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

Abstract

Background:Functional groups, especially herbivorous fishes, are important for mediating benthic community structure on coral reefs. Herbivorous and detritivorous fish 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, specifically 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 fishing regulations, such as no-take restricted zones and open-fishing general use zones. Although marine protected areas have been implemented to conserve reef fish species; further precise management based on ecological behaviour of functional groups is necessary.Results:Scrapers and grazers which were mostly parrotfishes and surgeonfishes were more abundant on reef flats and also displayed the highest feeding rates on reef flats. 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 rabbitfishes, were seldom observed and patchily gathered on the reef flat and slope in both zones. Thus, fishing protection did not appear to benefit grazers and browsers, whereas scrapers gathered on shallow reef flats 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 benefits 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 influenced 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 fishing gear and size limit regulations are needed to help maintain fisheries and diversity on coral reefs in Taiwan.

Herbivorous fish of Sinai marine protected areas (Gulf of Aqaba): Structure baseline for potential thermal stress impact management

“…Alternatively, observations made by other studies suggest that herbivorous fish abundances, in particular parrotfish family appeared to be more influenced by management status (Price et al, 2021), environmental conditions (McClanahan and Muthiga, 2020), and habitat characteristics (Vallès and Oxenford, 2014) rather than fishing effect. Similarly, density of surgeonfish species was influenced more by the changes to benthic composition than protection status (Russ et al, 2018).…”

“…However, this study suggests that the increasing of abundance of rabbitfish family might be affected more by environmental factors as mentioned by (Olds et al, 2013;Roff et al, 2019) rather than predation or fishing effect. Price et al (2021) found that abundances of grazers and browsers increased in the fished areas with high algal cover. Personal observations suggest the presence of seagrass beds and/or mangroves close to fished reefs (particularly at Nabq), could be an important factor in determining the significance of Siganids associated with them.…”