Abstract
On 9 June 2008, the UK's largest mass stranding event (MSE) of short-beaked common dolphins (Delphinus delphis) occurred in Falmouth Bay, Cornwall. At least 26 dolphins died, and a similar number was refloated/herded back to sea. On necropsy, all dolphins were in good nutritive status with empty stomachs and no evidence of known infectious disease or acute physical injury. Auditory tissues were grossly normal (26/26) but had microscopic haemorrhages (5/5) and mild otitis media (1/5) in the freshest cases. Five lactating adult dolphins, one immature male, and one immature female tested were free of harmful algal toxins and had low chemical pollutant levels. Pathological evidence of mud/seawater inhalation (11/26), local tide cycle, and the relative lack of renal myoglobinuria (26/26) suggested MSE onset on a rising tide between 06∶30 and 08∶21 hrs (9 June). Potential causes excluded or considered highly unlikely included infectious disease, gas/fat embolism, boat strike, by-catch, predator attack, foraging unusually close to shore, chemical or algal toxin exposure, abnormal weather/climatic conditions, and high-intensity acoustic inputs from seismic airgun arrays or natural sources (e.g., earthquakes). International naval exercises did occur in close proximity to the MSE with the most intense part of the exercises (including mid-frequency sonars) occurring four days before the MSE and resuming with helicopter exercises on the morning of the MSE. The MSE may therefore have been a “two-stage process” where a group of normally pelagic dolphins entered Falmouth Bay and, after 3–4 days in/around the Bay, a second acoustic/disturbance event occurred causing them to strand en masse. This spatial and temporal association with the MSE, previous associations between naval activities and cetacean MSEs, and an absence of other identifiable factors known to cause cetacean MSEs, indicates naval activity to be the most probable cause of the Falmouth Bay MSE.
Highlights
Cetacean mass stranding events (MSEs) are commonly described as two or more cetaceans of the same species coming ashore, usually alive, at the same time and place [1]
Gross necropsies Carcasses were recovered from the intertidal zone and all 26 dead common dolphins were systematically examined using a standard necropsy protocol [11] beginning within 8 hours of being found dead and terminated 3 days later
The locations of the live and dead dolphins reported in this MSE are shown in Figs. 1 and 2
Summary
Cetacean mass stranding events (MSEs) are commonly described as two or more cetaceans (excluding a cow-calf pair) of the same species coming ashore, usually alive, at the same time and place [1]. At least 19 cetacean species have been affected, with some species, including false killer whales (Pseudorca crassidens), long-finned pilot whales (Globicephala melas), short-finned pilot whales (Globicephala macrorhynchus), Atlantic white-sided dolphins (Lagenorhynchus acutus) and white beaked dolphins (Lagenorhynchus albirostris), stranding more often than others [1,2]. The cause of these strandings has puzzled humans for centuries and, numerous theories have been developed, few MSEs have been studied in detail and seldom has a definitive cause been established (reviewed in [1]). Species-specific behaviour in response to ‘‘panic’’ is suggested as a potential factor explaining why some cetacean species mass strand more frequently than others (reviewed in [1])
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
