Rainbow Trout (Oncorhynchus mykiss) Production Dynamics and Relations with Abiotic Factors in Two Southern Appalachian Mountain Streams

Abstract

Rainbow trout (Oncorhynchus mykiss) annual production was estimated over two years in Laurel Branch and South Fork Citico Creek, Tennessee. Both streams are softwater, second order streams of the southern Appalachian Mountains with low inherent productivity (alkalinity <100 μeq·L−1 or 5 mg·L−1 as CaCO3). Annual production over the two years averaged 12.4 kg·ha−1 in Laurel Branch and 6.2 kg·ha−1 in South Fork Citico Creek. The majority of annual production (77%) occurred during the December-April period in Laurel Branch and was dominated by age-2 trout (44%). Though lower overall than Laurel Branch, annual production in South Fork Citico Creek was also dominated by age-2 trout (47%) but was more evenly distributed throughout the year. Seasonal mean flows and water chemistry measures were related to production and growth rates of age-1 and age-2 trout but not age-0 or age-3 trout. Annual production estimates represented the lowest reported values for rainbow trout and were similar to regional estimates for brook trout (Salvelinus fontinalis). Findings suggest that trout production in these streams is below worldwide averages for infertile streams and may be related to abiotic factors which may in effect regulate salmonid production in these streams annually.