Ecological Archives A025-134-A1

Kimberly L. Dibble, Charles B. Yackulic, Theodore A. Kennedy, and Phaedra Budy. 2015. Flow management and fish density regulate salmonid recruitment and adult size in tailwaters across western North America. Ecological Applications 25:21682179. http://dx.doi.org/10.1890/14-2211.1

Appendix A. Description of flow, biological, and other predictor variables used in generalized linear mixed models of rainbow and brown trout recruitment and mean adult length.

Table A1. Metrics used as predictor variables in generalized linear mixed models of rainbow and brown trout recruitment and mean adult length. Range and means are from the rainbow and brown trout catch datasets, non-lagged data.

Predictors

Metric

Nomenclature

Units

Range

Mean

Flow

Mean coefficient of variation (CV) of subdaily flow (Q; m3s-1), averaged over previous water year (WY; Oct. 1-Sept. 30).

HydropeakingL

NA

0.01–0.25

0.05

 

Proportion of mean daily Q, averaged over previous WY, relative to mean Q across WY.

Relative annual flowL

Proportion

-0.77–1.18

-0.02

 

Mean daily Q, averaged across WY, divided by mean channel width at gage.

Specific discharge

m2s-1

0.04–1.23

0.30

 

1st axis from Principal Component Analysis (PCA) of seasonal flow (mean daily Q averaged within a season relative to mean Q over WY). Results indicate summer (June 1-Sept. 30) accounted for highest variability on axis 1.

PC1 (summer)L

Factor scores (standardized)

-3.70–3.71

0.00

 

2nd axis from PCA of seasonal flow. Results indicate winter (Oct. 1-Jan. 31), and then spring (Feb. 1-May 31) accounted for highest variability on axis 2.

PC2 (winter/spring)L

Factor scores (standardized)

-5.33–4.11

0.00

Biological

Rainbow trout (RBT) catch in the 150-300 mm size class, divided by the total number of fish captured >150 mm, for the year immediately prior to the year being modeled. Metric only used in RBT length models.

Relative new adult cohort strength (RBT)L

Proportion

0.00-0.99

0.40

 

Catch of RBT >150 mm captured in pass #1 on a particular sample date, divided by the number of kilometers electrofished. Metric only used in RBT length models.

RBT Catch

# fish/km

1.7–943.4

101.2

 

Catch of RBT 150-300 mm captured in pass #1 on a particular sample date, divided by the number of kilometers electrofished. Metric only used in brown trout (BT) models.

Sub-adult RBT Catch

# fish/km

0.0–2885.0

52.9

 

Catch of RBT >300 mm captured in pass #1 on a particular sample date, divided by the number of kilometers electrofished. Metric only used in BT models.

Adult RBT Catch

# fish/km

0.0-525.4

56.7

 

BT catch in the 150-350 mm size class, divided by the total number of fish captured >150 mm, for the year immediately prior to the year being modeled. Metric only used in BT length models.

Relative new adult cohort strength (BT)L

Proportion

0.00-1.00

0.50

 

Catch of BT >150 mm captured in pass #1 on a particular sample date, divided by the number of kilometers electrofished. Metric only used in BT length models.

BT Catch

# fish/km

0.48–2044.0

184.4

 

Catch of BT 150–350 mm captured in pass #1 on a particular sample date, divided by the number of kilometers electrofished. Metric only used in RBT models.

Sub-adult BT Catch

# fish/km

0.0–1791.6

182.0

 

Catch of BT >350 mm captured in pass #1 on a particular sample date, divided by the number of kilometers electrofished. Metric only used in RBT models.

Adult BT Catch

# fish/km

0.0–572.3

50.1

Other

Binary variable indicating whether trout of any length were stocked in the year of fish data. Species-specific in each model.

Fish stocking

Yes/No

0/1

NA

 

Binary variable indicating whether whirling disease had been detected in the tailwater prior to the fish collection date.

Whirling disease

Yes/No

0/1

NA

 

Number of years since the dam was closed, relative to the year fish data was collected.

Dam age

Years

3–105

49.4

 

Elevation of the top of the dam at the spillway structure relative to sea level.

Altitude

Meters above sea level

295.7–2843.8

1689.2

 

Latitude of the location in the tailwater where fish were collected.

Latitude

°N

36.81–48.40

41.32

 

Mean reservoir capacity in WY divided by the maximum reservoir capacity at the crest of the dam.

Reservoir storage in WY

Proportion

0.16–1.00

0.69

 

Ratio of maximum reservoir capacity to mean total flow across WY.

Reservoir storage capacity

Proportion

0.00–3.40

1.29

L Indicates this metric is also lagged by calculating the metric during the previous water year and applying it to the following year of fish data.


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