Hong Kong hosts some surprisingly large and interesting rays. Some are resident and some like the giant Manta ray are migratory and pass Hong Kong in the summer months. Here is a incomplete list of rays known from Hong Kong waters.
(This list is still under construction.)
Round ribbontail Ray / Black-spotted stingray (Taeniura meyeni)
A bottom-dwelling inhabitant of lagoons, estuaries, and reefs, generally at a depth of 20–60 m (66–197 ft). Reaching 1.8 m (5.9 ft) across. Generally nocturnal, the round ribbontail ray can be solitary or gregarious, and is an active predator of small, benthic molluscs, crustaceans, and bony fishes. Although not aggressive, if provoked the round ribbontail ray will defend itself with its venomous tail spine. In Hong Kong, it is found mainly in the relatively clear southern and eastern waters, but it has also been found in the northern part of Lantau and in brackish water near the Pearl River estuary. It is also one of the species that has been found on Hong Kong’s artificial reefs. Check out Eric Keung’s spooky photo of a this stingray in Hong Kong waters.
Between July 2005 and June 2008 there were two cases of people being stung by stingrays in HK – fortunately with mild outcomes. The sting and its venom can cause bluish or greyish discoloration around the wound, disproportionate pain, muscle cramp, weakness, seizure, hypotension, cardiovascular toxicity, deep wounds and lacerations. In other words, stingrays are dangerous! Just watch from a distance and don’t touch!
Blue-Spotted Stingray (Neotrygon kuhlii)
The body is rhomboidal and green with blue spots with a maximum width estimated at 46.5 centimeters (18.3 in). The rays coloration is a warning for the highly poisonous barbs, thus few animals attempt to overpower this ray. In HK, they are more easily seen in summer in the shallow water along the coast, on coral reefs and in mangrove areas. Because of the venomous sting observers should not get too close or try to touch it!
Pale-edged stingray (Dasyatis zugei)
A bottom-dwelling ray most commonly found over sandy areas shallower than 100 m (330 ft) and in estuaries. It measures up to 29 cm (11 in) across, has a diamond-shaped pectoral fin disc, a long projecting snout, small eyes, and a whip-like tail. It is chocolate-brown above and white below and feeds mainly on small crustaceans and fishes. In HK it is mainly found in the western Pearl River estuary south of Lantau Island.
Butterfly Ray (Gymnura sp.)
Its is not clear exactly which species occur in HK waters. Most likely the Longtail butterfly ray (Gymnura poecilura) which grows up to 92 cm (36 in) across and is colored brown to gray above with many small, light spots. Its a bottom-dweller and frequents sandy or muddy coastal waters shallower than 30 m (98 ft) where it feeds on bony fish, molluscs, and crustaceans. In HK, they are mainly found in the western Pearl River estuary south of Lantau Island.
Spotted Eagle Ray (Aetobatus narinari)
You can see these magnificent rays in Ocean Park’s Atoll Reef aquarium, but one specimen was also caught on October 24th 1931 at Kowloon Docks in the Harbour. That ray measured nearly 1 m in width. I have also heard from HK divers that this species is occasionally seen in HK waters. Interestingly HK has another species of Eagle ray called Aetobatus narutobiei, which was identified by Japanese researchers in 2013. Its is very similar to the spotted eagle ray, but is uniformly greenish grey to brownish and lacks the white spots. In fact, the spotted eagle ray may not actually occur in HK, and the new species A. narutobiei could have been mistaken for a spotted eagle ray in earlier records. Either way, there is a species of eagle ray in HK (and Ocean Perk definitely has spotted eagle rays, even if that does not count).
Banded Eagle Ray (Aetomylaeus nichofii)
Flapnose Ray (Rhinoptera javanica)
Brown above, white below, it grows to a max length of 1.5 m and max weight of 4.5 kg . It is found in bays, estuaries, and near coral reefs, over sand and mud bottoms. Large schools with up to 500 individuals have been reported in other parts of the world. Feeds on clams, oysters and crustaceans.
A large specimen of this species was caught off Kowloon Docks in the Harbour on October 19th, 1931, which was over 2 m in length and weighed between 40 and 50 lbs (18-22 kg) – although this somewhat contradicts our current knowledge of the size and weight of this species (see above)!
You can also see this species at Ocean Park’s Atoll Reef aquarium.
Manta Ray (Manta birostris)
Needs very little introduction! The largest type of ray in the world can grow to a disc size of up to 7 m (23 ft) with a weight of about 1,350 kg (2,980 lb) but the average size is commonly 4.5 m (15 ft). They are circumglobal and are typically found in tropical and subtropical waters, but can also be found in temperate waters. But does it occur in HK? There is one record of a specimen caught off Big Wave Bay. And basically HK is within its known range, and is sometimes seen south of HK waters at oil rigs. In a recent article about diving in HK I spotted the following quote by Stephen Au, director of Diving Adventure: Explaining that it’s rare to spot large marine animals locally, he adds that he once swam with a manta ray “the size of a table” just 15 minutes from Sai Kung, near Sharp Island.
So divers keep eyes open – though I doubt you would miss this one if it came near!
Japanese Electric Ray (Narke japonica)
This electric ray grows up to 40 cm long and lives in shallow, sandy areas near rocky reefs. Fairly inactive in nature, it spends much of its time lying buried on the sea floor. It can produce an electric shock of 30–80 volts to ward off predators. The shock from the Japanese electric ray is strong but not life-threatening to humans. This and other species of electric rays are used in biomedical research because their electric organs have an abundance of ion channels and acetylcholine receptors, and can serve as a model for the human nervous system.
In HK it is mainly found on sand or gravel bottoms in North Lantau near the Pearl River estuary. In the coastal areas of southern China, including Guangdong, the “Tanka” ethnic group of fishermen called this ray “shock hand” (鯆).
Black-Spotted numbfish (Narcine timlei)
The black-spotted numbfish grows to a maximum length of 38 cm and is found in continental waters, both inshore and offshore. It occurs over soft bottoms and feeds on bottom-living organisms. Although it also possesses electric organs, very little is known about its biology. In HK waters it is found on sand or gravel shores in the southwest of Lantau Island near the Pearl River estuary.
Chinese name: 蒂姆勒氏雙鰭電鰩