Devil Rays Are Deepest Divers
Chilean devil rays are one of the ocean's deepest and fastest divers, a new study reveals
Tags attached to 15 Chilean devil rays (Mobula tarapacana) show that the fish previously thought to live near the surface basking in the sun, in fact, regularly dive to depths of nearly 2,000m and descend at astounding speeds — a dizzying six metres per second, or 22 kph.
'M. tarapacana is among the deepest-diving ocean animals,' declared the study, led by Simon Thorrold of the Woods Hole Oceanographic Institution in Massachusetts.
The deep-dive record for an air-breathing animal is held by a Cuvier’s beaked whale, with a dive of 2,992m. The deepest observed dive for a fish is 1,926m, by a whale shark — a massive animal compared to the devil ray, which grows to about three metres long and about 350 kilograms (770 pounds).
The devil rays were recorded reaching depths of up to 1,896m (6,162 feet) and in water temperatures of just 3.6°C. The report says that probably explains why they spend long periods at the surface warming up.
The deep dives generally followed two distinct patterns. The most common involved descent to the maximum depth followed by a slower, stepwise return to the surface with a total dive time of 60 to 90 minutes. The tagged rays generally only made one such dive during a 24-hour period. In the second dive pattern, individuals descended and then remained at depths of up to 1,000m (3,280 feet) for as long as 11 hours.The rays also turned out to be extensive travellers, covering distances of up to 49 km per day.
Large numbers of the ray and other mobulas are killed to supply a growing demand for their gills in Asia for 'traditional' medicine, or are taken accidentally as bycatch in tuna fishing.
The International Union for Conservation of Nature (IUCN) lists the Chilean devil ray — also called the box ray — as 'data deficient' on its endangered species list.