MEPS 523:175-185 (2015)  -  DOI: https://doi.org/10.3354/meps11173

ABSTRACT: Species belonging to the family Pomacentridae play a key role in altering algal assemblages in tropical systems, but our understanding about this family’s role in temperate systems is limited. We examine the role of the abundant and territorial pomacentrid Parma mccullochi as an herbivore in temperate waters of southwestern Australia. Through dietary analyses, we showed that this species consumed predominantly red foliose and filamentous algae that were positively selected based on electivity indices. The species composition of macroalgae differed significantly between inside and outside P. mccullochi territories, with commonly ingested algae such as Hypnea spp. characterising the territory assemblages, while brown algae such as kelp Ecklonia radiata, and other foliose or coralline red algae characterised reef area outside the territories. Total algal biomass was significantly lower, while species richness was higher, inside compared to outside territories. In contrast, a caging experiment inside P. mccullochi territories showed that species composition, species richness and biomass of recruiting algae did not differ significantly in treatments where damselfishes were excluded or able to forage. A visual census indicated that P. mccullochi territories covered nearly 40% of the reef in the study region. We conclude that, while other biological or physical processes are likely to create the patches within kelp canopies where P. mccullochi territories are established, the species appears to have a strong and extensive influence in maintaining lower standing crop and higher diversity in turf-forming algal assemblages in this temperate region. Understanding the role of herbivores in temperate regions is becoming increasingly important due to the effects of climate change through the shifting ranges of tropical species into temperate systems.

KEY WORDS: Herbivory · Pomacentridae · Algal composition · Recruitment · Diet