SUMMER FOR HUMPBACK WHALES IN ALASKA IS ALL ABOUT FORAGING.  In the winter, North Pacific humpbacks travel to the sub-tropical waters of Hawaii, Mexico and Japan to mate and give birth, but in the spring they return north to feed. Therefore, if we want to understand their behavior in Alaska, we must consider their prey as well.

There's no way around it, surveying whale prey can be tedious work. For several field seasons, volunteers piloted rigid-hull inflatable boats (RIBs) along thousands of miles of predetermined transects at a slow 5 knots for 12 hours each day. The boats were outfitted with a sonar - a high tech fish finder that uses echolocation to shed light on what is happening below the waves - and a plankton net to collect krill samples.  There weren’t always whales around.  In fact, sometimes there weren’t even prey.  But in science, the absence of something is often important data (so goes the aphorism: 'absence of evidence is not evidence of absence'), so the volunteers pressed on regardless.

NORTH TO THE FEEDING GROUNDS: Pretty much everything a humpback does in Alaska is related to feeding

NORTH TO THE FEEDING GROUNDS: Pretty much everything a humpback does in Alaska is related to feeding

KRILL CRUSADER Volunteers surveyed over 5,000 miles of  transects, rain or shine using sonar and plankton nets mounted on rigid-hull inflatable boats.

KRILL CRUSADER Volunteers surveyed over 5,000 miles of  transects, rain or shine using sonar and plankton nets mounted on rigid-hull inflatable boats.

So what can be done with all these prey data?  For one, they can tell us a lot about prey dynamics in this comparatively unstudied region: How much does prey availability vary within or across years? Are there consistent prey ‘hot-spots’?  Do different prey species vary in their reproductive and/or life history strategies?  They can also provide the foundation for understanding whale abundance, distribution and behavioral patterns, and perhaps most importantly, how these patterns might change as our oceans succumb to rising temperatures, acidification and the overexploitation of marine resources.  

Click HERE for Dr. Szabo's publication on krill reproduction in Southeast Alaska, and HERE for his publication on humpback predation - or lack therefor - on juvenile krill.  And stay tuned, as there are more to follow.