Increased Whale Deaths Prompts Investigation

Oct 4, 2015 | Amy L. Sonricker Hansen | Outbreak News

Since May 2015, 30 whale carcasses have been found in the Gulf of Alaska and areas surrounding Kodiak Island, Afognak Island, Chirikof Island, the Semidi Islands, and the southern Alaskan Peninsula [1, 2]. In addition, there have been large numbers of whale standings off the coast of British Columbia, Canada [3]. The recent deaths have prompted the issuance of an Unusual Mortality Event (UME) by the National Oceanic and Atmospheric Administration (NOAA). The deaths in the Gulf of Alaska include 11 fin whales, 14 humpback whales, 1 gray whale, and 4 unidentified species [1]. In the Pacific Ocean along British Columbia 1 fin whale, 1 sperm whale, and 4 humpback whale carcasses have been reported [3].


An Unusual Mortality Event is defined as “a stranding event that is unexpected, involves a significant die-off of any marine mammal population, and demands immediate response.” The Working Group on Marine Mammal Unusual Mortality Events uses a specific set of seven criteria to determine if an event is “unusual”. A recommendation is given to NOAA to issue an UME if one or more of the criteria are met [3, 4]. The declaration of an UME provides extra expertise and access to additional funding for the ongoing investigation [3].


Unfortunately for the investigating scientists, many of the whales found have been floating and not retrievable, or in severe decomposition unable to be sampled [3]. Of the 2 whales that were available for necropsy there were no obvious signs for what may have caused their deaths and their deaths remain unexplained [5]. Further testing for biotoxins, bacterial, and viral agents may be conducted, as additional samples are collected. At the present time it is unknown if there is any infectious disease risk to humans [3].  


While NOAA continues its investigation, scientists are speculating that the large number of whale deaths may be due to a record-breaking toxic algae bloom in the Pacific Ocean [5, 6].  The toxic bloom may be the largest ever recorded off of the United States’ West Coast [7]. Climate change is being blamed for the warmer waters spurring the more frequently occurring algae blooms. The algae contain domoic acid, a neurotoxin, which contaminates the krill and sardines that whales eat. Affected animals become disoriented and may suffer seizures and death [5, 6]. While this theory is still just speculation, mortality events due to biotoxins from algae blooms have become more prevalent since 1996 according to data on UMEs available from NOAA [8]. The algae bloom is expected to dissipate with the arrival of winter, however there is a heightened possibility that this is something that may happen more frequently in the future [6]. Lastly, it is also unknown if this event is related to the ongoing strandings of Guadalupe Fur Seals or California Sea Lions along the coast of California [9, 10].













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