Photo credit: Shutterstock

Devilfish in diabolical decline

News comes this week that the Giant Devil Ray (Mobula mobular) has declined so much in abundance in recent years that it has been listed as endangered on the World Conservation Union's Red List of Threatened Species (according to Dulvy et al. writing in Aquatic Conservation: Marine and Freshwater Ecosystems). This vast fish has a wingspan that can top five metres and spends most of its time flapping gracefully near the surface, straining plankton and small fish from the water. It lives in the Mediterranean and eastern North Atlantic and has fallen victim to longline fishing. The Giant Devil Ray is part of the manta ray family, a group of species that inhabit tropical and warm temperate seas and grow to extraordinary sizes. While this species sometimes punctuates its tranquil days with spectacular leaps, it can hardly be considered devilish. It was probably named after the two leathery ‘horns' that funnel plankton laden-water into a permanent open-mouthed grin. There is a more colourful explanation for the name. Few 19th century books on ocean life were complete without a vivid description of some hapless pearl diver falling victim to a devil ray. Some books included illustrations of divers carried to the bottom wrapped in the wings of a ray, eyes bulging with fear as they succumbed to its clammy embrace. Harpooning a manta ray in the Gulf of Mexico in 1870 But in truth, these were groundless tales from distant seas. Devil rays had more to fear from people than the other way around. Rays basking at the surface were often speared and hooked for sport by adventurers, or simply sailors maddened with boredom far from land. The rays often outwitted their hunters, towing boats with effortless strength until lines parted. Today, fishers have the upper hand, although few target the rays directly. Harpooning and hauling a manta ray on deck in the 1880's. The Mediterranean and eastern Atlantic is criss-crossed with a giant web of hundreds of thousands of kilometres of longlines, studded with millions of hooks. They are set by fishers who seek valuable tunas and billfish in nutrient rich frontal zones where the water is thickened by plankton and prey fish, and where devil rays congregate. There are probably few devil rays above reproductive age (about 3 years) that have not at some point encountered a longline. While the rays are probably unimpressed by longline baits, they become entangled and some are hooked. In the 21st century, the tables are turned. It is devil rays that are gripped in a death clasp. Unless we reduce fishing pressure and take the lines into deeper waters beyond the reach of rays, this species may disappear for good. What a sorry end that would be for a most devilish fish. ———- Callum Roberts is Professor of Marine Conservation at the University of York in England and the author of The Unnatural History of the Sea. Click here to visit his website.