Reductions in Eastern North Pacific gray whale blubber quality during unusual mortality events measured via adipocyte abundance and total lipid content
Cetacean nutritional physiology has been difficult to investigate due to the free ranging nature of these animals, however, evaluation of dead animals might provide further insights. Dead Eastern North Pacific gray whales (Eschrichtius robustus) could provide that context with the ongoing unusual mortality event (UME), declared in 2019, allowing for a comparison between normal and anomalous years. Here we examined full blubber thickness samples through adipocyte area and total lipid percent from dead gray whales that stranded within UMEs as wellas non-UME years. The blubber was divided into four sections, following the normal striation pattern, targeting the outer, mid superficial, mid deep and inner layers for evaluation. We foundthe adipocyte area was lower in the outer, mid superficial and mid deep layer in UME years and higher in non-UME years. We also found similar findings for the total lipid percent with the midsuperficial, mid deep and inner blubber layer being lower in UME verses non-UME years. Evaluation of these two blubber attributes can serve as a template for other mysticete species to provide insight into the nutritional physiology during mortality events, thereby pinpointing key evaluation locations within the blubber for future study
