Right on top of the concerns about big “W” ? chronic wasting disease in deer (Feb. 16 column) ? comes the other “W” ? whirling disease in trout. Unlike CWD, which is not yet in Maryland, whirling disease is here and likely here to stay for awhile.
The disease infestation required destroying 83,000 trout in the state Bear Creek rearing station and a state-used privately owned hatchery. This brings the total number of trout to be stocked for this season down from 420,000 to 337,000 fish, an approximate 20 percent reduction.
The disease parasite eats the cartilage in the skull and spine of trout, deforming their skeleton to cause them to swim in circles, thus the name of the disease. It does not affect humans.
Whirling disease is another of those nasty invasive species, the parasite Myxobolus cerebralis, which landed here with imported brown trout. Brown trout, another invasive species (but one we like), have been imported since the late 1800s.
Through evolving with the disease in Europe, brown trout are basically immune to it. The disease affects rainbow trout and can affect brook trout in hatchery situations. Approximately 90 percent of trout stocked in Maryland are rainbows; about 10 percent browns.
The whirling disease parasite arrived in western states in the 1950s, according to Bob Lunsford, the Maryland Department of Natural Resources director of freshwater fisheries. A host for the parasite is bottom-living tubifex worms, commonly sold as fish food by pet stores. Young fry and fingerling rainbow trout, which hatch in the spring, eat the worms, which are infected with the parasite. Fall-spawning brown and brook trout are not as likely to eat the worms during winter months.
While trout and fisheries managers must solve the disease problem, trout fishermen can help prevent its spread. First, Lunsford suggested that trout anglers should not “take a year off” just because fewer trout will be stocked. He noted that the fisheries service relies heavily on license sales, and any reduction of funds delays recovery of the fishery and elimination of the disease.
In addition, trout anglers can do several things while fishing:
» Do not clean trout along a stream, since this can reintroduce the disease into the water.
» Clean all fishing gear and boots with stream water before moving onto a new stream. Mud in the cleats of waders or hip boots can carry the host tubifex worms to new areas.
» Don?t conduct your own “stocking program” by moving trout from one body of water to another, since this can introduce infected trout to uninfected streams.
The good news is that trout managers, assuming a normal year in rainfall and other conditions, expect that they can prevent future infestations. Stockings next season should be up to the 420,000 fish norm.
“We?re taking steps to disinfect the Bear Creek rearing facility, and we will begin a wild trout survey to determine the extent that [whirling disease] is found in the wild,” Lunsford said.
C. Boyd Pfeiffer is an internationally known sportsman and award-winning writer on fishing, hunting, and the outdoors, and is currently working on his 25th book. He can be reached at [email protected].
