Assessing temporal variation and autocorrelation in fish habitat use

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research Centre

MDFRC item.

We assessed the extent of temporal variation and autocorrelation in fish habitatuse based on an experimental study of individual 0+ juvenile barbel, Barbus barbus, in anartificial flume. Five treated and five control fish were individually subjected to an increasein discharge (intervention) halfway through each experiment and kept at baseline dischargethroughout, respectively. Preference curves for velocity were generated for each of 60 trials perexperiment and for each combination of treated/control (fish) × before/after-intervention. Therewere large between- and within-individual differences in velocity preference, both in treated andin control fish. Most barbel explored the entire range of velocities, whereas some individualsused a more limited range. Temporal variation in behavioural responses was assessed by a PCAbasedmethodology. Autocorrelation (i.e. correlation between sequential trials) was diagnosedin most response profiles, supporting recent findings that individuals may have a ‘memory’of their past velocity usage. The relevance of the results for numerical habitat models of fishhabitat assessment is discussed, as well as the importance of incorporating temporal variabilityinto fish habitat use models (e.g. PHABSIM), not only as ontogenetic intervals but also aslongitudinal data of individual behaviours. A warning is also re-issued about the erroneous beliefof ‘pseudoreplication’ simply arising from repeated measurements in time.