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Author: Leslie Tsen (B.S.) Ecology, Evolution & Natural Resources. Wildlife Conservation
Foxfaces (Siganus vulpinus or Siganus unimaculatus) and 27 other rabbitfish species are found exclusively under the Siganidea family which consists of only a single genus Siganus. Commonly known as the blotched foxface, Siganus unimaculatus is virtually identical to its sister species the foxface rabbitfish (Siganus vulpinus) except that each side of its upper back has a notable dark spot (blotch). Despite of this major disparity, Siganus unimaculatus are frequently observed interacting and forming social groups with Siganus vulpinus individuals due to the overlapping habitat of both species (though Siganus vulpinus is geographically more widely distributed).
The characterized elongated mouth of a foxface is thought to resemble a fox’s muzzle, thus giving birth to the generic name “foxface”. In the wild, both blotched foxface and foxface rabbitfish are most commonly found in the shallow (~30m max) tropical and subtropical reef regions of the Indo-pacific where ambient temperature is fairly consistent throughout the year. Foxfaces are social fish. Adults of both species are known to form long-term monogamy and travel in pairs while juveniles and subadults sometimes congregate in sizable school to feed on surface algae growing on dead corals. A healthy foxface living in pristine environment can sometimes live to its 9 and 10-year-old birthday, though in many documented cases a foxface life expectancy ranges from 5 to 8 years. Adult foxfaces are capable of reaching a little bit over 20cm including tail length (TL), weighing at least 400g.
The foxfaces possess about 10-13 dorsal spines and 7-10 anal spines, most of which are connected to venom glands. Easily frightened, foxfaces are common seen erecting their dorsal, anal and pelvic spines in response to any immediate perceivable threat from their surroundings. In the wild, these spines are used to deter predators since foxface are generally too big to hide between tight crevices. Although foxfaces' venomous sting is generally non-life-threatening to adult humans, they sure can inflict great pain to foolish challengers who dare to mess with them. It is found that foxfaces' venoms are made up of heat sensitive protein (heat-labile protein)1. If stung, soaking the wound in warm water of at least 43.3°C and higher for 30 to 90 minutes can help to relieve the immense pain.
Unlike the short, curved mouth of other rabbitfish species, foxfaces' mouth is more elongated and snout-like. This has provided them with an edge over other short-snouted species that are incapable of reaching algae growing between the tight crevices of coral frames. When a foxface is stressed, drastic color change (from a bright yellow to dark grey with shades of white) can be observed from its entire body. The major color shift often looks so drastic that some owners thought their fish is suffering from some kind of terminal illnesses! Fear not, for your fish will return to its bright yellow state once it has finally calmed down. In some occasions, foxfaces change their color at night to camouflage to their surroundings. They also rely mostly on their eyesight to identify food sources, seek out mate, and detect predators. As a result, foxface are most active throughout the day (diurnal species).
Foxface are primarily herbivorous and secondarily detritivorous. The unique elongated mouth of a foxface has made it an algae grazing specialist feeding mainly on diverse algal materials. When their primary food sources are rare in the wild, foxface are also known to consume detritus (which includes feces from piscivorous and zooplanktivorous fish), sediment and cyanobacteria2,3. In household aquaria, foxface can be fed with small food pellets and flakes that are formulated primarily using vegetative materials such as Spirulina, kelp, and other micro/macroalgae. Nori seaweed, lettuce (cooked/boiled to breakdown cellulose), and cucumber can also be fed occasionally to diversify your foxface’s diet. Be sure to remove any uneaten foods 30 minutes after feeding to avoid spoiling your water quality.
Foxfaces are avid explorers. They require at least 400L of swimming space due to their biological potential of growing to an intermediate-sized fish when being kept in an aquarium. When housing foxfaces, sufficient (but not excessive) lighting is equally important as they rely heavily on their eyesight to carry out daily activities. Corals and liverocks are excellent addition to your aquarium as they provide the perfect platform for natural algae to grow, thus providing a natural food source for your fish. Foxfaces are generally docile thus can be safely housed with other types of fish. However, it is often recommended NOT to house different rabbitfish species together (with the exception of a bi-species Siganus unimaculatus and S. vulpinus tank) to avoid interfamily aggression. The ideal water parameter to keep foxfaces is similar to the water parameter in keeping most tropical reef fish at a water specific gravity of 1.020-1.026, pH 8.0-8.4, and a stable temperature range from 24-28°C.
Foxfaces are naturally skittish. Even the smallest sudden movement can trigger their survival response to erect those venomous spines for protection. Therefore, we strongly recommend using a fish net of the appropriate size to capture your foxface whenever handling is necessary. Under no circumstances should you be using bare hands to capture a foxface no matter how shallow your tank water is. Serious injury CAN occur when it started to thrash. Be extremely careful when netting and getting your fish out of the net as their spiky spines can get caught on the fine mesh. Any forceful attempt to untangle the twist specially when your fish is struggling will only cause its spines to snap, causing wound that could be infected by opportunistic bacteria, protists, annelids, nematodes, crustacean parasites, and fungi from your tank water. Be sure to only net one fish at the time. You do not want a panicking foxface to impale its buddy getting caught up in the same net.
1Meier, J., & White, J. (2008). Handbook of Clinical Toxicoloy of Animal Venoms and Poisons. New York, NY: Informa Healthcare USA, INC.
2Robertson, R. (1982). Fish Feces as Fish Food on a Pacific Coral Reef. Marine Ecology Progress Series, 7(3), 253-265. Retrieved February 12, 2018, from http://www.jstor.org/stable/24814551
3Hoey, A. S., Brandl, S. J., & Bellwood, D. R. (2013). Diet and Cross-shelf Distribution of Rabbitfishes (f. Siganidae) on the Northern Great Barrier Reef: Implications for Ecosystem Function. Coral Reefs, 32(4), 973-984. doi:10.1007/s00338-013-1043-z
Disclaimer: This article contains materials referred from published scientific journals and is strictly meant for educational purposes only. It must NOT be substituted for any forms of medical care, treatment, and consultation from veterinarians, aquatic experts or other licensed professionals. NO compensation shall be reimbursed by Harvest Fish & Pet for the direct or indirect loss, damage, injury, or death of both living (user included) and non-living beings caused by the application of information from this article either in full or in part.