By Christine Harris
Throughout North America new thinking about old enemies has led to innovative, and sometimes profitable, uses for some of the most noxious invasive species.
Those who spend time on the beaches or in the salt marshes along the northeast coast of the United States have likely encountered one of the most prolific and destructive marine invasive species: the European green crab (Carcinus maenas). Arriving in the Cape Cod area in the mid-1800s, it can now be found as far north as Nova Scotia and as far south as Virginia. The European green crab is a fierce predator and has contributed to declines of marketable species such as softshell clams, blue crabs, and lobsters and to a decrease in eel grass beds, an important marine habitat for many species.
Traditionally there has been little commercial value for green crabs due to the fact that they don’t have much appeal as an edible species for human consumption. Fortunately fishermen have recognized that a commercially valuable species, the American lobster (Homarus americanus), enjoys dining on green crab. A new commercial fishery has developed in Nova Scotia to capture green crabs for use as lobster bait. Currently 53 commercial green crab fishermen are registered with Nova Scotia’s Department of Fish and Oceans and a special trap has been developed for the fishery. With current market values, a fisherman needs to catch about 600 green crabs to make $100. This may sound like a lot of work for a small return, but take into account that one trap can catch over 1,000 green crabs in one night and you get a sense of how profitable the industry could be and of the abundance of these invasive crabs.
Deliberately brought to the Midwest in the 1970’s to clean up fish farms, invasive Asian carp species have become so prolific that the biomass in some stretches of the Missouri, Mississippi, and Illinois Rivers consists of 95 percent invasive carp. Carp eat low on the food chain which means that they disrupt the food supply of most other species where they are found. They have also proven to be a serious safety hazard to boaters. One of the introduced carp species, the silver carp, reacts to the sound of boat motors by leaping into the air. With some individuals weighing over 50 pounds these fish can do serious damage to a person or their boat.
Though flying fish may seem scary to some, they provide excitement for others, and thus the Redneck Fishing Tournament was born. This annual competition awards cash prizes to the fishermen who can net the most of these fish and works to lower their population at the same time. Though the tournament takes only a tiny dent out of the overall population, some are hopeful that marketing invasive carp species as an edible fish will help to decrease their abundance.
For those who are willing to give it a try, Asian carp are a palatable fish similar to cod in taste and texture. Recently a Parisian chef working in Baton Rouge, Louisiana has gotten federal approval to market the fish under the name “silver fin” to eliminate the stigma traditionally associated with the name carp. Currently no large scale fish processing plant can accommodate Asian carp, a species that is anatomically different from the fish those plants process now. If a processing plant were developed to process them, Asian carp could become a valuable commercial fishery, aiding in keeping the population in check.
There is no doubt that invasive species are one of the greatest threats to the integrity of ecosystems and the health of our environment. Though most will never be eradicated, with some ingenuity more invasive species could be put to good use and their populations reduced at the same time.