Tilapia Invasion in Hilo Highlights Risk of Introduced Species

October 27, 2019, 10:41 PM HST · Updated October 27, 10:42 PM

A new influx of Nile tilapia in Hawaiʻi Island waters is concerning biologists.

DLNR officials say the species is dominating Wailoa River in Hilo, as large schools of them are visible with the “naked eye.”


“Our biggest concern right now, is the Nile tilapia is competing with the native mullet (‘ama‘ama) for habitat and resources and potentially affecting the fishery,” Hilo-based aquatic biologist Troy Sakihara explained in the release.

“What makes them particularly troublesome as a potential invasive species, is they can survive and take over in a wide-variety of habitat conditions. Their very hardiness makes them an issue.”

Fishermen also reported seeing large schools of mostly juvenile tilapia along Kauaʻiʻs Nāpali Coast a few months ago.

Two years ago, this species of tilapia was reclassified by the State Board of Agriculture as a restricted species only for research – to permit importation for aquaculture facilities to farm raise them.

While there’s no evidence that a recent invasion of the tilapia in fresh water streams has anything to do with commercial farming operations, DLNR leadership and biologists say it confirms the fears they expressed when board members were debating whether or not to allow the state Dept. of Agriculture to revise its rules for importing Nile tilapia.

Biologists in Hilo are currently determining how to control the burgeoning population of Nile tilapia, including an open fishing tournament.

There are no restrictions or bag limits on tilapia and for now biologists say, “catch and eat as many as you want.”

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