Zebrasoma flavescens

Yellow tangs, Zebrasoma scopas, are reef fish found in the waters west of Hawaii and east of Japan in the Pacific Ocean. They mainly live off the coast of Hawaii, but are also found in the more western ranges of their habitat, including the islands Ryukyu, Mariana, Marshall, Marcus, and Wake. They prefer subtropical waters. (Agbayani, 2008; Waikïkï Aquarium, 1999)

Yellow tangs are reef-associated fish. Their preferred water temperature is around 21 degrees Celsius. They inhabit coral reefs in subtropical waters, but generally do not live in tropical seas. Yellow tangs mainly live in the sub-surge zone of a coral reef, this is the area with the least wave action. Zebrasoma scopas live at depths of 2 to 46 meters. The clear larva of yellow tangs develop into marine plankton, in this stage they are carried close to reefs where they settle in coral crevices. (Agbayani, 2008; Ogawa and Brown, 2001; Reynolds and Casterlin, 1980; Waikïkï Aquarium, 1999)

Yellow tangs have a clear larval stage before developing into juveniles. Juveniles and adults have a narrow, oval body. They have an average length-weight ratio between 2.93 and 3.16. They have a long snout for eating algae, a large dorsal fin with four to five spines, and an anal fin with three spines. Like other surgeonfish and tangs (Acanthuridae), yellow tangs have a white, scalpel-like spine on both sides of the tail that can be used for defense or aggression. Yellow tangs are named for their bright yellow coloring; the only area that is not yellow is the white spine. At night, this bright yellow color changes to a darker, grayer yellow with a white lateral line. (Agbayani, 2008; Froese, 1998; Guiasu and Winterbottom, 1998; Waikïkï Aquarium, 1999; Wood, 2008)

Yellow tangs begin their lives as fertilized eggs floating in open water. After hatching, the clear, pelagic larvae develop in the plankton. They enter the acronurus larva stage where they develop an oval body, dorsal and ventral fins, and spines. After about ten weeks, they enter a planktonic stage. Here, waves carry them to a coral reef where they take refuge and continue to develop and grow. (Brough and Brough, 2008; Sale, et al., 1984; Waikïkï Aquarium, 1999; Wood, 2008)

Zebrasoma scopas can spawn in groups or in pairs. When in groups, females release eggs and males release sperm into open water where fertilization occurs. When in pairs, the male courts a female by changing colors and exhibiting a shimmering movement. The two fish then swim upward and simultaneously release their eggs or sperm into the water. Males may spawn with multiple females in one session, while females typically spawn only once a month. (Brough and Brough, 2008; Waikïkï Aquarium, 1999; Wood, 2008)

Yellow tangs reproduce externally. Their spawning peaks from March to September, but some fish spawn at all times throughout the year. An average female can release about 40,000 eggs. (Agbayani, 2008; Detroit Zoological Society, 2008; Lobel, 1989)

There is no parental investment in yellow tangs beyond the fertilization of eggs.

Not much is known about the lifespan of yellow tangs. However, some sources have found them living up to about 30 years on the reef and 10 years in captivity. (Dodds, 2007; Parrish and Claisse, 2005)

Juvenile yellow tangs are often territorial. This trait usually diminishes as the fish mature and start to roam wider areas of the reef. Adult tangs live singly or in small, loose groups. These groups sometimes contain other species of fish, like sailfin tang (Zebrasoma veliferum). Yellow tangs are diurnal. During the day, tangs move from place to place, grazing on algae; at night, they generally rest alone in coral reef crevices. (Agbayani, 2008; Atkins, 1981; Brough and Brough, 2008; Wood, 2008)

When they are juveniles, yellow tangs have small home ranges that they defend, often staying within a few meters of one area. Not much is known about the home ranges of adult yellow tangs. (Parrish and Claisse, 2005)

When mating, males change colors and exhibit a shimmering movement to attract females. In defense or aggression, yellow tangs extend their fins to full length, greatly increasing their size. They also expose their scalpel-like scales on their fins as a warning sign. They use these not only to defend themselves from predators, but also to scare away competitors for food or territory. (Brough and Brough, 2008; Waikïkï Aquarium, 1999)

Yellow tangs have a long, down-turned mouth with small teeth that are specialized for grazing on algae. Because they are mainly herbivores, they spend a large amount of their time grazing either alone or in groups. A large portion of their diet consists of uncalcified and filamentous algae that grows on coral reefs. In addition to smaller types of algae, yellow tangs feed on macroalgae, such as seaweed. Yellow tangs will also eat some types of zooplankton. (Guiasu and Winterbottom, 1998; Waikïkï Aquarium, 1999; Wylie and Paul, 1988)

Predators of Zebrasoma scopas include larger fish and predatory invertebrates such as crabs and octopi. Yellow tangs rely on camouflage and their scalpel-like fins to protect themselves. To humans, these fish appear bright yellow, but, to other fish, yellow tangs blend in very well with coral reef backgrounds. According to Marshall et al. (2003) wavelength differences between yellow and average reef color become negligible at the depths where yellow tangs are found. In addition to camouflage, Zebrasoma scopas use their scalpel-like fins for defense. (Barry and Hawryshyn, 1999; Detroit Zoological Society, 2008; Marshall, et al., 2003; Waikïkï Aquarium, 1999)

Yellow tangs, along with other algae feeders, are crucial parts of coral reef ecosystems. They feed on algae and seaweed that grow on the reefs, preventing them from overgrowing and killing corals. Yellow tangs are also a food source for larger fish and invertebrates. (Detroit Zoological Society, 2008; Waikïkï Aquarium, 1999)

Yellow tangs are important for tourism and the aquarium trade. Their bright yellow color is well recognized by scuba divers and other tourists on Hawaiian reefs. They are also a valuable resource in aquarium trade; they are the number one collected fish for export out of Hawaii. Their coloring, hardiness, and low cost all attribute to their popularity in marine aquariums, making them one of the ten most popular fish. (Brough and Brough, 2008; Ogawa and Brown, 2001; Waikïkï Aquarium, 1999)

Yellow tangs, along with other surgeonfish (Acanthuridae), are not generally dangerous. When they are young, they possess venom glands. As they age into juveniles and adults, they lose these glands. If yellow tangs are provoked, they can inflict deep injuries with the sharp blades on their tails. (Agbayani, 2008; Waikïkï Aquarium, 1999)

Zebrasoma scopas is not a threatened or endangered species.