Trout disease found in Md. for 1st time


November 02, 1995|By Peter Baker | Peter Baker,SUN STAFF

Recently, a routine screening of trout being raised by the Department of Natural Resources found a small group of fish that had been infected with whirling disease, which can lead to fish being unable to feed and susceptible to predation.

Whirling disease, according to DNR, is caused by a protozoan parasite that attacks cartilage in the head where the fish's balance is controlled. Once infected, a fish may begin to whirl or chase its tail and be unable to function normally.

The disease, which was isolated in a group of fish that had been temporarily placed in net pens on the North Branch of the Potomac River, is not a threat to humans and cannot be transmitted from fish to fish.

This is the first known incidence of whirling disease in Maryland, although 20 other states, including Pennsylvania, West Virginia and Virginia, have reported trout with the infection.

The disease has created a stir among biologists and sportsmen because the infected fish were found in the net pens near Jennings Randolph Dam. In the stretch of the North Branch below the dam, Maryland has been creating a world-class trout fishery from what once was virtually a dead river.

DNR says, however, that whirling disease does not pose a threat to that fishery because it is based on wild brown trout, which are resistant to the disease, and rainbows that are stocked at an age when they cannot be affected by the disease.

DNR is testing fish from all state hatcheries and wild fish from the North Branch to ensure that the infected fish have been isolated.

While the disease cannot pass directly from fish to fish, spores released from dead infected fish may live in river bottom sediments for years before they are eaten by a Tubifex worm, which allows the spore to change into the parasitic form that can attack other fish.

Trout Unlimited suggests the following precautions for fishermen, who might unknowingly help spread the spores or Tubifex worms that are the host for the parasite.

* When leaving the water, wash off waders, boots, boats, trailers and gear with fresh water or a weak solution of water and chlorine bleach.

* Drain water from boat bilges, coolers, live wells, etc.

* Don't transfer fish from one body of water to another because there is a possibility that even baitfish can carry the infection in some form.

Fall turkey season opener

Maryland's fall hunting season for wild turkey opens Saturday in areas of the state west of I-81 in Washington County, and DNR game managers say conditions of flock and feed could produce a hunt as good as or better than last year's.

Mast crops throughout most of Western Maryland are good, which means that turkeys will be spread out rather than concentrated in limited areas with good feed.

Brood surveys revealed that turkey production this spring was similar to that of 1994 and birds should be plentiful, including good numbers on public hunting lands.

Last year Maryland's 9,000 turkey hunters took 559 birds, with Allegany County recording the highest kill at 281.

Savage River State Forest (Garrett), Green Ridge State Forest and Dan's Mountain WMA (Allegany), and Indian Springs WMA (Washington) are among the more popular public lands for turkey.

The season closes Nov. 10.

Young-of-the-year index

Each year fisheries biologists survey the rockfish's four major spawning areas in the state to determine reproductive success. The results of the net surveys are called the striped bass young-of-the-year index, and for the fourth successive year the JTC result is above the nationally recognized level that indicates a healthy striped bass population.

This year the survey, which includes 22 sites in the Upper Bay, Choptank, Potomac and Nanticoke rivers, produced an average of 9.3 young of the year per pull of the net, well above the index level of 8 that federal and state fishery managers say shows a healthy rate of reproduction.

The 41-year average for the index, however, is 9.6.

The upper bay was the only system in the survey with a below average result this year, reading 4.4, far below the long-term average of 12.2. In 1993 and 1994, the upper bay had levels of 23.0 and 23.5, and fisheries managers say that those strong year classes will offset the poor reproduction of this year.

The three other major spawning areas all were above long-term averages -- Choptank, 17.7-12.5; Nanticoke, 10.5-6.5; Potomac, 8.7-7.2.

Baltimore Sun Articles
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.