In September, the National Oceanic Atmospheric Administration (NOAA) and University of Hawai‘i marine scientists will publish a study describing a complete absence of the introduced, invasive bluestriped snapper or ta‘ape, across a large region of the Northwestern Hawaiian Islands (NWHI).

Deep coral reefs between 130 and 330 feet in the northwestern half of the Papahānaumokuākea Marine National Monument (which encompasses the NWHI) were found to be completely devoid of the widespread invasive fish species. In comparison, large schools of ta‘ape are common on shallow and deep reefs across all of the inhabited main Hawaiian Islands and also in the southern half of Papahānaumokuākea.

“Ta‘ape are widespread throughout the main Hawaiian Islands, and are considered to be an invasive species with the potential to compete with our native species,” said Randall Kosaki, NOAA deputy superintendent of PMNM and one of the co-authors of the study. “This finding indicates that deep coral reefs of Papahānaumokuākea represent a large zone where native species can thrive in the absence of introduced invasive species.”

In 2016, scientists discovered that deep coral reefs between 300 and 330 feet at Kure Atoll, the northernmost of all the NWHI, had fish communities composed exclusively of Hawaiian endemic species, or fishes that are found only in Hawai‘i.

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The study further found that schools of ta‘ape were typically found in close association with more desirable food fish such yellowfin goatfish (weke ‘ula) and sleek unicornfish (opelu kala) on shallow reefs. On deeper reefs below 130 feet, ta‘ape were associated with soldierfish (‘u‘u or menpachi).

“Although research has not conclusively demonstrated any detrimental impacts to more preferred native species of fishes, the ta‘ape is nevertheless considered to be a nuisance species by local fishermen, because they frequently bite on hooks intended for more desirable fishes,” said Brian Hauk, PMNM resource protection manager and co-author of the study.

Using advanced closed-circuit rebreather dive technology, scientists were able to survey reefs at depths of up to 330 feet (100 meters), which is much deeper than any research conducted using conventional scuba gear.

Greatest abundances of ta‘ape, schools of many hundreds of fish, were recorded at French Frigate Shoals in 170 to 200 feet. At all atolls and islands further north, scientists saw zero ta‘ape on deep reefs between 130 and 330 feet.

For more information, visit www.papahanaumokuakea.gov.