Size matters: experimental partitioning of the strength of fish herbivory on a fringing coral reef in Moorea, French Polynesia

作者：Fong Peggy^*; Frazier Nicholas M; Tompkins Cook Cameron; Muthukrishnan Ranjan; Fong Caitlin R

来源：Marine Ecology-An Evolutionary Perspective, 2016, 37(5): 933-942.

DOI：10.1111/maec.12298

• Algae
• assembled community
• coral reef
• fishing
• herbivory
• partition
• size class

While the importance of top-down control by grazers in maintaining tropical reef community structure is well known, the effect of fishing down the food web', which simultaneously changes the abundance and size of herbivorous fishes, has received less attention. As many fishing practices target the biggest fish and regulations often set minimum size limits, understanding size-dependency of this controlling force is important. We evaluated the hypothesis that reduction in the abundance and size of fish, regardless of species identity, reduces the role of herbivory in controlling algal abundance on reefs and assessed variation in efficacy of this top-down control on different types of common macroalgae. We quantified herbivory rates within cages of differing opening sizes on assemblages of four common algal species (Padina boryana, Dictyota bartayresiana, Halimeda opuntia and Galaxaura fasciculata) on two fringing reefs in Moorea, French Polynesia. Small acanthurids (<15cm length) were the dominant herbivorous fish while other herbivorous fish were rare. For the two most palatable algae, the majority of herbivory occurred in open plots, with herbivory reduced by >50% in the largest opening cages (6x6cm) where the maximum size fish entering was 12cm in length (mean=7.6, SE=0.4). Fish entering medium (4.5x4.5cm openings, maximum fish length=8cm, mean=6.3, SE=0.4) and small (3x3cm openings, no fish observed entering) cages had herbivory rates approximately equal to the control treatment (1x1cm openings). Consumption varied among algal species, with minimal consumption of physically and chemically defended algae and no pattern across treatments. Our results demonstrate a need for management plans to not only maintain the overall abundance of herbivorous fish but to protect the largest sizes for effective top-down control of algal communities.

• 出版日期2016-10