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Marine Ecology Progress Series

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MEPS 489:213-224 (2013)  -  DOI: https://doi.org/10.3354/meps10379

Food intake by the parrotfish Scarus ferrugineus varies seasonally and is determined by temperature, size and territoriality

Y. Afeworki1,2,*, Z. A. Zekeria2, J. J. Videler1, J. H. Bruggemann3

1Department of Ocean Ecosystems, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands
2Department of Applied Marine Science, College of Marine Science and Technology, PO Box 170, Massawa, Eritrea
3Laboratoire d’Ecologie Marine (ECOMAR) – FRE CNRS 3560, Université de la Réunion, CS 92003, 97744 Saint Denis, La Réunion, France

ABSTRACT: On coral reefs, feeding by parrotfishes may prevent coral to macroalgal phase shifts by keeping algae in a cropped state. To predict the response of grazers to changing conditions, knowledge of the factors that affect feeding intensity is needed. Therefore, we studied food intake of the parrotfish Scarus ferrugineus on an inshore fringing reef in the southern Red Sea, Eritrea, where seasonality and extreme summer temperatures were expected to influence feeding rates. Bite rates (bites min-1), defecation rates (defecations min-1) and yield per bite (mass ingested bite-1) were estimated for 3 life-phase categories: 20 to 25 cm initial phase (IP), 30 to 35 cm terminal phase (TP) and 30 to 35 cm territorial terminal phase (TTP). The bite rates increased from low levels in the morning to peak values in the afternoon. IP bite rates increased linearly with seawater temperature. For TP, the temperature-bite rate relationship was quadratic, with maximum bite rates at ~32°C and lower rates at higher temperatures. Yield per bite in both IP and TP did not differ with time of year. Throughout the year, the total daily bites were highest in IP and lowest in TTP, resulting in ~23% lower daily intake in TTP compared to similar-sized TP males. Daily intake of ash-free dry mass of epilithic algal matrix (g AFDM d-1) was 7.5 to 9.6 for IP, 12.4 to 17.5 for TP and 8.7 to 13.2 for TTP. Intake and defecation rates and hence gut turnover rates peaked from April to July. The quadratic temperature response of TP suggests that large individuals may be close to their upper thermal limit, implying that temperature rises are likely to negatively affect grazing by large-bodied parrotfishes.


KEY WORDS: Coral reefs · Herbivory · Grazing rate · Extreme environments · Southern Red Sea · Resilience


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Cite this article as: Afeworki Y, Zekeria ZA, Videler JJ, Bruggemann JH (2013) Food intake by the parrotfish Scarus ferrugineus varies seasonally and is determined by temperature, size and territoriality. Mar Ecol Prog Ser 489:213-224. https://doi.org/10.3354/meps10379

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