Download or read book A Method to Reduce Survey Bottom Trawl Variability written by A. Engas and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Surveys of Fisheries Resources written by Donald R. Gunderson and published by John Wiley & Sons. This book was released on 1993-05-06 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: Commences with a discussion of biological and statistical considerations involved in designing an effective survey. Examines sampling equipment and techniques used in conducting direct surveys with equal attention to trawl, acoustic, ichthyoplankton and sighting studies. Alternative approaches used in each type of survey are reviewed and numerous case histories illustrate successful applications.
Download or read book Effects of Trawling and Dredging on Seafloor Habitat written by National Research Council and published by National Academies Press. This book was released on 2002-08-09 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concerns over the potential ecological effects of fishing have increased with the expansion of fisheries throughout the marine waters of the United States. Effects of Trawling and Dredging on Seafloor Habitat describes how assessment of fishing impacts depends on gear type, number and location of bottom tows, and the physical and biological characteristics of seafloor habitats. Many experimental studies have documented acute, gear-specific effects of trawling and dredging on various types of habitat. These studies indicate that low mobility, long-lived species are more vulnerable to towed fishing gear than short-lived species in areas where the seabed is often disturbed by natural phenomena. Trawling and dredging may also change the composition and productivity of fish communities dependent on seafloor habitats for food and refuge. The scale of these impacts depends on the level of fishing effort. This volume presents color maps of fishing effort for all regions with significant bottom trawl or dredge fisheries-the first time that such data has been assembled and analyzed for the entire nation.
Download or read book Bottom Trawl Surveys written by W. G. Doubleday and published by Department of Fisheries and Oceans = Ministère des pêches et des océans. This book was released on 1981 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal of Northwest Atlantic Fishery Science written by and published by . This book was released on 1999 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Alternative Sampling and Estimation Methods for Multispecies Trawl Surveys written by Sherri Christine Dressel and published by . This book was released on 2004 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Multispecies demersal trawl surveys are used in the United States and internationally to estimate the relative abundance of commercial and non-commercial fish species. Their usefulness for estimating species' abundance is often limited by the variance associated with estimates. This study implemented and evaluated alternative sampling and estimation methods, with the goal to incorporate additional sources of information for increased precision of individual species' estimates from multispecies trawl surveys. First, habitat characteristics and past spatial distributions of four flatfish species' density were incorporated into a multispecies trawl survey design conducted in Kalsin and Middle Bays, Kodiak Island, Alaska. Stratification by depth and percent sand produced estimates of relative abundance with lower CV s than those from unstratified sampling. Additional decreases in relative precision were generally not achieved by estimating the relative abundance of multiple species from regions of species-specific suboptimal habitat. Second, a poststratification technique was used to incorporate species-specific habitat characteristics and previous distributions of species' density into the estimation of species' abundance from the Kalsin and Middle Bays' trawl survey. Poststratification by habitat gave estimates with lower variance and/or less design-bias than an unstratified estimator for all species in all years. Poststratification by habitat and fish density produced estimates with the least design-bias for all species in all years and the lowest variance when stratum sample sizes were sufficient. Third, mixed model linear regression (MMLR), empirical Bayes (EB) and hierarchical Bayes (HB) estimation methods were used to incorporate historical trends of yellowfin sole, Limanda aspera biomass from the eastern Bering Sea trawl survey into annual biomass estimates. Using MMLR, EB, and HB methods resulted in biomass estimates that were less anomalous than survey estimates with respect to a linear regression trend. Estimates for all three methods had lower CV s than surveys in most years. The results of this thesis suggest that incorporating additional information into survey design and estimation can decrease the variability of survey estimates and/or correct for possible bias. Methods that can incorporate additional information, therefore, have the potential to improve survey assessments for management use"--Leaf iii-iv.
Download or read book Norwegian Spring spawning Herring Northeast Arctic Cod written by Odd Nakken and published by Tapir Academic Press. This book was released on 2008 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: Norwegian spring-spawning herring and Northeast Arctic cod are two of the largest and commercially most important fish stocks in the North Atlantic. Both these stocks have their spawning fields along the Norwegian coast and they have been the major target species for Norwegian fisheries for a millennium. They are also among the few fish stocks in the world which have been systematically investigated and monitored for more than a century. The scientific results, arrived at early in the 20th century for these two stocks, formed the basis for much of the development in international fisheries science later on. This book describes how fisheries, fisheries science, and management for Norwegian spring-spawning herring and Northeast Arctic cod developed during the 20th century. Over time, both populations developed serious decline in stock size and yield due to overfishing. The herring stock was in a state of collapse for about 20 years. Management measures that were then introduced permitted both stocks to recover in the 1990s. The contributors to the book have all been working as fisheries scientists at the Institute of Marine Research in Bergen.
Download or read book Technical guidelines for scientific surveys in the Mediterranean and the Black Sea written by Food and Agriculture Organization of the United Nations and published by Food & Agriculture Org.. This book was released on 2020-05-01 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the Mediterranean and the Black Sea, the assessment of demersal stocks mainly relies on scientific surveys (bottom and beam trawl) while the assessment of pelagic stocks is essentially based on acoustic surveys using acoustic techniques with mid-water trawling. These routine surveys-at-sea provide essential information, which in turn are crucial to fine-tune the assessments of the status of resources and to estimate more precisely indicators at the population and fish community levels. However, survey practices differ from one subregion to another, each approach having its own strengths and limitations. In addition, there is still a lack of large-scale standardized surveys aimed at analysing the diversity and distribution of the main demersal and pelagic species across the Mediterranean and the Black Sea. One way of tackling this issue is to carry out international scientific surveys covering the main demersal and pelagic stocks based on a common methodology. The methodology presented in this publication aims at supporting the planning and implementation of regional demersal (bottom and beam) trawl and pelagic acoustic surveys. It can be useful for the implementation of new surveys-at-sea in areas where demersal trawl and pelagic acoustic surveys are not regularly carried out. It can also contribute to increasing comparability between existing surveys thanks to the standardization of methods, sampling of catches and data recording and analysis. Finally, it represents a valuable tool to define minimum requirements towards sustainability and management objectives at the regional and subregional level.
Download or read book Estimating Confidence in Trawl Efficiency and Catch Quantification for the Eastern Bering Sea Shelf Survey written by Duane E. Stevenson and published by . This book was released on 2016 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Alaska Fisheries Science Center’s Resource Assessment and Conservation Engineering (RACE) Division has been conducting annual multispecies bottom trawl surveys of the eastern Bering Sea continental shelf using the same standardized gear and trawling procedures since 1982. The data and results from these surveys are available to the general public. However, because the use of these data and results by researchers outside RACE is not monitored, users should be aware of the limitations of this information and design their analyses accordingly. In particular, there are multiple sources of variability in the sampling efficiency of the trawl gear used for the survey, both species- and size-specific, that may affect inferences about the nature of the overall catches and relative animal densities. Furthermore, the quality and specificity of catch quantification (weighing and counting) at sea of many taxa can vary depending on the overall size of the catch and the species composition of the sample, particularly for non-commercial taxa of small size. This document is an assessment of the relative reliability of survey catch weights, numbers, and catch per unit effort estimates derived from the eastern Bering Sea shelf bottom trawl survey and is intended to serve as a guideline for researchers interested in using the survey data and results. Included within is a confidence matrix of sampling efficiency and catch quantification for all fishes and invertebrates identified during the shelf survey. [doi:10.7289/V5/TM-AFSC-335 (http://dx.doi.org/10.7289/V5/TM-AFSC-335)]
Download or read book CCAMLR Science written by and published by . This book was released on 1999 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Management Techniques for Elasmobranch Fisheries written by Food and Agriculture Organization of the United Nations and published by Food & Agriculture Org.. This book was released on 2005 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Elasmobranch - describes a group of fish without a hard bony skeleton, including sharks, skates, and rays.
Download or read book NOAA Technical Report NMFS written by and published by . This book was released on 1984 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aquatic Sciences and Fisheries Abstracts written by and published by . This book was released on 1995-07 with total page 738 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Future of Fisheries Science in North America written by Richard J. Beamish and published by Springer Science & Business Media. This book was released on 2009-02-07 with total page 736 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fisheries science in North America is changing in response to a changing climate, new technologies, an ecosystem approach to management and new thinking about the processes affecting stock and recruitment. Authors of the 34 chapters review the science in their particular fields and use their experience to develop informed opinions about the future. Everyone associated with fish, fisheries and fisheries management will find material that will stimulate their thinking about the future. Readers will be impressed with the potential for new discoveries, but disturbed by how much needs to be done in fisheries science if we are to sustain North American fisheries in our changing climate. Officials that manage or fund fisheries science will appreciate the urgency for the new information needed for the stewardship of fish populations and their ecosystems. Research organizations may want to keep some extra copies for a future look back into the thoughts of a wide range of fisheries professionals. Fisheries science has been full of surprises with some of the surprises having major economic impacts. It is important to minimize these impacts as the demand for seafood increases and the complexities of fisheries management increase.
Download or read book Working Towards a Blue Future Promoting Sustainability Environmental Protection and Marine Management Examples from the UK Government Blue Belt Programme and Current International Initiatives written by Paul Whomersley and published by Frontiers Media SA. This book was released on 2022-03-14 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book South African Journal of Marine Science written by and published by . This book was released on 2001 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Assessment of Sea Turtle Abundance in Six South Atlantic U S Channels written by and published by . This book was released on 1995 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
