| Autor: |
Rohner CA; Marine Megafauna Foundation , Praia Do Tofo, Inhambane , Mozambique ; Oceans and Atmosphere Flagship , Csiro Marine and Atmospheric Research, Ecosciences Precinct , Dutton Park, Brisbane, QLD 4102 , Australia., Armstrong AJ; Oceans and Atmosphere Flagship , Csiro Marine and Atmospheric Research, Ecosciences Precinct , Dutton Park, Brisbane, QLD 4102 , Australia., Pierce SJ; Marine Megafauna Foundation , Praia Do Tofo, Inhambane , Mozambique ; Wild Me , Tofo Beach, Inhambane , Mozambique., Prebble CE; Marine Megafauna Foundation , Praia Do Tofo, Inhambane , Mozambique., Cagua EF; Red Sea Research Center , King Abdullah University of Science and Technology , Thuwal 23955 , Saudi Arabia., Cochran JE; Red Sea Research Center , King Abdullah University of Science and Technology , Thuwal 23955 , Saudi Arabia., Berumen ML; Red Sea Research Center , King Abdullah University of Science and Technology , Thuwal 23955 , Saudi Arabia., Richardson AJ; Oceans and Atmosphere Flagship , Csiro Marine and Atmospheric Research, Ecosciences Precinct , Dutton Park, Brisbane, QLD 4102 , Australia ; Centre for Applications in Natural Resource Mathematics (CARM) , School of Mathematics and Physics , The University of Queensland , St Lucia, QLD 4072 , Australia. |
| Abstrakt: |
Large planktivores require high-density prey patches to make feeding energetically viable. This is a major challenge for species living in tropical and subtropical seas, such as whale sharks Rhincodon typus . Here, we characterize zooplankton biomass, size structure and taxonomic composition from whale shark feeding events and background samples at Mafia Island, Tanzania. The majority of whale sharks were feeding (73%, 380 of 524 observations), with the most common behaviour being active surface feeding (87%). We used 20 samples collected from immediately adjacent to feeding sharks and an additional 202 background samples for comparison to show that plankton biomass was ∼10 times higher in patches where whale sharks were feeding (25 vs. 2.6 mg m -3 ). Taxonomic analyses of samples showed that the large sergestid Lucifer hanseni (∼10 mm) dominated while sharks were feeding, accounting for ∼50% of identified items, while copepods (<2 mm) dominated background samples. The size structure was skewed towards larger animals representative of L.hanseni in feeding samples. Thus, whale sharks at Mafia Island target patches of dense, large, zooplankton dominated by sergestids. Large planktivores, such as whale sharks, which generally inhabit warm oligotrophic waters, aggregate in areas where they can feed on dense prey to obtain sufficient energy. |
