Showing papers by "Donald L. DeAngelis published in 1993"

Growth Rate Variation and Larval Survival: Inferences from an Individual-Based Size-Dependent Predation Model

Abstract: We used an individual-based Monte Carlo simulation model to explore how changes in the mean and variance of growth rates of individuals in a larval fish cohort interact with size-dependent predatio...

Fish Cohort Dynamics: Application of Complementary Modeling Approaches

Abstract: The recruitment to the adult stock of a fish population is a function of both environmental conditions and the dynamics of juvenile fish cohorts. These dynamics can be quite complicated and involve the size structure of the cohort. Two types of models, i-state distribution models (e.g., partial differential equations) and i-state configuration models (computer simulation models following many individuals simultaneously), have been developed to study this type of question. However, these two model types have not to our knowledge previously been compared in detail. Analytical solutions are obtained for three partial differential equation models of early life-history fish cohorts. Equivalent individual-by-individual computer simulation models are also used. These two approaches can produce similar results, which suggests that one may be able to use the approaches interchangeably under many circumstances. Simple uncorrected stochasticity in daily growth is added to the individual-by-individual models, and it is shown that this produces no significant difference from purely deterministic situations. However, when the stochasticity was temporally correlated such that a fish growing faster than the mean 1 d has a tendency to grow faster than the mean the next day, there can be great differences in the outcomes of the simulations.

Linking Life History Theory, Environmental Setting, and Individual‐Based Modeling to Compare Responses of Different Fish Species to Environmental Change

Abstract: We link life history theory, environmental setting, and individual-based modeling to compare the responses of two fish species to environmental change, Life history theory provides the framework for selecting representative species, and in combination with information on important environmental characteristics, it provides the framework for predicting the results of model simulations. Individual-based modeling offers a promising tool for integrating and extrapolating our mechanistic understanding of reproduction, growth, and mortality at the individual level to population-level responses such as size-frequency distributions and indices of year-class strength. Based on the trade-offs between life history characteristics of striped bass Morone saxatilis and smallmouth bass Micropterus dolomieu and differences in their respective environments, we predicted that young-of-year smallmouth bass are likely to demonstrate a greater compensatory change in growth and mortality than young-of-year striped bas...

Modeling Growth and Survival in an Age-0 Fish Cohort

Abstract: We applied an individual-based model to an age-0 cohort of smallmouth bass Micropterus dolomieu to simulate the cohort's growth and survivorship through its first growing season. The purpose was to determine whether the stock–recruitment characteristics of the age-0 fish could be predicted. The model smallmouth bass were exposed to size-dependent predation, size-independent mortality, and starvation mortality resulting from depletion of their prey supply. Survivorship curves were produced by model simulations. When survivorship at a given time was plotted against initial egg density during the early growing season, the curve resembled the peaked pattern of a Ricker-type curve. In contrast, curves for survivorship during the late growing season had no noticeable peak or maximum. Other results showed (1) strong density dependence of the mortality rate early in the growing season and density independence late in the growing season; (2) a distinct critical time (CT) during which the slope of the surv...

Further Considerations on the Debate Over Herbivore Optimization Theory.

Abstract: Criticism of the basis and use of the herbivore optimization theory is discussed. It is argued here that evidence from theory and agricultural practice support the view that compensation and overcompensation of total primary production can occur in plant populations and communities subjected to grazing. However, whether this will occur depends on specific circumstances. Modeling and carefully designed field studies should be used to determine the responses of rangeland systems under a variety of environmental conditions and grazing intensities.

Spatial simulation of smallmouth bass in streams

Abstract: The hydropower industry and its regulators are hampered by the inability to predict the relationship between alternative flow regimes and fish population response. We have developed a spatially explicit, individual-based model of populations of small-mouth bass in streams as part of the Compensatory Mechanisms in Fish Populations Program (see Sale and Otto 1991). In the model, the profitability of alternative stream locations varies in response to habitat depth and velocity through changes in the frequency of prey encounters and the metabolic costs experienced by fish. We conducted an evaluation of our hydraulic simulation at the scale of individual stream cells. The potential error in predictions for individual cell velocities suggests that larger-scale model predictions for the representative reach are most appropriate. At this scale, the model appears to produce realistic patterns in the growth and dispersal of young-of-year small-mouth bass. This verification step allows us to proceed with greater confidence in evaluating the original question of how small-mouth bass populations respond to alternative flow regimes.