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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 15 (1999), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Initial appraisals of the status of endangered large-mammal populations may have to depend on indices of population trend. Such indices may possibly be improved by using auxiliary variables. Various models were studied for populations of the Florida manatee (Trichechus manatus latirostris), Yellowstone grizzly bear (Ursus arctos horribilis), and Hawaiian monk seal (Monachus schauinslandi). Several criteria for checking validity of the fitted models were considered, and the simple R2 criterion appears to provide useful comparisons. Multiple regression models overestimated the rate of change of the East Coast manatee population as determined from three other sources (a covariance model, a non-linear model, and the rate estimated from reproductive and survival data). A multiple regression model for grizzly bears using three auxiliary variables exhibited a fairly high R2 (0.84) and appeared to provide a better fit than did a non-linear model. A beach count index for Hawaiian monk seals seemed to be unreliable for year-to-year comparisons in contrast to total population counts and estimates from a capture-recapture method. The use of auxiliary variables for checking and improving trend index data appears feasible and well worthwhile.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 10 (1994), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Sea otters may give birth in any month of the year, so obtaining reproductive rates by observation is difficult. Reproductive rates may be estimated directly (births per otter-year observed) or by determining the time interval between births. Both methods give the same result for long sequences of observations, but field data are limited to shorter periods. Monte Carlo simulations were conducted to compare the two approaches, and showed that the interval method overestimates true reproductive rates.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 21 (2005), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This paper attempts to project the trends of Steller sea lion (Eumetopias jubatus) populations in six subdivisions of the western Alaska population. The overall Western Alaska population has declined dramatically since the 1970s. Trends in half of the areas appear to have leveled-off and possibly to be on the increase. Bootstrapping has been used to provide confidence intervals on predictions for the 2004 counts. For the three areas in which we expect increases, the 95% confidence intervals on predictions were: Eastern Gulf (2,430–3,740), Central Gulf (3,260–3,660) and Central Aleutians (5,160–6,580). The Western Gulf counts have been somewhat erratic, with a gradual rate of decrease (about 2% per year) and wide confidence limits on a linear prediction (logarithmic scale) of 2,690–3,240. Trends in the Eastern Aleutians have been even more erratic, so that about all that can be inferred is that the population may be roughly stabilized. Only the Western Aleutians appear to be rapidly declining at about 10% per year, with a 95% confidence interval on a linear trend of 610–1,100. The predictions were made before the 2004 counts and are in reasonable accord with the 2004 counts. Age structure changes do not appeat to provide a viable explanation for the changing trends.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 13 (1997), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 13 (1997), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The Pacific walrus (Odobenus rosmarus divergens) population is an important ecological and economic resource of the Bering Sea region. We describe population change, beginning with a low in 1950, through a high in about 1980, and ending in 1989. Estimates of abundance for the years after 1989 were not attempted due to the lack of harvest data and other population parameters. Selective hunting practices resulted in biased data regarding population composition and reproductive performance. Rates of reproduction had to be estimated from ovarian data, which indicated a dramatic drop in the 1980s. High harvests in the 1980s likely contributed to a decline in the population, but uncertainties as to accuracy of population estimates and other data raise reasonable doubts, especially with respect to the number of males, for which the most recent (1985) population estimate suggests a sharp decline. Past population estimates were revised upwards to compensate for walruses underwater and not seen in aerial surveys. The weaknesses in the available data make it clear that effective management of the population will require many improvements in collection of data regarding harvests, population structure, reproduction, and population trend.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 8 (1992), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: A new method, the “dynamic response method,” was developed (DeMaster et al. 1982) in an attempt to use time series data on relative population sizes to satisfy the requirements of the Marine Mammal Protection Act of 1972 for maintaining an “optimum sustainable population” of marine mammals. Three methods of implementing this approach were studied, using a computer simulation of stochastic population growth with density-dependence operating on first-year survival in the form of a generalized-logistic function. Methods developed by Gerrodette (1988) and Boveng et al. (1988) appeared to be less sensitive than desirable when used with the simulated population data. The third method, developed in this study, offers better protection against “Type II error” (failing to identify populations in the optimum sustainable population range), particularly when combined with Gerrodette's (1988) approach.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 204 (1964), S. 238-240 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] KNOWLEDGE of the inherent variability of radio -nuclide burdens of plants and animals is obviously of considerable importance in planning any kind of radiological survey of such populations, whether for research or health-protection purposes. A potentially important additional feature of such ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 230 (1971), S. 60-62 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The data of Fig. 1 were obtained using DDT labelled with chlorine-36 on the phenyl ring. This DDT was applied in an inert granular carrier7 from a helicopter to an enclosed 4 acre marsh at the south-western edge of Lake Erie in July 1964, at a rate of 0.2 pounds of technical grade DDT/acre (220 ...
    Type of Medium: Electronic Resource
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