Manta birostris, predator of the deep? Insight into the diet of the giant manta ray through stable isotope analysis
This study addresses the challenges in understanding the diet of the giant manta ray (Manta birostris), a species known for its extensive movements and the difficulties associated with sampling its stomach contents. Traditionally, knowledge of their diet has been limited to surface feeding observations during daylight. However, the recent discovery of aggregation sites off mainland Ecuador has provided researchers with a unique opportunity to delve deeper into the dietary habits of this elusive species.
To determine the significance of surface zooplankton in the diet of the giant manta ray, researchers conducted stable isotope analysis (15N and 13C) on muscle tissue samples from M. birostris and compared them with surface zooplankton. The findings suggest that giant manta rays occupy a trophic position of approximately 3.4, categorizing them as secondary consumers. However, there was notable variation in δ15N and δ13C values among individuals, indicating variability in their diet.
Contrary to the assumption that giant manta rays feed primarily on surface zooplankton, the δ13C values in their muscle tissue revealed a diet that is largely derived from mesopelagic (mid-water) sources. This insight into their feeding behavior is crucial for understanding the ecological role of giant manta rays and highlights the importance of mesopelagic zones in their diet.
Given the conservation concerns surrounding these large planktivores, including their conservative life history and the pressures from fisheries, this study underscores the need for a thorough understanding of their trophic interactions and foraging strategies. Such knowledge is vital for informing conservation strategies and ensuring the long-term survival of the giant manta ray.
This research not only sheds light on the complex dietary preferences of Manta birostris but also contributes to the broader understanding of marine trophic dynamics and the conservation of vulnerable species.
