Video reveals one week of a blue whale negotiating with heavy vessel traffic
- Blue whales are having their feeding disturbed by sea vessels.
- This study identifies the areas where this happens most.
- The researchers suggest better management of vessels to avoid whale crashes.
A study is revealing what blue whales have to go through just to feed. The animals that are now endangered have to fight off heavy vessel traffic just to get nutrition.
Vessels honing in on blue whales' feeding areas
Research published in Nature magazine reveals that in the South Pacific alone, up to 1000 vessels can overlap the feeding areas of endangered whales. It all has to do with the concentration of chlorophyll-a that attracts krill, the primary source of nutrition for blue whales.
“Species distribution models (SDM) have shown that austral spring chlorophyll-a concentration, prior to the whales’ arrival, and thermal fronts are important oceanographic proxies for describing the abundance and distribution patterns of blue whales within the NCP. Krill, the primary prey of blue whales, can take advantage of seasonally enhanced productivity for biomass production, with some time lag linking early life-history stages (e.g., larval recruitment) with adult densities,” state the researchers in their study.
“Adult krill biomass is subsequently concentrated by thermal fronts into high-density patches which blue whales prey upon. This prey aggregation effect driven by thermal fronts could be critical for blue whales, and other large baleen whales, given their energetically costly feeding behavior. We hypothesize that both the time-lagged distribution of primary productivity and the thermal front aggregating effect generates foraging conditions for blue whales within NCP. To further test predictions from this hypothesis, here we propose that individual blue whales modify their behavior within areas of high spring chlorophyll-a concentrations and/or thermal front occurrence. As foraging behavior cannot be directly assessed solely by inspecting tracking data, we consider area-restricted search behavior (ARS, lower velocity, and less directional persistence) as a proxy for this type of behavior.”
Vessel collisions abound
This concentration of blue whales’ prey has caused vessel collisions that have thus far been a cause of injuries both for humans and the large mammals, the researchers further explained. But data concerning these incidents has been rare.
The researchers aimed in their study to fix this by evaluating three factors:
ii) model-derived spatial predictions of how whales use the area based on prevailing oceanographic conditions during the tracking period, iii) spatial estimates on the relative probability of encountering blue whales based on the integration of movement model predictions with those of a previous SDM, and iv) spatial estimates on the relative probability of whales encountering vessels as a measure of risk for four different vessel fleets operating in NCP.
As such, they were able to identify the key areas that require observation in order to avoid the additional loss of blue whales.
Using this data, a company called Wand released a map that showcased how vessel heavy the feeding grounds of the blue whales are. In the visualization, you can see why a whale-vessel collision would be highly likely in this type of environment and why it may be difficult for the endangered species to feed.
“The results of this study clearly pinpoint specific areas where management actions are urgently needed, especially considering the undetermined number of vessels strike and levels of noise exposure in the region. This information should be considered by Governmental and International organizations to inform, design, and rapidly implement mitigation action using existing national and international conservation instruments,” concluded the researchers.
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