Cephalopod remains in the diet of striped dolphins (Stenella coeruleoalba) and Risso's dolphins (Grampus griseus) in the eastern Mediterranean Sea

Abstract

Cephalopod remains from the stomachs of three striped dolphins (Stenella coeruleoalba) and two Risso's dolphins (Grampus griseus) taken as bycatch in the swordfish fishing in the eastern Mediterranean Sea off Turkish coast were examined. Totally 478 lower beaks were identified as belonging to 14 cephalopod species. For the striped dolphins, Abralia veranyi was the most common prey (51.2% of all the beaks found in this species), followed by Onychoteuthis banksii and Heteroteuthis dispar. For the Risso's dolphins, Histioteuthis reversa was the most common species (60.9%) and all the other species shared less than 10% of all the beaks found. In the stomachs of the striped dolphins, there were remains of some fish and shrimps, while only cephalopod remains were detected in those of the Risso's dolphins. Most prey species were oceanic cephalopods, with wide vertical distribution and diurnal movement. Many of the cephalopods identified in the diet of these dolphins are bioluminescent suggesting that these dolphins use bioluminescence as a target when feeding on cephalopods.