Reef manta rays forage on tidally driven, high density zooplankton patches in Hanifaru Bay, Maldives

Manta rays forage for zooplankton in tropical and subtropical marine environments, which are generally nutrient-poor. Feeding often occurs at predictable locations where these large, mobile cartilaginous fishes congregate to exploit ephemeral productivity hotspots. Investigating the dynamics that lead such feeding aggregations remains a key question understanding their movement ecology. The aim of this study is investigate environment largest known aggregation reef manta Mobula alfredi world. We sampled throughout tidal cycle, recorded M. activity behaviour, alongside environmental variables Hanifaru Bay, Maldives. constructed generalised linear models possible relationships between dynamics, parameters, how they influenced abundance, foraging strategies. Zooplankton biomass changed rapidly events were significantly related high biomass. switched from non-feeding behaviour prey density threshold 53.7 mg dry mass m ?3 ; more than double calculated estimates needed theoretically meet metabolic requirements. highest numbers observed Bay corresponded when engaged behaviour. community composition was different (dominated by copepods crustaceans) compared present but not (more gelatinous species samples). dominant Undinula vulgaris . This large-bodied calanoid copepod blooms oceanic waters, suggesting offshore influences site. Here, we have characterised aspects identified some conditions may result large threatened planktivore, information can help inform management economically important protected area.