Defense Date

12-6-2023

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Andrew Bauman

Second Advisor

Fraser Januchowski-Hartley

Third Advisor

Rene Abesamis

Keywords

predator-prey interactions, browsers, human impacts, predator models, no-take zones, small-scale marine protected areas, macroalgae removal, ecosystem function, phase shifts

Abstract

Predation influences animal behavior and shapes ecological structure and function through lethal effects and fear effects. On coral reefs, fear effects can alter the distribution and intensity of herbivory by herbivorous reef fishes. This includes the browsing functional group, which potentially reverses macroalgal phase shifts and promotes reef recovery. Herbivory by multiple functional groups may increase on coral reefs through the use of NTZs (no-take zones) but few studies have examined the extent to which small-scale NTZs (< 0.5 km2) influence fear effects and perceived predator presence on reefs. This study aimed to determine whether fear effects on browsers on coral reefs differ between small-scale NTZs and unprotected fished reefs by documenting how browsing fishes respond to predator models stationed on four reefs: two within NTZs (Manta and Twin Peaks) and two outside of these NTZs. We found that there was significantly greater browser presence (MaxN) and total and mass standardized bites in NTZ sites compared to fished sites, and that predator model assays experienced significantly less feeding, with no significant difference between the effect of two predator models that were used. Additionally, macroalgal removal, and total and mass standardized bites differed between the two NTZs, being higher in Manta than in Twin Peaks. Ultimately, we found that small-scale NTZs can potentially result in greater browser biomass and the ecosystem function of macroalgal removal. Further research should explore the usefulness of small-scale NTZs in sustaining other ecosystem functions apart from macroalgal removal on coral reefs.

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