Zooplankton size structure in the Gulf of Tadjoura (Djibouti) during whale shark sighting: a preliminary study.
Iole DI CAPUA1, Primo MICARELLI2, Jonathan TEMPESTI3, Francesca Romana REINERO2 and Isabella BUTTINO2,4,5*
(1) Marine Organism Taxonomy Core Facility, Department Infrastructures for Marine Biological Resources,
Stazione Zoologica Anton Dohrn, Villa Comunale, 80123 Naples, Italy
(2) Sharks Studies Center – Scientific Institute, Via della Cava, Massa Marittima, Italy
(3) Department of Biology, University of Pisa, Italy
(4) Italian Institute for Environmental Protection and Research (ISPRA), Livorno, Italy
(5) Dept of Integrative Marine Ecology, Stazione Zoologica Anton Dohtn, Villa Comunale, 80123 Naples, Italy
Abstract: Zooplankton, collected in the Gulf of Tadjoura (Republic of Djibouti) during a cruise conducted to study the feeding behavior of the whale shark Rhincodon typus, was analyzed in terms of size class, abundance and species composition. This pilot study was aimed to better understand a possible correlation between mesozooplankton composition and size spectra, collected up to 10 m depth, and different feeding behaviour of R. typus. Our data indicate that holoplankton accounted from 93 to 100% of the total community, copepods represented more than 80% of the zooplanktonic community, with 14 copepod genera and 9 species. Our preliminary results suggest an association between suction feeding activity of R. typus and high abundance of small copepod species. Passive feeding was recorded during the lowest abundance of zooplankton, mainly composed by large chaetognaths and larvae of Belbezub hansenii belonging to the family of Luciferidae (Sergestids). These first results highlight the importance of analyzing the dimensional structure of mesozooplankton in the aggregation areas of whale shark and open up new and intriguing investigative approaches to better understand the biology of R. typus.