Biotelemetry Study of Trout in the
Lake Cumberland Tailwater

The Kentucky Department of Fish and Wildlife Resources (KDFWR) is involved with an intensive study on trout movement in the Lake Cumberland Tailwater.  Biologists observed that numbers of brown and rainbow trout declined in November electrofishing surveys in both 2003 and 2004.  There is evidence that the declines seen in both years may be related to the release of warmer water with low dissolved oxygen levels from Wolf Creek Dam in the late summer and fall.  These declines in water quality are related to the heavy amounts of spring precipitation that occurred in 2003 and 2004.  It is not known if the trout died as a result of the water quality problems or simply moved further down river to areas having better water.  It’s also not known how heavy spring releases from Wolf Creek Dam affect the movements of trout in the tailwater.

To obtain more information, the KDFWR initiated a trout movement study through Eastern Kentucky University .  In July 2005, a total of 30 brown trout and 30 rainbow trout were surgically implanted with sonic transmitters.  A total of 6 brown trout and 6 rainbow trout were collected, implanted, and released at each of 5 sites.  The fish tagged ranged from 15 to 20 inches in length.  These 5 release sites are: 1) Above Helms Landing, 2) Below Helms Landing, 3) Rainbow Run, 4) Big Willis Creek, and 5) Crocus Creek.  Weekly tracking of the tagged fish occurred from August until the end of October in 2005, which are the critical months when water quality in the tailwater can decline.  Fortunately, 2005 was a dry year and the water quality problems observed in the autumns of 2003 and 2004 did not occur.  Tracking is continuing and will be conducted once a month until weekly tracking begins again in July 2006.  Tracking will continue until the conclusion of the study in October 2006.  The main study area is from the dam downstream to Burkesville.  In addition to the tracking, 3 submersible receivers that monitor tagged fish’s downstream movement were placed near the Hwy 61 bridge, Cloyd’s Landing and McMillan’s Ferry.

It should be mentioned that in a study of this type, we do not expect to find all 60 fish each week.  Some fish may be illegally harvested, others may be in a side channel and go undetected at the time of tracking, or some will simply die from natural causes or post-surgery complications.  The transmitters used in this study emit ultrasonic sound waves that are detected by the use of a hydrophone, essentially an underwater microphone.  If a fish containing a transmitter leaves the water, for any reason, then that individual can no longer be detected.  It is not uncommon in a telemetry study to “lose” up to 60-70 % of the original starting number, especially for a study of long duration such as this.

The accompanying maps give the locations of fish found for each tracking event (each time it takes two days to cover the entire river).  The brown and rainbow trout are differentiated by two marker shapes, a circle for rainbow trout and a triangle for brown trout.  The release sites are color coded so the color of the marker can be matched with where that fish was originally released.  The river miles, in terms of distance below the dam, are indicated with a series of small black dots.  A few major tributaries, access points, boat ramps, roads and other features are also depicted for reference.  Initial tracking locations are depicted on a single map.  However, as fish have moved further downstream, two maps were required so that the map scale did not have to be reduced.