Stephen E. Moore

Encroachment of Exotic Rainbow Trout into Stream Populations of Native Brook Trout in the Southern Appalachian Mountains

Abstract Since 1900, the distribution of native brook trout Salvelinus fontinalis has shrunk in the southern Appalachian Mountains area. Initial reductions were caused by logging and heavy fishing pressure but, in later years, encroachment by exotic rainbow trout Salma gairdneri may have contributed. Historical and current field evidence supports the hypothesis that the modern contraction of the brook trouts range is due to encroachment by rainbow trout. In Great Smoky Mountains National Park, Tennessee-North Carolina, brook trout formerly occurred from headwaters to low-gradient streams near the park boundary. They retain this longitudinal distribution in a few streams today, but only in those lacking rainbow trout. The typical pattern in other streams is for allopatric brook trout to be in upper stream reaches, allopatric rainbow trout in lower reaches, and a zone of sympatry (up to about 3.2 km long) between the two pure populations. Few age-0 rainbow trout occur in zones of sympatry unless adult broo...

Summer food limitation reduces brook and rainbow trout biomass in a southern Appalachian stream

Abstract We assessed salmonid production in summer in a second- and third-order montane stream in eastern Tennessee in 1987. We sampled three stream sections, one containing exclusively brook trout Salvelinus fontinalis, one containing exclusively rainbow trout Oncorhynchus mykiss, and a third with a mixture of both species. Population estimates for July and October 1987 revealed reductions in biomass over the 4-month period that ranged from 31 to 49%, whereas population densities declined by 32–46% during the same period. Total net production during the 4-month period was low and ranged from 0.38 to 0.45 g/m2. From June through September, the mean number of prey items per stomach ranged from 4.2 to 29.9, whereas the mean relative weight of stomach contents ranged from 0.12 to 1.34 mg dry weight per gram wet weight offish flesh. There was a strong positive correlation between the mean relative weight of stomach contents and the mean condition factor for a given date. Calculated energy intake was below the...

Population control of exotic rainbow trout in streams of a natural area park

Expansion of the distribution of exotic rainbow trout is thought to be a leading cause for the decline of native brook trout since the 1930s in Great Smoky Mountains National Park, USA. An experimental rehabilitation project was conducted from 1976 to 1981 using backpack electrofish shockers on four remnant brook trout populations sympatric with rainbow trout. The objectives were to evaluate the effectiveness of the technique to remove the exotic rainbow trout, to determine the population responses by native brook trout, and to evaluate the usefulness of the technique for trout management in the park.Rainbow trout populations were greatly reduced in density after up to six years of electrofishing, but were not eradicated. Rainbow trout recruitment, however, was essentially eliminated. Brook trout populations responded by increasing in density (including young-of-the-year), but rates of recovery differed among streams. The maximum observed densities ir each stream occurred at the end of the project.The findings suggest that electrofishing had a major negative impact on the exotic species, which was followed by positive responses from the native species in the second and third order study streams. The technique would probably be less effective in larger (fourth-order) park streams, but as an eradication tool the technique may have its highest potential in small first order streams. Nonetheless, the technique appears useful for population control without causing undue impacts on native aquatic species, although it is labor intensive, and capture efficiency is greatly influenced by fish size and stream morphology. To completely remove the exotic fish from selected streams, different technologies will have to be explored and developed.

Multiple Electrofishing Removals for Eliminating Rainbow Trout in a Small Southern Appalachian Stream

Abstract We evaluated multiple electrofishing removals of rainbow trout Oncorhynchus mykiss as a management tool for the restoration of native brook trout Salvelinus fontinalis in a small southern Appalachian stream. Six, three-pass depletion removal efforts were conducted between Jun 1996 and Oct 1997. Four removals successfully eliminated rainbow trout reproduction. Five removals were required to successfully eliminate rainbow trout from Mannis Branch. During the study, 428 rainbow trout were removed from the treatment area. The initial removal collected 296 (70%) of the total rainbow trout removed and was dominated by adults. Subsequent removals were dominated by age-0 rainbow trout (57–83%). The initial two removals successfully eliminated 96% of the reproductively mature adults as well as 86% of the age-0 fish. In Oct 1996, 105 native southern Appalachian brook trout of various age-classes were reintroduced into Mannis Branch. Surveys conducted in May 1997 indicated adult brook trout successfully spa...

Three-Pass Depletion Sampling Accuracy of Two Electric Fields for Estimating Trout Abundance in a Low-Conductivity Stream with Limited Habitat Complexity

Abstract We evaluated three-pass depletion sampling for both AC and pulsed-DC electrofishing for estimating the population size of rainbow trout Oncorhynchus mykiss in a representative low-conductivity (20-μS/cm) southern Appalachian stream with limited habitat complexity. Trout capture efficiencies in such streams could be expected to exceed those observed in streams in which habitat is more complex; thus, depletion estimates could be much more accurate in the former. We also compared the results for two trout length-groups to investigate size-related differences. Measured capture efficiency was 0.88 ± 0.04 (95% confidence interval) for trout greater than 100 mm (typically adults) and 0.65 ± 0.09 for trout less than 100 mm (age 0). Population size was underestimated in each depletion sample. The errors for trout over 100 mm were generally small (mean, 12%; range, 3–23%), and the upper 95% confidence limits were usually within 10% of the true population size (N). Underestimates of N were larger for trout ...

Observations of the Distributions of Five Fish Species in a Small Appalachian Stream

Abstract The notion has been growing that resident stream fishes exhibit a greater capacity for movement than was previously thought. In this study, we recorded the distributions of four resident fish species (longnose dace Rhinichthys cataractae, blacknose dace R. atratulus, mottled sculpin Cottus bairdi, and rainbow trout Oncorhynchus mykiss) and one nonresident species (central stoneroller Campostoma anomalum) in Rock Creek, a small tributary of Cosby Creek in Great Smoky Mountains National Park, over the period 1979-1995. During this study, 1,998 individuals of resident species were collected from stream sections considered to be within a common area of distribution for each species. Forty-five individuals of resident and nonresident species were captured upstream of these areas, and eight of these fish were considered to be larger than individuals considered typical for each species. Small mammal dispersal theory concepts were used to classify and describe fish movements outside of common areas of di...

Angling and Electrofishing for Removing Nonnative Rainbow Trout from a Stream in a National Park

Abstract An experimental 9-week fishery was conducted in a Great Smoky Mountains National Park stream (Lynn Camp Prong) to evaluate the use of angling and electro fishing as techniques for reducing the density of a non-native rainbow trout (Salmo gairdneri) population. Most anglers were local residents in Tennessee. Angler visits were highest during the first 2 weeks and declined steadily thereafter. Anglers harvested 5,655 rainbow trout whose total lengths fell within the 80-and 280-mm size classes. The electrofishing crew caught fish in length classes between 30 and 280 mm. The adjusted preseason electrofishing catch per unit effort (CPUE) was 3.71 fish/h based on the time taken for daily preparation, travel, and electrofishing. When based on electrofishing time only, the CPUE was 5.90. The CPUE for one clerk at a creel station was projected to be substantially greater (6.70) than that for the electrofishing crew. In addition, total costs were far greater for the electrofishing crew because of equipment...

A Case History in Fishing Regulations in Great Smoky Mountains National Park: 1934–2004

Abstract Since the establishment of Great Smoky Mountains National Park (GRSM) in 1934, fisheries managers have utilized about every angling regulation in the toolbox to manage salmonids. Our objectives here were to summarize the regulation history of GRSM and determine whether regulations affected the age or size structure, growth, and population dynamics of wild populations of rainbow trout Oncorhynchus mykiss within GRSM. Data inconsistencies made data comparisons among regulation periods difficult; however, where feasible, comparisons revealed similar population dynamics among periods. The number of legal rainbow trout per kilometer of stream ranged from 215 to 885 throughout the 70-year study period, regardless of regulation. There were no statistical differences in rainbow trout relative stock densities (RSDs) on Little River among the 1930s, 1950s, 1980s, and 1990s, despite liberal regulations prior to 1960. Rainbow trout mean length at age data indicate no differences among populations for age-1 t...

Recovery of Native Brook Trout Populations Following the Eradication of Nonnative Rainbow Trout in Southern Appalachian Mountains Streams

AbstractNonnative Rainbow Trout Oncorhynchus mykiss have displaced native Brook Trout Salvelinus fontinalis in many southern Appalachian Mountains streams. We monitored the population recovery of Brook Trout following Rainbow Trout eradication at 10 sites in seven allopatric Rainbow Trout streams located in Great Smoky Mountains National Park, USA. Rainbow Trout were successfully eradicated by electrofishing or Fintrol (also known as antimycin-A), and Brook Trout were reintroduced at low densities (39–156 fish/km) from streams located within the park. Within 2 years after reintroduction, the density and biomass of adult Brook Trout recovered to levels comparable to the prerestoration density and biomass of Rainbow Trout. Spawning in the first autumn after reintroduction was assumed by the presence of young-of-the-year fish in seven out of nine sites surveyed during the following summer. Brook Trout density and biomass 3–5 years after restoration did not significantly differ from those in natural allopatri...