Scraping and grazing herbivorous/detritivorous fish display opposite feeding behaviours under different protection regulations

Abstract

Background:Functional groups, especially herbivorous shes, are important for mediating benthic community structure on coral reefs. Herbivorous and detritivorous sh display complex feeding behaviour, and research into schooling feeding behaviour and feeding rates, and how these change with environmental and social behavioural variables is lacking. Such knowledge is imperative to infer how herbivory/detritivory will change, in light of changing resources and communities, speci cally whether reefs can recover from disturbance. Differences in abundance, feeding rate, body length, diet preferences, and schooling size of three major functional groups, scrapers, grazers and browsers were examined across reef habitats under different shing regulations, such as no-take restricted zones and open-shing general use zones. Although marine protected areas have been implemented to conserve reef sh species; further precise management based on ecological behaviour of functional groups is necessary. Results:Scrapers and grazers which were mostly parrot shes and surgeon shes were more abundant on reef ats and also displayed the highest feeding rates on reef ats. Although scrapers mainly resided inside the restricted zone, more grazers were found in the general use zone where macroalgae abundance was highest, indicating a higher availability of nutritional resources. Browsers, mostly rabbit shes, were seldom observed and patchily gathered on the reef at and slope in both zones. Thus, shing protection did not appear to bene t grazers and browsers, whereas scrapers gathered on shallow reef ats in the protection zone. Lastly, scraper and grazer feeding rates increased from an individual to paired feeding, and increased with body size, these factors led to variations in feeding behaviours on different habitats under different protection regulations. Conclusions:Fishing protection bene ts scrapers which subsequently appears to be resulting in a reduction in algal coverage, and variation in feeding rates was largely related to school sizes. The density of these functionally important grazers was in uenced more by changes to benthic composition than protection status. The opposite feeding behaviours of two herbivorous/detritivorous functional groups indicates not only protection status, but shing gear and size limit regulations are needed to help maintain sheries and diversity on coral reefs in Taiwan.

From Plates to Baits: Using a Remote Video Foraging System to Study the Impact of Foraging on Fouling Non-Indigenous Species

“…Ultimately, a low horizontal competition can increase the relative importance of consumers (grazers and predators) in the biotic resistance exerted by the ecosystem. Regarding this matter, the foraging on fouling can promote a more heterogeneous fouling assemblage, whether the total NIS and cryptogenic species abundance in the fouling community may decrease, increase or remain the same [48,89,99,100]. In other words, the empty patches created by the foraging activity can be re-colonised by NIS and cryptogenic species [11].…”