Box plots of shelter occupation time of the benthic fish species stone loach (a, b) and bullhead (c, d), kept either alone (Control; n = 20) or in the presence of spinycheek crayfish (+Spinyceek; n = 20) or signal crayfish (+Signal; n = 20) during the day and night times (line: median, box: 25,75% percentiles, whiskers: 5%,95% percentile, dots: outliers).