Too many tilapia in Hawaii

Kauai’s fishery managers are saying they are in full emergency-mode after a report of blackchin tilapia in the island’s nearshore ocean, a discovery that could have heavy implications.

The state Department of Land and Natural Resources announced Thursday that fishermen have been reporting schools of tilapia along the Napali coastline for the past two weeks.

Pressley Wann, member of the North Shore community group Hui Maka’ainana o Makana, says he reported the “invasion” to DLNR after his daughter and grandson saw the fish during a project at Nualolo.

“They saw the pile showing up and they reported it to me,” Wann said Friday. “I got the report from my grandson and I right away called Dennis Eguchi on the Westside. He was getting reports, too.”

Theories are that the blackchin tilapia started in one of the ditch systems on the Westside and washed into the ocean.

Native to Africa, the species has been introduced to Asia and North America. It was first imported to Hawaii as a test baitfish for tuna in 1962 by the Federal Bureau of Commercial Fisheries (now National Marine Fisheries Service), according to U.S. Fish and Wildlife.

That was after redbreast tilapia were introduced to Hawaii in 1957 as a way to combat aquatic weeds.

The Oahu population was most likely built from escapees from the fish station where the test fish were being held. USFWS says they were also accidentally introduced to reservoirs that gave them an outlet to the ocean.

On Kauai, officials are still investigating how the fish ended up in Westside streams and ditches.

Blackchin tilapia are unique in the tilapia family in that they can survive in fresh water and salt water.

“I guess they raise them in Japan, breed them in fresh water and put them in pens in the ocean on the fish farm and they make sashimi out of the tilapia,” Wann said.

The fish seem to be dining on limu when they’re young and graduate to a carnivorous and cannibalistic diet when they get bigger.

“They’re very aggressive and in big schools, maybe 20 feet across and bigger,” Wann said. “There’s a lot of papio and ulua that are right outside of these piles.”

The amount of rain Kauai has lately been receiving has potentially contributed to the problem, diluting the nearshore waters just a bit and creating an inviting environment for the invasive fish.

“They seem to be migrating more north, really close to shore. We’ve had reports of them eating in Ha’ena and they’re probably the single greatest threat (to the fishery),” Wann said.

Thursday DLNR announced they’re taking steps to secure permits so community members can remove some of the fish with a surround net.

“I consider this an emergency situation. We don’t want this species proliferating down the coast. We need to remove them before winter swells make it difficult or impossible to do anything,” Ka‘ili Shayler, a fish and habitat monitoring coordinator with Division of Aquatic Resources said in the Thursday announcement.

Friday, Wann used the word “emergency” as well: “As far as our fisheries everything is in emergency mode. We’re trying to organize and follow through with DAR. It looks like it’s going to be a community effort.”

Online, the Kauai community has already started coordinating, suggesting meet-ups and cookouts to help get rid of the invasive, but edible fish while the state is moving through its process.

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Jessica Else, environment reporter, can be reached at 245-0452 or jelse@thegardenisland.com.

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