Solving the mystery of the Chukotka stinky gray whales

Gray whales (Eschrichtius robustus) constitute an important part of the diet of Chukotka Native population, reaching 30% of consumed food for the inland Chukchas. Over one hundred licenses for whale hunting are issued on an annual basis. After the USSR collapse natives had to hunt whales near the shore from the small boats. The problem of "stinky" whales arose immediately, as the meat of some harvested species possessed a strong medicinal/chemical odour. The hypotheses explaining the phenomenon ranged from biotoxins, to oil spills. To understand the problem, various tissues of normal and stinky Gray whales were collected in 2020-2021 and analyzed using headspace solid phase microextraction with Gas Chromatography - Mass Spectrometry. Here, we show that dozens of smelly organic compounds were identified among over 500 compounds detected in the samples. The most interesting analytes related to the off odour are bromophenols. The most probable suspect is 2,6-dibromophenol with strong iodoformic odour, perfectly matching that of the "stinky" whales. Quantitative results demonstrated its levels were up to 500-fold higher in the "stinky" whales' tissues. The source of 2,6-dibromophenol is likely polychaetes, producing 2,6-dibromophenol and colonising near shore waters where whales feed. Therefore, the mystery of the stinky whales may be considered resolved.