If there were a social fish ladder, the slimy carp, which thrive in pollution-filled waters, would surely occupy the bottom rung.
But when federal officials moved to put one variety on the list of invasive species, they opened a can of worms. The effort had the potential to restrict sales of the carp.
The Asian black carp has been used on fish farms for more than two decades — not because it tastes good but because it has a taste for snails, which carry parasites that can kill or otherwise hurt their crop like a boll weevil damages cotton.
Without another option to control the snail population in their ponds, fish farmers feared the worst for their industry, which is one of the few economic success stories in the otherwise poor Mississippi Delta.
That region accounts for more than 90 percent of domestic catfish production, which in total generates an estimated $3 billion in economic power.
“This is one of the few industries that shows real promise in this region,” said professor Carole Engle, the director of the aquaculture and fisheries department at the University of Arkansas at Pine Bluff.
But in what soon became another fault line in the battle between environmental protection and economic development, the United States Fish and Wildlife Service (F&WS) worried the carp had the potential to wreak havoc on native species if they ever escaped the confines of the farm and moved to limit their use.
In addition to snails, the carp, which can grow to be as long as 5 feet, also fancy freshwater shrimp and crawfish. The carp could cut the food supply of native fish, birds, raccoons, otters and muskrats, officials feared.
The government’s initial proposed rule would have prohibited interstate transportation of the black carp, stating that the “likelihood of release or escape of black carp is high.”
Federal officials worried in particular about local mollusk populations, many of which are endangered. The Mississippi Interstate Cooperative Resource Association, a group of natural-resource officials from 28 states in the Mississippi River basin, was the first to call for blacklisting the black carp in a Feb. 24, 2000.
“This Asian carp species has the potential to adversely impact endangered mollusk populations and perhaps even drive some species to extinction,” the group said.
But although F&WS officials first proposed a rule to limit use of the carp in 2002, the rule remains just a proposal, as Delta farmers mounted a fierce campaign against it.
Members of Congress who represent the region — including Sen. Blanche Lincoln and Rep. Marion Berry, both Arkansas Democrats — sought out meetings with F&WS officials to express their concern about the initial proposed rule.
Engle wrote a 13-page rebuttal to the rule, which she called appalling for both inaccurately identifying the type of parasite in question and for its use of “inflammatory and exaggerated” language to depict the environmental threat the black carp represented.
“It’s politically correct to oppose all types of invasive species,” Engle said.
In total, the proposed rule spawned 103 responses. The strong opposition forced federal officials to extend the comment period by several months and otherwise put off a final decision.
Two weeks ago, the F&WS released a new series of questions it sought comments on.
One key complaint with the original rule was that it did not distinguish between the diploid and triploid varieties of black carp.
It’s a key distinction. The diploid can reproduce, but the triploid is sterile.
Advocates of putting the black carp on the injurious-species list say that even if sterile fish get out they can still cause problems. The fish can live as long as 15 years and can eat 3 to 4 pounds of mollusk a day.
But critics told Office and Management and Budget officials, who are reviewing the proposed rule, during a meeting in July that limiting the use of black carp would have dire consequences on the industry.
White pelicans are thought to be the original carrier of the parasite, which is thought to be bolbophorus damnificus. The birds leave the parasite behind in the water. The parasite then attaches itself to the snail, an intermediate host. The parasite becomes free-floating and can penetrate the fish.
A recent Mississippi State University study surveyed 1,500 fish farms. It found that 30 percent were infected with the parasite.
Yields decreased 25 percent at infected fish farms, the study found. Even if the fish don’t die from the infestation, the research led to a troubling new finding: Infected fish don’t eat as much as healthy fish.
“Farms cannot survive a 25 percent drop in production,” Engle said.
Both sides acknowledge there is reason to be concerned about black carp getting out. But Mike Freeze, who co-owns Keo Fish Farms in Arkansas, said the best way to ensure the black carp doesn’t create havoc in the wild is to limit the ones that reproduce to a small area.
Sterile varieties, which pose less of a risk, should be allowed to be transferred state to state to help farmers fight against a disease that could easily ruin their business, he said.
There’s nothing sacred about this black carp,” Freeze said. “If we could find a chemical or a native fish that would work, we would gladly switch to it.”