Abundance (left) and length (right) of fragments on L (a, b) and H (c, d) jute matting during time. Open and grey boxplots denote to Elodea canadensis and Myriophyllum spicatum, respectively. Significant differences between the species at given month are marked by asterisk, non‐significant ones by ‘NS’. Different letters denote significant difference (p < 0.05) among months in either species (Elodea canadensis = small letters, Myriophyllum spicatum = small letters in italics). Box limits correspond to upper and lower quartiles, horizontal bar to the median, and points show outliers outside the 1.5 times interquartile range among species.