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July 24, 2001 BY THE COLORADO DIVISION OF WILDLIFE DENVER — Colorado Division of Wildlife officials are asking anglers to help in minimizing the effects of a disease that is affecting trout in some of the state’s rivers. Hot summer temperatures and low water levels are causing some trout to die from a disease known as furunculosis. The disease is taking its toll on both rainbow and brown trout, especially in the Eagle River corridor. The bacterium that causes the disease exists in most of the major rivers in Colorado, but is stress mediated. In the case of the Eagle River, the outbreak is believed to be caused by warm temperatures, low water flow and a concentration of heavy metals or pollutants or both. Furunculosis is a circulatory bacterial infection. The causative bacterium is contained in the slime on fish in most major river corridors. It is usually not a threat to the fish until they are stressed in some way. Brown trout are the most susceptible and it is usually the largest most valuable individuals that succumb before the smaller ones. Angling can cause a furunculosis die-off to be more severe. Stress from improper catch and release practices can seal the fate of fish under such trying circumstances. Anglers are asked to do what they can to keep trout from dying, especially on the Eagle. If the temperature on the Eagle gets above 70 degrees anglers are asked to fish other bodies of water such as Sylvan Lake and Brush Creek. Outfitters on the Eagle are being alerted to the problem. Currently, the water temperature on the Eagle is holding steady in the low to mid 60’s. Pete Walker, senior fish pathologist for the Division, said the summer die-off is occurring throughout the state. "I have been receiving reports from fishery and field troops almost statewide of mostly minor fish kills in all types of waters," Walker said. "I may find an assortment of pathogens and environmental insults if I am able to investigate each case, but the real cause behind it all is almost certainly the nearly 3-week period of hairdryer weather that we recently suffered statewide. As one of my mentors used to say, ‘stress compounds exponentially.’" Division officials conducted saturation patrolling while floating the Eagle River on the 6th and 7th of July and got reports of dead fish in the Eagle River, between Edwards and Wolcott, and on the Colorado below the Pumphouse. On the section above Gypsum on July 10th, there were three dead fish found in 10 miles. From Edwards to Wolcott water temperatures were 61 to 64 and in the 6-mile section a total of 17 dead trout were found. Visibility was excellent and officers estimate they netted 95 percent of the dead fish present. 16 of the fish were brown trout and one was a rainbow. Four of the brown trout showed obvious furunculosis lesions. Three showed no obvious cause of death. The rest were severely overgrown with Saprolegnia fungus, and several exhibited the fungus in finger-like patterns on their sides. "Had we done the Edwards-Walcott float on the 8th we would doubtless seen more dead fish," said Alan Czenkusch, area fishery manager. "It is likely that this monsoon flow is a respite rather that an end to the problem. When the pattern changes and it gets hot again, we’ll see more corpses." The last major furunculosis kill in the Eagle River was reported in 1987. It was a more severe event. There have also been major outbreaks in the East River and The Rio Grande in the past. Fishing pressure could be playing a major role in the die-offs as officials reported that the numbers of dead fish were directly related to areas known to have high fishing pressure. "We would like to see people catching brook trout in the streams at higher elevations," Walker said. Bob Nock, owner of Eagle River Anglers, a fly shop and guide service in Eagle, would like to see an even more aggressive stance taken by anglers who frequent the Eagle River. From behind the counter of his shop he encourages anglers to head for cooler waters to practice their craft when the Eagle River hits 65 degrees or higher. "I think the biggest thing we could do when it comes to saving these fish is get a thermometer in every fisherman’s hands," Nock said. "These fish are already stressed by the warm temperatures and the low water flow. Catching them when the temperature hits 65 degrees or higher is the straw that breaks the camel’s back." Nock said he sells thermometers for fewer than five dollars and views them as a critical piece of gear for any angler who wants to see a healthy trout population remain in the Eagle River. The fact that four of the trout carcasses found on the Eagle had distinct finger marks where the fish had been handled by someone with dry hands didn’t surprise Nock. He said he estimates that 60 percent of the customers that visit his shop do not know how to correctly release a trout. Dry hands will damage the thin layer of slime that encapsulates a trout. The slime protects the fish from bacteria, fungus and other pathogens. When dry hands damage the coat of slime, it leaves the fish vulnerable to pathogens. Anglers should always wet their hands in the river or lake before handling a trout. "It was clear what had happened to at least four of those fish," said Nock, who accompanied division officials while they floated the river. "They had four finger prints on one side and one thumb print on the other. I always joke that my customers have to wet their hands before they enter the store." Officials are predicting the furunculosis outbreak will be a statewide problem if the hot weather pattern continues. Walker said the extent of the die-off, over the course of the summer, will depend on weather patterns. "It depends upon what Mother Nature has stacked up for us," Walker said. "Overcast sky and cool temperatures are what we need to keep it to a minimum. We also need fishermen to do what they can to keep it from getting any worse." The Division of Wildlife offers these tips for keeping fish stress to a minimum while practicing catch and release: Anglers should not play the fish to exhaustion. If using a fly rod, they should use the heaviest tippet they can without spooking the fish and land the fish as soon as they can. Anglers should wet their hands in the river or lake they are fishing before handling a trout. Anglers should never touch a trout with dry hands. If possible, anglers should not remove the fish from the water while they remove the hook. If anglers need to remove the fish from the water (e.g., for photos), they should support the weight of the fish evenly with both hands. As they remove the fish from the water they should take a breath and hold it. When the angler needs to take a breath, so does the fish. At that time the fish needs to go back in the water. Anglers should remove the hook gently. They should not squeeze the fish or put their fingers in its gills. If the fish is deeply hooked, anglers should not try to pull the hook out. They should cut the line. The hook will eventually rust out. Anglers should release the fish in the coolest, most oxygenated water available. |
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