Estimating cross-population variation in juvenile compensation in survival for bull trout (Salvelinus confluentus): a Bayesian hierarchical approach

Juvenile compensation in survival, quantified as compensation ratio (CR), is critical for fish population persistence. At present, no estimate of this key parameter exists for bull trout (Salvelinus confluentus). This species has a conservation listing and is targeted by recreational angling in portions of its range. Obtaining accurate estimates of CR is crucial to aid recovery efforts and develop sustainable fisheries policies. This investigation develops a hierarchical Bayesian meta-analysis to estimate CR and explore the functional form of stock–recruitment for bull trout. Results show bull trout have high scope for density-dependent compensation evidenced by CR estimates generated herein and by previous research. This demonstrates changes in habitat quality and quantity are likely limiting recovery of many populations. However, owing to lack of data, variance is high. Limitations in available data for this analysis are due to the high cost and operational difficulty of sampling, and high uncertainty in CR estimates. This study highlights the importance of collecting additional paired stock–recruitment data to facilitate future investigations and reduce variance in CR estimates for bull trout.

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Quirky patterns in time-series of estimates of recruitment could be artefacts

ICES Journal of Marine Science ◽

10.1093/icesjms/fsu022 ◽

2014 ◽

Vol 72 (1) ◽

pp. 111-116 ◽

Cited By ~ 14

Author(s):

M. Dickey-Collas ◽

N. T. Hintzen ◽

R. D. M. Nash ◽

P-J. Schön ◽

M. R. Payne

Keyword(s):

Time Series ◽

Stock Assessment ◽

Meta Analysis ◽

Reference Points ◽

Fish Stocks ◽

Stock Recruitment ◽

Modelling Assumptions ◽

Meta Analyses ◽

Recruitment Model ◽

Recruitment Time

Abstract The accessibility of databases of global or regional stock assessment outputs is leading to an increase in meta-analysis of the dynamics of fish stocks. In most of these analyses, each of the time-series is generally assumed to be directly comparable. However, the approach to stock assessment employed, and the associated modelling assumptions, can have an important influence on the characteristics of each time-series. We explore this idea by investigating recruitment time-series with three different recruitment parameterizations: a stock–recruitment model, a random-walk time-series model, and non-parametric “free” estimation of recruitment. We show that the recruitment time-series is sensitive to model assumptions and this can impact reference points in management, the perception of variability in recruitment and thus undermine meta-analyses. The assumption of the direct comparability of recruitment time-series in databases is therefore not consistent across or within species and stocks. Caution is therefore required as perhaps the characteristics of the time-series of stock dynamics may be determined by the model used to generate them, rather than underlying ecological phenomena. This is especially true when information about cohort abundance is noisy or lacking.

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Genetic clustering methods reveal bull trout (Salvelinus confluentus) fine-scale population structure as a spatially nested hierarchy

Conservation Genetics ◽

10.1007/s10592-009-9969-y ◽

2009 ◽

Vol 11 (4) ◽

pp. 1421-1433 ◽

Cited By ~ 28

Author(s):

Will G. Warnock ◽

Joseph B. Rasmussen ◽

Eric B. Taylor

Keyword(s):

Population Structure ◽

Bull Trout ◽

Fine Scale ◽

Clustering Methods ◽

Salvelinus Confluentus ◽

Scale Population ◽

Nested Hierarchy ◽

Genetic Clustering

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Geographic distribution, species displacement, and niche overlap for lake trout and bull trout in mountain lakes

Canadian Journal of Zoology ◽

10.1139/z93-034 ◽

1993 ◽

Vol 71 (2) ◽

pp. 238-247 ◽

Cited By ~ 57

Author(s):

David B. Donald ◽

David J. Alger

Keyword(s):

Trophic Structure ◽

Lake Trout ◽

Niche Overlap ◽

Mountain Lakes ◽

Bull Trout ◽

Salvelinus Confluentus ◽

East Central ◽

Allopatric Populations ◽

Trout Population ◽

The One

Indigenous lacustrine populations of bull trout (Salvelinus confluentus) and lake trout (S. namaycush) are spatially separated within the southern part of the zone of distributional overlap (northern Montana, southwestern Alberta, and east-central British Columbia). In this area, lake trout occurred primarily in mountain lakes of 1032–1500 m elevation, while bull trout were found primarily in lakes between 1500 and 2200 m. Introductions of lake trout in the twentieth century and data obtained from beyond the study area indicated that both fishes can establish significant allopatric populations (more than 5% of the catch) in large, deep lakes (>8 ha in area and >8 m deep) over a wide elevation range. We tested the hypothesis that lake trout displace or exclude bull trout from lakes by determining the outcome of introductions of lake trout into two lakes that supported indigenous bull trout. Lake trout were introduced into Bow Lake in 1964, and by 1992 the bull trout population was decimated there and in another lake (Hector) situated 15 km downstream. Thus, lake trout can displace bull trout and may prevent bull trout from becoming established in certain low-elevation lakes. Population age-structure analyses also suggest that lake trout adversely affected bull trout. Bull trout populations in sympatry with lake trout, including the one extirpated from Hector Lake, had few old fish (18% were more than 5 years old; N = 40 fish from three lakes) compared with allopatric populations (49% were more than 5 years old; N = 235 fish from seven lakes). Niche overlap and the potential for competition between the two char species were substantial. In lakes with trophic structure ranging from simple to complex, bull trout and lake trout fed on similar foods and had similar ecological efficiencies (growth rates). Predation by lake trout on bull trout was not documented during the study.

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