Why is this bad sometimes? Imagine a crab species living in a bay with just enough food or space available to survive. Then a new kind of crab is introduced into the same habitat. This new species may be bigger and faster than the old one and outcompete it for food or space. This new species could quickly take over.
A different problem may arise when a species such as a mussel is introduced into a new habitat with no natural enemies. Its population can grow to huge numbers, causing all sorts of problems like clogging water lines, damaging piers, or overgrowing the settlements of other mussel species.
The monetary damage created by invasive species on fishes that people eat, on the fishes’ communities, and industry has reached many billions of dollars. Learn about the native species in your area and be aware when new species are introduced.
Horst Felbeck, Marine Biologist
Marine Biology Research Division
Scripps Institution of Oceanography, UC San Diego
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