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Zebrasoma flavescens 

Scope: Global
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Perciformes Acanthuridae

Scientific Name: Zebrasoma flavescens
Species Authority: (Bennett, 1828)
Common Name(s):
English Yellow Tang, Yellow Sailfin Tang, Somber Surgeonfish, Lemon Sailfin
Synonym(s):
Acanthurus flavescens Bennett, 1828

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2012
Date Assessed: 2010-05-07
Assessor(s): McIlwain, J., Choat, J.H., Abesamis, R., Clements, K.D., Myers, R., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B.
Reviewer(s): Edgar, G. & Kulbicki, M.
Justification:
This species is widespread in the west and central Pacific. It achieves high abundances in Hawaii but is rare elsewhere. It is the number one collected aquarium fish in Hawaii (Walsh et al. 2004) and accounts for approximately 80% of the fish caught for the aquarium trade in West Hawaii in recent years (Claisse et al. 2009, Williams et al. 2009). There have been decreases in Yellow Tang density in areas open to fishing in West Hawaii. The decrease in open areas is attributable to the life history characteristics of this species as well as the increase in the number of aquarium collectors and collected animals. Several additional management actions have been proposed in response to the continuing decline of this species in areas open to collecting, these include restricting which species can be collected and  the establishment of a limited entry program for the fishery (Walsh et al. 2010). In addition, Yellow Tang is protected in Fish Replenishment Areas (FRAs) and in a number of marine reserves in parts of its range and the trade is closely monitored in Hawaii. It is therefore listed as Least Concern. We recommend continued monitoring of the harvest and trade of this species. This is especially important because it has a complicated life history with adults settling in deeper, coral rich areas then migrate into shallow water after maturity. This characteristic has only been recently recorded, the 10 yr population monitoring set up in 1999 was targeting juvenile habitats and surveys in the shallow adult habitat has occurred only once in 2006. Studies have shown that the FRAs West Hawaii will become important in maintaining the breeding population with increased fishing pressure.

Geographic Range [top]

Range Description:Zebrasoma flavescens is found in the central and western Pacific from the Hawaiian Islands and Johnston Island to the Marshall Islands, Wake, Mariana Islands, Philippines, Ogasawara and Ryukyu Islands, Japan. It was also recorded from southern Taiwan.

Sightings of Z. flavescens were made at three sites in southern Florida by the REEF Fish Survey Project between 1993 and 2002. These were the result of a deliberate aquarium release. The authors report this species did not establish itself and there was no significant impact to the community composition of local fish (Semmens et al. 2004).
Countries occurrence:
Native:
Guam; Japan; Marshall Islands; Micronesia, Federated States of ; Northern Mariana Islands; Palau; Philippines; Taiwan, Province of China; United States Minor Outlying Islands (Johnston I., Midway Is., Wake Is.)
Introduced:
United States (Hawaiian Is. - Native)
FAO Marine Fishing Areas:
Native:
Pacific – eastern central; Pacific – northwest; Pacific – western central
Additional data:
Lower depth limit (metres):81
Upper depth limit (metres):1
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:

Yellow Tang (Zebrasoma flavescens) is abundant only in Hawaii, rare elsewhere. It is the number one collected aquarium fish in Hawaii (Walsh et al. 2004). It accounts for approximately 80% of the fish caught for the aquarium trade in West Hawaii in recent years (Claisse et al. 2009, Williams et al. 2009). It made up 43.5% of the catch and 57.1% of the value of the overall aquarium catch in fiscal years 2004 through 2006. Reported catch from FY 2004-2006 was 366,317 individuals caught per year with a value of $896,048 per year (Friedlander et al. 2006).

Williams et al. (2009) state recent surveys of Hawaiian Islands by Hawaii Division of Aquatic Resources reveal no populations comparable in size to that of West Hawaii. Of 60 locations surveys across the Hawaiian archipelago, Yellow Tang was ranked 9 by index of relative dominance (Freq occurrence x percent biomass) (Friedlander and DeMartini 2002).

Reported Yellow Tang catch increased 30-fold between 1976 and 2007. The reported Yellow Tang catch has increased from ~10,000 fish per year in the 1970s to ~ 400,00 fish in 2006 (Friedlander et al. 2007, Williams et al. 2009). In 2007, reported catch declined to 291,013; although less than the catch in 2006, the catch in 2007 was still the third highest on record. The number of active collectors increased from 16 in 1999, to 37 in 2007 (Williams et al. 2009). Reported catches statewide of 3,386,860 individuals caught from FY 1976-2003 with a total value of $5, 567, 252.60 (Walsh et al. 2004).

The Yellow Tang is the most collected aquarium species in West Hawaii. There was a significant increase in overall density across Fish Replenishment Areas (FRAs) surveyed from 1999-2009. The FRAs were shown to be effective in terms of increases inside the FRAs relative to long term marine protected areas. The total number of individuals collected over the past five years was 1,621,053 with a total value of $5,035,883. There was a delayed increase in abundance in all areas surveyed following a strong recruitment in 2002. Even with low recruitment in 6 of the past 11 years adult populations increased by 57% in the FRAs since establishments (Walsh et al. 2010)

In West Hawaii, approximately 3,000 fish/km are harvested annually from areas open to fishing (Williams et al. 2009). A study by Tissot et al. (2004) conducted three years after the establishment of Fish Replenishment Areas (FRA) reported 78% higher Yellow Tang density in FRAs than in open areas. The monitoring stations for this study were located in mid-depth high-complexity reefs, which largely comprises of juveniles (Tissot et al. 2004, Williams et al. 2009). Adult densities in FRAs of West Hawaii are expected to increase as the total length of the fishery closure is short relative to the longevity of the fish (40 years) (Williams et al. 2009).

Prior to MPA establishment, densities were similar at sites open to fishing and those slated for closure: ~10-15 per 100 m2, whereas densities at Long-term Protected (LTP) sites were ~20-25 per 100 m2. By 2003, and in all subsequent years, mean yellow tang densities in Fish Replenishment Areas (FRA) sites had risen to values similar to those at LTP sites and were higher than at sites which remained open to fishing. Between 1999 and 2007, mean density increased by 72% at FRA sites, remained stable at LTP sites and declined by 45% at sites which were open to fishing (Williams et al. 2009). Adult Yellow Tang densities were highest within protected areas and in open areas adjacent to protected areas. Densities were lowest in open areas far from protected areas. 

Williams et al. (2009) showed within-MPA effects, including density of targeted juveniles (5-10 cm) within FRAs as five times that of fished areas. Adult Yellow Tang densities were 48% higher in FRAs than in non-boundary open sites in 2006. Williams et al. (2009) showed within-MPA effects, including density of targeted juveniles (5-10 cm) within FRAs as five times that of fished areas. Adult yellow tang densities were 48% higher in FRAs than in non-boundary open sites in 2006. Densities of adults in open areas <1 km from the nearest MPA boundary, were significantly higher than in open areas far from MPA boundaries, indicating spillover effect (Williams et al.  2009).

The establishment of the FRAs have been attributed to higher catches with 2004 (5 yrs after their establishment) recording the highest catch for the entire 38 yr history of the fishery. The CPUE is highest in West Hawaii compared to other Hawaii islands, and is showing signs of increasing (Tissot et al. 2009). Recent genetic evidence involving parentage analysis suggest there is self-recruitment on the Big Island which might explain the possible increases in adult biomass since the FRAs were established (M. Christie unpub. PhD thesis).

Current Population Trend:Stable
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:Yellow Tang (Zebrasoma flavescens) is found in inshore coral reefs, protected bay and lagoons. It may be seen in less than 1 m, but occurs deeper on exposed outer-reef areas (Randall 2001a). It is classified as a grazer/detritivore (Choat 1991).  Yellow Tang in the west coast of the Hawaiian Island settle primarily into mid-depth (10 to 25 m) reef habitat with a high percentage of coral cover (Walsh 1984, Ortiz and Tissot 2008, Claisse et al. 2009). Males and females of this species in West Hawaii each showed a clear ontogenetic pattern of habitat use. When Yellow Tang reach sexual maturity, adults leave the deeper coral reef areas for shallower reef habitat. For females this occurs at approximately 4-5 years of age and for males at age 5-7 years (Claisse et al. 2009).
 
The ontogenetic habitat shift in Yellow Tang coincides with the size at which there is a clear increase in reproductive output. The sexual difference in size at habitat transition, combined with sexual size dimorphism (mean asymptotic maximum length - male: 17.9 cm; female: 15.6 cm) results in differences in size distributions of both sexes in the two habitats (Claisse et al. 2009).

Growth

Yellow Tang is a long-lived species; the oldest individual collected was 41 yrs old (Claisse et al. 2009). It displays the typical Acanthurid square growth curve with high initial growth rates that rapidly decrease after the first few years (Choat and Axe 1996, Choat and Robertson 2002). Yellow Tang exhibits sexual difference in growth. Growth rates for both sexes are 300 mm per year during the first year of life to (0 to 1 yr), but males grow substantially faster than females from year 2 to 3, a trend that continues until the asymptotic size is approached. Sexual size dimorphism resulted from a higher growth rate for males through the juvenile period (Claisse et al. 2009)

Reproduction

Yellow Tang is gonochoristic (Bushnell 2007) and like its sister species, Zebrasoma scopas (Guiasu and Winterbottom 1998, Clements et al. 2003), is macroandric (Robertson 1985). The sexes are separate among the acanthurids (Reeson 1983). There is possibility of sexual dimorphism in Zebrasomas with cloacas bigger in females (Bushnell et al. 2010). Annual fecundity for an average adult Yellow Tang female is estimated at 1,055,628 (SE 120,596) eggs per year. (Bushnell et al. 2010). Size at maturity for females is 132 mm TL (5.1 yrs), which is the median size/age at which they migrate to adult habitat (Claisse et al. 2009, Bushnell et al. 2010).

Yellow Tang in West Hawaii make crepuscular migrations away from daytime shallow turf-dominated foraging habitat to spawn at sunset in the deeper coral-rich habitat, primarily along the edge of the deeper reef slope (Walsh 1984). Each evening males return repeatedly to the same temporary spawning territory (J.T. Claisse unpub. data) and court passing females in what has been described as a linear lek (Loiselle and Barlow 1978, Walsh 1984).

In Hawaii, peaks in recruitment of this species occur during the summer months from June to August. There was considerable inter-annual variability in the recruitment of this species over a 51 month period with 80 recruits during 1977 compared with a maximum of 15 per year in the following years (Walsh 1987).

In Johnston Atoll peaks in spawning of Yellow Tang occur during the outgoing tide, when current velocity is greatest and occurred predominately in the reef channel (Sancho et al. 2000). In the same location they are group spawners, with a promiscuous mating system, releasing pelagic eggs between 16:00-18:00 hrs.

Systems:Marine

Use and Trade [top]

Use and Trade: Yellow Tang (Zebrasoma flavescens) is the primary coral reef fish species taken in Hawaii for the aquarium trade (Claisse et al. 2009). It accounts for over 50% of all aquarium fish collected of Kona, Hawaii (Kusumaatmadja et al. 2004) and is the most collected aquarium species in West Hawaii (Walsh et al. 2010). The Yellow Tang fishery largely targets young juvenile fish in the size range of 5-10 cm, which corresponds to two years or younger (Williams et al. 2009).

Threats [top]

Major Threat(s): This is the primary coral reef fish species taken in Hawaii for the aquarium trade (Claisse et al. 2009). There have been decreases in Yellow Tang density in areas open to fishing in West Hawaii. The decrease in open areas is attributable to the life history characteristics of this species as well as the increase in the number of aquarium collectors and collected animals (Walsh et al. 2010).

Surgeonfishes show varying degrees of habitat preference and utilization of coral reef habitats, with some species spending the majority of their life stages on coral reef while others primarily utilize seagrass beds, mangroves, algal beds, and /or rocky reefs. The majority of surgeonfishes are exclusively found on coral reef habitat, and of these, approximately 80% are experiencing a greater than 30% loss of coral reef area and degradation of coral reef habitat quality across their distributions. However, more research is needed to understand the long-term effects of coral reef habitat loss and degradation on these species' populations. Widespread coral reef loss and declining habitat conditions are particularly worrying for species that recruit into areas with live coral cover, especially as studies have shown that protection of pristine habitats facilitate the persistence of adult populations in species that have spatially separated adult and juvenile habitats (Comeros-Raynal et al. 2012).

Conservation Actions [top]

Conservation Actions: In Hawaii, nine Fish Replenishment Areas (FRAs) were established in 1999. These areas prohibit marine aquarium organism collecting within approximately 30% of the Kona coast nearshore habitat (Kusumaatmadja et al. 2004). In addition, several additional management actions have been proposed in response to the continuing decline of Yellow Tang in areas open to collecting, these include restricting which species can be collected and  the establishment of a limited entry program for the fishery (Walsh et al. 2010). In 2002, the Marine Aquarium Council initiated a three-year project designed to enhance coral reef conservation in the islands by facilitating MAC certification of qualifying aquarium industry operators and encouraging market incentives (MAC 2003).

Citation: McIlwain, J., Choat, J.H., Abesamis, R., Clements, K.D., Myers, R., Nanola, C., Rocha, L.A., Russell, B. & Stockwell, B. 2012. Zebrasoma flavescens. The IUCN Red List of Threatened Species 2012: e.T178015A1521949. . Downloaded on 24 August 2016.
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