Bluespotted Stingrays

Q. I recently saw a beautiful fish called a bluespotted stingray at a local aquarium store. It was about 14 inches long and round like a small plate. I asked the store manager about this fish and he told me that it ate clams and pieces of shrimp and could be kept in a 70-gallon aquarium. Is this true?

What about the stinger? Is it poisonous? If so, just how poisonous is it? Any information you could provide me on the biology of this ray and what I need to know to keep it alive would be helpful.

A. There are two species of batoids referred to as bluespotted stingray. The most common one in aquarium stores is Taeniura lymma, which is more appropriately called the bluespotted ribbontail ray. You're right, this is a gorgeous animal, but it rarely thrives in the home aquarium. This species has an oval disc and a distinct color pattern consisting of a yellowish-brown, reddish-brown or olive-green dorsum with bright-blue spots, and blue lines on the tail.

The bluespotted ribbontail ray is born at a disc width of about 4 inches, attaining a maximum disc width of 12 inches and a total length of at least 28 inches. Some authors report that these fish can reach a disc width of 35 inches and a total length of 8 feet, but these figures are apparently erroneous.

This species ranges from the east coast of Africa, including the Red Sea, east to the Philippines, Australia, Melanesia and Polynesia. Most specimens that make it into the aquarium trade originate from the Philippines. The bluespotted ribbontail ray occurs in shallow intertidal areas to depths of at least 66 feet. It is common in lagoons, on tidal flats and on sand patches on the fore reef.

At flood tide it often moves into the tidal zone to feed on worms, shrimp, hermit crabs and small bony fishes. It feeds throughout the day and may also hunt at night (although no data exists documenting this). It is sometimes found refuging under table corals, staghorn coral beds and shipwreck debris, but it rarely buries under the sand.

You often see this ray being cleaned by the bluestreak cleaner wrasse (Labroides dimidiatus). The ray facilitates the cleaner by lifting the edges of its pectoral fins and raising the posterior part of its disc on its pelvic fins. This enables the wrasse to clean its ventral surfaces. These fish may remove parasitic crustaceans and monogenetic flukes, as well as ingest the nutrient-rich slime of the ray.

As I noted above, this ubiquitous ray rarely does well in home aquariums. Often they never accept food. On other occasions, however, they will, but then they will suddenly die or cease feeding for no apparent reason. A few hobbyists and some large public aquariums have had success keeping them for long periods of time.

The prerequisites for keeping stingrays include plenty of swimming room, good water quality, a varied diet, no or minimal decor and a fine sand substrate (e.g., live sand, beach sand, fine grade of coral sand). The bluespotted ribbontail ray tank should have a ledge that the fish can hide under, but make sure this structure is very stable or it may topple over and seriously injure your ray.

You could keep a young T. lymma in a 70-gallon aquarium, but if the animal survives (and in the case of this animal this is a big if), it will outgrow a tank of this size. A large adolescent or adult animal could be kept in a 240-gallon tank.

The bluespotted ribbontail ray should be kept at water temperatures between 72 to 80 degrees Fahrenheit, but will tolerate even warmer water. Although a few hobbyists have had success with the long-term maintenance of bluespotted ribbontail rays, the best way to ensure the survival of one of these delicate creatures is to leave it in the ocean!

The other species that shows up infrequently in fish stores is the bluespotted ray (Dasyatis kuhlii). This ray has a diamond-shape disc, with slightly convex anterior and posterior margins and eyes that are slightly smaller than the interorbital width. The dorsal color is reddish-brown to olive drab, with blue spots and smaller black spots, and the tail often has white bands. This species attains a maximum disc width of 12 inches and a total length of 26 inches. Males reach maturity at a disc width of about 10 inches, making this an ideal candidate for captive breeding programs.

The bluespotted stingray ranges from the Indian Ocean and Red Sea to Samoa, Japan and Australia, and is found at depths ranging from the intertidal zone to 165 feet. It occurs on sandy bottoms near coral and rocky reefs and is usually found in deeper parts of the lagoon or on the reef face. However, it will move onto the reef flat and into shallow lagoon waters at high tide. This is typically a solitary species except during the breeding season, when it forms aggregations. Males have been observed biting females on the tail at this time.

This ray feeds on crabs and shrimp. It digs with its pectoral fins to uncover hidden prey and is often accompanied by wrasses, goatfishes and jacks, which share similar food preferences.

It is a much hardier aquarium species than the bluespotted ribbontail ray and will usually accept food within the first two or three days of its captive life. During the acclimation period it should not be disturbed — the aquarium should have a layer of fine sand on the bottom so that the ray can bury if threatened. Live glass shrimp are a favorite food in captivity. This ray should be maintained at water temperatures between 72 to 80 degrees Fahrenheit.

All stingrays are very sensitive to low levels of copper and other inorganic pollutants. Because these ions may be present in your tap water, you should use reverse osmosis (RO) or deionized (DI) water to fill the tank, perform water changes or replace evaporated water. Also, never use copper-based medications when treating a tank that contains a ray. A protein skimmer is useful to help keep the level of dissolved organic materials in check, as are monthly water changes of about 20 to 25 percent of the tank volume.

Stingrays should not be kept with any fish that feed on encrusting invertebrates, like butterflyfishes, angelfishes, triggerfishes or pufferfishes. These fish will often nip at the ray's eyes, fins and skin. This can cause physical damage and lead to secondary bacterial infections.

The spine on the stingray's tail is venomous, but "stings" are rarely lethal. In those cases where people died as a result of being stuck by a batoid spine, the victim was usually killed when a large specimen jabbed this weapon into a vital organ or cut a major blood vessel. However, these stings can be extremely painful (take it from someone who knows!). The spine is a defensive weapon that will only be used if the ray is threatened, so if you're careful you have nothing to worry about.

For more information on these elasmobranchs, and many others, look for my book Keeping Sharks and Rays in the Home Aquarium.