Trends in wild adult steelhead (Oncorhynchus mykiss) abundance in British Columbia as indexed by angler success

2000 ◽  
Vol 57 (2) ◽  
pp. 225-270 ◽  
Author(s):  
Barry D Smith ◽  
Bruce R Ward ◽  
David W Welch
Keyword(s):  
British Columbia ◽  
Time Series ◽  
Oncorhynchus Mykiss ◽  
Coastal Upwelling ◽  
Fiscal Year ◽  
Climate Indices ◽  
Factors Affecting ◽  
Gradual Introduction ◽  
Trends Over Time ◽  
Over Time

Intraregional similarities and interregional differences in wild steelhead (Oncorhynchus mykiss) abundance trends over time throughout British Columbia were identified using catch-per-angler-day (CpAD) as an index of abundance. This index was calculated using sport angler catch and effort data obtained by an ongoing mail-out questionnaire begun in the fiscal year 1967-1968. Despite high interannual variability in CpAD for individual rivers, its validity as an index of trends over time in wild steelhead abundance for geographic regions or watersheds is reinforced by similar trends yielded by both fishery-dependent and fishery-independent data. Time series methods generally could not build statistical support for the hypotheses that sudden regulation changes, or the gradual introduction over time of a catch and release philosophy, are generally important factors affecting trends over time in CpAD. This bolsters our confidence that the general patterns in mean CpAD over time within regions and watersheds reasonably index actual wild adult in-river steelhead abundance. We propose that the trends that we observe in wild steelhead CpAD are primarily driven by environmental influences. Some candidate environmental time series currently being considered and investigated are coastal upwelling, various ocean and atmospheric climate indices, freshwater discharge histories, and ultraviolet radiation.

Trends in wild adult steelhead (Oncorhynchus mykiss) abundance for coastal regions of British Columbia support the variable marine survival hypothesis

2000 ◽  
Vol 57 (2) ◽  
pp. 271-284 ◽  
Author(s):  
Barry D Smith ◽  
Bruce R Ward
Keyword(s):  
British Columbia ◽  
Oncorhynchus Mykiss ◽  
West Coast ◽  
Coastal Upwelling ◽  
Vancouver Island ◽  
Fiscal Year ◽  
Coastal Regions ◽  
Queen Charlotte Islands ◽  
Marine Survival

Wild adult steelhead (Oncorhynchus mykiss) abundance for rivers in British Columbia was indexed using catch-per-angler-day (CpAD) calculated from data obtained using an angler questionnaire. Mean annual CpAD for primarily winter-run steelhead in rivers of four rainfall-driven coastal regions of British Columbia showed similar trends from the fiscal year 1967-1968 to 1989-1990. After 1989-1990 the trends diverged. The generally remote rivers of the west coast of Vancouver Island and the Queen Charlotte Islands maintained a steady or increasing trend in CpAD after 1989-1990. The long-term trend for these two regions correlated well with a joint index of winter and summer upwelling for the Coastal Upwelling Domain for the years that steelhead are at sea and is consistent with studies that relate marine survival of salmon to oceanic-atmospheric climate. In contrast with west coast Vancouver Island and the Queen Charlotte Islands, most rivers of the east coast of Vancouver Island and the lower mainland near Vancouver revealed declining trends since 1989-1990. Most of these rivers drain into the Strait of Georgia. Reasons for the discrepancy among regions after about 1990 are discussed. They include high angling pressure related to hatchery supplementation, differences in riverine and marine conditions, and smolt migration distance.

Declining patterns of Pacific Northwest steelhead trout (Oncorhynchus mykiss) adult abundance and smolt survival in the ocean

2017 ◽  
Vol 74 (8) ◽  
pp. 1275-1290 ◽  
Author(s):  
Neala W. Kendall ◽  
Gary W. Marston ◽  
Matthew M. Klungle
Keyword(s):  
British Columbia ◽  
Time Series ◽  
Oncorhynchus Mykiss ◽  
Pacific Northwest ◽  
State Space Model ◽  
Puget Sound ◽  
Survival Rates ◽  
Steelhead Trout ◽  
Factors Affecting ◽  
Adult Abundance

Examination of population abundance and survival trends over space and time can guide management and conservation actions with information about the spatial and temporal scale of factors affecting them. Here, we analyzed steelhead trout (anadromous Oncorhynchus mykiss) adult abundance time series from 35 coastal British Columbia and Washington populations along with smolt-to-adult return (smolt survival) time series from 48 populations from Washington, Oregon, and the Keogh River in British Columbia. Over 80% of the populations have declined in abundance since 1980. A multivariate autoregressive state-space model revealed smolt survival four groupings: Washington and Oregon coast, lower Columbia River, Strait of Juan de Fuca, and Puget Sound – Keogh River populations. Declines in smolt survival rates were seen for three of the four groupings. Puget Sound and Keogh River populations have experienced low rates since the early 1990s. Correlations between population pairs’ time series and distance apart illustrated that smolt survival rates were more positively correlated for proximate populations, suggesting that important processes, including those related to ocean survival, occur early in the marine life of steelhead.

Trends in wild adult steelhead (Oncorhynchus mykiss) abundance for snowmelt-driven watersheds of British Columbia in relation to freshwater discharge

2000 ◽  
Vol 57 (2) ◽  
pp. 285-297 ◽  
Author(s):  
Barry D Smith
Keyword(s):  
British Columbia ◽  
Oncorhynchus Mykiss ◽  
Freshwater Discharge ◽  
Low Velocity ◽  
Factors Affecting ◽  
Ocean Climate ◽  
Juvenile Mortality ◽  
Annual Index ◽  
Time Series Analyses ◽  
Discharge Potential

Snowmelt-driven rivers of British Columbia support primarily summer-run steelhead (Oncorhynchus mykiss) that may spend up to 5 years as juveniles in freshwater. Time series analyses revealed significant negative correlations between an annual index of wild adult steelhead abundance (catch-per-angler-day, CpAD) for these rivers and summer freshwater discharge when these steelhead were juveniles. The strength of these relationships was related to latitude, with the more northerly rivers generating the strongest relationship between CpAD and freshwater discharge. Potential mechanisms by which interannual variation in freshwater discharge can modulate adult steelhead abundance include reduced juvenile mortality due to lower flow velocities during the warm summer months and to the creation of more juvenile habitat in low-velocity refuges. Alternatively, interannual variability in adult steelhead abundance is driven by variability in ocean climate of which freshwater discharge is an index. Interpretation of the data and analyses was encumbered in part by particular factors affecting CpAD as an index of abundance. However, the analyses support an interpretation that steelhead survival to adulthood might be influenced by freshwater conditions more so in northern snowmelt-driven rivers than in rainfall-driven rivers because steelhead from those rivers spend more years in freshwater as juveniles.

Genetic parameters and phenotypic trends in the mean and variability of number of stillborn piglets and changes in their relationships with litter size and gestation length

2013 ◽  
Vol 53 (5) ◽  
pp. 395 ◽  
Author(s):  
Craig R. G. Lewis ◽  
Susanne Hermesch
Keyword(s):  
Genetic Parameters ◽  
Gestation Length ◽  
Genetic Associations ◽  
Large White ◽  
Factors Affecting ◽  
Breed Differences ◽  
Trends Over Time ◽  
The Mean ◽  
Using Data ◽  
Over Time

This study examined changes in genetic and phenotypic factors affecting stillborn piglets (SB). Over 15 years, 76 851 litter records were available from Large White (LW), Landrace (LR) and Duroc (DU) sows to investigate SB. The analyses focussed on trends over time in SB and the changes in the number of SB per litter, in factors associated with SB and in genetic parameters for SB. Breed differences were identified with DU producing more SB than the white breeds (mean of 1.46 ± 0.02 vs 1.11 ± 0.01 and 1.07 ± 0.01). However, maximum differences between levels of each factor were 0.73 and 0.65 SB for parity and herd, respectively. Over the 15 years studied, SB had increased by 0.2 piglets accompanied by an increase in the total numbers of piglets born per litter (TB) of ~0.5 piglets. This increase in SB was driven by higher occurrence of more than two SB within a single litter. The effect of TB on SB changed over time with solutions of 0.127 ± 0.002 and 0.150 ± 0.002 SB/TB in 1996 and 2010, respectively. Heritability estimates for SB ranged from 0.06 ± 0.01 to 0.09 ± 0.01 for alternative models and time periods. The unfavourable genetic correlation between SB and TB of 0.46 ± 0.03 based on all data available was slightly lower using only data from the first 5 years (0.38 ± 0.07) versus using data from the last 5 years (0.46 ± 0.06). However, this increase in phenotypic and genetic associations between SB and TB over time may be larger in populations that have observed a larger increase in TB.

Who’s prone to drone? A global time-series analysis of armed uninhabited aerial vehicle proliferation

2020 ◽  
pp. 073889422096657
Author(s):  
Michael Horowitz ◽  
Joshua A Schwartz ◽  
Matthew Fuhrmann
Keyword(s):  
Time Series ◽  
Export Market ◽  
Regime Type ◽  
Security Threats ◽  
Time Series Dataset ◽  
Status Seeking ◽  
Aerial Vehicle ◽  
Trends Over Time ◽  
Original Time ◽  
Over Time

What determines whether countries pursue and obtain armed drones? Using an original time-series dataset, we conduct the first comprehensive analysis of armed drone proliferation from 1994 to 2019. We theorize and find evidence that security threats—like terrorism—are not the only factors driving proliferation. Regime type also has a significant effect, but it varies over time. From 1994 to 2010 regime type had no significant effect. However, non-democracies became significantly more likely to pursue and obtain armed drones from 2011 to 2019 owing to China’s entrance into the drone export market, which asymmetrically eased supply-side constraints for non-democracies. We also find that status-seeking states are more likely to pursue armed drones. Our results contribute to the broader academic literature on proliferation by demonstrating how supply shocks can lead to changes in proliferation trends over time and lending further credence to the importance of prestige in international politics.

scholarly journals Adaptive monitoring of coral health at Scott Reef where data exhibit nonlinear and disturbed trends over time

2021 ◽  
Author(s):  
Pubudu Thilan Abeysiri Wickrama Liyanaarachchige ◽  
Rebecca Fisher ◽  
Helen Thompson ◽  
Patricia Menendez ◽  
James Gilmour ◽  
...  
Keyword(s):  
Time Series ◽  
Coral Reef ◽  
Information Gain ◽  
Ecological Monitoring ◽  
Adaptive Designs ◽  
Series Data ◽  
Adaptive Monitoring ◽  
Trends Over Time ◽  
Over Time ◽  
Modelling Approaches

Time series data are often observed in ecological monitoring. Frequently such data exhibit nonlinear trends over time potentially due to complex relationships between observed and auxiliary variables, and there may also be sudden declines over time due to major disturbances. This poses substantial challenges for modelling such data and also for model-based adaptive monitoring. We propose novel methods for finding adaptive designs for monitoring when historical data show such nonlinear patterns and sudden declines over time. This work is motivated by a coral reef monitoring program that has been established at Scott Reef; a coral reef off the Western coast of Australia. Data collected for monitoring the health of Scott Reef are considered, and semiparametric and interrupted time series modelling approaches are adopted to describe how these data vary over time. New methods are then proposed that enable adaptive monitoring designs to be found based on such modelling approaches. These methods are then applied to find future monitoring designs at Scott Reef and form a set of recommendations for future monitoring. Through applying the proposed methods, it was found that future information gain is expected to be similar across a variety of different sites, suggesting that no particular location needed to be prioritised at Scott Reef for the next monitoring phase. In addition, it was found that omitting some sampling sites/reef locations was possible without substantial loss in expected information gain, depending upon the disturbances that were observed. The resulting adaptive designs are used to provide recommendations for future monitoring in this region, and for reefs where changes to the current monitoring practices are being sought. Furthermore, as the methods used and developed throughout this study are generic in nature, this research has the potential to improve ecological monitoring more broadly where complex data are being collected over time.

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