Return of the native Brook trout
On a cool, foggy morning, the fisheries crew began their day’s work, hiking uphill along the babbling Lynn Camp Prong near Tremont to take their place at stream-treatment stations. The crew this day consisted of fisheries biologists Steve Moore and Matt Kulp, seasonal fisheries employees, biologists from agencies throughout the southeast, and a representative of the Environmental Protection Agency (EPA). The treatments were a new way for the Smokies to remove unwanted species—in this case, rainbow trout—from the water and restore the habitat for the once-abundant native brook trout.
At designated pools and turns in the river, people broke off from the group singly or in pairs and carried their gear to the streamside, where a stand with 5-gallon buckets filled with a piscicide—a fish pesticide to remove non-native fish—sat poised over the water. When everyone in the group had reached their stations, the biologists farthest upstream released a green flourescein dye into the water. Then they turned a valve on the buckets, and the piscicide—in this case an antibiotic called Antimycin A—began dribbling into the stream. As the dye traveled downstream past other stations, the biologists at each station turned on their valves to release more Antimycin, thus beginning a continuous eight hour treatment for that section of stream. Soon the top reaches of the water shimmered with the green dye marking the antibiotic. As the piscicide flowed downstream, leaves and the tumbling cold water broke down compounds within it, but release stations at set points released more to maintain the antibiotic’s concentration at eight parts per billion.
The progress of the antibiotic was slow. The green dye that flowed with the Antimycin crept downstream for hours. Finally, Fisheries biologist Matt Kulp and the EPA representative saw what they had been waiting for: the roaring white of the waterfall shifted to roiling neon green. This meant that the antibiotic had reached the end of the treatment section, and it was time to turn on the detoxification station.
With the turn of a valve, jugs of potassium permanganate dribbled deep purple liquid into the water. This chemical neutralized any remaining antibiotic so that fish downstream would be safe from the piscicide’s effects. It also turned deep pools along the lower reaches of Lynn Camp Prong an eerie red hue. Graduate students from Tennessee Tech collected aquatic macroinvertebrates below this detoxification station to monitor the effects of the neutralizing chemical on these tiny organisms.
Removing and Restoring FishThis day on Lynn Camp Prong was one of many in a long-term effort to treat the Smokies’ streams for non-native fish. The antibiotic Antimycin is toxic to all fish, including the non-native brown and rainbow trout. It interferes with the oxygen transfer at the cellular level in a fish’s body, eventually shutting down internal organs.
In preparation for these treatment days, fisheries biologists waded through miles of deep pools and hidden pockets to find brook trout and other native fish such as the blacknose dace that they wanted to save in Lynn Camp Prong and its tributaries. They electroshocked the native fish—stunned them with a low amplitude current—and gathered them all in holding tanks, which they then transported to a “foster” stream in the same watershed that had been treated four years earlier for this purpose. There the brook trout would wait through the winter until they could be released once again to Lynn Camp Prong.
People have long managed waterways for certain species. Even the original introduction of the non-native brown and rainbow trout was a kind of management: before the Park existed, people released the fish into Smokies’ streams so anglers would have more fish to catch.
NPS archive photo.
In 1987 the park began restoring brook trout, and in 2000 began treating streams with Antimycin. Because this antibiotic has been accepted as relatively safe and can be neutralized when biologists want to treat a small area or for a short amount of time, National Parks and other protected areas choose it to treat their streams and lakes. The EPA representative at the Lynn Camp Prong treatment was there to observe and gather information about its field use in a protected area.
Of course, moving fish, treating streams, and restoring fish is only part of the whole brook trout restoration story. Read on for more information about how biologists are coming to understand the movements and backgrounds of the brook trout.
In addition to studying fish in their habitats to see if and where they’re surviving, scientists study fish DNA. Researchers from Penn State University, the U.S. Geologic Survey, the University of Tennessee, and Tennessee Tech have—or are currently—conducting genetic studies on brook trout.
The genetic studies aim to answer several questions:
These questions are complex and require years of data collection and analysis. In some cases, the answer depends on observing fish breeding success and long-term survival, so researchers will have to wait and watch through many generations of brook trout.
To collect DNA from brook trout, fisheries biologists electroshock the fish and catch their stunned bodies in nets before the fish drift downstream. When they have collected 30 fish—the minimum sample size for statistical analysis—they carry the sloshing bucket of fish to the shore, prepare the labeled vials that they’ll take back to the lab, and begin clipping a fin off of each fish. This body part will give the researchers blood and body tissue that they need to extract DNA. The fin they select is the adipose fin, the small one on the fish’s back behind the dorsal fin. The fish doesn’t need the adipose fin for swimming and it heals quickly, so researchers can collect genetic material without killing fish.
Learning about brook trout genetics is vital to restoration programs in the Park and statewide. The National Fish Habitat Action Plan and the Eastern Brook Trout Joint Venture aim to restore brook trout to watersheds where populations have dropped by as much as 90 percent, as they have in the Smokies.
Early DNA research results
Other research supplements biologists’ understanding of brook trout in the park. Graduate student Keil Neff from the University of Tennessee studies the impacts of sulfate and nitrate contamination on brook trout health. He looks particularly at how fish fare at sub-lethal levels, which stress the fish but do not kill them. To read more about his research and other University of Tennessee Water Quality & Fisheries research, go to the Partner Profile: Taking the pulse of Smoky Mountain streams.
All of these studies help park fisheries biologists plan and undertake their long-term brook trout restoration program.
Where are they now?
Status of brook trout reintroductions
The process of bringing the brook trout back is similar to moving them in the first place: biologists—and a lot of helpers—electroshock the fish, load them into holding tanks, and truck them back to the trailheads. From there, fisheries crews haul the trout in batches up the trail, releasing them back into the cool rushing water. Through fall 2009, native brook trout will be returning to the waters they call home, and hopefully settling in to reproduce and thrive.
The reintroduction project on Lynn Camp Prong will bring the total miles of restored stream to about 30, or three-quarters of the roughly 40 miles of streams they originally identified as one-time brook trout habitat. Restoring streams is a long-term project, but with dedicated Smokies biologists and research by Park partners, these native fish should be around for hundreds of years.
Return to Dispatches from the Field: Issue 4.