The effect of kelp bed disturbance on the abundance and feeding behaviour of fishes on high-relief reefs

On high-relief reefs, research has shown that the abundance and diversity of non-cryptic fishes is greater in kelp beds cleared of their canopy compared to those left intact. Greater abundance may be caused by an increase in the availability of food resources associated with damaged kelp, exposed understory algae and newly colonised turfing algae. We investigate the effect of a disturbance to the kelp canopy on two response variables, the abundance and feeding behaviour of six common non-cryptic fish species. We found that Kyphosus sydneyanus (herbivore) and Notolabrus parilus (generalist carnivore) move preferentially into 1-month old clearance plots to feed, whereas Kyphosus cornelii and Odax cyanomelas only graze in these plots incidentally. Kyphosus sydneyanus responded with greater abundance and feeding rate in 1-month old clearance plots that were dominated by the microscopic filamentous brown alga, Hincksia mitchelliae. Small-scale disturbances that remove kelps from kelp canopies result in a shift towards filamentous algae that either supplements dietary needs or is a preferred food choice for K. sydneyanus.