Temperate territorial damselfish act like tropical damselfish, but have no measurable effect on algae within their feeding areas

Abstract

Areas of high habitat heterogeneity support a high diversity of fauna in both terrestrial and aquatic systems. In altering the rate of consumption of benthic communities, tropical damselfish affect the rate and trajectory of succession, and maintain habitat heterogeneity. Such algal ‘farming’ behaviour is well documented for many tropical damselfish species in coral reef environments. Our study aimed to test the behavioural potential of the temperate water damselfish Parma mccullochi (McCulloch's scalyfin) to modify algal assemblages within their territories, and to assess the effect of any such behaviour on algal assemblages. We found that P. mccullochi behave in a similar way to tropical damselfish that maintain extensive algal farms: P. mccullochi feed over a large multispecies area, maintain a temporally consistent feeding rate (disturbance), and defend the territory against other herbivorous fish. However, we detected no change in the algal assemblage with the exclusion of resident fish from parts of their feeding areas. In contrast to many tropical damselfishes this feeding disturbance does not have any measurable short term effects on the algal composition of their feeding areas. Our study synthesises and builds upon the few published studies on temperate damselfish, all of which report no measurable change to the alga of the feeding area. However,we propose that disturbance by these species instead plays a longer termrole in reducing the rate of re-colonisation of clearanceswithin the algal canopy, and thus maintaining habitat heterogeneity on canopy dominated rocky reef.