Spiny butterfly ray   (Gymnura altavela)

Classified as Vulnerable (VU) on the IUCN Red List (1).

The spiny butterfly ray (Gymnura altavela) gets its name from its wide, characteristically  wing-like pectoral fins, and its short, sharp tail, which has serrated spines on both sides, used to stun prey (3) (4).

The upperparts of the spiny butterfly ray are usually brown to grey, sometimes with reddish-brown shading at the margins of the ‘wings’. Small dark or light spots and blotches may produce a marbling effect across the back. The colouration of the spiny butterfly ray, along with its wide, flat, disc-shaped body enable it to effectively camouflage itself in sand beds (5) (6). The underside is generally white, brown or rosy-coloured. The spiny butterfly ray has a blunt snout, and the jaws contain many rows of teeth (4) (5).

The juvenile spiny butterfly ray has paler skin, which darkens to brown as it matures (4).

The spiny butterfly ray has a very patchy distribution in the coastal tropical and temperate waters of the Atlantic Ocean, the Mediterranean and the Black Sea. This species can be found in areas on both sides of the Atlantic, in the western coastal waters of North and South America, and in eastern coastal waters from Portugal to Angola (1). 

The spiny butterfly ray can be found over sandy and muddy sea floors in shallow coastal waters, normally around depths of 50 to 55 metres. Its patchy distribution means that the spiny butterfly ray is abundant in some areas, and scarcely found in others (1). 

Little is known about the biology of the spiny butterfly ray. However, it is known that this species’ sharp pectoral fins are used to stun prey such as crustaceans, molluscs, plankton and small fishes. The spiny butterfly ray also may predate small sharks and squids, and may in turn be preyed upon by larger sharks (7).  

The spiny butterfly ray reproduces annually. This species is ovoviviparous, and the gestation period lasts between four and nine months. The litter size of the spiny butterfly ray is between two and eight, depending on location (1).

The spiny butterfly ray may be infected by parasites, most notably by the tapeworm Anthobothrium altavelae (7). 

Intense fishing in the southwest Atlantic, particularly around the coast of Brazil has led to declines in spiny butterfly ray populations. In 23 years, the percentage of trawl catches has reduced by an estimated 99 percent (1). 

The spiny butterfly ray is less threatened in US waters, where fishing levels are are lower. However, in the Mediterranean Sea, there is much higher demand for the spiny butterfly ray’s meat. It is now so rare in the Mediterranean, the spiny butterfly ray has been absent from the Mediterranean International Trawl Survey (MEDITS) records since they began in 1994 (1).

Along the coast of West Africa, large mesh bottom gillnets are used to target the spiny butterfly ray in huge numbers. Even in protected marine areas, the average size of caught spiny butterfly rays has reduced as larger adults from the population are removed (1). 

Despite the rapidly declining numbers of the spiny butterfly ray, there are currently no specific conservation management programmes in place, and intensive trawling continues throughout this species’ range. However, the spiny butterfly ray is fully protected in the Banc d'Arguin National Park in Mauritania. Monitoring of spiny butterfly ray populations and protection in areas where it is heavily fished are needed (1). 

• Florida Museum of Natural History - Spiny butterfly ray:
  http://www.flmnh.ufl.edu/fish/Gallery/Descript/SpinybflyRay/spinybflyray.html