TABLE 1.
Pertinent details of trials conducted to assess the response of Atlantic mackerel (Scomber scombrus) to crowding stress. Groups of wild‐caught S. scombrus were crowded at different densities and durations in sea cages
| Period | Trial name | Dates | Treatment duration (decimal hours) | No. fish exposed to treatment | No. of fish sampled for colour during treatment | Mean (± 95% c.i.) fork length a (cm) | Mean weight (± 95% c.i.) a (g) | Pre‐treatment density (kg/m3) | Mean (± 95% c.i.) pre‐treatment oxygen concentration (mg/L) | During‐treatment density (kg/m3) | Mortality proportion (95% c.i. b ) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| May/June | Control 1 | 21 May 2019–21 May 2019 | 1.87 | 149 | 16 | 38.57 ± 0.97 | 816.57 ± 54.51 | 0.76 | 10.10 ± 0.01 | 0.76 | No survival monitoring |
| Control 2 | 28 May 2019–6 June 2019 | 0.68 | 116 | 10 | 39.33 ± 1.09 | 830.20 ± 77.16 | 0.61 | 9.89 ± 0.002 c | 0.59 | 0.00 (0.00, 0.04) | |
| High & Prolonged 1 | 22 May 2019–22 May 2019 | 1.13 | 78 | 22 | 38.13 ± 1.12 | 752.43 ± 67.53 | 0.41 | 10.95 ± 0.003 c | (182.75 d ) | No survival monitoring | |
| Low | 29 May 2019–6 June 2019 | 0.25 | 231 | 8 | 37.77 ± 1.30 | 719.23 ± 52.19 | 1.19 | 9.88 ± 0.002 | 92.00 | 0.00 (0.00, 0.02) | |
| High & Prolonged 2 | 6 June 2019–6 June 2019 | 1.15 | 91 | NA e | 37.95 ± 0.83 | 730.20 ± 66.68 | 0.45 | 9.62 ± 0.001 | 182.75 | No survival monitoring | |
| August/September | Control 3 | 21 August 2019–17 September 2019 | 0.75 | 175 | 10 | 38.40 ± 0.83 | 677.47 ± 41.34 | 0.78 | 8.36 ± 0.002 | 0.76 | 0.00 (0.00, 0.02) |
| Moderate | 22 August 2019–9 November 2019 | 0.22 | 131 | 7 | 38.17 ± 1.18 | 646.00 ± 71.05 | 0.59 | 7.86 ± 0.01 | 146.21 | 0.03 (0.01, 0.07) | |
| High | 28 August 2019–17 September 2019 | 0.25 | 150 | 9 | 38.64 ± 0.93 | 678.79 ± 62.10 | 0.64 | 8.24 ± 0.007 | 179.87 | 0.31 (0.23, 0.39) |
a
Calculated from fish sampled prior to or during treatment only.
b
Confidence intervals calculated using Wilson score intervals.
c
Measured <1.5 h after treatment period.
d
Data not collected due to logistical constraints on the day of the trial. Therefore, density assumed to be the same as for the “High & Prolonged 2” trial.
e
Skin colour data not collected due to logistical constraints on the day of the trial but reported here because of the supporting data it provides regarding crowding density.