The common eagle ray or bullray (Myliobatis aquila) is a species of fish in the family Myliobatidae. It inhabits the eastern Atlantic Ocean (North Sea to South Africa), the Mediterranean Sea and the south-western Indian Ocean.

Description

The common eagle ray reaches up to 183 cm (6.0 ft) in total length and has a disc width up to 80 cm (2.6 ft). Most specimens are, however, smaller. Females grow to be larger than males. The dorsal surface is brown or black while the ventral surface is white. It has a rhomboidal disc with a pair of large, triangular pectoral fins projecting on either side, and a single dorsal fin. The blunt snout is rounded and the tail is long and slender, with a large spine at its base but no tail fin. On average, males have 72 spine serrations and females have 66 spine serrations. The spine makes about 70% of the male's length and 65% of the female's length. The mid dorsal groove, which contains the glandular tissue necessary for venom injection, extends along 10–40% the tail. It has one or two excretory channels for the venom.

Habitat

This species occurs in the eastern Atlantic Ocean, including the North Sea, from the British Isles to South Africa, extending to the Indian Ocean. It is also found in the Mediterranean Sea. It occurs both close to the shore and further out, at depths down to about 800 m (2,600 ft), but much of its time is spent in shallower water at less than 50 m (160 ft). It typically prefers more open sandy areas. It has also been found in a semi-enclosed lagoon on Gran Canaria Island, particularly in winter (March to April) and summer (August to October), where it was founded to prefer rocky and mixed bottoms.

Feeding & diet

Benthic invertebrates form an important part of the common eagle ray's diet. The species largely feeds on crustaceans and bivalve molluscs that it excavates from the seabed. Other items in its diet include polychaete worms, gastropod molluscs, sea pens and small fish. Larger individuals consume more fish than smaller individuals. Instead of having pointed teeth, it has flattened hexagonal bars and plates arranged in a mosaic pattern on its jaws; with these, it crushes the shells of its prey.

Mollusks and teleost fish were found to be the most important food items for individuals living in the Sea of Marmara, although polychaetas and crustaceans were also frequently found amongst the stomach contents. Calliostoma lusitanicum and Stramonita haemastoma are the most common prey species off the coast off the Azores.

Reproduction

This species is known to gather in groups of dozens of individuals during the reproductive period. Reproduction is oviviviparous. A clutch of three to seven young develop inside the mother, receiving nourishment at first from their egg yolks, but later from fluids secreted by their mother into her uterus. The gestation period is 6–8 months long, after which the female gives birth to between three and seven live pups. The smallest juveniles were caught around France between May and September off the coast of France. They still had a unhealed scar on the lower surface, suggesting they were neonates. A study conducted in South Africa in 1983 found juveniles in November. Juveniles were also found at Gran Canaria Island in October.