almost significantP = 0.062
The observation that some sites constantly showed a higher or lower maximum annual abundance was statistically confirmed for the 5-year monitoring at 4 sites ( χ 2 = 10.920, df = 3, P = 0.012) and was almost significant for the monitoring of 7 sites for 3 years ( χ 2 = 12.00, df = 6, P = 0.062) using Friedman’s ranking tests.