Smoothtail mobula  (Mobula munkiana)

Classified as Near Threatened (NT) on the IUCN Red List (1).

In common with other species in the Mobulidae family, the smoothtail mobula has long, pointed, pectoral fins which it strokes up and down, like wings, for propulsion (2) (3). On either side of the head, and in front of its prominent eyes, are two fleshy lobes that project forward to funnel food into the mouth (3) (4). The dorsal fin is small, and the tail is long, flattened and spineless. The upper surface of its body is generally dark purplish to mauve-grey, while the underside is white, becoming blue-grey towards the ‘wing-tips’ (3) (5).

The smoothtail mobula occurs in coastal waters of the eastern Pacific, from the Gulf of California, Mexico, south to Peru, and inclusive of the Galapagos, Cocos, and Malpelo Islands (1).

Found in shallow coastal waters (1).

Having only been discovered as recently as 1988, information on the biology of the smoothtail mobula is still relatively fragmentary (1). However, it is well known for forming large schools, appearing as conspicuous dark patches slowly cruising along the shallow coastline. Typically, its occurrence in any particular location is unpredictable, with large numbers sometimes gathering in an area for a few days, before disappearing for weeks or even months (1) (6). Another remarkable feature of this species is the frequency with which individuals breach the water’s surface, often simultaneously. The breaching behaviour is characterised by a variety of acrobatic manoeuvres, including head over tail somersaulting and high vertical leaps, followed by loud belly slaps (6).

The smoothtail mobula is thought to commonly forage along the seafloor, with mysid shrimp being its main prey, but more research is needed to assess feeding behaviour and dietary preferences (1). Likewise, very little is known about its migratory habits, other than that it is common in the Gulf of California over winter, when other mobulid species are rare or absent (6). It reproduces ovoviviparously, with each mature female producing just a single pup per litter (1).

Owing to its schooling behaviour and apparent benthic feeding habit, the smoothtail mobula is highly vulnerable to gillnet fishing. As may be expected of a highly mobile schooling species, large numbers are caught episodically in traditional fisheries in the Gulf of California. Although there is no fishery information outside of Mexico, there is also a high possibility that it is caught as bycatch in numerous other fisheries throughout its range. Consequently, there is great concern that catch rates may be unsustainable, particularly given this species’ low reproductive output (1).

More research is vital to determine the impact of target and non-target fisheries on the smoothtail mobula. It is thought likely that the availability of additional fisheries information will reveal an urgent need for conservation measures including restrictions on harvest and trade (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about the conservation of rays and sharks, see:

• Save Our Seas Foundation:
  www.saveourseas.com
• IUCN Shark Specialist Group:
  www.iucnssg.org