Age At Maturity Of The Pacific Coast Salmon Of The Genus Oncorhynchus Microform
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Age At Maturity Of The Pacific Coast Salmon Of The Genus Oncorhynchus Microform
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Author : British Columbia. Provincial Fisheries Department
language : en
Publisher:
Release Date : 1912
Age At Maturity Of The Pacific Coast Salmon Of The Genus Oncorhynchus Microform written by British Columbia. Provincial Fisheries Department and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1912 with Pacific salmon categories.
Age At Maturity Of The Pacific Coast Salmon Of The Genus Oncorhynchus Microform
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Author : Charles H (Charles Henry) Gilbert
language : en
Publisher: Legare Street Press
Release Date : 2021-09-09
Age At Maturity Of The Pacific Coast Salmon Of The Genus Oncorhynchus Microform written by Charles H (Charles Henry) Gilbert and has been published by Legare Street Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-09-09 with categories.
This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. To ensure a quality reading experience, this work has been proofread and republished using a format that seamlessly blends the original graphical elements with text in an easy-to-read typeface. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.
Changes In Size And Age At Maturity Of Columbia River Upriver Bright Fall Chinook Salmon Oncorhynchus Tshawytscha
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Author : Roy E. Beaty
language : en
Publisher:
Release Date : 1992
Changes In Size And Age At Maturity Of Columbia River Upriver Bright Fall Chinook Salmon Oncorhynchus Tshawytscha written by Roy E. Beaty and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992 with Chinook salmon categories.
The average size and age of chinook salmon (Oncorhynchus tshawytscha) caught in commercial fisheries along the Pacific Coast of North America have decreased substantially in this century. These declines might be caused in part by changes in size and age at maturity within the stocks contributing to those fisheries. Upriver Brights (Brights), a stock of fall chinook salmon in the Columbia River, are one of those stocks. The purposes of this study were to (1) determine if average size and age at maturity of Brights have declined, (2) gain a better understanding of the factors that may contribute to such declines, and (3) describe potential consequences of these changes. Data from in-river fisheries suggest that the average weight of mature Brights returning to the Columbia River has decreased approximately 2.7 kg since the 1910s, an average rate of about 0.1 lb·yr−1 (45 g·yr−1). Most of the potential biases in these data tend to make this estimate conservative. Insufficient data were available to describe changes in average age at maturity. There are many potential causes for the decline in average size of mature Brights, including factors that affect very early life stages. Other researchers have determined that size at maturity appears to be highly influenced by inheritance, gender, and growth rate. I describe how maternal size can influence -- through time of spawning, choice of spawning site, and egg size -- the viability of the young, which carry the dam's genes for size. The size-related ability to produce viable offspring may have been changed by modifications in the environment. Very little is known about how changes in the natural environment for spawning, incubation, and rearing may have contributed to a decline in average size at maturity. Artificial propagation and rearing, such as at Priest Rapids Hatchery, seems to produce adult Brights that are smaller, younger, and more likely to be male than their natural counterparts. The net result is that the average hatchery fish may have only about 0.80 of the reproductive potential of the average natural fish. Changes in growth conditions in the ocean probably did not contribute to the change in size, although the ocean fisheries of Southeast Alaska and British Columbia appear to select, in the genetic sense, against large size and old age in Brights. Since 1978, in-river commercial fisheries have caught larger Brights and a higher proportion of females than are found in the escapement of the Priest Rapids Hatchery component of the stock, but the fisheries impact the two sexes differently by taking the larger males and the smaller females. The effect on the natural component may differ because of their apparently larger average size. I found no evidence that larger fish or more females were caught when 8-in. minimum restrictions were in effect on gillnet mesh size relative to periods when mesh size was not restricted. Impounding the mainstem during the last 50+ yr may have removed obstacles to migration (e.g., Celilo Falls) that selected for large size in Brights, but that hypothesis could not be tested. The perserverance of larger and older phenotypes in the Bright stock suggests that countervailing selection -- perhaps during spawning, incubation, and/or early rearing -- may have resisted the effects of a century of size- and age-selective fisheries. That resistance, however, may reduce the productivity of the stock. Declines in average size and age at maturity can have undesireable consequences. Lower average size means less biomass landed and lower commercial value. Lower average fecundity and a diminished ability to reproduce in some environments are also expected. Loss of size and age classes may reduce the ability of the stock to adapt to environmental variations. These results are relevant to several management practices. A holistic approach to fishery management issues is necessary to avoid erroneous conclusions based on narrow perspectives. Measuring reproductive potential of the catch and escapement would be superior to the conventional practice of simply counting numbers of fish. Many aspects of artificial propagation can be improved, including broodstock aquisition, mating regimes, and rearing practices. Stock abundance is a major factor in determining the effect of many management practices on the stock. In general, fisheries managers must be mindful that they manage very complex natural systems.
Methods For Measuring The Acute Toxicity Of Effluents And Receiving Waters To Freshwater And Marine Organisms
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Author :
language : en
Publisher: DIANE Publishing
Release Date : 2002
Methods For Measuring The Acute Toxicity Of Effluents And Receiving Waters To Freshwater And Marine Organisms written by and has been published by DIANE Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Water quality biological assessment categories.
Coastal Fishes Of The Pacific Northwest
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Author : Andy Lamb
language : en
Publisher: Harbour Publishing Company
Release Date : 2010
Coastal Fishes Of The Pacific Northwest written by Andy Lamb and has been published by Harbour Publishing Company this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Nature categories.
Written by a marine biologist and illustrated in colour by a prizewinning underwater photographer, Coastal Fishes of the Pacific Northwest identifies each fish by its common name and is illustrated with full-colour photographs and labelled sketches. Special sections present catching tips for anglers and commercial fishermen; location hints for divers, beachcombers and pleasure boaters; and cooking ideas for seafood gourmets. The information included in these sections provides a brief but detailed description of each fish's habitat, physical characteristics and behaviour--everything that a fisherman or an amateur naturalist needs to know!
A Handbook Of Global Freshwater Invasive Species
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Author : Robert A. Francis
language : en
Publisher: Routledge
Release Date : 2012-03-12
A Handbook Of Global Freshwater Invasive Species written by Robert A. Francis and has been published by Routledge this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-03-12 with Science categories.
Invasive non-native species are a major threat to global biodiversity. Often introduced accidentally through international travel or trade, they invade and colonize new habitats, often with devastating consequences for the local flora and fauna. Their environmental impacts can range from damage to resource production (e.g. agriculture and forestry) and infrastructure (e.g. buildings, road and water supply), to human health. They consequently can have major economic impacts. It is a priority to prevent their introduction and spread, as well as to control them. Freshwater ecosystems are particularly at risk from invasions and are landscape corridors that facilitate the spread of invasives. This book reviews the current state of knowledge of the most notable global invasive freshwater species or groups, based on their severity of economic impact, geographic distribution outside of their native range, extent of research, and recognition of the ecological severity of the impact of the species by the IUCN. As well as some of the very well-known species, the book also covers some invasives that are emerging as serious threats. Examples covered include a range of aquatic and riparian plants, insects, molluscs, crustacea, fish, amphibians, reptiles and mammals, as well as some major pathogens of aquatic organisms. The book also includes overview chapters synthesizing the ecological impact of invasive species in fresh water and summarizing practical implications for the management of rivers and other freshwater habitats.
The Bering Sea Ecosystem
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Author : National Research Council
language : en
Publisher: National Academies Press
Release Date : 1996-05-08
The Bering Sea Ecosystem written by National Research Council and has been published by National Academies Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996-05-08 with Science categories.
The Bering Sea, which lies between the United States and Russia, is one of the most productive ecosystems in the world and has prolific fishing grounds. Yet there have been significant unexplained population fluctuations in marine mammals and birds in the region. The book examines the Bering Sea ecosystem's dynamics and the relationship between man and the ecosystem, in order to identify potential reasons for the population fluctuations as well as identify ways the Sea's living resources can be better managed by government.
A History Of Fishing
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Author : Dietrich Sahrhage
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
A History Of Fishing written by Dietrich Sahrhage and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
Described here are the origin and general trends in the development of fishing from the earliest times up to the present in various parts of the world. The techniques applied and the economic and social problems involved are covered. Fishing methods have not changed much since the Stone Age, but continuous technical improvements like the construction of sea-worthy ships, more efficient gear, and finally mechanization of fishing have led to enormous development and a high fish production, of now 100 million tons per year. Extensive utilization has caused heavy overexploitation of the resources and consequently growing concern. The book concludes with an evaluation of perspectives for the future utilization of living resources.
Agrindex
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Author :
language : en
Publisher:
Release Date : 1993
Agrindex written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with Agriculture categories.
Lake Biwa Interactions Between Nature And People
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Author : Hiroya Kawanabe
language : en
Publisher: Springer Nature
Release Date : 2020-08-25
Lake Biwa Interactions Between Nature And People written by Hiroya Kawanabe and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-08-25 with Science categories.
Although, the first edition had a similar focus, more than five years have passed since its publication and the biological and social circumstances of the lake have drastically changed due to, for example, the further expansion of alien species, the decrease of indigenous species, the progress of integrated watershed management by the Union of the Kansai Government which was established in 2010, the legislation of the Conservation and Restoration Act of Lake Biwa in 2015 and more. The new edition will therefore feature updated and new information on the above and more topics as well as updated and revised data based on the latest research. Inventories of respective taxa, especially those of small animals, are also revised based on the latest studies. Furthermore, this volume covers the characteristics of the biota of this ancient lake, but at the same time, it will also approach it as a ‘culture ancient lake’. Other topics also include water pollution, lakeshore development, the effects of global warming in the past and present, the influence of people, and countermeasures by local and national governments. Moreover, the volume also provides a comprehensive view on the future of Lake Biwa and that of its residents. Miraculously enough, this ancient lake has kept its water quality clear even until today despite the fact of more than 1.4 million people living on its shores. Finally, the book also gives indispensable information to those engaged in improving and conserving water regimes of lakes and other water bodies all over the world and to those interested in the culture and history of Japan. Lake Biwa is not only one of the rarest ancient lakes of the world, but the people’s involvement with the lake also goes back a long way. This is shown in the diverse culture developed in this area and in the various archaeological finds that date back as early as the Jomon Period, nearly 10.000 years ago. Today Lake Biwa fulfills an important role as a water resource by providing domestic, commercial, industrial, and agricultural water for over 14 million residents living around the Lake Biwa-Yodo River drainage basin. This updated volume focuses on the geological and biological features of the lake as well as on the long-term interactions between the people and the lake.