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Relative abundance

In all, 1,465 fish were captured, representing 15 species and seven families. Overall, 222 efforts were made. 

To evaluate if there was a difference in fish abundance between the two investigated streams a Two -way ANOVA was carried out with stream ID and channelization as given factors. The ANOVA showed no significant difference between the two streams (F=1,22 P=0,291). However there was a significant difference between the grades of channelization (F=4,9 P= 0,023).

Further, a three-way ANOVA was used to determine whether channelization, stream velocity or depth influenced the number of fish. The results showed a highly significant result of channelization (F = 24,5 P< 0,001) while the other factors tested showed no significant difference in variance (stream velocity F= 0 P= 0,983, depth F= 1,24 P= 0,293)

Species richness

The rare faction curves shows considerable differences in species richness . Especially between channelization one and channelization three where almost twice as many species are to be expected in channelization degree three. Also the Species composition differed between the degrees of channelization. Trout were only caught in the 0 areas, constituting 6% of the fish. Smelt, Zander and vimba were exclusive for channelization grade 3 and together with Idus bream and rudd they were only caught in channelized sections of grade 2 two and 3, together constituting 10 % of the fish. Perch, roach, ruffe, bleak and bullhead were caught in all four grades of channelization.

Effect on guilds

The relative proportions of the guilds varied in regards to channelization severeness . Proportionally the rheophilic species showed a rapid decline from channelization 0 to channelization 3. An opposite trend can be seen among the limnophilic fish species where catches increased with channelization severeness. The proportion of euryotopic species followed the same pattern as the total abundance of fish with the lowest abundance at channelization rate 1. The proportions are based on the CPUE ( Catch per unit effort).


Responsible for this page: Agneta Johansson
Last updated: 05/23/13