title: Prey Density Threshold and Tidal Influence on Reef Manta Ray Foraging at an Aggregation Site on the Great Barrier Reef.
abstract: Large tropical and sub-tropical marine animals must meet their energetic requirements in a largely oligotrophic environment. Many planktivorous elasmobranchs, whose thermal ecologies prevent foraging in nutrient-rich polar waters, aggregate seasonally at predictable locations throughout tropical oceans where they are observed feeding. Here we investigate the foraging and oceanographic environment around Lady Elliot Island, a known aggregation site for reef manta rays Manta alfredi in the southern Great Barrier Reef. The foraging behaviour of reef manta rays was analysed in relation to zooplankton populations and local oceanography, and compared to long-term sighting records of reef manta rays from the dive operator on the island. Reef manta rays fed at Lady Elliot Island when zooplankton biomass and abundance were significantly higher than other times. The critical prey density threshold that triggered feeding was 11.2 mg m-3 while zooplankton size had no significant effect on feeding. The community composition and size structure of the zooplankton was similar when reef manta rays were feeding or not, with only the density of zooplankton changing. Higher zooplankton biomass was observed prior to low tide, and long-term (~5 years) sighting data confirmed that more reef manta rays are also observed feeding during this tidal phase than other times. This is the first study to examine prey availability at an aggregation site for reef manta rays and it indicates that they feed in locations and at times of higher zooplankton biomass.
authors.affiliation: Project Manta, The University of Queensland, St Lucia, QLD, 4072, Australia.|School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia.
authors.forename: Asia O
authors.initials: AO
authors.lastname: Armstrong
authors.affiliation: Project Manta, The University of Queensland, St Lucia, QLD, 4072, Australia.|School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia.
authors.forename: Amelia J
authors.initials: AJ
authors.lastname: Armstrong
authors.affiliation: Project Manta, The University of Queensland, St Lucia, QLD, 4072, Australia.|Biophysical Oceanography Group, School of Geography, Planning and Environmental Management, The University of Queensland, St Lucia, QLD, 4072, Australia.|Manta Ray and Whale Shark Research Centre, Marine Megafauna Foundation, Tofo Beach, Inhambane, Mozambique.
authors.forename: Fabrice R A
authors.initials: FR
authors.lastname: Jaine
authors.affiliation: Project Manta, The University of Queensland, St Lucia, QLD, 4072, Australia.|School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia.|Aix-Marseille Université, Mediterranean Institute of Oceanography (M.I.O), UMR 7294, UR 235, Campus de Luminy, Case 901, 13288, Marseille, Cedex 09, France.
authors.forename: Lydie I E
authors.initials: LI
authors.lastname: Couturier
authors.affiliation: Lady Elliot Island Dive Shop, Lady Elliot Island Eco Resort, Great Barrier Reef, QLD, Australia.
authors.forename: Kym
authors.initials: K
authors.lastname: Fiora
authors.affiliation: CSIRO Oceans and Atmosphere Flagship, EcoScience Precinct, Brisbane, QLD, 4102, Australia.
authors.forename: Julian
authors.initials: J
authors.lastname: Uribe-Palomino
authors.affiliation: Biophysical Oceanography Group, School of Geography, Planning and Environmental Management, The University of Queensland, St Lucia, QLD, 4072, Australia.
authors.forename: Scarla J
authors.initials: SJ
authors.lastname: Weeks
authors.affiliation: Project Manta, The University of Queensland, St Lucia, QLD, 4072, Australia.
authors.forename: Kathy A
authors.initials: KA
authors.lastname: Townsend
authors.affiliation: Project Manta, The University of Queensland, St Lucia, QLD, 4072, Australia.|School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia.
authors.forename: Mike B
authors.initials: MB
authors.lastname: Bennett
authors.affiliation: Project Manta, The University of Queensland, St Lucia, QLD, 4072, Australia.|CSIRO Oceans and Atmosphere Flagship, EcoScience Precinct, Brisbane, QLD, 4102, Australia.|Centre for Applications in Natural Resource Mathematics, School of Mathematics and Physics, The University of Queensland, St Lucia, QLD, 4072, Australia.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Richardson
mesh_terms: D000818:Animals; D001315:Australia; D057894:Coral Reefs; D005247:Feeding Behavior; D011235:Predatory Behavior; D012860:Skates, Fish / Q000502:physiology*; D014872:Water Movements; D015048:Zooplankton