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Marine Ecology Progress Series

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MEPS 686:141-157 (2022)  -  DOI:

Impacts of overfishing and sedimentation on the feeding behavior and ecological function of herbivorous fishes in coral reefs

Yuichi Akita1,*, Takeo Kurihara2, Masato Uehara3, Toshiyuki Shiwa4, Kenji Iwai4

1Department of Agriculture, Forestry and Fisheries, Fisheries Division of Okinawa Prefecture, 1-1-2 Izumizaki, Okinawa 900-0021, Japan
2Fisheries Technology Institute, 1551-8 Taira, Nagasaki, Nagasaki 851-2213, Japan
3Onna Village Fisheries Cooperative, 59 Maeganeku, Onna, Okinawa 904-0414, Japan
4Okinawa Prefectural Sea Farming Center, 853-1 Ohama, Motobu, Okinawa 905-0212, Japan
*Corresponding author:

ABSTRACT: Coral reef environments are currently experiencing a global crisis. For restoration and conservation of such environments, substratum suitable for coral recruitment is important. Herbivorous fishes are likely to facilitate the survival and growth of coral reefs by removing sediment and epilithic algae on corals in the course of their feeding behavior. However, this facilitative function can be greatly impaired by anthropogenic stressors such as overfishing, which decreases the biomass of fishes, and by excessive sediment deposition due to land development, which might decrease the frequency of feeding. To examine these hypotheses, we conducted observations and experiments at 4 reefs with different degrees of anthropogenic stress in subtropical Japan. Our findings were as follows: (1) Underwater visual censuses, sediment trap surveys, and an analysis of fishery statistics revealed that biomass, population density, and species richness of herbivorous fishes were generally lower in reefs with high densities of fishermen and high sedimentation rates. (2) Caging experiments showed that, compared to control plots, caged plots inaccessible to herbivorous fishes had greater accumulation of sediment and epilithic algae. (3) Sediment removal experiments found that, compared to control plots, experimental plots with the sediment removed were more heavily grazed by some functional groups of herbivorous fishes (grazers). These results suggest that excessive deposition of sediment and overfishing depress the facilitative function of herbivorous fishes, which can further exacerbate the deposition of sediment.

KEY WORDS: Herbivorous fish · Fishing pressure · Sediments · Coral reef resilience · Ecological function · Epilithic algal matrix

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Cite this article as: Akita Y, Kurihara T, Uehara M, Shiwa T, Iwai K (2022) Impacts of overfishing and sedimentation on the feeding behavior and ecological function of herbivorous fishes in coral reefs. Mar Ecol Prog Ser 686:141-157.

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