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Marine Ecology Progress Series

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MEPS 673:107-116 (2021)  -  DOI:

The neglected role of omnivore fish in the overgrazing of Mediterranean rocky reefs

Orestis Papadakis*, Konstantinos Tsirintanis, Vasiliki Lioupa, Stelios Katsanevakis

University of the Aegean, Department of Marine Sciences, University Hill, 81100 Mytilene, Greece
*Corresponding author:

ABSTRACT: Sea urchins are considered the most important grazers in Mediterranean shallow sublittoral rocky reef ecosystems, but fish can also have an important role in overgrazing and the reduction of habitat complexity. In this study, the trophic behavior of fish was recorded when provided access to experimental surfaces with increased macroalgal biomass and associated benthic fauna, created by herbivore exclusion cages. After a sufficient period for substantial algal growth, the cages were removed and the activity of fish on these surfaces was recorded for 3 h by an automated photographic camera system. Control surfaces with no restriction on grazers were defined on similar substrates for comparison. To quantify the effects of fish feeding activity on macroalgal coverage, photographic samples were taken immediately after the opening of the cages and after each 3 h recording. The response of fish when the cages were removed was immediate and intense. Feeding activity by 13 different fish species was recorded in total, of which the most frequent were the omnivores Diplodus vulgaris, Coris julis and Thalassoma pavo, and to a lesser extent the herbivore Sarpa salpa. The coverage of erect algae was substantially decreased on the experimental surfaces due to fish feeding activity. The algae were either directly consumed by the fish or cut off when the fish were feeding on macroinvertebrates. We conclude that in addition to grazing by herbivores, fish of higher trophic levels can also significantly affect macroalgal assemblages and restrict the recovery of erect algae in overgrazed reefs where prey is scarce.

KEY WORDS: Herbivore exclusion · Algal forests · Algal growth · Sea urchins · Rocky subtidal reefs · Cystoseira

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Cite this article as: Papadakis O, Tsirintanis K, Lioupa V, Katsanevakis S (2021) The neglected role of omnivore fish in the overgrazing of Mediterranean rocky reefs. Mar Ecol Prog Ser 673:107-116.

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