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

Abstract

On high-relief reefs, research has shown that the abundance and diversityof non-cryptic fishes is greater in kelp beds cleared of their canopycompared to those left intact. Greater abundance may be caused by anincrease in the availability of food resources associated with damaged kelp,exposed understory algae and newly colonised turfing algae. We investigatethe effect of a disturbance to the kelp canopy on two response variables, theabundance 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 plotsto feed, whereas Kyphosus cornelii and Odax cyanomelas only graze in theseplots incidentally. Kyphosus sydneyanus responded with greater abundanceand feeding rate in 1-month old clearance plots that were dominated bythe microscopic filamentous brown alga, Hincksia mitchelliae. Small-scaledisturbances that remove kelps from kelp canopies result in a shift towardsfilamentous algae that either supplements dietary needs or is a preferredfood choice for K. sydneyanus.