Fisheries Research & Projects: January, 2009

Brook trout genetics

The Brook trout (Salvelinus fontinalis) in Great Smoky Mountains is one of only two salmonid species native to the eastern United States, and they may be even rarer than scientists thought.

Recent genetics research indicates that brook trout found in streams within and south of the New River, Virginia watershed (which includes all of the streams in the Great Smoky Mountains) are genetically distinct from their northern “cousins” on at least a sub-species level. That means that while they may be able to breed with one another, these different sub-species might have distinct adaptations: resistance to disease, tolerance of different temperatures or pollution levels, or other characteristics that could help them survive.

Within this southern range, these “Southern Appalachian brook trout” have been reduced to only 62 percent of their former habitat. Prior to European settlement, brook trout were known to occupy nearly 440 of the 2,100 miles of streams within Great Smoky Mountains National Park. Today, brook trout occupy less than 117 miles of their former range, which is about 30 percent less habitat. The reasons for the decline include logging by early settlers, the introduction of non-native rainbow trout for fishing stock, and more recently, acid deposition in rain, snow, clouds, and dry air from regional power plant and vehicle pollution.

Does fishing reduce fish populations?

This may sound like a silly question at first, but it’s crucial to the survival of the brook trout. Often, fishing has meant taking the “keeper-size” fish home to fry or mount on the wall. But to more and more people now, fishing is just catching—testing one’s skill at selecting the right lure and casting into just the right spot to attract a fish—and then releasing the fish. While we might assume that a population doesn’t decline as a result of legal fishing, few studies had been conducted to see if, in fact, fishing and harvest harmed the sensitive fish that scientists wanted to protect.

To see if fishing harmed the brook trout, fisheries biologists at Great Smoky Mountains National Park opened eight streams (four in Tennessee, and four in North Carolina) to fishing and harvest for three years. People fishing there of course had to comply with NPS fishing regulations (5 fish creel limit, 7-inch size limit, single hook artificial lures). In addition to opening the eight streams to fishing, they chose eight more streams in which people couldn’t fish to compare the results. The streams without fishing served as a scientific “control,” so biologists could see if differences in fish population could also be due to factors in the streams that weren’t related to people fishing, such as temperature, water levels, and acid deposition. Scientists hoped to take the stream results and combine them with results from surveys with anglers to make decisions about fishing and harvest of brook trout in the Park.

After the three years, scientists found:

  • no significant differences (most importantly, no declines) in adult brook trout density in 7/8 of the streams opened to brook trout fishing (fished streams)
  • no significant declines in young brook trout densities in fished streams
  • no reduction in the average size of brook trout caught in the fished streams

In addition, although anglers surveyed said that “catching a brook trout” was the primary reason for fishing the particular stream they chose, 87 percent of them said they did not want to harvest (keep) the brook trout, just to catch and release them. Managers concluded that current fishing regulations—and most people’s practice of catch-and-release fishing—are effective in protecting brook trout populations.

A new way to remove non-native invasive fish from National Park waters: using Antimycin A against non-native invasive rainbow trout

The native “Southern Appalachian” type of brook trout (Salvelinus fontinalis) in Lynn Camp Prong, a stream near Tremont, are the most threatened population in Great Smoky Mountains National Park. Threats include non-native rainbow trout (Oncorhynchus mykiss), which are taking over food and habitat for the trout, and acid deposition from power plant and vehicle pollution. The only habitat in which brook trout do not have to compete with the introduced rainbow trout for food and shelter is a length of high elevation stream about two-thirds of a mile long.

Over three weeks last September, 2008, NPS biologists and over thirty partners from ten federal and state agencies, universities, and volunteer groups successfully removed non-native rainbow trout from eight miles of Lynn Camp Prong.

The new treatment was with an Environmental Protection Agency (EPA) approved piscicide (fish poison) called antimycin A. According to NPS fisheries biologists, antimycin A (commercially called Fintrol®) and Rotenone® have long been the piscicides of choice throughout the United States for restoring native fish species in streams and lakes. Because every creature and plant in a stream—and the entire stream itself—is protected within the National Park, there are strict regulations about which chemicals can be used. Biologists at Great Smoky Mountains National Park use antimycin for restoration projects because it has no effect on other plants and animals in the stream or surrounding area, fish do not detect it, and it can be used in the cold waters of the Smokies. This project was important because it involved so many federal agencies, including the Environmental Protection Agency, and set up rules for every other National Park to use when they need to apply a piscicide.

The Lynn Camp restoration project was the largest successful antimycin project of its kind in the eastern United States. Park biologists used the project as a training opportunity on the use of antimycin for State and federal agency staff. Many of the trained staff members are planning similar projects in their respective areas. Pre- and post-treatment studies on small aquatic invertebrates (animals without backbones) from Lynn Camp Prong and previous projects indicate that impacts to them are minimal and short term: often populations are as dense two months after the piscicide treatment as they were before.

In June of 2009, with the help of local volunteers, roughly 1,500 southern Appalachian brook trout will be collected from streams surrounding the park and relocated throughout the treatment area. Following successful reintroduction, brook trout will occupy over 125 miles of their former range in Great Smoky Mountains National Park.

You can read about how the biologists applied antimycin A in “A field manual for the use of antimycin A for restoration of native fish species,” available from NPS fisheries biologists Steve Moore and Matt Kulp (click here to email), and U.S. Fish and Wildlife Service Fisheries Biologists Bruce Rosenlund and Jim Brooks, and New Mexico Department of Game and Fish Ichthyologist David Propst, Ph.D.

The manual provides fisheries managers with standard operating procedures for conducting a safe, effective, and lawful native fish restoration projects with antimycin A. Using the standard operating procedures specified in this document, fisheries managers learn how to apply antimycin A consistently to remove unwanted fish species from streams, impoundments, or small lakes (<50ha) with subsequent re-establishment of natural aquatic communities. The manual provides a thorough understanding of antimycin A use with regard to planning and implementing a project, bioassays, environmental planning, permitting, legalities, history, chemistry, safety precautions, application materials, treatment concentrations, application techniques, deactivation procedures, reporting, and project monitoring protocols. The standardized and consistent use of antimycin A will help reduce potential for human exposure and unintended adverse ecological effects. The U.S. Environmental Protection Agency (EPA) is adopting the manual as the Standard Operating Procedures (SOP) for antimycin use and will include the manual as part of the new antimycin A label during the current re-registration process.

Acidic storms

Researchers Robinson, Roby, Buchanan, and Barnett from the University of Tennessee and NPS Fisheries manager Steve Moore have found that many streams reach dangerously acidic levels during storms. Their project began simply: they installed four probes to continuously monitor water quality in a stream near a construction site. But when they analyzed the data after just four months, they noticed that the pH (measure of acidity) of the stream had dropped dramatically each time it rained. Scientists hadn’t necessarily been noticing this sudden drop to very acidic water before, because they sampled each stream on a monthly or bi-monthly schedule. Sampling on a single day in a month is an excellent way to show overall trends year to year, but it loses the sudden changes in acidity that happen before, during, and after a rain storm over the course of a single day.

The sudden “flushes” of acid were dramatic. The falling rain itself had a pH between 5.1 - 4.1, which is 100 to 1,000 times more acidic than neutral water (pH 7.0). The acid rain, combined with acid washed off tree leaves where it had settled from the air, made the pH of the stream drop 0.5 - 1.0 pH units. In addition, turbidity (cloudiness from minerals dissolved by the acid) increased to levels that were unhealthy for the stream-dwellers.

Scientists are now studying what impact the sudden “flushes” of acid will have for the plants and animals living in that stream. Take the brook trout, for example: according to monthly monitoring data, many streams are listed as having an average pH level of 6.0. This is slightly acidic, but the trout can survive. During rain storms, when rain tinged with sulfate and nitrate pollutants from power plants and car exhaust pours into the stream, the trout may not be able to tolerate the 4.5 - 5.0 pH levels to which the water can drop.

Return to Resource Roundup: January, 2009.

Last updated: April 14, 2015

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