Latin name

Gymnura poecilura

Other name

Gymnura poecilura

Identification

The snout of the long-tailed butterfly ray is short and broad with a protruding tip. The anterior edge of the snout is curved. Behind the medium-sized eyes are large, spread-out eyes with smooth edges. On the ventral side of the disc is a rather large curved mouth, nostrils and 5 pairs of gill slits. The nostrils and mouth are close together. Between the nostrils is a short and wide skin flap with smooth edges. There are more than 50 teeth on each jaw, the number increasing with age. Teeth are small, narrow and pointed. The skin is free of scales. 

Features of fish fins

The pectoral fins of these fish are elongated in the form of broad "wings" that are almost twice as long as they are wide. They merge into a diamond-shaped disk. The pelvic fins are small and rounded. The tail is filamentous. Caudal, anal and dorsal fins are absent. There are dorsal and ventral ridges at the end of the caudal peduncle. Sometimes there is one, rarely two spines on the dorsal surface at the base of the caudal peduncle. 

Fish colouring

Dorsal coloration is greenish brown or gray with many small pale spots and sometimes a few black spots. The tail is covered with alternating black and white stripes, the number of which varies from 9 to 12. Ventral surface of the disc white, dark at the edges. 

Distribution

Widespread in the Indo-Pacific region from Somalia to Sri Lanka, China, Japan, the Philippines, and the western islands of Indonesia, including Borneo, Sumatra, and Java. There is evidence of their presence in the waters of French Polynesia. They are quite abundant in some parts of their range. 

Habitat

These groundfish are found in shallow coastal waters at depths of 10 to 30 meters, preferring sandy and muddy bottoms. 

Size

The maximum recorded length is 92 cm and the disk width is 2.5 cm.

Behavior

Seasonal movements are not observed. Long-tail butterfly rays use their spines, located on the stem of the tail, for defense. 

Food and feeding habits

Longtail butterfly rays prey on fish of the ponyfish family. They feed on crabs, shrimp, clams and small fish.

Reproduction

Reproduction by oviparity. Embryos develop in the uterus and feed on egg yolk and histotrophs. Females have two functional ovaries and two uteruses. Breeding occurs throughout the year, peaking between April and October. Females give birth annually, probably twice a year. There may be up to 7 newborns in a litter. Litter size is independent of female size. The length of the newborns is 20-26 cm. They are a miniature replica of an adult stingray, lacking the spine. Newborns from the same litter may differ in coloration. Males and females reach sexual maturity at 45 and 44 cm, respectively.

Fishing

They are fished commercially and artisanal in India, Thailand and Indonesia. They are also caught as bycatch in bottom trawling and triple net fisheries. These rays are vulnerable to overfishing. 

Relationship with a person

Harmless. The flesh of these fish is eaten as food.