| Continent/country | | |
| Europe/Hungary (Reference) | 0 | 0 |
| Africa/Nigeria (SE) | 32.35 (15.4)* | 32.18 (12.68)* |
| Asia/Iran (SE) | 1.08 (11.37) | 38.31 (9.9)*** |
| I2 (%) | 93.77 | 93.63 |
| R2 (amount of heterogeneity accounted for) (%) | 9.92 | 57.55 |
| Sperm application | | |
| Dry external fertilization (Reference) | 0 | 0 |
| Ovarian lavage (SE) | –16.45 (9.03) | –19.54 (12.23) |
| I2 (%) | 94.23 | 98.24 |
| R2 (amount of heterogeneity accounted for) (%) | 10.22 | 9.15 |
| Species | | |
| Clarias gariepinus (Reference) | | 0 |
| Danio rerio (SE) | –34.38 (12.28)** | - |
| Cyprinus carpio (SE) | –9.3 (14.58) | - |
| Rhamdia quelen (SE) | 6.27 (13.67) | - |
| Hybrid (Clarias gariepinus × Heterobranchus longifilis) (SE) | 3.22 (21.2) | 16.22 (23.58) |
| Sander lucioperca (SE) | –55.58 (33.6) | - |
| Esox lucius (SE) | –10.9 (11.74) | 33.29 (11.97)** |
| I2 (%) | 93.5 | 97.15 |
| R2 (amount of heterogeneity accounted for) (%) | 20.3 | 30.75 |
| Sperm treatment types | | |
| Fresh sperm (Reference) | 0 | 0 |
| Cryopreserved sperm (SE) | –53.4 (19.23)*** | –55.52 (18.1)** |
| Cryopreserved sperm + fresh sperm for dry external fertilization (SE) | –59.3 (17.27)*** | –60.72 (15.46)*** |
| Fresh sperm 2 hrs. before stripping (SE) | –30.2 (18.32) | - |
| Fresh sperm 12 hrs. before stripping (SE) | –35.9 (18.9) | - |
| Fresh sperm hormone mix (SE) | –3.50 (8.12) | –35.90 (16.73)* |
| Fresh sperm hormone mixes + fresh sperm for dry external fertilization (SE) | –1.8 (15.6) | - |
| Fresh sperm to the left ovary and NaCl-dissolved hormone to the right ovary (SE) | 10.8 (13.65) | - |
| Fresh sperm from transgenic males but without males in aquaria (SE) | –64.3 (13.97) | - |
| Fresh sperm from transgenic males and males separated by a transparent plastic screen in aquaria (SE) | –65.1 (19.4)*** | - |
| Fresh sperm insemination after 72 hours of hormone injection intramuscularly (SE) | –16.4 (10.8)*** | 12.88 (12.8) |
| Fresh sperm insemination after 72 hours of hormone insemination into ovaries (SE) | –22.1 (10.8)* | 13.59 (12.7) |
| Fresh sperm for dry external fertilization and hormone insemination (SE) | –11.3 (11.12) | 17.98 (12.47) |
| I2 (%) | 81.12 | 93.64 |
| R2 (amount of heterogeneity accounted for) (%) | 78.32 | 76.18 |
| Overall | 62.53 | 65.91 |