The Functional Importance of Herbivores: Tying the knot between fish biomass, parrotfish feeding and benthic structure on Kenyan coral reefs
Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
Herbivory is considered a key ecosystem process on coral reefs as it enhances reefs resilience by preventing shifts to macroalgal states. In trying to understand mechanisms and consequences of such shifts, research have taken on a variety of approaches, from the effect of declining habitat condition on (herbivorous) fish communities to the roles of specific herbivore functional groups and size classes therein. This study aimed to incorporate these different foci by investigating the interplay between roving herbivore biomass (surgeonfish and parrotfish), parrotfish functional impact and a coral-macroalgal gradient, represented by four Kenyan reefs. The feeding function (here, the amount and type of algae removed) was measured at the parrotfish community level and an in-depth assessment was made of two target species (Chlorurus sordidus and Scarus psittacus) to determine the effect of benthic condition and fish size. Both herbivore biomass and the parrotfish community functional impact declined over the coral-macroalgal gradient, and the transition was found at herbivore biomass of ~300 kg ha-1. Interestingly, benthos appeared to only have limited effect on the function of individual parrotfish, whereas size was highly important as large fish were found to be functionally superior. It was the discussed how herbivore biomass and level of herbivory can be both cause and consequence of benthic community structure, and whether biomass can serve as a measure of function. Lastly, the question is raised on how to balance the trade-off between fish for food or fish for function, discussing management implications that can allow for fishing without undermining function provided.
Place, publisher, year, edition, pages
2014. , 57 p.
herbivore, coral reefs, ecosystem process, parrot fish, surgeonfish, Kenya
Ecology Social Sciences Interdisciplinary
IdentifiersURN: urn:nbn:se:su:diva-105723OAI: oai:DiVA.org:su-105723DiVA: diva2:730927