Have you heard about the new proposed rules to help protect Hawaii’s coral reef grazers? The State Division of Aquatic Resources (DAR) recently proposed several new rules related to the catch of grazing fish, including size limits and daily bag limits for both recreational and commercial fisheries, and an updated commercial permit system with annual catch limits. The commercial harvest of certain species would also be prohibited during peak spawning months. Regulated species would include parrotfish (uhu) and surgeonfish (kala, manini, and kole).
A female spectacled parrotfish (Chlorurus perspicillatus, uhu ‘ahu’ula) and other reef fish help keep the reef clear of too much algae. (Photo credit: Lindsey Kramer).
The Board of Land & Natural Resources (BLNR) voted in late May to continue public meetings throughout the state to discuss these rule updates. Be sure to attend a meeting near you and make your voice heard!
Why is grazing so important?
Coral reef grazers are a critical part of reef ecosystems in Hawai‘i. Grazers, also referred to as herbivores, help keep coral reef areas healthy and resilient by consuming and removing most types of algae. This regular clearing of algae creates space for corals to grow and also opens up the reef for new larval corals to settle.
Grazing on reefs can occur in a variety of ways, including both delicate browsing for specific algal types or more dramatic deep bites / excavations that dig into fresh reef substrate. Some grazers, like nenue, can consume drift algae and help prevent algal settlement into new reef areas. Certain types of surgeonfish prefer to eat diatom and algal mats occurring over deep sand. Damselfish establish small territories to “farm” algae, which they later consume at their leisure. Invertebrate grazers, like wana (urchins), typically work their way across the reef substrate and consume all types of turf algae that cross their path, helping to promote the growth of beneficial crustose coralline algae. Given this diverse array of preferences and unique ecological roles, Hawaii’s grazers collectively help corals persist and regrow.
Limu versus invasive algae
Importantly, algae (limu) come in a variety of forms in Hawaiʻi. Some limu are rare, delicate, edible, and an important part of subsistence fishing in Hawaiʻi. Other types of algae, most often introduced species, can aggressively overgrow reef areas, overtaking corals and other types of reef cover. Examples of invasive algae include leather mudweed (Avrainvillea amadelpha), hookweed (Hypnea musciformis), smothering seaweed (Kappaphycus spp.), and gorilla ogo (Gracilaria salicornia), which have formed large, reef-stifling blooms on Maui and Oʻahu. Poor water quality conditions, such as increased run-off from golf courses and coastal cesspool seepage can enhance the growth of invasive algae, but a strong grazer community can help keep invasive algal blooms under control.
Learn more about invasive algae on the Eyes of the Reef website: https://youtu.be/jR-UDMMng4I
These white-spotted surgeonfish (ʻapi, Acanthurus guttatus) prefer filamentous algae in shallow, surgy reef areas (Photo credit: Lindsey Kramer).
Why were the new grazer rules proposed?
Since the devastating loss of coral due to bleaching in some areas of the state in 2015 and 2016, DAR has been working to develop new rules to promote reef resilience. Because of their important ecological role, enhanced protection of grazers was a top strategy for promoting reef recovery following recent coral bleaching events. Additional recommended strategies included water quality improvements, invasive species prevention, and developing proactive coral restoration techniques.
To learn more about recommended coral reef recovery strategies, including how grazers can improve reef resilience, check out the State Coral Bleaching Recovery Plan at: dlnr.hawaii.gov/reefresponse/current-rapid-responses/coral-bleaching-recovery-plan/
When will the new proposed rules go into effect?
The new rules are currently still in the development phase, so be sure to weigh-in at the next public meeting in your area! Scheduling announcements will be made on the DLNR-DAR website at: dlnr.hawaii.gov/holomua/herbivoremanagement/participate-in-the-process/.
Learn more about the proposed statewide herbivore rules at: dlnr.hawaii.gov/dar/files/2023/07/HAR-13-95revdr3.pdf
Yellow tang (lau’īpala, Zebrasoma flavescens) will sometimes form large, grazing schools that collectively consume algae along shallow reef areas (Photo credit: Lindsey Kramer).
