Stranding patterns and feeding ecology of striped dolphins, Stenella coeruleoalba, in Western Iberia (1981–2014)

The striped dolphin, Stenella coeruleoalba, is one of the most abundant cetacean species off the Western Iberian coast, however, studies on the species regarding biology, ecology, threats or conservation efforts are lacking. This study investigates stranding patterns (years 1981–2014) and diet (2002–2014) of striped dolphins (Stenella coeruleoalba) off the Portuguese mainland coast. Stranded animals were sampled along the whole coast (n = 252). Most stranded striped dolphins were recorded in the first half of the year and strandings increased over time. Analysis of stomach contents (n = 36) showed that striped dolphins in the area are mostly piscivorous (80% by number and weight of the diet), taking pelagic, meso-pelagic and demersal species. In terms of reconstructed biomass prey, sardine (Sardina pilchardus) and blue whiting (Micromesistius poutassou) were the most important. Prey items revealed that both sexes forage at a range of depths (pelagic and demersal systems) in both neritic and oceanic habitats, although females feed more often in coastal waters. Moreover, diet results also indicate that striped dolphins may co-occur with other neritic cetacean species, such as the common dolphin, Delphinus delphis, thus sharing some preferred prey species. The study revealed that striped dolphins on the Iberian coast interact with coastal fisheries sharing the same target species. Management measures for fisheries will need to be consistent with an ecosystem-based approach
This work was funded by projects SafeSea EEA-Grants and European Commission’s Life Programme (MarPro NAT/PT/00038). This study received Portuguese national funds from FCT - Foundation for Science and Technology through project UIDB/04326/2020. This study was also partly supported by the Portuguese Foundation for Science and Technology (FCT) with grants SFRH/BPD/64889/2009 to A. Marçalo, SFRH/BD/51416/2011 to L. Nicolau, and SFRH/BD/30240/2006 to M. Ferreira. Additionally, this study received Portuguese national funds from FCT - Foundation for Science and Technology through project CCMAR UIDB/04326/2020
With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)