Smalleye Stingrays

In 2008 MMF researchers made a landmark discovery: a large population of the gigantic and elusive smalleye stingray, Megatrygon microps, living off the coast of Mozambique. The discovery represented a range extension for the species of over 5000 km, and some of the first live sightings of the species. Elsewhere, sightings of this enormous stingray are infrequent, suggesting it remains rare and patchily distributed.

A Mysterious Giant

Despite being the largest known marine stingray, little is known about the biology or ecology of smalleye stingrays. The species is currently listed as ‘Data Deficient” on the IUCN’s Red List of Threatened Species. Regular sightings on inshore reefs in southern Mozambique confirm that this area is not only a critical habitat for the species but is also the best area to study them. 

Conservation Needs for Smalleye Stingrays

A marked increase in the use of indiscriminate fishing practices such as gill-netting, long-lining, and seine netting along the Mozambican coast represents a clear threat to smalleye stingrays. The large size of this species, and their curiosity towards people, make them easy targets. To exacerbate the problem, large stingrays typically take years to reach adulthood and have small litters, making them particularly susceptible to overexploitation. Considerable research on this species is needed to address the lack of biological data and these conservation concerns.

Now that we have determined that the natural spot patterning on these stingrays is stable enough to use in long-term individual identification studies we are beginning to estimate the abundance and movements of these rays along the southern Mozambican coast.

Acoustic telemetry is now allowing us to study the movements of this large and unusually mobile ray for the first time. Rays fitted with acoustic tags are detected automatically whenever they pass one of our receivers, building a picture of their home ranges, habitat use, daily movement patterns, depth preferences, and general behavior that no amount of diving could assemble on its own. The collection of small tissue samples from individual rays allows us to examine their ecological role in the area.

We will also be monitoring artisanal fisheries to quantify catches of this species along the coast and to identify ‘hotspot’ areas for further investigation.

First tracking results

The first years of acoustic tracking have produced two findings that were impossible to establish from sightings alone. Tagged smalleye stingrays have shown year-round residency inside the Bazaruto Archipelago National Park, appearing consistently across the receiver network rather than passing through — evidence that the park’s reefs are sustained habitat for the species, not an occasional stop. And their movement is strongly crepuscular, peaking at dawn and dusk, which is consistent with a foraging strategy tied to low light.

That matters for conservation. A species that is resident inside a protected area benefits directly from that protection, and a species that concentrates its activity into predictable windows can be monitored, and protected, far more efficiently. Further rays were tagged at Tofo in August 2026, and analysis of the growing acoustic dataset is underway.