Publication Abstract

An analysis of 0+ barbel (Barbus barbus) response to discharge fluctuations in a flume 

L. Vilizzi and G.H. Copp

We studied the response in velocity use and time in a refuge area of 0+ juvenile barbel (Barbus barbus) to an increase in discharge (intervention) in an artificial stream. Each of five treated and five control fish were observed individually in separate experiments each lasting eight hours. Observations (trials) were arranged within an hierarchically-structured, semi-randomised sampling schedule consisting of four time levels: phase (4 h) É period (2 h) É sub-period (30 min) É trial (120 s). Generic and specific pooled responses were modelled by MANOVAR and ANOVAR, respectively, and individual responses were examined by Intervention Analysis (IA). Increased discharge caused treated barbel to use higher velocities than control individuals, with individual differences in behaviour present at the various temporal tiers. Individual responses were modelled as either random walk or short-memory processes, and those by treated fish were generally abrupt and permanent, with only one individual showing a gradual and permanent use of the higher velocities. Time in refuge area was not affected by increased discharge except for one fish, which sought shelter after intervention. There was a significant relationship for most treated individuals between selection of lower velocities and time in refuge area, and most barbel (both treated and control) showed significant deviations of used from mean channel velocities. The potential of the proposed approach to assess fish responses to discharge and, more generally, population-level processes of fish behaviour is discussed, and the mosaic of barbel behaviours observed is compared with available laboratory and field studies.

Reference:

L. Vilizzi and G.H. Copp (2005). An analysis of 0+ barbel (Barbus barbus) response to discharge fluctuations in a flume. River Research and Applications, 21: 421-438.