Ecosystem Concepts in Fish and Game Management

Wagner, Frederic H.

doi:10.1016/b978-0-12-713450-5.50016-6

Cited by 20 publications

(8 citation statements)

References 56 publications

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“…This is an interesting result and indicates the importance of environmental variables to the study of Mallard population dynamics. DISCUSSION An essential point in population ecology is how a population responds to predation or exploitation (Wagner 1969, Huffaker 1970. Mech (1966:167), studying moose and wolves on Isle Royale in Lake Superior, noted, "The important question is whether wolves merely substitute for other factors or whether they kill more animals than other factors would.…”

Section: Hypothesis Testingmentioning

confidence: 99%

Optimal Exploitation Strategies for an Animal Population in a Markovian Environment: A Theory and an Example

Anderson

1975

Ecology

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Optimal exploitation strategies were studied for an animal population in a Markovian (stochastic, serially correlated) environment. This is a general case and encompasses a number of important special cases as simplifications. Extensive empirical data on the Mallard (Anas platyrhynchos) were used as an example of general theory. The number of small ponds on the central breeding grounds was used as an index to the state of the environment. A general mathematical model was formulated to provide a synthesis of the existing literature, estimates of parameters developed from an analysis of data, and hypotheses regarding the specific effect of exploitation on total survival. The literature and analysis of data were inconclusive concerning the effect of exploitation on survival. Therefore, two hypotheses were explored: (1) exploitation mortality represents a largely additive form of mortality, and (2) exploitation mortality is compensatory with other forms of mortality, at least to some threshold level. Models incorporating these two hypotheses were formulated as stochastic dynamic programming models and optimal exploitation strategies were derived numerically on a digital computer. Optimal exploitation strategies were found to exist under the rather general conditions. Direct feedback control was an integral component in the optimal decision—making process. Optimal exploitation was found to be substantially different depending upon the hypothesis regarding the effect of exploitation on the population. If we assume that exploitation is largely an additive force of mortality in Mallards, then optimal exploitation decisions are a convex function of the size of the breeding population and a linear or slight concave function of the environmental conditions. Under the hypothesis of compensatory mortality forces, optimal exploitation decisions are approximately linearly related to the size of the Mallard breeding population. Dynamic programming is suggested as a very general formulation for realistic solutions to the general optimal exploitation problem. The concepts of state vectors and stage transformations are completely general. Populations can be modeled stochastically and the objective function can include extra—biological factors. The optimal level of exploitation in year t must be based on the observed size of the population and the state of the environment in year t unless the dynamics of the population, the state of the environment, and the result of the exploitation decisions are completely deterministic. Exploitation based on an average harvest, or harvest rate, or designed to maintain a constant breeding population size is inefficient.

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Section: Hypothesis Testingmentioning

confidence: 99%

Optimal Exploitation Strategies for an Animal Population in a Markovian Environment: A Theory and an Example

Anderson

1975

Ecology

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“…In this paper we will define "regulation" as the action of those processes tending to restore the population to a steady-state density (K of the logistic) following perturbation from that density. As such this is a process distinct from that of determining the steadystate density (Wagner et al 1965, Wagner 1969, Wilbert 1969). Wilbert called the latter process "determination."…”

Section: Population Changementioning

confidence: 99%

“…Hence rm values can be used to compare suitabilities of empty habitats by extrapolating from a series of r. values determined at varying densities within a habitat (Wagner 1969). Also r, values in the same habitat can be compared directly to assess density effects.…”

Section: Population Changementioning

confidence: 99%

Population Ecology of Uinta Ground Squirrels

Slade¹,

Balph²

1974

Ecology

192

101

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Abstract. The behavior and ecology of Uinta ground squirrels (Spermophilus armatus) at the Utah State University Forestry Field Station northeast of Logan, Utah, were studied 1964-71 to determine the role of behavior in population regulation. In 1968 the population was reduced experimentally to about one-half the previous density.The study area consisted of a lawn area where resident squirrels more than replaced themselves, and an area of mixed shrubs and grasses where they did not. Surplus squirrels from the lawn raised the population density off the lawn. Also, habitat suitabilities varied with population densities. Hence, densities in the two areas were not proportional to habitat preferences.Before the reduction the population density fluctuated widely but the mean change for 5 yr was approximately zero. A potentially high rate of increase was curtailed by disappearance of juveniles and yearlings; juveniles tended to disperse from the natal burrow. The principal changes following the reduction were increases in percentage of yearling squirrels breeding and of juveniles remaining on the study area. Litter size and proportion of adult females breeding did not change significantly, but losses during hibernation, due in part to badger predation, decreased. Dispersal of squirrels from the study area played a key role in population regulation.Dispersers probably suffered higher mortality than sedentary squirrels, but dispersal was not necessarily maladaptive for the individual. Dispersers may have been unable to produce young at high densities; thus emigration offered the only opportunity for reproduction.

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“…The concept of biological production has long served as a cornerstone in the development of the theory of resource management (Watt 1968). An early focus on this issue in fisheries research distinguished it from other approaches in population biology in the emerging field of ecosystem-based fisheries management (EBFM : Wagner 1969). In their classic monograph on the dynamics of exploited fish populations, Beverton & Holt (1957) provided an elegant treatment of the harvesting problem with an emphasis on production of individual species at the cohort and population levels.…”

Section: Introductionmentioning

confidence: 99%

Assembly rules for aggregate-species production models: simulations in support of management strategy evaluation

Gaichas¹,

Gamble²,

Fogarty³

et al. 2012

Mar. Ecol. Prog. Ser.

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Ecosystem-based fisheries management (EBFM) emphasizes sustainability at multiple levels of organization beyond single target species. Therefore, biological reference points (BRPs) for aggregated groups are required, which optimize yields while preventing overexploitation of individual species. We evaluate the tradeoffs between yield and biodiversity objectives for a wide range of aggregation strategies using multispecies surplus production models and comparing 2 simulated fish communities. We simulated population trajectories with an operating model detailing predation and competitive interactions for all individual species within each community, and with additional stochastic environmental variability for one community. Species trajectories were then aggregated by functional feeding guild, taxonomy, habitat association, size class, and at the entire community level. We estimated production parameters and BRPs (e.g. maximum sustainable yield, MSY) using a simple assessment model applied to each aggregated time series, then we applied the MSY fishing rates to each simulated community as alternative fishing strategies and compared equilibrium biomass and yield under each strategy. We were able to define multi-species reference points to meet both yield and biodiversity objectives across full system, taxonomic, habitat, feeding, and size-based aggregations. Species complexes were best able to meet both objectives when species with broadly similar productivity, environmental sensitivity and species interactions were aggregated into the complex. The impacts of simulated environmental variability on BRPs were substantial for certain species and aggregates, so including the combined impacts of environmental variation and species interactions in precautionary reference points appears critical to EBFM.

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Ecosystem Concepts in Fish and Game Management

Cited by 20 publications

References 56 publications

Optimal Exploitation Strategies for an Animal Population in a Markovian Environment: A Theory and an Example

Optimal Exploitation Strategies for an Animal Population in a Markovian Environment: A Theory and an Example

Population Ecology of Uinta Ground Squirrels

Assembly rules for aggregate-species production models: simulations in support of management strategy evaluation

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