News / Species Spotlight / Species Spotlight - One Spot Rabbitfish (Siganus unimaculatus) (12/08/16)

Species Spotlight - One Spot Rabbitfish (Siganus unimaculatus)

Species Spotlight - One Spot Rabbitfish (Siganus unimaculatus)
The Foxface Rabbitfish is a classic reef fish which youd expect to find at just about any reasonably well-stocked retailer. This cheery yellow herbivore has endeared itself to aquarists with its bright colors and hard-working attitude, but few stop to notice that this fish is not always the samesometimes they have a big, black spot and sometimes they dont. But, why?

As it turns out, ichthyologists recognize the specimens having this spot as a distinct species, Siganus unimaculatusthe name literally means one spot. On the reefs of the Indo-Pacific, this fish has a relatively small distribution, occurring mainly around the Philippines, Taiwan and the Ryukyu Islands of Japan. Elsewhere, it is replaced by its spotless colleague, the Foxface (S. vulpinus). But the two can often be found cavorting about together in places where their ranges overlap, so its hard to say just how distinct these two really are.

The care of the One Spot Rabbitfish is essentially identical to its more-commonly seen yellow compatriot. In the wild, this fish normally occurs in pairs once they reach an adult size (typically 6-8), though we know relatively little about how they interact with one another. Studies done on other rabbitfishes have shown that the pairs are sometimes same-sex and that the pairs regularly leave their normal territories to head to what is assumed to be communal breeding grounds. This is timed with the lunar cycle, but we still know relatively little about this phenomenon. The true function of their pairing behavior may be for defense, rather than mating. With two sets of eyes, one fish can plunge its head down into the reef for a bite of algae while the other stands guard.

In an aquarium, juveniles can easily be kept singly or in groups, but, since its virtually impossible to tell the sexes apart, mixing multiple adults comes with greater risk. Rabbitfishes are thought to stay the same sex they are born as, a condition known as gonochorism, so, unless added together as juveniles or acquired as a proven pair, it is usually best to stick to a single specimen.

The largely herbivorous diet of this fish necessitates a regular supply of greens, such as sheets of nori and other dried algae, lettuce, spinach, etc. Many aquarists purchase these fishes with the hope that they will annihilate whatever pestiferous algae might be plaguing their tank, but, like most algae eaters, S. unimaculatus tends to ignore most hair algae and Bryopsis. But, they will quite happily consume any meaty food thrown their way, and even in the wild they are known to opportunistically feed upon the occasional animal morsel. In a reef tank, specimens are known to occasionally nibble upon things they shouldnt, causing consternation for many a hapless aquarist who thought their Siganus was a safe addition. Corals like brains, acans and scolys seem to be high on the list, so proceed with caution.

Whether you prefer your Foxface spotted or not, this beautiful fish makes for an enjoyable addition to an aquarium, rarely causing any trouble and able to swim peacefully with a wide range of tankmates. But, remember, those fin spines are venomous, so no touching!