Browsing by Author "Lackey, Robert T."

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    Analysis of catchable trout fisheries management by computer simulation
    Hammond, Dennis Edward (Virginia Tech, 1974-03-05)
    Although strategies to meet most management objectives are relatively clearcut in single-species catchable trout programs, strategies become much more complex when two or more species are involved. A difficult problem that must be faced in evaluating catchable trout fisheries management strategies is defining management objectives. One approach to testing alternative management strategies in complex resource systems, such as catchable trout fisheries, is systems simulation. A computer-implemented catchable trout fishery simulator (CATS) was developed to evaluate fishery response under various management strategies in a multi-species stocking program. The user of CATS can select alternative management strategies and functions which generate predictions of fishing pressure on a particular fishery. To evaluate the effect of each system component, CATS was exercised over a wide range of potential system component alterations. Predominant stocking of brook trout appreciably increased average catch per angler hour and percentage return to creel. Altering the stocking ratio to favor brown trout substantially increased the number of angler hours. Stocking predominantly rainbow trout reduced the effects caused by stocking predominantly brook or brown trout. Estimates of expected angling pressure ru1d catchability coefficients of each species stocked are of primary importance because of their considerable effect on other system components. A user must have a sound objective before deciding where, when, which species, and how many fish to plant. The primary utility of CATS is to enable the user to evaluate management strategies prior to implementation.
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    Analysis of exploited fish populations
    Lackey, Robert T.; Hubert, Wayne A. (Sea Grant, Extension Division, Virginia Polytechnic Institute and State University, 1977)
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    Analysis of exploited fish populations
    Lackey, Robert T.; Hubert, Wayne A. (Sea Grant, Extension Division, Virginia Polytechnic Institute and State University, 1978)
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    Computer-Implemented Simulation as a Planning Aid for State Fisheries Management Agencies
    Clark, Richard D., Jr.; Lackey, Robert T. (Virginia Tech. Division of Forestry and Wildlife Resources, 1975)
    A basic job of fisheries management agencies is to forecast the demand and produce the necessary supply of fishing opportunities. Present day angling consumption rates often exceed managers' ability to supply fishing opportunities of the desired quality. Therefore, a primary means for improving fisheries management may be to regulate angling consumption. Operations research techniques are well suited for handling the complexities involved with planning multiple action policies for regulating angler consumption. PISCES is a computer-implemented simulator of the inland fisheries management system of Tennessee, but is adaptable for use in any state. The purpose of PISCES is to aid in planning fisheries management decision policies at the macro-level. PISCES generates predictions of how fisheries management agency activities will affect angler use for a fiscal year. Subjective probability distributions for random variables and Monte Carlo simulation techniques are employed to produce an expected value and standard deviation for each prediction. Test runs under realistic hypothetical situations and discussions with personnel of Tennessee Wildlife Resources Agency suggest that PISCES may help fisheries management agencies to improve budget allocation decisions, to formulate multiple action policies for regulating angler use, and to enhance fisheries development. A hypothetical application of PISCES in Tennessee is given.
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    A General Population Dynamics Theory for Largemouth Bass
    Jester, Douglas B. Jr.; Garling, Donald L. Jr.; Tipton, Alan R.; Lackey, Robert T. (Virginia Tech. Division of Forestry and Wildlife Resources, 1977)
    In this report, we develop a general theory of the relationship between life history and population structure for largemouth bass. In its most usable form the model is represented by a stochastic integral equation that is analogous to the classical Lotka model for age structure of populations. The corresponding differential equations can also be used successfully when closed-form solutions are available or when the phenotype dimension is low enough to permit numerical solution. Three general conclusions are presented. First, population dynamics may be appropriately viewed as a consequence of life history phenomena. This view suggests that, at least where prediction of population structure or where explanation of the phenomena is desired, such phenomena as density-dependence may be most appropriately described by analyzing effects of population structure and density on life history in the population. The second conclusion is that variation in life history may be important in determining population structure. Terms describing effects of variation are explicitly included in the model equations. The magnitude of these terms, however, is completely unknown for any life histories with which we are familiar. The third conclusion to be drawn is that population structure, at least averaged over time, should be fairly stable in large populations. Effects of variation in small populations, on the other hand, have not been analyzed and might be important.
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    A general population dynamics theory for largemouth bass fisheries
    Jester, Douglas B. Jr. (Virginia Polytechnic Institute and State University, 1977)
    Resolution of the main issues in largemouth bass management will require the ability to predict the effects of exploitation on population structure, optimally select size limits, relate bass population structure to prey population structure, and predict the effects of fluctuations in recruitment on production and yield. A general model of population structure was developed for use in studying these problems. The model was derived by examining the relationship between life history and population structure. Life history processes are described as mixed continuous and jump stochastic processes. The model was derived in two forms, an integro-differential equation and a stochastic integral equation, which include all of the classical continuous-time population models as special cases. Two general results concerning the model were proven. First, the stochastic integral equation was shown to predict the same expected population structure as a deterministic model using average birth and death rates whenever the processes are uncorrelated. However, it is very unlikely that birth rate, death rate, and density will be independent, so the stochastic and deterministic models will generally diverge. Second, it was shown that with density-independence the expected population structure in the stochastic model is asymptotically stable. Special cases of the model were used to illustrate the possible effects of exploitation on average catchability and population structure. Methods for calculation of optimal length limits and production and yield were illustrated for simple cases. Use of the full power of the model, however, must await more detailed description of factors influencing mortality and growth, especially the effect of the density and size structure of available prey.
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    Introductory fisheries science
    Lackey, Robert T. (Sea Grant, Extension Division, Virginia Polytechnic Institute and State University, 1974)
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    Pisces: a computer simulator to aid planning in state fisheries management agencies
    Clark, Richard Dean (Virginia Tech, 1974-10-02)
    Some fisheries management activities have clearer relationships with angler consumption than others, end the clarity is usually reflected by the amount of historical data available upon which to base the relationship. Adequate historical data exists to derive the relationships between angler-days and access development, water development, regulation changes, and catchable trout stocking, so these relationships are probably the most reliable in PISCES. Little historical data exists to assess the effects of research and information and education activities upon angler-days. Therefore, the segments of PISCES accounting for research and information and education are probably the least reliable parts of the model. PISCES can be improved before it is utilized in decision analysis. First, the efficiency of the computer program could be improved. PISCES is functional, but computer time and storage space might be saved by altering the program. Second, sensitivity analysis of input variables would provide important information to future users of PISCES. And finally, an application study would reveal any unforeseen problems which might arise in using PISCES. If PISCES is never used to formulate management decision policies, it is hoped that some of the modeling techniques employed will prove useful in future efforts to model natural resource systems.
  • Seven pillars of ecosystem management
    Lackey, Robert T. (Amsterdam, Netherlands: Elsevier Science B.V., 1998)
    Ecosystem management is widely proposed in the popular and professional literature as the modern and preferred way of managing natural resources and ecosystems. Advocates glowingly describe ecosystem management as an approach that will protect the environment, maintain healthy ecosystems, preserve biological diversity, and ensure sustainable development. Critics scoff at the concept as a new label for old ideas. The definitions of ecosystem management are vague and clarify little. Seven core principles, or pillars, of ecosystem management define and bound the concept and provide operational meaning: (1) ecosystem management reflects a stage in the continuing evolution of social values and priorities; it is neither a beginning nor an end; (2) ecosystem management is place-based and the boundaries of the place must be clearly and formally defined; (3) ecosystem management should maintain ecosystems in the appropriate condition to achieve desired social benefits; (4) ecosystem management should take advantage of the ability of ecosystems to respond to a variety of stressors, natural and man-made, but all ecosystems have limited ability to accommodate stressors and maintain a desired state; (5) ecosystem management may or may not result in emphasis on biological diversity; (6) the term sustainability, if used at all in ecosystem management, should be clearly defined, the time frame of concern, the benefits and costs of concern, and the relative priority of the benefits and costs; and (7) scientific information is important for effective ecosystem management, but is only one element in a decision-making process that is fundamentally one of public and private choice. A definition of ecosystem management based on the seven pillars is: 'the application of ecological and social information, options, and constraints to achieve desired social benefits within a defined geographic area and over a specified period'. As with all management paradigms, there is no 'right' decision but rather those decisions that appear to best respond to society's current and future needs as expressed through a decision-making process. There are, however, wrong management decisions, including the decision not to make a decision.
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    Teaching water resource management with the aid of a computer-implemented simulator
    Lackey, Robert T. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1975)