A Bayesian life-cycle model to estimate escapement at maximum sustained yield in salmon based on limited information

2019 ◽  
Vol 76 (2) ◽  
pp. 299-307
Author(s):  
Jan Ohlberger ◽  
Samuel J. Brenkman ◽  
Patrick Crain ◽  
George R. Pess ◽  
Jeffrey J. Duda ◽  
...  
Keyword(s):  
Life Cycle ◽  
Time Series Data ◽  
Coho Salmon ◽  
Reference Points ◽  
Series Data ◽  
Limited Information ◽  
Maximum Sustained Yield ◽  
Sustained Yield ◽  
Life Cycle Models ◽  
Marine Survival

Life-cycle models combine several strengths for estimating population parameters and biological reference points of harvested species and are particularly useful for those exhibiting distinct habitat shifts and experiencing contrasting environments. Unfortunately, time series data are often limited to counts of adult abundance and harvest. By incorporating data from other populations and by dynamically linking the life-history stages, Bayesian life-cycle models can be used to estimate stage-specific productivities and capacities as well as abundance of breeders that produce maximum sustained yield (MSY). Using coho salmon (Oncorhynchus kisutch) as our case study, we show that incorporating information on marine survival variability from nearby populations can improve model estimates and affect management parameters such as escapement at MSY. We further show that the expected long-term average yield of a fishery managed for a spawner escapement target that produces MSY strongly depends on the average marine survival. Our results illustrate the usefulness of incorporating information from other sources and highlight the importance of accounting for variation in marine survival when making inferences about the management of Pacific salmon.

Semidiscrete biomass dynamic modeling: an improved approach for assessing fish stock responses to pulsed harvest events

2012 ◽  
Vol 69 (10) ◽  
pp. 1710-1721 ◽  
Author(s):  
Michael E. Colvin ◽  
Clay L. Pierce ◽  
Timothy W. Stewart
Keyword(s):  
Time Series Data ◽  
Reference Points ◽  
Series Data ◽  
Fish Stock ◽  
Parameter Estimates ◽  
Maximum Sustained Yield ◽  
Biomass Dynamic ◽  
Biomass Dynamics ◽  
Discrete Manner ◽  
Dynamics Models

Continuous harvest over an annual period is a common assumption of continuous biomass dynamics models (CBDMs); however, fish are frequently harvested in a discrete manner. We developed semidiscrete biomass dynamics models (SDBDMs) that allow discrete harvest events and evaluated differences between CBDMs and SDBDMs using an equilibrium yield analysis with varying levels of fishing mortality (F). Equilibrium fishery yields for CBDMs and SDBDMS were similar at low fishing mortalities and diverged as F approached and exceeded maximum sustained yield (FMSY). Discrete harvest resulted in lower equilibrium yields at high levels of F relative to continuous harvest. The effect of applying harvest continuously when it was in fact discrete was evaluated by fitting CBDMs and SDBDMs to time series data generated from a hypothetical fish stock undergoing discrete harvest and evaluating parameter estimates bias. Violating the assumption of continuous harvest resulted in biased parameter estimates for CBDM while SDBDM parameter estimates were unbiased. Biased parameter estimates resulted in biased biological reference points derived from CBDMs. Semidiscrete BDMs outperformed continuous BDMs and should be used when harvest is discrete, when the time and magnitude of harvest are known, and when F is greater than FMSY.

Reference points for coho salmon (Oncorhynchus kisutch) harvest rates and escapement goals based on freshwater production

2000 ◽  
Vol 57 (4) ◽  
pp. 677-686 ◽  
Author(s):  
Michael J Bradford ◽  
Ransom A Myers ◽  
James R Irvine
Keyword(s):  
Reference Point ◽  
Historical Data ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Reference Points ◽  
Data Sets ◽  
Ocean Productivity ◽  
Freshwater Habitats ◽  
Marine Survival ◽  
Stick Model

We describe a simple scheme for the management of coho salmon (Oncorhynchus kisutch) population aggregates that uses reference points derived from an empirical analysis of freshwater production data. We fit a rectilinear "hockey stick" model to 14 historical data sets of female spawner abundance and resulting smolt production and found that at low spawner abundance, the average productivity was about 85 smolts per female spawner. Variation in productivity among streams may be related to the quality of the stream habitat. We show how freshwater productivity can be combined with forecasts of marine survival to provide a limit reference point harvest rate. Our method will permit harvest rates to track changes in ocean productivity. We also used the historical data to estimate that, on average, a density of 19 female spawners·km-1 is required to fully seed freshwater habitats with juveniles. However, there was considerable variation among the streams that might limit the utility of this measure as a reference point. Uncertainty in the forecasts of marine survival and other parameters needs to be incorporated into our scheme before it can be considered a precautionary approach.

Age, Generations, and Participation

2017 ◽  
Author(s):  
Russell J. Dalton
Keyword(s):  
United States ◽  
Time Series ◽  
Life Cycle ◽  
Millennial Generation ◽  
Time Series Data ◽  
Direct Action ◽  
The United States ◽  
Series Data ◽  
Online Participation ◽  
Modes Of Action

Political scientists debate whether the Millennial generation is disengaging from politics in contemporary democracies. The ISSP surveys show that the generational decline in participation is largely limited to voting and other forms of partisan activity. At the same time, younger citizens are often more engaged in non-electoral activities, such as direct action, protest, and online participation. Time-series data for the United States disentangles the effects of life-cycle changes and generations. More recent generations display a clear decline in voting across the 1967–2014 period. In contrast, life-cycle increases in participation are more common for non-electoral activity. Both factors influence participation but in contrasting ways for different modes of action.

scholarly journals Indicators of the health of the North Sea fish community: identifying reference levels for an ecosystem approach to management

2006 ◽  
Vol 63 (4) ◽  
pp. 573-593 ◽  
Author(s):  
Simon P.R. Greenstreet ◽  
Stuart I. Rogers
Keyword(s):  
North Sea ◽  
Time Series Data ◽  
Size Structure ◽  
Single Species ◽  
Ecosystem Approach ◽  
Reference Points ◽  
Series Data ◽  
Anthropogenic Activity ◽  
Data Sets ◽  
The North

Abstract The shift in emphasis away from the single-species focus of traditional fisheries management towards an ecosystem approach to management requires application of indicators of ecosystem state. Further, an ecosystem approach to management requires the identification of ecological reference points against which management objectives might be set. In applying indicators, identifying reference points, and setting objectives, an obvious requirement is that the indicators respond primarily to the anthropogenic activity being managed and are sufficiently sensitive that impacts of the activity and the responses to management action are clearly demonstrable. Here we apply a suite of 12 indicators to Scottish August groundfish survey data collected in the northern North Sea over the period 1925–1997. These include indicators of size structure, life-history character composition, species diversity, and trophic structure within the community. Our choice of analytical design has two purposes; first to show that fishing has unequivocally affected these various aspects of the structure of the groundfish community, and second to illustrate an approach by which long time-series data sets might be used to identify possible management reference points. The results are discussed in the context of selecting ecological indicators in support of an ecosystem approach to management and determining appropriate reference points for objective-setting.

scholarly journals Identifying the potential of anadromous salmonid habitat restoration with life cycle models

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0256792
Author(s):  
Jeffrey C. Jorgensen ◽  
Colin Nicol ◽  
Caleb Fogel ◽  
Timothy J. Beechie
Keyword(s):  
Life Cycle ◽  
Chinook Salmon ◽  
Habitat Restoration ◽  
Coho Salmon ◽  
Life Stage ◽  
Fine Sediment ◽  
Life Stages ◽  
Beaver Pond ◽  
Barrier Removal ◽  
Life Cycle Models

An investigation into the causes of species decline should include examination of habitats important for multiple life stages. Integrating habitat impacts across life stages with life-cycle models (LCMs) can reveal habitat impairments inhibiting recovery and help guide restoration efforts. As part of the final elements of the Habitat Restoration Planning model (HARP; Beechie et al. this volume), we developed LCMs for four populations of three species of anadromous salmonids (Oncorhynchus kisutch, O. tshawytscha, and O. mykiss), and ran diagnostic scenarios to examine effects of barrier removal, fine sediment reduction, wood augmentation, riparian shade, restoration of the main channel and bank conditions, beaver pond restoration, and floodplain reconnection. In the wood scenario, spawner abundance for all populations increased moderately (29–48%). In the shade scenario, spring-run Chinook salmon abundance increased the most (48%) and fall-run Chinook salmon and steelhead were much less responsive. Coho responded strongly to the beaver pond and floodplain scenarios (76% and 54%, respectively). The fine sediment scenario most benefitted fall- and spring-run Chinook salmon (32–63%), whereas steelhead and coho were less responsive (11–21% increase). More observations are needed to understand high fine sediment and its impacts. Our LCMs were region-specific, identifying places where habitat actions had the highest potential effects. For example, the increase in spring-run Chinook salmon in the wood scenario was driven by the Cascade Mountains Ecological Region. And, although the overall response of coho salmon was small in the barrier removal scenario (6% increase at the scale of the entire basin), barrier removals had important sub-regional impacts. The HARP analysis revealed basin-wide and regional population-specific potential benefits by action types, and this habitat-based approach could be used to develop restoration strategies and guide population rebuilding. An important next step will be to ground-truth our findings with robust empirically-based estimates of life stage-specific survivals and abundances.

Population viability of coho salmon, Oncorhynchus kisutch, in Oregon coastal basins: application of a habitat-based life cycle model

1998 ◽  
Vol 55 (11) ◽  
pp. 2383-2392 ◽  
Author(s):  
Thomas E Nickelson ◽  
Peter W Lawson
Keyword(s):  
Life Cycle ◽  
Habitat Quality ◽  
Coho Salmon ◽  
Extinction Risk ◽  
Oncorhynchus Kisutch ◽  
Population Viability ◽  
Life Cycle Model ◽  
Cycle Model ◽  
Coastal Basins ◽  
Marine Survival

To assess extinction risk for Oregon coastal coho salmon, Oncorhynchus kisutch, we developed a life cycle model based on habitat quality of individual stream reaches estimated from survey data. Reach-specific smolt output was a function of spawner abundance, demographic stochasticity, genetic effects, and density- and habitat-driven survival rates. After natural mortality and ocean harvest, spawners returned to their natal reaches. Populations in reaches with poor habitat became extinct during periods of low marine survival. With favorable marine survival, high productivity reaches served as sources for recolonization of lower quality reaches through straying of spawners. Consequently, both population size and distribution expanded and contracted through time. Within a reach, populations lost resilience at low numbers when demographic risk factors became more important than density-dependent compensation. Population viability was modeled for three coastal basins having good, moderate, and poor habitat. With constant habitat conditions, extinction risk in 99 years was negligible in basins with good and moderate habitat and 5-10% in the basin with poor habitat. Reductions in habitat quality up to 60% in 99 years resulted in reduced coho salmon populations in all basins and significantly increased extinction risk in the basin with poor habitat.

Graphical Exploratory Data Analysis for Categorical Longitudinal and Time Series Data

2013 ◽  
Author(s):  
Stephen J. Tueller ◽  
Richard A. Van Dorn ◽  
Georgiy Bobashev ◽  
Barry Eggleston
Keyword(s):  
Time Series ◽  
Data Analysis ◽  
Exploratory Data Analysis ◽  
Time Series Data ◽  
Series Data ◽  
Exploratory Data
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