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Geology topics

C.P. Goodyear

Publications and source records attributed to C.P. Goodyear.

At least 19 recordsLinked to original sources
USGS1985

Toxic materials, fishing, and environmental variation: Simulated effects on striped bass population trends

Decreased survival of larval striped bass Morone saxatilis resulting from toxic chemicals in the environment and decreased survival of adults caused by fishing both are suspected as agents contributing to the decline in the Chesapeake Bay stock since the mid‐1970s. The relative power of each type of mortality to cause population declines was evaluated with simulation techniques. Equivalent levels of added mortality induced qualitatively identical and quantitatively similar trends in population simulations for all conditions examined except if strong density‐dependent mortality preceded the contaminant toxicity. In this case the contaminant effect caused a greater reduction in yield, but the population did not tend toward extinction. The results indicate that the observed downward trend in the Chesapeake Bay population can be halted or reversed by a reduction in fishing mortality, even if contaminant toxicity is the proximate cause for the decline.

Maryland↗
USGS1985

Maryland striped bass: Recruitment declining below replacement

A mathematical technique was developed to examine interrelationships among first‐year survival rates, adult fecundity, and adult survival of striped bass Morone saxatilis based on indices of year‐class strength. Application of this technique to striped bass in Maryland waters of the Chesapeake Bay provided evidence for reduced survival in the life cycle. If adult fecundity and survival have remained constant, first‐year survival declined significantly from 1969 to 1983, and averaged less than that needed for replacement for the last 10 years. Treatment of the individual spawning grounds separately indicated that the downward trend in survival for the pooled data was the result of declines in the upper bay and, to a lesser extent, in the Choptank River. Alternatively, if first‐year survival and adult fecundity were assumed to have remained constant, an annual decline of about 1.9% in adult survival would have been required to produce the observed trend in the pooled year‐class data. This would be consistent with increased fishing mortality and implies declining recruitment because of declining stock size. Continuing declines in first‐year or adult survival would eliminate the Maryland striped bass stock and the fishery it supports. Conversely, an increase in adult survival could offset the effect of the unknown factor or factors responsible for the apparent decline in first‐year survival.

Maryland↗
USGS1985

Relationship between reported commercial landings and abundance of young striped bass in Chesapeake Bay, Maryland

The ability to predict subsequent landings of striped bass Morone saxatilis from the indices of abundance of juveniles (young of the year) determined annually by the Maryland Department of Natural Resources was evaluated by multiple‐regression techniques. About 57% of the variation in reported landings could be accounted for by the juvenile indices 2, 3, 4, and 5 years prior to the year of the landings for the period 1959–1983. Elimination of the first 4 years of record (1959–1962) increased the R 2 to 0.83. The regressions of reported landings on the indices of ages 2–5 striped bass for the periods 1964–1973 and 1974–1983 indicated that mortality in the fishable stock increased between the two periods. These results support the use of the juvenile indices for monitoring recruitment into the population and as a basis for management decisions.

Maryland↗
USGS1984

Bias-elimination in fish population models with stochastic variation in survival of the young

The addition of random variation in survival to a single prereproductive age class in a Leslie matrix population model can alter population growth in the modeled system. Methods are presented to characterize the stochastic variation in survival and to determine a correction factor that, when included in the model, will eliminate the propensity for the modeled population to systematically deviate from the initial conditions. This ability is important for applications of fish population models that seek to evaluate probability distributions of population trends that are associated with stochastic variations in survival, and to forecast the effects of changes in fishing mortality rates in fluctuating environments.

Transactions of the American Fisheries Society↗
USGS1984

On the ability to detect the influence of spawning stock on recruitment

Simulated observations of spawning stock size, recruitment, and two random environmental variables were obtained from a density-independent Leslie matrix model. Recruitment to Age 1 was directly proportional to population fecundity but strongly influenced by the effects of the random environmental variables. The simulated observations were subjected to multiple regression analysis which detected the influence of the random environmental variables but did not reliably detect the influence of spawning stock. These results indicate that multiple regression is unreliable in detecting the influence of stock on recruitment when annual variations in recruitment are primarily due to environmental factors.

North American Journal of Fisheries Management↗
USGS1984

Analysis of potential yield per recruit for striped bass produced in Chesapeake Bay

The yield of striped bass ( Morone saxatilis ) in biomass and numbers was estimated for constant recruitment of young fish into the population on the basis of vital statistics of the Maryland stock. Separate computations were performed for males, females, and sexes combined. Yield in biomass per individual entering the population was highest when the minimum legal length was in the range of 80-90 cm fork length and no upper size limits were imposed. The yield would increase at these size limits in both the Bay and Coastal fisheries, although the Coastal fishery would gain a slight relative advantage because the escapement of immature females from the Bay would increase. The most significant negative effect associated with an increase in the size limits would be the elimination of the traditional fisheries that focus on panfish (male and immature female striped bass 28-40 cm long). Although the length limits recommended in an existing Interstate Fisheries Management Plan for Striped Bass will increase yield per recruit, more stringent regulations would further increase the yield.

Maryland↗
USGS1984

Assessing the tolerance of fish and fish populations to environmental stress: The problems and methods of monitoring

Environmental stress is an inescapable aspect of life in the aquatic environment. The chemical and physical demands of life underwater impose somewhat rigorous constraints on aquatic species (Smith, 1982a). Superimposed on such demands may be the additional. physiological constraints of particular ecological niches. It is true that aquatic species are adapted to these conditions, but this does not imply the absence of energy drains (Lugo, 1978). For example, thermophilic fishes must still cope physiologically with the demands of high temperatures even though they are adapted to high temperatures per se.

Book chapter↗
USGS1984

Disease caused by environmental stressors

The use of the terms 'stress' and 'stressor' is sometimes inconsistent (e.g., Pickering, 1981). The term 'stressor' should be used to describe environmental or other factor intensities severe enough to require a compensatory response at any level of biological organization. A stressor is normally extrinsic. The term 'stress' indicates the organismic response initiated by the stressor, also at any level of biological organization. Thus, the original concept of Selye (1950) that stress is 'the sum of all the physiological responses by which an animal tries to maintain or re-establish a normal metabolism in the face of a physical or chemical force' has evolved into the concept that stress is the biological effect of any force that challenges homeostatic or stabilizing processes and extends them beyond their normal limits, at any level of biological organization - individual, population, or ecosystem (Esch and Hazen, 1978; Bayne, 1980).

Book chapter↗