And now, let’s take a look at some of the worst offenders and most invasive species!

Shore Crab (the image above the title is a Shore Crab)

This handsome lad originates in the northeast Atlantic and the Baltic Sea and has spread to places like Australia, South America, and South Africa. Shore crabs cause an estimated average of $22 million a year in damages in the U.S. alone due to the effect they have on aquaculture and fisheries, feeding on mollusks, worms and small crustaceans.  In addition to this, in some areas they prey on oysters and Dungeness crabs or simply out-compete them for resources. If the name Dungeness crab rings a bell, that’s because it’s among the most popular items on many seafood restaurant menus, and oysters have been enjoyed by humans for about as long as we’ve been living along coastlines. The Green Shore Crab we talked about in the last lesson is a prime example of this ‘most wanted’ invader.

So how are we fighting back?  Rather ironically, we’re cooking them.  But there’s a slight problem with that strategy:  they aren’t very good, especially compared to other native crab which they are displacing.  There are, however, studies into ways to integrate them into other sea foods as a way to sort of boost food volume by adding the cheap, less flavourful crabs into foods like soups, fritters, and stocks.

Northern Pacific Seastar

Everyone knows the Seastar, sometimes called starfish, but what you might not know is they eat everything in their path, ravaging the environment. This seastar, which comes from Russia, China, Japan, and both South and North Korea, has become a real problem on the coasts of Australia. They arrived by way of the ballasts of ships and consume practically everything, causing a huge amount of ecological harm.

Part of the problem with Seastars is that they have voracious appetites, eating virtually everything in their path as they move along through an environment. That means, that as they travel, they devastate the food sources of all of the native species, leaving little or no food behind to support the locals.

 Rainbow Trout

The rainbow trout, which is native to North America, was introduced for either aquaculture or recreational purposes and can now be found everywhere from the Arctic Circle to areas around the equator such as Kenya and Uganda. Unfortunately, the rainbow trout can spread disease, feed on local fish, and even cause hybridization (breeding between species), which is threatening some species with extinction.

Killer Algae

It’s not just fish and snails and mollusks; sometimes underwater plants can cause just as much damage. Take for instance Caulerpa Taxifolia, better known as Killer Algae. A strain of this green seaweed, native to the Indian and Pacific Oceans, has escaped from public and private aquariums in California, Japan, Australia, and Monaco. It has spread widely in the Mediterranean, replacing native plants and depriving marine life of food and habitat they were meant for. In California, it was eradicated at considerable cost using toxic chemicals, which is obviously little better for the environment.

So now we’ve seen several examples of invasive species and the harm they can do.  What can we do to prevent these aggressors from taking over?