1,720,970 research outputs found
Utilizing Multi-Source Abundance Estimation And Climate Variability To Forecast Pacific Salmon Populations
Get PDFDissertation (Ph.D.) University of Alaska Fairbanks, 2004Data limitation is a common property of many fisheries. Some Pacific salmon populations are a typical example of this situation because the monitoring of numerous tributaries within an area becomes logistically intractable. Fishery management often responds to this scenario with qualitative stock assessments in the form of harvest projections In some cases, fishery data, although limited, exists in a variety of sources and may be integrated to develop quantitative population estimates. The first objective of this investigation is to generate a modeling process that combines multiple data sources to estimate abundance and escapement estimates for data-limited salmon populations. Second, we consider the reliability of these estimates by testing for robustness to various simulated levels of measurement error in the data. Finally, we perform rigorous development and selection on an age structured spawner-recruit model that incorporates abundance and escapement estimates and identifies potential environment-recruit relationships. We demonstrate our technique with a case study on summer chum salmon from the Kuskokwim and Yukon Rivers, Alaska. Recent declines of summer chum returns to this salmon-dependent region have created hardships for the local area residents. We developed a maximum likelihood statistical framework that synchronously combined all available data sources from this management region to estimate abundance and escapement. Successful estimation was dependent on an independent estimate of abundance for a least a few years. We provide error estimates of the modeling process through bootstrap methods. Simulations showed that measurement error had negligible effect on abundance estimates, whereas performance for escapement estimation was tied to the sequence of abundance years. High explanatory power was attained by including environmental variables in the spawner-recruit relationship developed from these population estimates. We used a three-stage modeling process to maintain biological realism in the predictor variables. Recent changes in variables chosen for the best model were consistent with poor environmental conditions and estimates of forecasting error were much lower than models using no environmental information. Based on our findings, we recommend that managers consider the utility of multiple source estimation and environmental variability with our modeling approach for future regulatory decisions of Pacific salmon fisheries in data-limited regions
Balancing biological sustainability with the economic needs of Alaska's sockeye salmon fisheries
Get PDFThesis (M.S.) University of Alaska Fairbanks, 2009"The total revenue of the Bristol Bay, Alaska sockeye salmon, Oncorhynchus nerka, fishery has continued to decline despite strong run sizes. This decline is primarily attributed to increases in production of farmed Chilean rainbow trout O. mykiss and coho salmon, O. kisutch. Although wild salmon managers have less control over production than salmon farmers, there may be some opportunity to regain value to the fishery by altering management strategies. To explore this potential, we first simulated three management strategies for sockeye salmon: a fixed escapement range strategy, a fixed harvest strategy and a fixed harvest rate strategy. Yields from these simulations were then combined with a forecast of farmed Chilean trout and salmon production and a model of international trade flows for Alaskan sockeye and Chilean coho salmon and rainbow trout to generate forecasts of exvessel price and total revenue for 2010. All three management strategies were able to achieve a run size equilibrium indicating biological sustainability. The highest median yield resulted from the fixed escapement strategy and the lowest median yield was generated by the fixed harvest strategy. Exvessel prices and total revenue were highest under the fixed harvest strategy. These results demonstrate a switch to an inelastic market environment and reveal the need to modify current management strategies to improve the economic health of the fishery"--Leaf iiiAlaska Sea Grant, project number ASG 05-02General introduction -- 1. Alternative management strategies for Bristol Bay sockeye salmon to improve economic stability -- 2. Exploring the effect of Chilean production of farmed salmon and trout and on the value of Alaskan sockeye salmon -- General conclusion -- Appendix: time series analysis of spawner-recruit relationships
Inter-decadal change in sablefish, Anoplopoma fimbria, growth and maturity in the Northeast Pacific Ocean
Get PDFThesis (M.S.) University of Alaska Fairbanks, 2008Errors in growth and maturity estimates can drastically affect the spawner-per-recruit threshold used to recommend commercial fish catch quotas. Growth and maturity parameters for Alaskan sablefish, Anoplopoma fimbria, have not been updated for stock assessment purposes for 20 years, even though sablefish aging has continued. In this study, the old length-stratified data set (1981-1993) was updated and corrected for bias. In addition, newer, randomly collected samples (1996-2004) were analyzed, and new length-at-age, weight-at-age, and maturity-at-age and length parameters were estimated. A comparison of the two datasets showed that in recent years, sablefish are growing larger and maturing later and that growth and maturity differ somewhat among regions. The updated growth information improves data fits in the sablefish stock assessment model. It also provides results that are biologically reasonable. These updated and improved estimates of sablefish growth and maturity help ensure the continued proper management of this commercially important species in Alaskan waters
Fishing for pollock in a sea of change: a history and analysis of the Bering Sea pollock fishery
Get PDFThesis (M.S.) University of Alaska Fairbanks, 2011The development and evolution of the eastern Bering Sea fishery for walleye pollock (Theragra chalcogramma) is retraced, its current economic and institutional structure is modeled, and the resiliency of that structure to substantive changes in pollock biomass and fuel costs is explored. Small variations in exvessel prices, total allowable catches, or allocation of catches between seasons and among industry sectors can lead to large changes to first wholesale revenues. Similarly, changes in fuel prices, changes in technology, changes in regulation, and changes in the spatial distribution of catches can lead to changes in harvesting or processing costs. Together, these changes affect the relative profitability of the inshore and offshore sectors, which can, in turn, affect the benefits that accrue to communities, the evolution of regulation, and create pressure to reallocate sector shares. The model indicates that first wholesale revenues are maximized when pollock harvests are maximized. However, legal barriers to the transfer of allocations between sectors can lead to under-harvests when product prices are low, fuel costs are high, or when the most productive fishing grounds are in the northwest regions of the eastern Bering Sea Exclusive Economic Zone.National Marine Fisheries Service Fisheries Development and Research Program award NA08NMF4270420, University of Alaska Fairbanks1. An historical analysis of the Bering Sea pollock fishery -- 2. Institutional structure and revenue maximization in the Eastern Bering Sea pollock fishery
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Age, growth and productivity of juvenile sockeye salmon in two high latitude lakes, Alaska
Get PDFThesis (M.S.) University of Alaska Fairbanks, 2009"The growth of Seward Peninsula sockeye salmon (Oncorhynchus nerka) from Salmon and Glacial lakes is related to their physical environment. Dermal scales collected over many years were measured to document the annual age specific growth of smolts and adults. The effect of fertilization on fry growth was examined using the first year of growth. The growth histories of Salmon Lake sockeye salmon were compared to Glacial Lake sockeye salmon through smolting and in the marine environment. Annual age specific fry growth had no direct relationship to fertilization; however, there were interactions between biomass of salmon prey and fertilization, and between prey biomass and age of smolting. Glacial Lake age-1 smolts are the same size as Salmon Lake age-1 smolts, but age-1.3 Salmon Lake juveniles after their first year in the ocean are smaller than age-1.3 Glacial Lake juveniles suggesting lower size based mortality. The differences in growth histories show each population's response to lake production and mortality experienced by smolt between the rearing lake and the ocean"--Leaf iiiArctic Yukon Kuskokwim Sustainable Salmon InitiativeGeneral introduction -- Sockeye salmon ecology -- Lake fertilization -- Seward Peninsula sockeye salmon -- Objectives -- 1. Lower trophic relationships and the effect of fertilization on the growth of sockeye salmon fry in a high latitude lake -- 2. Juvenile sockeye salmon (Oncorhynchus nerka) growth histories on the Seward Peninsula, Alaska -- General discussion
Pacific sleeper sharks in the Northeast Pacific Ocean: relative abundance, plausible incidental exploitation rates, trophic ecology, and habitat use
Get PDFDissertation (Ph.D.) University of Alaska Fairbanks, 2017Pacific sleeper shark relative abundance indices in the eastern Bering Sea and Gulf of Alaska were developed from sablefish longline surveys and the sustainability of a plausible range in Pacific sleeper shark incidental exploitation rates in the Gulf of Alaska was evaluated with a risk analysis using Monte Carlo simulation for use in fisheries management. A significant increase in Pacific sleeper shark relative abundance was identified in the Gulf of Alaska during the years 1989-2003. The aggregate risk of ending in an overfished condition in the Gulf of Alaska increased from 0% under a low exploitation rate scenario to 59% under a high exploitation rate scenario. Baseline information about Pacific sleeper shark trophic ecology and habitat utilization in the eastern Bering Sea and Gulf of Alaska was developed for use in ecosystem-based fishery management. Analysis of stable isotope ratios of nitrogen (δ¹⁵N) and lipid normalized carbon (δ¹³C′) identified significant geographic and ontogenetic variability in the trophic ecology of Pacific sleeper sharks in the eastern Bering Sea and Gulf of Alaska and revealed wider variability in the feeding ecology of Pacific sleeper sharks than previously obtained from diet data based on stomach contents alone. Time series analysis of Pacific sleeper shark electronic tag data from the Gulf of Alaska identified a simple autoregressive relationship governing short-term movements (hours) throughout the time series which included substantial variation in longer time period movement patterns (months) and demonstrated that statistical inference about habitat utilization could be drawn from simultaneous analysis of an entire time series depth profile (six months of data) stored on an electronic archival tag
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