Mobula rays, often called devil rays, are cartilaginous fish found in tropical and subtropical waters worldwide. Relatives of sharks and other rays, they are distinguished by their unique feeding strategies. This article explores their diet and the specialized methods they employ to gather sustenance.
Their Primary Food Sources
Mobula rays are primarily planktivores, meaning their diet consists largely of plankton. Their main food items include various types of zooplankton, such as copepods, krill (euphausiids), and mysids. These tiny crustaceans form the foundational part of the rays’ diet, often found in dense concentrations within the water column.
Some Mobula species also consume the larval stages of fish and other invertebrates, supplementing their planktonic intake. While zooplankton constitutes the bulk of their diet, certain species are known to feed on small schooling fish, such as sandy sprat or myctophid fishes. These fish prey can be up to 100 millimeters in size. The specific composition of their diet can vary geographically and seasonally, influenced by prey availability.
How They Feed
Mobula rays employ a specialized filter-feeding mechanism to capture their prey. They swim with large mouths open, allowing water to flow over comb-like gill plates or gill rakers. These plates act as sieves, trapping plankton particles while allowing excess water to exit through their gills.
Their paddle-like cephalic fins direct plankton-rich water inwards. Mobula rays exhibit various efficient feeding behaviors, including “ram feeding,” where they continuously swim forward with open mouths. Individual rays may also engage in “somersault feeding,” or barrel rolling, performing tight backward loops to concentrate prey, maximizing their intake from dense patches.
Mobula rays also display coordinated group feeding strategies. These include “chain feeding,” where individuals line up to filter feed in succession, and “cyclone feeding,” where large groups form a spiraling, vortex-like formation to concentrate plankton. This cooperative behavior allows efficient food harvesting in abundant prey areas.
Diet’s Influence on Their Behavior and Environment
Food availability and distribution significantly influence Mobula ray behavior, especially their large-scale migrations. These rays undertake journeys to follow nutrient-rich upwellings and plankton blooms. Such movements align with cyclical ocean changes that concentrate their food. Aggregation behaviors, where hundreds or thousands gather, are often driven by the pursuit of dense food patches.
Mobula rays play a role in the marine ecosystem by consuming vast quantities of plankton, influencing plankton abundance and nutrient cycling. Changes in ocean conditions, such as rising sea surface temperatures, can affect their food supply. El Niño cycles, for instance, can lead to warmer, less productive waters, causing rays to seek more productive areas. Additionally, passive ingestion of microplastics during feeding activities can introduce contaminants into their systems.