For Vince Smith, owner of Nemo Bait Co. in northeast Missouri, all crayfish were pretty much the same.
That is, until the fall of 2003 when he retrieved a batch of crayfish sold to more than a dozen bait stores from Kirksville to St. Louis, put them in garbage bags and killed them.
The executions, which Smith conducted in a walk-in freezer, came after the Missouri Department of Conservation told Smith that his company was supplying bait stores and anglers with rusty crayfish, an exotic species that could potentially hurt the state’s fish population.
Nemo Bait purchased the crayfish from a Wisconsin supplier.
“We destroyed them all,” Smith said. “Every place we had sold them, we picked them up and refunded all their money.”
The rusty crayfish is one of several fish that will soon be illegal to possess in Missouri because of their status as invasive species. The list includes snakehead fish, zebra mussels and the brushtail possum, as well as various mammals, birds and invertebrates.
Invasive species, which can include plants and animals, are exotic species that cause environmental or economic harm. In the case of the rusty crayfish, that means destroying the plants that other fish rely on for food as well as a habitat conducive to spawning and nursing.
A new rule in the state’s wildlife code that makes it illegal to possess invasive species is scheduled to take effect Sept. 30. Although Missouri already has regulations on invasive plants, this is the first state law regulating invasive animals.
Under the wildlife code, it has always been illegal to release animals into the wild. The possible damage caused by invasive species is so severe that the animals on the list may no longer be kept as pets or used as bait because of the risk of their release, regulators said.
“With the exception of endangered species, we’ve never before had any regulations on what’s held in aquariums or kept as a pet,” said Mike Kruse, a state fisheries programs supervisor who helped draft the list. “For some animals ... the risk of them becoming invasive is so high that we can’t risk them being kept as pets.”
Most of the species banned on the list are on a federal list of injurious wildlife species, Kruse said.
Once introduced, an invasive species may out-compete the local wildlife population or decrease it by spreading diseases. Invasive species impact almost half of the threatened or endangered species on the federal list, according to the National Invasive Species Council.
The U.S. Fish and Wildlife Service estimates that invasive species cost the United States $100 million in damages annually. Invaders can interfere with businesses, too. Zebra mussels, for example, attach themselves to pipes, docks, boats and wildlife, suffocating native animals and costing industries.
Bob DiStefano, a resource scientist for the Missouri Department of Conservation who specializes in crayfish, visited lakes in Canada where walleye and bass used to live before rusty crayfish invaded.
“The fisheries crashed,” he said.
Once a population is established, invasive species are extremely difficult and costly to remove, experts say.
For aquatic invaders, one way to eliminate them is to kill all organisms in the affected stream, DiStefano said, although this radical step is rarely taken.
For animals that fly or move on land, this measure is unavailable.
States have enacted regulations to try to keep invasive animals outside state borders. Many of the animals on Missouri’s list are already prohibited in other states.
“You have to be proactive,” said Chris Taylor, who studies invasive species for the Illinois Natural History Survey, a branch of the state’s Natural Resources Department. “You have to look at other states’ experiences with them and get them on a list before they move in.”
Because these animals can travel across state boundaries through waterways or interstate pet trade, some believe a unified approach is necessary.
“Species don’t stop at a country border or a state border,” said David Lodge, the former chairman of the National Invasive Species Advisory Committee and a biologist at the University of Notre Dame. “In some senses, the protection (for a state) is only as good as the weakest state in the region.”
The National Invasive Species Council was created in 1999 to deal with these invaders. This council, which spans several federal departments, drafts a management plan every two years to provide a coordinated effort to prevent the introduction of invasive species and minimize the harm caused by them.
Lodge would like to see a screening process to determine which species should be let into the country.
“We need to be moving toward making deliberate decisions on each species as opposed to our current default policy which is to let in every species until we learn — by painful experience — that they’re harmful,” Lodge said.
The conservation department has sent letters to pet shop and bait shop owners notifying them of the newly prohibited species. Initially, people will not be prosecuted as long as they give up these animals, administrators said.
The only way someone could legally possess one of these species would be with the written approval of the director of the conservation department.
Individuals who discover that they possess a species on this list should contact their conservation agent.
Terry Roberson, the conservation department’s field chief for its protection division, said initially the department is focusing more on educational efforts than enforcement. However, he added, visits to pet shops or bait stores to check for these species are “not out of the picture.” Additionally, the conservation department responds to complaints regarding these species, he said.
Possession of one of these species is a Class A misdemeanor, the maximum penalty being $1,000 and a year in jail.
A portion of this report first aired Wednesday during the “ABC 17 News at 10.”
For a complete list of the newly prohibited species, go to the Missouri Register online at www.sos.mo.gov/adrules/moreg/current/2005/v30n11/v30n11b.pdf