Excerpt from Fluctuations in Age Composition and Growth Rate of Cutthroat Trout in Yellowstone Lake Oliver B. Cope. 1961. 62 pp. 56. Limnology of Yellowstone Lake in Relation to the Cutthroat Trout, by Norman G. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
Age composition, growth rate, and year-class strength of Yellowstone Lake cutthroat trout from collections made in 1948 and from 1950 to 1959 are analyzed to relate total catch changes in age composition and growth rate. An increase in growth rate of fish fully recruited to the fishery and a decrease in percentages of fish belonging to age groups VI and VII are attributed to an increase in fishing pressure. Mean age of the catch varied with year-length of the catch has remained high, suggesting that production is more efficient now than in past years. Maximum equilibrium yield may be near. If the catch continues to increase at the present rate, it may become excessive within the next few years.
Age composition, growth rate, and year-class strength of Yellowstone Lake cutthroat trout from collections made in 1948 and from 1950 to 1959 are analyzed to relate total catch changes in age composition and growth rate. An increase in growth rate of fish fully recruited to the fishery and a decrease in percentages of fish belonging to age groups VI and VII are attributed to an increase in fishing pressure. Mean age of the catch varied with year-length of the catch has remained high, suggesting that production is more efficient now than in past years. Maximum equilibrium yield may be near. If the catch continues to increase at the present rate, it may become excessive within the next few years.
Equilibrium yield of the cutthroat trout, Salmo clarki lewisi Girard, in Yellowstone Lake, Wyo., is determined from data on catch and spawning runs from 1945 to 1961. Changes in growth rate, spawning runs, mortality rates, and year-class strength are related to differences in total catch. Three stages of exploitation of the stock are defined and the maximum safe catch or equilibrium yield is estimated at 325,000 trout. Management of the sport fishery according to equilibrium yield is discussed with reference to regulations, distribution of fishing pressure, planting, and interspecific competition. The Yellowstone River fishery is treated briefly.
Fluctuations in strength of year classes from 1945 to 1956 of Yellowstone Lake cutthroat from Pelican and Chipmunk Creeks are compared with the parental stock and several climatically influenced factors of the environment. Variations in year-class strength in the two tributaries were highly correlated with fluctuations in lake water levels. Strong year classes occurred in yeas of low water. Female spawner escapement, timing of the runs, and summer air temperatures were not significant factors. A formula based on water levels is presented for predicting year-class strength in Pelican Creek and in the Fishing Bridge area fishery. Stocking of fry in years of high water is suggested as a means of supplementing natural production. A method of forecasting lake water levels several months in advance of their occurrence is discussed.
Life-history organization of the cutthroat trout (Oncorhvnchus clarki) may be viewed at various levels, including species, subspecies, metapopulation, population, or individual. Each level varies in spatial scale and temporal persistence, and components at each level continually change with changes in environment. Cutthroat trout are widely distributed throughout the western USA, and during its evolution the species has organized into fourteen subspecies with many different life-history characteristics and habitat requirements. Within subspecies, organization is equally complex. For example, life-history traits, such as average size and age, migration strategy, and migration timing, vary among individual spawning populations of Yellowstone cutthroat trout (Oncorhvnchus clarki bouvieri) in tributary streams of Yellowstone Lake. In this study specific life-history traits of adfluvial cutthroat trout spawners from Yellowstone Lake were examined in relation to habitat of tributary drainages and subbasins of the lake. Results suggest that stream drainages vary along gradients that can be described by mean aspect, mean elevation, and drainage size. Approximately two-thirds of the variation in the timing of annual cutthroat trout spawning migrations and average size of spawners can be described by third-degree polynomial regressions with mean aspect and elevation as predictor variables. Differences in average size and growth of cutthroat trout suggested metapopulation substructure related spatial heterogeneity of environmental characteristics of individual lake subbasins. Evidence that polytypic species can adapt to heterogenous environments, even within a single lake, has implications for the conservation, restoration, and management of many freshwater fishes. Understanding the consequences of human perturbations on life-history organization is critical for management of the cutthroat trout and other polytypic salmonid species. Loss of diversity at the any hierarchical level jeopardizes long-term ability of the species to adapt to changing environments, and it may also lead to increased fluctuations in abundance and yield and increase risk of extinction. Recent emphasis on a holistic view of natural systems and their management is associated with a growing appreciation of the role of human values in these systems. The recreational fishery for Yellowstone cutthroat trout in Yellowstone National Park is an example of the effects of management on a natural-cultural system. Although angler harvest has been drastically reduced or prohibited, the recreational value of Yellowstone cutthroat trout estimated by angling factors (e.g., landing rate or size) ranks above all other sport species in Yellowstone National Park. To maintain an indigenous fishery resource of this quality with hatchery propagation is not economically or technically feasible. Nonconsumptive uses of the Yellowstone cutthroat trout including fish-watching and intangible values, such as existence demand, provide additional support for protection of wild Yellowstone cutthroat trout populations. A management strategy that reduces resource extraction has provided a means to sustain a quality recreational fishery while enhancing values associated with the protection of natural systems.
This paper is a compilation of 221 abstracts of publications on the biology, culture, distribution, and management of the cutthroat trout, Salmo clarki Richardson. The 1958 publication, "Annotated Bibliography on the Cutthroat Trout," contained 135 abstracts, which have been incorporated with recent ones to form the present report.
Distribution and abundance of Yellowstone cutthroat trout, Oncorhynchus clarkii bouvieri, has declined across the historic range because of anthropogenic influences. Habitat has been fragmented and non-native species have been introduced that compete with, feed upon, or interbreed with cutthroat trout. As a result, many cutthroat trout populations are now isolated in headwater streams and life-history forms are lost or reduced. The upper Yellowstone River basin, above Yellowstone Lake, offers a rare opportunity to study Yellowstone cutthroat trout in a large, intact, river system with few anthropogenic influences. Understanding of life-history forms present in the upper Yellowstone River basin assist in proper conservation and management of the watershed. To determine cutthroat trout life-history forms present, their abundance, and habitat preferences, a combination of radio-telemetry, electrofishing, underwater census, habitat assessment, and age and growth were used. Movements of 151 cutthroat trout were tracked by aircraft, 2003-2005. Most relocated fish (98%) followed a lacustrine-adfluvial life history migration pattern, spending an average 24 days in the river. Cutthroat began entering the river in April and most emigrated by August. Fish migrated as far as 67 km to spawn and spawning aggregations within the system were found in only 11 locations. Underwater census and electrofishing surveys were used to determine fish distribution and abundance in the Yellowstone River and its tributaries. Main stem cutthroat trout densities were low and not evenly distributed. A mean of 8 fish/500 m reach were sampled with the majority in 8 reaches. Juvenile (150 mm, 2 years old) and large adult (330 mm,4 years old) cutthroat trout were found in the main stem, but fish from 151-330 mm (age 3) were absent. Within tributaries, fish densities ranged from 1.7-49.5 fish/100 m reach. Fish up to 305 mm were sampled and ranged 1 to 4 years in age. Data from this study suggest most cutthroat trout in the upper Yellowstone River express a lacustrine-adfluvial life history, however, some fluvial fish are present in tributaries. These findings will be important in driving conservation and management decisions in this drainage and provide critical information in future ESA listing considerations.
Demographic data are sparse for Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri; YCT). Data for YCT in the spawning run (spring; 29 years) of a Yellowstone Lake tributary or caught in gill nets set (fall; 30 years) at established lake locations between 1977 and 2007 were examined. Female proportion in runs averaged 0.61 but was 0.48 among gillnetted "prespawner" YCT (i.e., mature fish whose excised gonads indicated the fish would have spawned the next year). Maturity proportion-total length (TL) relationships for gillnetted female and male YCT were logistic-shaped and similar in their inflection points; maturity onset occurred at 200?250 mm TL; ~95% of YCT [greater than or equal to] 400 mm TL were mature and 70% were prespawners. Fecundity was positively associated with YCT TL. Accuracy of scale-based YCT ages was affected by a frequently overlooked scale annulus and an inability to unequivocally identify fish of a single cohort on the basis of scale characteristics using associated, recognized ageing criteria for this population. Temporal differences in fits of a modified von Bertalanffy growth model to YCT TL at capture and scale-based age probably resulted from ageing errors evident among successive, annual scale analysts rather than differences in YCT growth. Nevertheless, when the age estimates of one, long-term analyst were used in analyses, the estimated growth parameters L[infinity] and [omega] were concordant with empirical observations of the maximum TL of YCT and TL of age-1 YCT in Yellowstone Lake, respectively. The demographic relationships and linking, parameterized growth model provide a useful foundation for age-structured population modeling.
