摘要:

We report on a 20-year integrated field, laboratory, and simulation study of the impact of thermal effluent from a nuclear power plant on the smallmouth bass Micropterus dolomieui population in Baie du Doré, Lake Huron. A quantitative model was constructed to forecast the range of likely effects of the plant on the population. The model was based on the findings of 50 years of basic research on smallmouth bass ecology in Ontario and on 15 years of environmental and biological data collected at Baie du Doré before the power plant became operational. The model embodies detailed descriptions of both the natural variation in water temperature at Baie du Doré, and the mechanisms whereby variations in temperature generate variations in cohort strength. Five years of monitoring data, collected after the plant became operational, were used to evaluate the forecasts of the model. Observed effects on timing of spawning and individual growth were generally within the range defined by the forecasts. The thermal effluent also altered the distribution of adult fish and this, in turn, led to an increase in the effectiveness of the angling fishery. Data from the postoperational period were used to refine the assessment model. The revised model was then used to evaluate the long-term effects on the population of the changes observed to date. We describe how the availability of extensive site-specific and species-specific data helped us to deal with technical problems that have plagued other impact assessment projects. We also discuss the contributions of basic research and quantitative modelling to the effectiveness of the study.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<631:AAOEM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Such facilities as power-generating stations, public water systems, and ore-processing plants draw off large quantities of water from estuaries, coastal seawaters, lakes, and rivers. In turn, large numbers of fishes are often drawn into these pumped intake systems and killed if not otherwise removed or diverted. The large mortalities associated with many intake systems threaten the perpetuation of indigenous stocks. The diversion and removal devices most commonly used for protecting fish life from such risks are presumed to operate on principles shown here to be erroneously conceived. In consequence of these faulty theories, the estimators and experimental designs of standard industry practice seldom reveal the true correlations necessary for improvements in fish conservation systems, nor do the assessments of small-scale experiments extend with reliability to full-scale system designs. Such passive devices as angled barrier screens are thought to guide fish in some way into pumped bypassing ducts, but an analysis of existing data supports instead a hypothesis of random encounter whereby the activities of entrapped fish are governed by the probabilistic mechanics associated with random walks and unlike boundary conditions. Experimental designs for separating and assessing time-dependent risks are developed for the case of competing devices in a given test system. From time-dependent comparisons between large and small systems (in particular, between a model system and its full-scale prototype), the net decrease in the probability of fish survival associated with increased system size is shown to be the consequence of increased exposure to the risk of death (increased residence time) rather than the consequence of increases in the unit risk of death itself. Where extensions of small-scale empirical results to full-scale system designs are wanted, arithmetic extrapolations yield erroneous results. Because displacement dependence (fish movement and system size) enters the risk analysis, the scaling problem must be resolved instead from a corresponding system of partial differential equations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<652:RAFFDE>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Microhabitat requirements were determined for eight species of native California stream fishes: Rainbow trout Salmo gairdneri; Sacramento sucker Catostomus occidentalis; Sacramento squawfish Ptychocheilus grandis; hardhead Mylopharodon conocephalus; California roach Hesperoleucus symmetricus; speckled dace Rhinichthys osculus; tule perch Hysterocarpus traski; and riffle sculpin Cottus gulosus. Two or three size classes were evaluated for each species. Each species had a preferred microhabitat (defined on the basis of depth, velocity, substrate), as did each size class within each species, but there was much similarity in microhabitat use within and among species. The amount of microhabitat available to each species differed in three stream reaches in which availability was quantified, but the differences were not enough to explain the differences in composition of the fish assemblage found at each site. This study indicates that recommendations for instream flows should be based on microhabitat use data collected on site together with habitat availability data. Even on-site data should be used cautiously because intraspecific interactions and changes in a stream's physical characteristics, especially in its temperature regime, may cause unexpected shifts in microhabitat use.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<695:MUBAAO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The effects of introduced green sunfish Lepomis cyanellus on native fish communities in headwater streams of North Carolina's Piedmont region were assessed from stream surveys and removal experiments. Green sunfish occurred in most first-order tributaries; when they were present, their abundance and biomass almost always exceeded that of any other coexisting species. Green sunfish also occurred in all second- and third-order streams surveyed, but they never dominated the fish community by numbers or weight in those situations. When green sunfish were removed from three first-order streams, most native species increased in numbers and biomass; in two streams the increase more than made up (within 2 years) the biomass that had been lost by removing green sunfish. These removal experiments indicate that green sunfish suppress native fish populations in Piedmont headwaters. Predation on the young of other species is one likely means by which they do this.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<705:SONFPB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

We examined population dynamics of rainbow smelt Osmerus mordax in South Bay of Lake Huron during intensive fishing of the spring spawning runs (1948–1957) and after exploitation was stopped (1958–1970). Modal ages of spawning rainbow smelt changed from 2 to 3 during the intensive fishing period to 3 and 4 after 1959. Percentage males in the spawning run samples from dip nets increased from 60% (1950–1957) to 78% (1958–1964). Percentage males in summer samples from gill nets increased from 39% to 50% between the same periods. Total annual mortality rate averaged 90% during exploitation and 67% after fishing stopped. Instantaneous natural mortality rate during 1948–1970 was estimated as 1.1. Relative stock sizes, estimated from cohort analysis, sharply increased after 1957; an extremely large 1960 year-class caused a peak in 1962. Growth of rainbow smelt to age 1 and to age 2 was decreasing while their own abundance and that of alewives Alosa pseudoharengus were increasing. Growth after age 2 was independent of abundance of 1-year-olds and total stock. Average fish growth for each cohort declined and abundance of 1-year-olds increased during and after exploitation, but growth slowed more rapidly after 1960 and greater numbers of 1-year-olds fluctuated more widely. Lengths at capture were much greater during 1948–1957 than during 1966–1970. Total abundance of rainbow smelt in South Bay increased and growth declined during exploitation because the stock was expanding to a carrying capacity not yet reached after a severe die-off in winter 1942–1943. We suggest that immigration of spawners into South Bay from a discrete stock in Lake Huron, and relatively faster growth to maturity, allowed the population to withstand the fishing pressure.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<713:DORSDA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The effects of vegetative cover and relative size of prey were tested on the forage preference of juvenile largemouth bass Micropterus salmoides offered blue tilapias Tilapia aurea and bluegills Lepomis macrochirus in laboratory electivity experiments. When offered forage at or near the maximum consumable size in tanks without vegetative cover, largemouth bass preferred bluegills, but consumed blue tilapias in the presence of vegetation. When offered forage smaller than the maximum consumable size in tanks without vegetation, largemouth bass selected blue tilapias. Differences between the forage species in body morphology and effective use of protective cover apparently caused the changes in prey selection. Our results suggest blue tilapias may be a suitable forage for largemouth bass, but that habitat characteristics and relative size distributions of other available forage may affect their use.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<725:EOCAPS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The avoidance response of juvenile coho salmon Oncorhynchus kisutch to L-serine and D,L-alanine was measured in a two-choice Y-trough. Threshold concentration for olfactory detection and avoidance of L-serine was 10−8M for zero-age parr, 10−7M for yearling parr, 10−5M for smolts in late April-early May, and 10−6M for smolts in June. Threshold for the avoidance of D,L-alanine was 10−7M for yearling parr, 10−6M for smolts in late April-early May, and 10−5M for smolts in June. These data suggest that (1) heightened olfactory sensitivity may not occur during smoltification or (2) smolts may be less disposed than parr to show avoidance behavior.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<732:OSDPAS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

As part of a study of the life cycle of the smallmouth bass Micropterus dolomieui, young of the year were sampled in the Baie du Doré, Lake Huron, during six summers to determine growth after dispersal from nests. Length-frequency distributions were plotted approximately weekly each of the summers. The changes through time of the mean size of fish in each cohort were described by a mathematical model that assumed a size-dependent growth rate and no size-dependent mortality for the fish. The constraint on the model to fit the empirical mean fish sizes through the growing season automatically produced time-varying standard deviations of the size distributions that compared closely to the empirical standard deviations for 5 out of the 6 years. The poor fit to the standard deviations of the sixth year was explicable in terms of unusual data on one sampling date. These results suggest that size dependence of the growth rate was an important mechanism in the spread in the length-frequency distribution and that size-dependent mortality played no significant role in determining the changes in this distribution through the growing season. Because winter mortality of first-year smallmouth bass in northern waters is important in their population dynamics and is size-dependent, the model provides a link in the understanding of smallmouth bass populations and their management.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<737:AEMOSD>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Several methods are available to estimate mortality from catch curves. These methods include least squares, a maximum-likelihood method developed by Chapman and Robson, and a “simple” estimator proposed by Ssentongo and Larkin. All three of these methods are based on similar models for mortality, but data requirements are different, and they can give considerably different estimates of mortality. These three methods are compared by applying them to catch curves for natural populations, to catch curves generated by a deterministic model, and to catch curves generated by a stochastic model. In general, the least-squares estimator is the most precise under conditions encountered in assessment of fisheries, but if variation is unusually high, the maximum-likelihood estimator developed by Chapman and Robson is more precise. The “simple” estimator developed by Ssentongo and Larkin can result in serious error.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<743:COCMFE>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The toxicity to young striped bass Morone saxatilis of a contaminant mixture composed of organic and inorganic chemicals was determined in fresh and saline waters when the fish were 35–80 d old. Decreases in water hardness and associated decreases in alkalinity and pH increased the toxicity of the mixture. This increase was attributed to changes in the speciation of inorganic chemicals in water of differing qualities. Under standard conditions for acute toxicity tests, cadmium, copper, zinc, nickel, and chromium were more toxic to striped bass in soft than in slightly saline water. Overall, striped bass were as sensitive as most salmonid species to seven inorganic chemicals and three organic insecticides, and much more sensitive than the cyprinids, ictalurids, and centrarchids that have been tested.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<748:SOYSBT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor