October 29, 2012
Fish Health Centers are a rather unknown part of the U.S. Fish & Wildlife Service (USFWS), though these low-budget laboratories dot the continental U.S. The USFWS first developed a fish health policy for its hatcheries in 1969. Over the next 10 years, training courses at the primary disease lab in Leetown, West Virginia, prepared trainees to return to their hatcheries and build labs to analyze fish diseases. In effect, these labs functioned as Centers for Disease Control for our fish populations. Fish diseases have decimated populations of bass, trout, salmon, stripers, and all other fish species, virtually shutting down major fisheries.
By the early 1980s, the laboratories and their staffs were consolidated into a system of centralized Federal Fish Health Centers. With the exception of Alaska, each of the USFWS's seven regions has at least one center.
The original charge of the Fish Health Centers was to monitor, inspect, and certify the health of fish raised in federal hatcheries and to advise states, tribes, and private aquaculturists on fish health problems. But as the roles of federal hatcheries have changed, so have the functions of the Fish Health Centers. Sophisticated and expensive tests are needed for viral detection, including the latest DNA analyses. Few state fish health laboratories can afford to conduct such tests, so the centers have experienced increased demands for their services.
Another shift in emphasis followed passage of the Endangered Species Act in 1973. Since then, state, tribal, and federal resource managers have used hatcheries to raise wild broodstock in order to bring listed and threatened fish back from the edge of extinction. Fish Health Centers ensure that hatcheries are not infected by the wild fish they bring in and that hatchery fish don't infect wild fish in the watersheds receiving stocked fish.
Fish Health Centers also are conducting more research on wild fish populations. An important impetus for this shift was the discovery in 1995 of whirling disease in both federal hatcheries and wild fish in Colorado and Montana. "Previously we'd focused on hatchery fish," says Crystal Hudson, project leader at the Bozeman, Montana, Fish Health Laboratory. "Wild fish were a missing piece of the puzzle. But whirling disease was occurring in wild fish, and that made it — and them — a major concern."
Whirling disease generated funding and research. The USFWS received a $1.5 million appropriation from Congress in 1997 to begin conducting a Wild Fish Health Survey that could provide baseline information nationwide on the health of wild fish populations. A second appropriation of $1.8 million was received in 1998, and $2 million is expected in 1999.
Mary Ellen Mueller, who wrote the proposal for the Wild Fish Health Survey funds, describes the program's goals: "Everything we knew about whirling disease was under hatchery conditions. We didn't understand the distribution of fish pathogens in the wild. But the Fish Health Centers put us in position to study them in order to meet the emerging needs of fisheries managers working with wild broodstock."
Like the federal Centers for Disease Control, Fish Health Centers are involved in epidemiological studies of disease as well as in clinical trials of new drugs to treat them. For example, Fish Health Centers can diagnose and in some cases treat deadly fish diseases like furunculosis, enteric redmouth, columnaris, coldwater disease, bacterial gill disease, and bacterial kidney disease in federal hatchery fish. They also can withhold certification to prevent the transfer of infected fish to other facilities or for release into the wild. In the case of nontreatable viral diseases, Fish Health Centers conduct virological testing and prevent the shipment of infected fish.
They also study new drugs. "It's difficult to get new drugs registered," explains John Thoeson, project director at the Pinetop Fish Health Center in Arizona. "We work closely with the Food & Drug Administration to get drugs tested and registered for use. But more of our work is preventive. For example, we're monitoring our region for whirling disease. So far, we haven't found it in Arizona, but adjoining regions have it, so our job is to prevent its spread to our hatcheries and waters.
"Our work also is restorative," Thoeson says. "One of our biggest challenges — as well as successes — is dealing with threatened and endangered species. The bonytail chub is probably the fish closest to extinction in this country. It's a difficult fish to culture, extremely delicate, and is easily stressed in transport. We collected four bonytails from Lake Mojave, and we're working to establish broodstock to revive the population. We're also working to prevent the extinction of razorback suckers, Gila trout, and Rio Grande cutthroat trout, so preventing the introduction of unknowns and pathogens into waters where these endangered species live is important."
Each region faces different challenges. In the Pacific Northwest, the first priority is to raise and release healthy salmonids. "From 90 to 95 percent of our returning salmon are hatchery fish," explains Bill Miller, complex manager for the Dworshak Fish Hatchery in Idaho. "Our wild stocks basically have been destroyed, so if we're to have any runs at all, they'll be from hatchery stock. That's why releasing only the healthiest fish is important.
"In the 1980s, we lost about 90 percent of our steelhead to infectious hematopoietic necrosis because it was present in the river water we used. It's now basically under control, except among sockeye. As for bacterial kidney disease, we cull spawners who test positive, so infection levels are down."
At the Lower Columbia River Fish Health Center in Washington, Susan Gutenberger agrees. "Bacterial kidney disease and infectious hematopoietic necrosis mortality depend on many factors. Whether or not they cause major disease outbreaks depends on water conditions, food, temperature, and other factors that stress fish." The importance of water quality, limiting fish densities in raceways, and minimizing handling to prevent stress are all emphasized.
"Integrating good disease control with captive rearing of endangered species is complicated," says Ray Brunson at the Olympic, Washington, Fish Health Center. "Recovery programs will depend almost entirely on captive rearing — but how can we do it without undue risk to existing hatchery stocks and to the wild fish we bring in? In the past, captive rearing was profit-oriented.
"Rearing programs now focus on optimal survival and health. In interior rivers of the Northwest, we're doing well if 0.01 percent of the salmonids we release return to spawn. On the coast, where hatcheries don't have dams or development to contend with, returns are higher — 5 percent for cohos and steelhead, 0.75 to 1 percent for chinook. But those numbers still remain dismal."
On the Atlantic Coast, a virus recently identified in Canadian pen-farmed Atlantic salmon threatens wild salmon stocks in Maine. John Coll, section chief at the Lamar, Pennsylvania, Fish Health Unit, speculates on its implications for the Northeast's troubled Atlantic salmon. "The virus was first identified in Norway aquaculture. We don't know if it was transferred from there to penned salmon in New Brunswick or if it migrated with wild Atlantic stocks. All we know is that we have to develop the technology to monitor our own brood stock."
Farther south, Fish Health Centers certify commercially raised grass carp as triploid (sterile) so they can be shipped to states that have banned fertile grass carp. Staff members also keep close watch on Pfisteria, zebra mussels, and Asiatic tapeworm, common among golden shiners in the Southeast since the 1970s. "Columnaris and furunculosis are common warmwater diseases, and we worry about whirling disease, too, because we have coldwater species in the mountains. More species than ever are being cultured in our region, and we're trying to determine what pathogens are of concern."
Challenges to Fish Health
"Ours is an agricultural region," says Richard Nelson at the Onaluska, Wisconsin, Fish Health Center. "We get windborne toxic material from crop spraying, and we have to determine the source of those toxins and the agricides running off into ponds. Sometimes we can offer advice; sometimes it's too late, as when aflatoxin gets into the feed and the fish can't absorb their food, ultimately starving to death.
"I see problems with baitfish in the future, because they're imported and often include several species, possibly immature sportfish, exotic ruffes, and gobies. As fish are moved from point A to point B, they may introduce health problems. We scrutinize salmon and trout, but baitfish have been overlooked. Some baitfish ponds are near rivers, allowing the fish and their diseases to enter new watersheds. Wisconsin is concerned about baitfish carrying parasites and diseases brought unregulated from out-of-state — worms, flukes, viruses.
"We've found whirling disease near Kalkaska on the Lower Peninsula of Michigan, near Lake Michigan," Nelson says, "and some whirling-disease-positive rainbows in hatcheries. The Great Lakes and Mississippi watersheds have huge recreational fisheries — $5 billion a year on the Great Lakes alone. Our Fish Health Center does the virological and bacteriological work for federal hatcheries in eight states, and waters from the Arkansas River to the Great Lakes.
"We're also studying threatened and endangered mussels, examining sea lampreys as possible vectors of disease, and training state, tribal, and private aquaculturists through our short courses and training manual. In the realm of fish disease, we have to consider the inter-relatedness of aquatic systems in North America. We can't afford to miss any links in the fish health arena."
* J.Z. Grover, Duluth, Minnesota, is a writer specializing in conservation topics.