Common dolphins, common in neritic waters off southern Israel, demonstrate uncommon dietary habits

Denna Brand, Dor Edelist, Oz Goffman, Nir Hadar, Aviad Scheinin, Dan Kerem

Research output: Contribution to journalArticlepeer-review

Abstract

During the last decade, the common dolphin (Delphinus delphis) has become the second most sighted species in Israeli coastal waters, after the common bottlenose dolphin. Documentation mostly relies on opportunistic, photo and/or video-backed second-party reports, delimited within a 10 km near-shore strip. Sightings occur year round, are confined to the southern part of the Israeli coast and typically comprise relatively large groups (mean ± SD: 21.5 ± 13.3), often with young calves. Strandings are relatively scarce, typically one per year, and have so far yielded five upper digestive tract contents for diet analysis. Cephalopods comprised 1.2% of the estimated number of prey items in the combined content. Surprisingly, by far the most abundant and prevalent prey item found (57% of pooled prey items; present and dominant in four out of five tracts) was the Balearic eel (Ariosoma balearicum), a sand burrower which is also a major dietary component of the common bottlenose dolphins. Bottlenose dolphins in Israel are known to forage in association with bottom trawlers, leading to the notion that common dolphins also make use of this foraging mode. Indeed, in addition to their association with purse seiners, they have been documented accompanying bottom trawlers, by both day and night. The slender Balearic eels are frequently found protruding from the net's eyes, presumably making easy prey for both dolphin species. Information gaps on common dolphins include range extension to the south/south-west, abundance estimation and genetic flow/isolation. Even so, its unusual diet and the fact that the closest known populations to the north/north-west are from the Aegean Sea, were major considerations in the recent designation of the ‘Coastal Shelf Waters of the South-east Levantine Sea’ as a Mediterranean Important Marine Mammal Area.

Original languageEnglish
Pages (from-to)15-21
Number of pages7
JournalAquatic Conservation: Marine and Freshwater Ecosystems
Volume31
Issue numberS1
DOIs
StatePublished - Apr 2021
Externally publishedYes

Bibliographical note

Funding Information:
The underlying diet research was partly funded by the Sir Maurice & Lady Hatter and the Jacob Recanati Scholarships to D. Brand. The authors wish to thank Danna Reininger and Shlomi Marco for plotting the observations, Noga Yoselevich for preparing the final map, Mia Elasar for editing the supplemented video clip and Nir Stern for reporting around-trawler behaviour and for reviewing and commenting on parts of the text. Hearty thanks are due to all seagoing citizens who contributed to the sighting database.

Funding Information:
The underlying diet research was partly funded by the Sir Maurice & Lady Hatter and the Jacob Recanati Scholarships to D. Brand. The authors wish to thank Danna Reininger and Shlomi Marco for plotting the observations, Noga Yoselevich for preparing the final map, Mia Elasar for editing the supplemented video clip and Nir Stern for reporting around‐trawler behaviour and for reviewing and commenting on parts of the text. Hearty thanks are due to all seagoing citizens who contributed to the sighting database.

Publisher Copyright:
© 2019 John Wiley & Sons, Ltd.

Keywords

  • coastal
  • distribution
  • feeding
  • fish
  • Levantine Basin
  • mammals
  • trawling

ASJC Scopus subject areas

  • Aquatic Science
  • Ecology
  • Nature and Landscape Conservation

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