Munk's devil rays (Mobula munkiana) are endemic to the Eastern Pacific, especially around the Gulf of California in Mexico. Despite their common sightings, much of their behavior remains a mystery for scientists. Being in a vulnerable conservation state, finding out more about them and their reproductive habits, could prove crucial for their protection.
These mobulas are renowned for their social behavior, gathering in big groups normally by size. During the past years, local fishermen and tourism operators had observed consistent aggregations of these rays in Ensenada Grande, a shallow bay in the Espiritu Santo Archipelago in the Gulf of California. A research team focused on this area, aiming to find out if a particular age group was predominant in these gatherings.
The team captured 95 rays in the bay during different periods, measured and classified them by their physical features as neonates, juveniles, or adults. Using conventional tagging and acoustic telemetry, they sampled their location and followed their movements for 22 months. The captured rays were mainly juveniles and neonates, and their tracking confirmed that the individuals stayed in Ensenada Grande for several months.
To find out if the juveniles and neonates appeared at the same time every year in this location, the scientists used professional photographs taken in recent years, which confirmed this hypothesis. These data lead to the conclusion that young mobulas use this shallow and protected bay as a nursery, where they grow until becoming less vulnerable.
Thanks to this study, the first nursery area for the Mobula munkiana has been discovered. Being mobulas under threat by targeted or accidental fishing, this finding could be vital for their conservation. By protecting this area, we could make sure their rare offspring has better chances of survival.