Table 1.
Population-level data (mean ± s.e.) on all fish (both intact and injured) according to drainage and relative predation pressure; n = 12–14 for forebrain, body size and condition measurements; n = 6–7 for cortisol measurements.
| population | relative predation pressurea | forebrain cell proliferation (PCNA+ cells mm−1) | basal cortisol (ng ml−1) | stress cortisol (ng ml−1) | body length (mm) | body conditionb |
|---|---|---|---|---|---|---|
| western drainage (Guarumo) | ||||||
| Camarón | low | 8321 ± 763 | 21.6 ± 5.1 | 58.5 ± 10.2 | 150 ± 5 | 0.003 ± 0.020 |
| Teribe | high | 6190 ± 511c | 36.0 ± 9.4 | 41.9 ± 6.7 | 146 ± 9 | −0.026 ± 0.041 |
| central drainage (Chagres) | ||||||
| Puente | low | 7698 ± 537 | 33.5 ± 8.1 | 45.1 ± 2.4 | 148 ± 6 | 0.034 ± 0.019 |
| Frijolito | high | 6456 ± 505c | 37.1 ± 6.5 | 53.7 ± 8.9 | 160 ± 6 | 0.061 ± 0.025 |
| eastern drainage (Bayano) | ||||||
| Tumagantí | low | 14 027 ± 719 | 37.4 ± 7.4 | 41.6 ± 10.1 | 155 ± 6 | −0.068 ± 0.023 |
| Tapagrilla | high | 10 603 ± 564b | 30.5 ± 6.1 | 61.9 ± 13.7 | 163 ± 9 | 0.034 ± 0.019c |
aBased on incidence of tail injury and density of predators. See the electronic supplementary material, table S1 for these data.
bBody condition is defined as residuals of the regression of log body mass and log body length across in all sampled fish. Positive value indicates fish that were heavier than predicted based on their body length.
cSignificantly different from the low-predation population within the drainage.