Alaska Trip 2022 -- Day 8 Humpback Whales and Bubble Net Feeding

Everyone had returned to the ship and we left Basket Bay about 5:30 to begin our trip south down Chatham Strait.

Orcas.  We had settled in to another wonderful dinner and the ship had begun its turn into Peril Strait when all of a sudden the cry went up from the other side of the dining room: Orcas!  Everyone went rushing to the windows on the port side.  Sure enough we could see the tall dorsal fins of three orcas (otherwise known as killer whales) in the distance.  They appeared to be moving rapidly.  The ship turned but they were quickly out of sight.

Today's route in cyan (turquoise), switching to black at midnight.  Morris Reef Buoy#35 is the green buoy in the center just above the small wiggly gps track.  Note the ship never went north of the buoy.

Even this fleeting glimpse of the orcas with no opportunity for pictures was exciting.  Orcas are common in Alaska, but are most often seen in southeast Alaska between May and early June.  There are only sporadic sightings in June through September.

Humpback whales.  We settled back down to dinner and had just about finished when there was more excitement.  Now it was humpback whales.  

I rushed back to the room to get my camera. As I came out onto deck I could see multiple humpback whales, including some fairly close to the ship.  Due to the limitations of my camera and my inexperience, I had discovered with our previous humpback sighting   that it was hard for me to find, focus, and shoot humpbacks before they had disappeared.  I therefore decided to try mostly videos and leave the still shots primarily for the Frog.  

Here is my attempt at capturing some of the activity in the area as I first made it on deck.  It was 7:29 pm and we were at the mouth of Peril Strait.  I think this shot is looking WNW as the ship was going mostly north (in the midst of making a U-turn going from west to going east).

The whales were blowing and fluking.  In the picture below you can also see Buoy #35, which is on the map with the gps track above. 

Humpback whale blows adjacent to buoy #35

It was funny to see all the cormorants and sea lions on the buoy.

Cormorants had claimed the top of the buoy, while sea lions were on the base.

 

 

Just seeing the whales blowing and fluking would have been more than enough for a very successful evening of whale watching, but it then became apparent some of the whales were surging upward in a variety of feeding activities.  

  

The whales were surging upward with their mouths open presumably through schools of small fish or krill (tiny shrimp).  Humpback whales are filter feeders.  They have no teeth and eat by scooping up water and small fish, then separating the fish from the water by pushing the water out through sieve-like baleen plates   The baleen plates are located on their upper jaw in the place of teeth.

Their throats expand tremendously during this process to accommodate up to 15,000 gallons of water.  This is made possible by the pleats or grooves that run from the top of the chin to their navel.  These can be seen in some of the pictures below.

 

Without teeth the whales cannot chew, so anything they eat must be swallowed whole.  Their throat through which they swallow is only about as big around as a grapefruit, so the food must be very small. Typical food include krill, herring, capelin,and sand lance

First the feeding seemed to be mostly among smaller groups of whales.  Eventually there were much larger groups.  At least one person next to me thought two of the groups had merged into a larger group.

Bubble net-feeding.  Although some of the early single or double whale events could have been merely lunge feeding through schools of fish, it soon became clear that many of these whales were bubble net-feeding.

What is bubble-net feeding?   It is a cooperative effort by some humpback whales.  A group of whales dives below a school of fish, then one whale releases a ring of bubbles from its air hole as it spirals upward around the fish.  The curtain of bubbles frighten and contain the fish, driving them into a tighter ball.  Upon an acoustic signal from the lead whale, the whales surge upward in unison with their mouths open through the mass of fish.  They then roll to their sides as they force the water from their throat out through the baleen plates.

Bubble-net feeding is not instinctual, but is a learned activity. It is actually quite complex.  It requires an experienced leader and amazingly the individual whales retain their same positions relative to one another for repeat bubble nets. 

The expanded bulging part is the whale's "chin".  It seems to often be covered in barnacles.

This is a blow-up of the picture above.  I think the white "furry" stuff on the upper inside of his mouth (on either side of the long white strip running the length of his mouth) is the baleen.

In the same sequence as the picture above.  Their mouths are now closing but their throats are enormous.

Yet another group with super throats

The whole process happens very fast, with the whales above the water for only a few seconds.  I was getting very frustrated because I was always looking in the wrong direction to catch them as they initially emerged from the water.  Somebody pointed out "watch the birds".  The gulls have learned that the bubbles mean fish will soon be rising to the surface.  When they see the bubbles, they make a bee line for it.  

Watching the birds was the trick.  I finally got a decent video, see below.  I recommend you view it full screen if possible.

As you can see in the above video, everything happens very quickly.  Below is the first portion of the above video slowed to half speed.  It makes it a bit easier to catch what is happening.

In the slow motion version it is easier to see not only the mouth movements but also their pectoral fins are more obvious.  The unusually long (15-18 foot) pectoral fins--i.e. "arms"--distinguish humpbacks from all other whales.  In fact the first half of their Latin name, Megaptera novaeangliae, means 'big winged" in Latin.  These long flippers enable humpbacks to make the extremely rapid and tight turns needed for bubble-net feeding.  Interestingly, recent speculation is that they also use the undersides, which are always white, to scare and hence herd the fish. 

 I don't know how many feedings occurred while we were watching, but when I reviewed the Frog's pictures there were images for ten unique feeding events.  There were at least three groups of whales and probably more feeding simultaneously. 

I am not certain why this location supported such a mega bubble-net event.   Clearly there must have been lots and lots of little fish of some kind.  I also stumbled across one other thing, but I do not know its significance.  In looking at the nautical map for the depth of Chatham Strait that I mentioned in the previous post, I noticed the water was extremely shallow just north of the #35 buoy, the exact location where we saw much of the bubble-net feeding.

 

Nautical map showing depth near buoy #35.  Very shallow water is in blue.

We felt truly privileged to see this spectacle which is apparently quite rare.  The crew, including the captain, later said they had never seen anything like it before.   One source indicates bubble-net feeding only happens for a few weeks each summer in southeast Alaska.  With a few exceptions, bubble-net feeding only happens in southeast Alaska, not in other parts of the world.  Even then, only 10% of southeast Alaska humpbacks actually bubble-net feed.

I don't think my writing does justice to this absolutely amazing event.  For a more poetic but still scientifically accurate description of bubble-net feeding, see this article in Smithsonian Magazine by filmmaker and writer Steve King.