Overwintering aggregation patterns of European catfish Silurus glanis

Table 1 Temperature and catfish characteristics in each winter from 2017 to 2020

	Winter 2017	Winter 2018	Winter 2019	Winter 2020
Period	12/02/2017 17:15 01/21/2018 11:15	12/03/2018 06:15 03/06/2019 20:30	11/10/2019 06:00 03/02/2020 05:30	11/22/2020 14:00 02/06/2021 19:00
Daily temperature (°C)	6.5 (1.5) [4.7; 8.9]	6.8 (2.3) [3.3; 11.4]	9.5 (1.3) [6.9; 13.9]	7.0 (2.0) [3.2; 11.0]
All individuals
n	10	42	42	42
Total length (mm)	893 (187) [727; 1465]	1028 (309) [727; 2150]	1056 (326) [727; 2150]	1064 (313) [727; 2150]
Small < 850 mm
n	5	9	9	8
Total length (mm)	791 (33) [727; 839]	812 (34) [727; 847]	812 (34) [727; 847]	812 (36) [727; 847]
Medium [850; 1100[ mm
n	4	26	24	23
Total length (mm)	876 (15) [855; 902]	942 (59) [855; 1060]	944 (59) [855; 1060]	945 (59) [855; 1060]
Large ≥ 1100 mm
n	1	7	9	11
Total length (mm)	1465	1623 (335) [1100; 2150]	1600 (311) [1100; 2150]	1495 (322) [1100; 2150]

The daily temperature (mean, (sd) and [range], in °C) at 3 m above the bottom of the lake at its deepest point (point 42 on Fig. 1), the number of tracked catfish (n) and their total length (mean, (sd) and [range], in mm) for all pooled individuals and for each class size are given for the extended aggregation period analyzed in each winter
Values in italics and in parenthesis correspond to the standard deviation of the parameter

ISSN: 2051-3933