Monday, August 16, 2010

Summer Field Work

TNACI scientists have been busy the past two weeks taking advantage of summer’s long days, warm weather, and clear skies. Last week, Lee Friedlander joined two graduate students from Tennessee Tech to survey the French Broad River for lake sturgeon. We used an electro-fishing boat to use electric current to temporarily stun any fish in the vicinity of the boat as it motors downstream next to the bank. When the fish are stunned, they float to the surface where they can be identified and recorded. Any lake sturgeon would have been netted on to the boat and measured before being released back into the water. The team was able to survey two of the three planned sites before bad weather ended the day early. Some of the species we identified in our survey included three species of redhorse, spotted suckers, smallmouth buffalo, yellow perch, smallmouth bass, four species of sunfish, and common carp- but no lake sturgeon! Is this a bad sign? Should we assume that because we did not find any lake sturgeon that there are not many lake sturgeon in the river despite our ongoing stocking efforts? Probably not- the Tennessee River is a big river system with miles and miles of available habitat. The only way for us to observe a lake sturgeon is to be sampling at the right place, at the right time. That’s a pretty tall order in a river system covering so much area.

Though we may have been “skunked” in our recent lake sturgeon sampling efforts, our work with a very different species the following week, the Conasauga logperch, had a lot more success. Conasauga logperch are a federally protected species known to only inhabit a 27 mile section of the Conasauga River in southeastern Tennessee and extreme northern Georgia. Conasauga logperch are habitat specialists, only inhabiting deeper pools with sandy bottoms with small stones usually just downstream of a faster moving riffles. These extremely rare fish feed by using their snouts to flip over small stones on the river bottom to look for tiny invertebrates to feed on. TNACI staff were joined in our search by biologists from the U.S. Forest Service and from Conservation Fisheries, Inc. We searched for these fish by snorkeling in the Conasauga River targeting areas with habitat where we knew we would likely find our target species. Because the water in this area is relatively clear, our team of snorkelers could locate fish relatively quickly…if they were there, we were pretty likely to find them. The first site we sampled turned up no Conasauga logperch, but at the second site, slightly downstream we were able to collect 11 individuals. As far as we know, this may have been the highest number of Conasauga logperch ever observed in a single day! Eight of these fish were sent off to our partner, Conservation Fisheries’ facility near Knoxville, TN for a propagation project. A small genetic sample was taken from the remaining three captured fish for genetic analysis and those fish were then returned to the river.

Compared to our efforts to find lake sturgeon, we had a lot more success finding Conasauga logperch. Does this mean that there are a lot more Conasauga logperch in the Conasauga River than there are lake sturgeon in the Tennessee River? Almost certainly not! It just means that with the right planning, Conasauga logperch may be easier to detect than lake sturgeon given their different habitats and behavior.


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