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Table 4 Results of study validity assessment using the critical appraisal tool (see Table 3)

From: What are the relative risks of mortality and injury for fish during downstream passage at hydroelectric dams in temperate regions? A systematic review

CategoryReasonProjects (#)
LowReplication: less than 50 fish released or not indicated28
Measured outcome: semi-quantitative1
Outcome metric: risk of entrainment/impingement, not mortality/injury per se2
Intervention and Comparator Bias: habitat type confounding19
Intervention and Comparator Bias: confounding sampling factors39
Intervention and Comparator Bias: confounding environmental factors15
Intra-treatment Performance Bias: variation within treatment/control samples (intervention type)12
Intra-treatment Performance Bias: variation within treatment/controls samples (sampling)8
MediumSample size: between 50 and 100 fish24
Measured outcome: quantitative approximations (estimates)16
HighControl-impact or randomized controlled trial design128
Sample size: greater than 100 fish76
Measured outcome: quantitative111
Outcome metric: related to fish mortality, injury, or productivity relative to control126
Intervention and Comparator Bias: habitat type homogenous109
Intervention and Comparator Bias: homogeneity in sampling distance/time89
Intervention and Comparator Bias: homogeneity, environmental factors113
Intra-treatment Performance Bias: No heterogeneity within treatment and control samples (intervention type)116
Intra-treatment Performance Bias: no sampling heterogeneity within treatment/control samples120
  1. Numbers indicates the number of projects that received the critical appraisal score for each criterion