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J Plankton Res. 2015 Mar;37(2):352-362. Epub 2015 Mar 17.

Whale sharks target dense prey patches of sergestid shrimp off Tanzania.

Author information

1
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.
2
Oceans and Atmosphere Flagship , Csiro Marine and Atmospheric Research, Ecosciences Precinct , Dutton Park, Brisbane, QLD 4102 , Australia.
3
Marine Megafauna Foundation , Praia Do Tofo, Inhambane , Mozambique ; Wild Me , Tofo Beach, Inhambane , Mozambique.
4
Marine Megafauna Foundation , Praia Do Tofo, Inhambane , Mozambique.
5
Red Sea Research Center , King Abdullah University of Science and Technology , Thuwal 23955 , Saudi Arabia.
6
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.

Abstract

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.

KEYWORDS:

biomass threshold; elasmobranch; filter feeding; tropical zooplankton

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