Marine protected areas risk becoming ‘paper parks’ that fail to provide adequate protection for fish and sea urchins controlling the growth of algae that can damage coral reef ecosystems, according to a study by the University of Hawai’i.
It calls for better management of the state’s marine protected areas, ahead of government plans to expand the number of MPAs in Hawai’i’s waters over the next 10 years. These areas are intended to protect marine ecosystems and habitat from over-fishing and commercial exploitation but the study argues that a review of management objectives – including enforcement of sustainable and no-take fisheries regulations – is needed
The researchers looked at populations of more than 20 herbivorous fish and sea urchin species in four marine protected areas in waters off Oahu – the third largest, most populated of the Hawaiian islands and home to the state capital Honolulu. It compared these populations to those found in waters outside of the MPAs. The species included fish described as grazers, scrapers and browsers of algae – such as parrotfish fish and surgeonfish – that are critical to maintaining the health of coral reefs.
The study is published online in the journal Coral Reefs .
Data analysis found three of the protected areas in Oahu’s waters – Pūpūkea, Kāne‘ohe Bay and Waikīkī – did not provide “biologically significant benefits for herbivorous fish populations compared to reefs outside these areas.” The fourth, in Hanauma Bay, showed some positive effects but fish diversity was limited.
Erik Franklin , one of the co-authors and associate research professor at the Hawai’i Institute of Marine Biology, said the study revealed herbivorous fish diversity was lower than expected across all the MPAs.
” Marine protected areas are a fishery management tool to limit or prevent fishing to help the recovery and maintenance of fish abundance and biomass inside the MPA,” he said in a University of Hawai’i statement.
“An effective MPA should lead to a considerably higher abundance and biomass of fishes inside the MPA boundaries that would otherwise be caught by fishers but that wasn’t what our study found.”
The study says the “limited benefits of MPAs for herbivorous fish and urchin populations around Oahu suggest a general need for improved fisheries management and enforcement, especially prior to the consideration of an expansion of the existing MPA network”.
Lead author and University of Hawaii marine biology postgraduate Noam Altman-Kurosaki said the research suggests there should be an increased focus by state government agencies on improved management of marine protected areas in Hawai’i.
“Our results suggest that prior to an expansion of MPAs in Hawaiian waters, more effort should be directed to effectively manage the existing MPAs to see if they meet the desired management objectives,” he said in a university statement.
“The addition of more MPAs throughout the state that have similar performance to the O’ahu MPAs would just lead to a series of paper parks that don’t provide biologically significant conservation benefits while decreasing fishing opportunities.”
Researchers compared the biomass, diversity and size of fish and sea urchin populations that contribute to the health of coral reef ecosystems by eating algae that can deplete oxygen and cause corals to die off.
“Herbivorous fishes and sea urchins contribute to the long-term health of coral reef ecosystems by eating algae that are competitive with corals, yet herbivorous fishes are frequently targeted by fishers. The deleterious effects of fishing on coral reef herbivore populations are thought to be decreased through the establishment of no-take marine protected areas,” the study says.
“The small size structure and densities of herbivorous fishes in MPAs across all regions limits their population-level functional and reproductive contributions. While MPAs serve as a popular fisheries management tool for coral reef environments, the limited benefits of MPAs for herbivorous fish and urchin populations around O‘ahu suggest a general need for improved fisheries management and enforcement, especially prior to the consideration of an expansion of the existing MPA network.”
The state government wants to expand marine protection by 2030 with an additional 25 per cent of Hawai’i’s ocean waters established as marine management areas. Currently, five percent of waters within three nautical miles of shore have some form of state conservation management, but no-take MPAs that ban fishing make up less than one-half of one percent of these protected waters.
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