Half a million tropical fish are scooped up into nets every year from the waters off Hawaii's largest island and flown to aquariums across the globe.
Scientists say the aquarium fishery off the Pacific island is among the best managed in the world. But it has become the focus of a fight over whether it is appropriate to remove wild fish from reefs to put in fish tanks.
Activists have launched a campaign to shut down the buying and selling of fish for aquariums, saying the practice, seen from Hawaii to the Philippines, is destroying coral reefs.
Mike Long, of the US-based Sea Shepherd Conservation Society, which is spearheading the campaign, said: "In this day and age, where the ocean faces a crisis ... there's absolutely no justification for a fishery for a hobby."
But a coalition of fishermen, state regulators and environmentalists say the group should focus its attention elsewhere.
They point to comprehensive aquarium fishery regulations and scientific research that shows fish stocks there are rebounding.
"We don't have a problem here any more," said Tina Owens, of the Lost Fish Coalition.
Surveys show numbers of yellow tang - the most commonly caught species on Hawaii's west coast - have jumped 88 per cent since the collection of aquarium fish was banned in 35 per cent of the waters. Numbers of goldring surgeonfish, the second most-caught fish, rose 37 per cent.
Scientists estimate the aquarium trade removes about 30 million fish from reefs around the world. Hawaii accounts for less than 2 per cent, while the vast majority comes from Indonesia and the Philippines.
Some fishermen in these countries pump cyanide into the water to make fish sluggish and easier to catch. The chemical could harm nearby marine life, as well as shorten the life span of the captured fish.
The Philippines has long prohibited cyanide fishing and in April banned certain types of fishing gear that destroy coral reefs and other marine habitat.
Hawaii collectors, who use nets, can sell one yellow tang for about US$4. With middlemen adding costs to store and ship them, the fish may retail for between US$30 and US$60.
Long said Sea Shepherd would also take the campaign to Indonesia and the Philippines.
The group is known for using aggressive tactics - even violence - to achieve its aims. Its members rammed Japanese whaling ships in Antarctica and hurled containers of acid at the vessels. A US federal judge called them pirates.
Conflict over the aquarium fish industry increased last month when Sea Shepherd activists with cameras approached two fish collectors working underwater in West Hawaii.
One collector swam to one of the activists and ripped her scuba air regulator out of her mouth.
Both the fish collector and the activist filed complaints against each other. Prosecutors are still reviewing the evidence.
Local activists have long pushed to shut down Hawaii's aquarium trade.
Robert Wintner, owner of the Hawaii dive shop chain Snorkel Bob's and vice-president of Sea Shepherd's board, sued the state in 2012, saying environmental studies should be conducted before collection permits are issued.
A state judge rejected the lawsuit, but the plaintiffs are appealing.