Investigating long-term trends in beluga whale body condition in the TN MPA

The Tarium Niryutait Marine Protected Area was created to protect important habitats in the Mackenzie Estuary that beluga whales return to every summer (Figure 1). Building on the long-term community-partnered, harvest-based Beluga Monitoring Program led by the Fisheries Joint Management Committee in the Inuvialuit Settlement Region, we looked at beluga blubber thickness and body girth across 16 years. These two measurements can tell us about the body condition of the beluga whale, which can help inform on their health.

Read this open access paper on the Arctic Science website.

Figure 1. The home range of the Eastern Beaufort Sea beluga.

OUR METHOD

Since measurements of blubber thickness and body girth collected in the field are influenced by factors such as beluga size and age, we developed specific indicators that considered those significant factors. This allowed us to create an annual index of mean body condition to examine trends from 2000 to 2015 (Figure 2). We found that male belugas had a thicker blubber thickness index later in the summer compared to earlier in the summer, and female belugas had a larger body girth index. There was variability over the years, with belugas having higher or lower body condition in some years (Figure 2).

Figure 2. Annual mean value for Male Girth and Male Blubber Thickness body condition indices from 2000–2015. The red line represents a zone of poor body condition developed from entrapped whales from the same population used in our study.

ENVIRONMENTAL DRIVERS

We asked if patterns in large-scale climate conditions matched the trends in beluga body condition over the 16-year dataset. We found that the Pacific Decadal Oscillation, a climate index that influences the beluga wintering habitat in the Bering Sea (Figure 1), was related to girth in male belugas.

RESULTS

While this finding suggests that conditions in their winter habitat influence beluga body condition in the summer, more research is needed to dive deeper into how both winter and summer habitat conditions impact beluga whale body condition. This information will strengthen our understanding of beluga health and ecological monitoring in the marine protected area.

Read the paper — Beluga whale body condition: evaluating environmental variables on beluga body condition indicators in the Tarium Niryutait MPA, Beaufort Sea by K. MacMillan, C. Hoover, J. Iacozza, J. Peyton, and L. Loseto