Unveiling Patterns in Cetacean Strandings Along Southern Atlantic Iberia: Temporal and Spatial Trends, Seasonality, and Causes of Death

ABSTRACT We compiled 46 years of cetacean strandings in the Algarve, Portugal, describing temporal–spatial patterns, size–sex structure, and causes of death (COD). We analyzed national records and years with a dedicated regional stranding network (SN) to assess annual/seasonal trends, spatial hotspots, and compare biometrics and COD. In total, 1231 strandings were recorded; 73.2% were identified to 19 species. Five species comprised almost 68% of events: common dolphins 39.0%, striped dolphins 8.9%, minke whales 8.0%, bottlenose dolphins 8.0%, and harbor porpoises 4.3%. GAMs confirmed that recorded strandings rose over time and were higher during SN years (mean 63 yr. −1 ). Stranding hotspots occurred near Cape Santa Maria (Faro–Olhão), Lagos–Portimão, and Sagres; minke whales and harbor porpoises concentrated east of Cape Santa Maria. Seasonality was significant only for minke whales (spring peak). Size–sex patterns were largely similar, with exceptions for larger stranded striped dolphin females and minke strandings dominated by juveniles. COD assignment improved with monitoring and was assessed for 75.6% of the observed carcasses. Bycatch was the leading COD for common dolphins, bottlenose dolphins, and minke whales. This study highlights the importance of a regional stranding network and a need for more ecological studies of cetaceans in the region.