Yellow Tang

The yellow tang is a bright yellow surgeonfish found on shallow Pacific reefs, from 2 to 46 metres deep, around the Ryukyu, Mariana, Marshall, Marcus, Wake and Hawaiian islands. Adults grow to about 20 centimetres and carry a white defensive spine on the tail base. It lives alone or in small groups and mainly eats filamentous turf algae, plus some zooplankton. At night its yellow fades slightly and a brownish patch with a white horizontal band appears, but the colour returns quickly at daylight. Spawning peaks around the full moon, with eggs left in open water and no parental care. In the wild it can live for over 40 years.

About the yellow tang

The yellow tang is a small, bright yellow reef fish of the Pacific Ocean and a member of the surgeonfish family, Acanthuridae, which also includes unicornfishes and other tangs. It grazes algae on shallow coral reefs from Hawaii west toward Japan and is one of the most popular fish in saltwater aquariums.

Its scientific name is Zebrasoma flavescens. The genus name refers to the zebra-like bars of its relative, the sailfin tang, and flavescens is Latin for yellowish. English naturalist Edward Turner Bennett first described the species in 1828 from fish collected in the Hawaiian Islands. Within its genus it forms a closely related pair with the scopas tang.

The body is tall, narrow and oval, flattened from side to side so that an adult is only 1–2 cm (0.4–0.8 in) thick. Adults reach about 20 cm (7.9 in) long, and males tend to be a little larger than females. A tall dorsal fin carries five spines and 23–26 soft rays, and the anal fin has three spines and 19–22 soft rays. The snout protrudes, ending in a small, down-turned mouth packed with closely set, spatula-shaped teeth for scraping algae. Juveniles have 12 upper and 14 lower teeth; adults have 18 and 22.

Almost every part of the fish is yellow. The one exception is the feature that gives surgeonfish their name: a white, scalpel-like spine on each side of the tail base, which the fish uses for defense and aggression. At night the color changes. The bright yellow fades, a brownish patch appears in the middle of the body, and a white horizontal band shows along the side. By daylight the fish is fully yellow again.

Behavior and diet

Yellow tangs are diurnal. By day they move around the reef grazing; at night they rest alone in crevices in the coral. Adults live singly or in small, loose groups, sometimes mixed with other fish such as the sailfin tang. Juveniles are territorial, defending small patches within a few meters of one spot, but that habit fades as they grow and start roaming more widely.

They are mainly herbivores. Most of the diet is uncalcified, filamentous turf algae growing on the reef, along with seaweed and other plant material and some zooplankton. That grazing matters to the reef, because algae-eaters keep algae and seaweed from overgrowing and killing coral. Yellow tangs have also been seen cleaning sea turtles, picking algae off their shells.

When threatened or challenging a rival, a yellow tang spreads its fins to full size to look bigger and flashes the scalpel spines at its tail. Very young yellow tangs have venom glands, which they lose as they grow into juveniles and adults. Predators include larger fish, sharks, crabs and octopuses. The vivid color is less conspicuous than it seems: to other fish, at the depths where tangs live, the yellow blends in well with the reef.

Spawning happens year-round, more often from March to September, and peaks around the full moon. Fish spawn in groups or in pairs. In a pair, the male courts the female by changing color and "shimmering," then the two swim upward together and release eggs and sperm into open water. Females spawn about once a month and can release about 40,000 eggs. There is no parental care. The clear larvae drift as plankton and can be carried more than 160 km (100 mi) before settling on a distant reef.

Range and habitat

The yellow tang lives in the Pacific Ocean, west of Hawaii and east of Japan. Most live around Hawaii, and the species also occurs around the Ryukyu, Mariana, Marshall, Marcus and Wake islands.

It lives on shallow reefs from 2 to 46 m (6.6 to 151 ft) deep and favors the sub-surge zone of the reef, where wave action is weakest. Young fish settle into coral crevices after their drifting larval stage and grow up there.

Stray yellow tangs have turned up far outside this range. There have been reports off Florida, and they had been spotted several times on reefs along Mexico's Riviera Maya as of July 2024. A single fish filmed in Spanish waters of the Mediterranean in 2008 was likely an aquarium release.

Conservation status

The yellow tang is listed as Least Concern on the IUCN Red List. Its bright color makes it a familiar sight for divers on Hawaiian reefs, and it has been the top fish collected for export from Hawaii. Its biggest pressure has been the aquarium trade. Hawaii was the main source, supplying up to 70 percent of aquarium yellow tangs, and 300,000 to 500,000 fish a year were collected there. By the late 1990s, stocks were collapsing.

Hawaii responded by creating nine marine protected areas, and more than 70 percent of the fish's natural range there is now off-limits to collection and fishing. A 2010 study showed that larvae spawned inside the reserves drift on currents and restock fished areas far away, and the fishery has been recovering. Hawaii later imposed a ban on collecting them for the aquarium trade.

Captive breeding offers another route. In response to demand from the aquarium trade, techniques were developed to breed the species in captivity, and researchers bred them successfully in 2015.