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Table 4 Summary statistics from the main analyses of abundance and biomass including for Control/Impact, within-year and interannual Before/After studies, and from taxonomic-specific analyses

From: How do changes in flow magnitude due to hydropower operations affect fish abundance and biomass in temperate regions? A systematic review

Analysis

Standardized mean difference (Hedges’ g)

Control/Impact

 

A.Global meta-analyses

 

 Abundance (k = 77)

− 0.001 (95% CI − 0.35, 0.34; p = 0.997)

 Biomass (k = 13)

− 0.16 (95% CI − 0.62, 0.30; p = 0.490)

B. Taxonomic analyses

 

 Abundance

 

  Catostomidae (k = 4)

− 0.46 (95% CI − 1.79, 0.88; p = 0.503)

  Centrarchidae (k = 6)

0.52 (95% CI − 0.83, 1.14; p = 0.753)

  Cyprinidae (k = 19)

− 0.09 (95% CI − 1.20, 1.03; p = 0.878)

  Percidae (k = 4)

0.32 (95% CI − 0.84, 1.49; p = 0.590)

  Salmonidae (k = 5)

0.18 (95% CI − 0.58, 0.93; p = 0.646)

 Biomass

N/A

Before/After—within year

 

C. Global meta-analyses

 

 Abundance—year 1(k = 19)

0.25 (95% CI − 0.04, 0.56; p = 0.091)*

 Abundance—year 2 (k = 5)

0.67 (95% CI − 0.09, 1.43; p = 0.084)*

 Abundance—year 3 (k = 4)

0.31 (95% CI − 0.62, 1.23; p = 0.516)

 Abundance—year 4 (k = 3)

0.20 (95% CI − 0.80, 1.20; p = 0.697)

 Abundance—year 1–4 (k = 19)

0.25 (95% CI − 0.02, 0.52; p = 0.072)*

 Biomass

N/A

D. Taxonomic analyses

 

 Abundance

  Salmonidae (k = 4)

0.81 (95% CI − 0.15, 1.76; k = 4, p = 0.099)*

 Biomass

N/A

Before/After—interannual

 

E. Global meta-analysis

 

 Abundance (k = 112)

0.19 (95% CI − 0.23, 0.61; p = 0.374)

 Biomass (k = 17)

0.46 (95% CI − 0.24, 1.15; p = 0.196)

F. Taxonomic analysis

 

 Abundance

 

  Acipenseridae (k = 5)

0.42 (95% CI − 1.98, 2.81; p = 0.733)

  Anguillidae (k = 5)

− 0.45 (95% CI − 1.44, 0.55; p = 0.379)

  Catostomidae (k = 8)

− 0.38 (95% CI − 1.84, 1.07; p = 0.606)

  Centrarchidae (k = 5)

7.14 (95% CI − 5.68, 19.96; p = 0.275)

  Cottidae (k = 5)

1.34 (95% CI 0.39, 2.29; p = 0.006)

  Cyprinidae (k = 15)

− 1.18 (95% CI − 3.26, 0.90; p = 0.266)

  Esocidae (k = 3)

0.37 (95% CI − 0.36, 1.10; p = 0.325)

  Ictaluridae (k = 3)

6.69 (95% CI − 6.86, 20.24; p = 0.333)

  Salmonidae (k = 59)

0.45 (95% CI 0.25, 0.65; p < 0.0001)

 Biomass

 

  Salmonidae (k = 11)

0.52 (95% CI − 0.38, 1.43; p = 0.258)

  1. N/A: Unable to conduct moderator analyses due to insufficient sample size or variability. A decrease in fish abundance from alterations to flow magnitude due to HPP compared to control groups is indicated by a value < 0 for Hedges’ g
  2. Hedges’ g is the standardized mean difference effect size. CI: 95% confidence interval. Bold indicates significant effect (p < 0.05); *Indicates marginally significant effect (p < 0.1). k: number of effect sizes
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Environmental Evidence

ISSN: 2047-2382