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Author: Jacob Ellsworth Reighard
Publisher:
ISBN:
Category : Freshwater animals
Languages : en
Pages : 86
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Book Description
Author: Jacob Ellsworth Reighard
Publisher:
ISBN:
Category : Freshwater animals
Languages : en
Pages : 86
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Book Description
Author: J. E. Reighard
Publisher:
ISBN: 9781331967941
Category : Science
Languages : en
Pages : 74
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Book Description
Excerpt from A Biological Examination of Lake St. Clair The remedy does not lie in restrictive legislation; it lies rather in an increasing of the effectiveness of methods of artificial propagation and perhaps also in an increase of the annual output of artificially hatched fish. "The first view is held for the most part by fish culturists, who favor restrictive legislation and increased facilities for artificial propagation. "The second view is held for the most part by fishermen, many of whom are not yet convinced of the value of artificial propagation. "When one who is neither fish culturist nor fisherman attempts to discover the grounds upon which the various opinions are based, he very soon finds that there are but few recorded facts. "In order to know whether the number of whitefish is increasing or diminishing for any locality or for all localities, it is necessary to have statistics extending over a term of years. Statements based on statistics which are taken in two years separated by an interval of five or ten years are nearly valueless for purposes of comparison for the reason that such statistics do not and cannot take into account the climatic conditions which make one year favorable and another year unfavorable. The fact that in the year 1880 the number of whitefish marketed was greater than in 1890 does not prove that the number of whitefish has diminished in this interval; it proves only that the number caught in 1890 was less than the number caught in 1880. This may have been due to a diminution in the number of fish, but it may also have been due to storms during the fishing season of 1890. Statistics to be conclusive should enable us to compare the average yield for the ten years 1870 to 1880 with the average yield for the ten years 1880 to 1890. "No such continuous series of statistics is in existence, so that.the assertions concerning a diminishing yield of whitefish rest either on a comparison of these statistics of isolated years or on the statements of fishermen concerning certain localities. "If we inquire into the facts concerning the sufficiency of the present methods of artificial propagation, we find that so far as concerns the whitefish there is no question as to the success of the earlier stages of the process. Several hundred million ova are taken annually and placed in the hatcheries and of these usually from 80 to 90 percent are hatched and placed in the waters of the Great Lakes - 165,000,000 in Lake Erie alone in 1888. "This is very nearly all that is known about these young whitefish. About their food habits we know only that in captivity that they eat certain species of Crustacea. Whether in their natural habitat they eat other animals in addition to these Crustacea or in preference to them we do not know. It is uncertain at what age they begin to take food or how much they require. We do not know their natural enemies. We do not know whether they thrive best in running water or in standing water, in shallow water or in deep water, whether at the surface or near the bottom. What changes of habitat or of food habits the fish undergo as they grow older is a still deeper mystery. "Our problem is to place young whitefish in the Great Lakes under such conditions that as large a number as possible of them shall grow into adult fish. It is clear that of one of the elements in this problem namely, the whitefish, we know but little. "What, then, do we know of the other elements of the problem, the Great Lakes themselves? About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com
Author: Michigan. State Board Of Fish Commission
Publisher:
ISBN: 9781293418130
Category :
Languages : en
Pages : 74
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Book Description
Author: Jacob Ellsworth Reighard
Publisher:
ISBN:
Category :
Languages : en
Pages : 60
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Book Description
Author: A. J. Pieters
Publisher:
ISBN:
Category :
Languages : en
Pages : 22
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Book Description
Author: Charles J. Krebs
Publisher: Benjamin-Cummings Publishing Company
ISBN: 9780321068798
Category : Science
Languages : en
Pages : 695
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Book Description
This best-selling majors ecology book continues to present ecology as a series of problems for readers to critically analyze. No other text presents analytical, quantitative, and statistical ecological information in an equally accessible style. Reflecting the way ecologists actually practice, the book emphasizes the role of experiments in testing ecological ideas and discusses many contemporary and controversial problems related to distribution and abundance. Throughout the book, Krebs thoroughly explains the application of mathematical concepts in ecology while reinforcing these concepts with research references, examples, and interesting end-of-chapter review questions. Thoroughly updated with new examples and references, the book now features a new full-color design and is accompanied by an art CD-ROM for instructors. The field package also includes The Ecology Action Guide, a guide that encourages readers to be environmentally responsible citizens, and a subscription to The Ecology Place (www.ecologyplace.com), a web site and CD-ROM that enables users to become virtual field ecologists by performing experiments such as estimating the number of mice on an imaginary island or restoring prairie land in Iowa. For college instructors and students.
Author: Arie Wallert
Publisher: Getty Publications
ISBN: 0892363223
Category : Art
Languages : en
Pages : 241
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Book Description
Bridging the fields of conservation, art history, and museum curating, this volume contains the principal papers from an international symposium titled "Historical Painting Techniques, Materials, and Studio Practice" at the University of Leiden in Amsterdam, Netherlands, from June 26 to 29, 1995. The symposium—designed for art historians, conservators, conservation scientists, and museum curators worldwide—was organized by the Department of Art History at the University of Leiden and the Art History Department of the Central Research Laboratory for Objects of Art and Science in Amsterdam. Twenty-five contributors representing museums and conservation institutions throughout the world provide recent research on historical painting techniques, including wall painting and polychrome sculpture. Topics cover the latest art historical research and scientific analyses of original techniques and materials, as well as historical sources, such as medieval treatises and descriptions of painting techniques in historical literature. Chapters include the painting methods of Rembrandt and Vermeer, Dutch 17th-century landscape painting, wall paintings in English churches, Chinese paintings on paper and canvas, and Tibetan thangkas. Color plates and black-and-white photographs illustrate works from the Middle Ages to the 20th century.
Author: Anonymous
Publisher: Applewood Books
ISBN: 0918222842
Category : History
Languages : en
Pages : 129
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Book Description
Presents an account, first published in 1622, of the Pilgrim's journey to the new world.
Author:
Publisher:
ISBN:
Category : Freshwater invertebrates
Languages : en
Pages : 150
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Book Description
Sediment contamination is a widespread environmental problem that can potentially pose a threat to a variety of aquatic ecosystems. The sediment test methods in this manual will be used by The United States Environmental Protection Agency (USEPA) to make decisions under a range of statutory authorities concerning such issues as: dredged material disposal, registration of pesticides and toxic substances, superfound site assessment, and assessment and cleanup of hazardous waste treatment, storage, and disposal facilities. The use of uniform sediment testing procedures by USEPA programs is expected to increase data accuracy and precision, facilitate test replication, increase the comparative value of test results, and ultimately, increase the efficiency of regulatory processes requiring sediment tests.
Author: Simone de Beauvoir
Publisher: Vintage
ISBN: 0679724516
Category : Social Science
Languages : en
Pages : 791
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Book Description
The classic manifesto of the liberated woman, this book explores every facet of a woman's life.
