Selective foraging by non-native rainbow trout on invertebrates in Patagonian streams in Argentina

Zoological Studies

Table 1 Physico-chemical parameters, annual mean standard deviation, and total range values from NyF and CVA streams (Patagonia, Argentina)

	NyF		CVA
Physical parameters	Mean ± SD	Range	Mean ± SD	Range
Water temperature (°C)	10.4 ± 2.7	7.6 to 13.6	6.5 ± 2.4	4.0 to 9.4
Wet width (m)	21.1 ± 3.1	17.5 to 25.0	7.2 ± 2.9	4.6 to 11.0
Depth (m)	0.2 ± 0.1	0.19 to 0.32	0.2 ± 0.0	0.20 to 0.28
Water velocity (ms⁻¹)	0.8 ± 0.2	0.68 to 1.0	1.1 ± 0.2	0.93 to 1.15
Discharge (m³ s⁻¹)	4.6 ± 2.4	2.71 to 8.0	1.9 ± 0.9	0.92 to 3.08
Substrate composition (%)
Boulder	20		15
Cobble	25		30
Pebble	10		15
Gravel	30		25
Sand	15		15
Chemical parameters	Mean ± SD	Range	Mean ± SD	Range
Conductivity (μS cm⁻¹)	114.0 ± 2.7	112.0 to 118.0	50.0 ± 14.0	38.0 to 63.0
Dissolved oxygen (mg l⁻¹)	8.8 ± 1.6	7.7 to 11.1	11.1 ± 1.7	9.7 to 13.0
pH	7.6 ± 0.4	7.2 to 7.9	7.3 ± 0.1	7.1 to 7.4
Turbidity (TNU)	4.2 ± 3.9	2.0 to 10.0	10.0 ± 15.0	0 to 27.0
Ammonium (μg L⁻¹)	1.05 ± 0.5	0.6 to 1.6	0.86 ± 0.7	0 to 1.7
Nitrate + nitrite nitrogen (μg L⁻¹)	0.18 ± 0.2	0.1 to 0.3	0.17 ± 0.2	0 to 0.3
Soluble reactive phosphate (μg L⁻¹)	0.37 ± 0.0	0.3 to 0.4	0.53 ± 0.2	0.2 to 0.7
Total suspended solids (mg L⁻¹)	2.74 ± 0.8	1.7 to 3.6	2.38 ± 1.8	0.7 to 4.4

During the study period (early autumn, late winter, late spring of 2005, and late summer of 2006). SD, standard deviation.