Humpback whale research in Southeast Alaska

We just returned from an amazingly successful field season tagging humpback whales and mapping their prey in the waters of Southeast Alaska.  We left from Sitka, AK on 16 April 2013 aboard an 80′ Yacht, the Northern Song (http://www.yachtalaska.com/pages/yacht.html) led by an experienced captain Dennis Rogers.  After a (planned) vessel transfer, we returned back to Sitka on 29 April 2013 aboard the 50′ Sailboat BOB (http://www.soundsailing.com/aboard-bob/aboard-bob/) led by skilled captain Blain Anderson and his wife Monique.

[photo size=’medium’ title=’The Northern Song’ align=’right’]http://superpod.ml.duke.edu/johnston/files/2013/05/DWJ-2013-04-2117-22-19.jpg[/photo] I have to say that the Northern Song was BY FAR the nicest boat I have ever been on in my life, let alone for a research trip!  We were served gourmet meals and three-course dinners with dessert every night by the talented chef Johann, and slept with down comforters in calm, quiet conditions!  The vessel was surrounded by windows so we could watch whales lunge feeding during our meals and take in the snow-capped mountains and temperate rain forests surrounding us, all in the warmth of the indoors!  We were not roughing it at all, I can assure you.  However it was not all sun and whales (but mostly it was).  Like most visitors to Southeast Alaska, we dealt with our share of rain, cold wind, rough seas, hail, and pelting snow.

Sometimes all in one day!  Most of the poor weather occurred during the last five-day leg of our trip aboard sailboat BOB.  Although the BOB was up to the challenge, we were not, and worked in small bays off of the mighty Chatham Straight to (mostly) avoid the rather unpleasant 6-8′ swells there.  But I’m getting ahead of myself.  Lets talk about the first awesome leg of our trip first.

[photo size=’small’ title=’Julia on a cold day’ align=’right’]http://superpod.ml.duke.edu/johnston/files/2013/05/IMG_0138-e1368202048698.jpg[/photo] [photo size=’small’ title=’Dinner’ align=’right’]http://superpod.ml.duke.edu/johnston/files/2013/05/IMG_0576.jpg[/photo]

It took us a few days to find our groove and get into the swing of things.  We traveled for a day or two before we had any whale sightings and the two whales we initially found proved difficult to tag.  So we moved on and struck the jackpot.  [photo size=’small’ title=’Dtag on humpback’ align=’right’]http://superpod.ml.duke.edu/johnston/files/2013/05/ASF_1911.jpg[/photo]Herring schools as high as a 12-story building getting ready to spawn in Tenakee Inlet, with 20-30 humpback whales remaining in the inlet taking advantage of the predictable prey.  Three-days straight of sunshine, flat seas, an 80′ yacht with gourmet meals, group-feeding, surface lunging humpbacks and awesome company and it really doesn’t get much better if you’re a whale biologist, I have to say.  For six consecutive days we deployed digital acoustic recording tags (Dtags) on group-feeding humpbacks.  Because the whales were so focused on feeding and there were a lot of whales to choose from, it was relatively easy to deploy the tags using a 24 foot long pole.  Check out this youtube video of Ari Friedlaender and Dave Johnston tagging a whale in Tenakee Inlet and keep your eye out for a surprise right as the tag goes on!

Once deployed, the tag, attached the the whale with suction cups, will record the whale’s depth, pitch, roll, and acceleration in three dimensions as the whale dives and maneuvers to capture prey.  The dive records from these whales tagged in Tenakee Inlet will be particularly interesting because they were feeding in groups of 10-15 whales and doing quite a bit of maneuvering in order to corral their prey into a tight bubble-net before they surfaced all together with their huge jaws wide open and the ventral pleats (extra folds of skin shown below) on the underside of their mouth fully distended.

[photo size=’big’ title=’Humpbacks feeding, Photo: Ari Friedlaender’ align=’right’]http://superpod.ml.duke.edu/johnston/files/2013/05/ASF_1388.jpg[/photo]

It was quite the sight to see.  Over and over and over.  Day after day, from before 8 am until after 7 pm these whales fed continously.  Different whales would come and leave the group, but the feeding continued.  Sometimes there would only be a few minutes between surface lunges, other times the whales would come up without feeding, occasionally they would surface VERY near the boat.  When this happened we all would usually stare in amazement (except for me who would miss many cool events because I was staring at a computer screen) and the captain would quickly put the boat into neutral so we did not injure the whales.  Dave made a hydrophone (underwater microphone) recording of one of these group feeding events.  You can hear one whale call out consistently and it is thought that this is the whale coordinating the feeding.  Have a listen yourself.

Once the tag was deployed, we would conduct a” focal follow” of the tagged whale, taking range (distance) and bearing (direction) measurements to the whale from the vessel every time the whale surfaced.  We were able to keep track of when the whale surfaced because the tag sent off a VHF (radio) signal when it was in air and the signal was picked up by a handheld antenna called a “Yagi”.  We used military-grade laser rangefinders to determine distance to the whale and a gyrocompass in the rangefinders to determine direction.  We recorded the location (latitude and longitude) of the boat with distance and bearing to the whale so we could go back and calculate location (latitude and longitude) of the whale.

[photo size=’medium’ title=’Echousounder output – the red blobs are herring schools’ align=’right’]http://superpod.ml.duke.edu/johnston/files/2013/05/AK2013Sounder.png[/photo]

While the focal follows were going on from the flying bridge (upper outside deck), I was in charge of mapping prey around the foraging whales.  To do this we use a scientific echosounder (fancy fish finder) to send sound waves down into the water.  The sound bounces off objects in the water column differently based on the density of the objects (strongest return for fish with gas-filled swim bladders).  We operated our echosounder at two frequencies 38 and 120 kHz.  Echosounders, or fish finders, are often mounted in the hull of many vessels, but our is a towed system so it can move around with us as we travel to different places for fieldwork.  We towed the echosounder from the Northern Song around the entire area where the whales were feeding to effectively map the prey in the region.  We “groundtruthed” echosounder data by fishing for herring and we also conducted CTD (Conductivity, Temperature, Depth) profiles to help us understand how the oceanography of the area affects the prey distribution in the water column.  All these data will be used as part of my dissertation research to better understand how prey characteristics, such as prey type (fish or krill), patch size, and density, affect the foraging behavior of humpback whales.

[photo size=’medium’ title=’Sailboat BOB’ align=’right’]http://superpod.ml.duke.edu/johnston/files/2013/05/IMG_0197.jpg[/photo]

During the last leg of our trip aboard the S/V BOB, we had an additional component of our research for PhD student, Ellen Chenoweth’s study to examine the predation of hatchery-release salmon by humpback whales.  Lucky for us, Hidden Falls hatchery just happen to be releasing some of their smolt (young salmon) when we were going to be in the area.  We towed the echosounder from the boom of S/V BOB (no sailing involved on this trip) and mapped out where the young salmon were in the water column immediately upon release.  Our initial thoughts on seeing the data are that the smolt stayed in the upper 20 m of the water column and were distributed diffusely (they did not school).   There were some additional activities that took place during this leg besides just prey mapping.  One of these included, much to my delight, a trip up the mast in the boatswain chair to look for whales.

[photo size=’small’ title=’Julia in the boatswains chair’ align=’left’]http://superpod.ml.duke.edu/johnston/files/2013/05/DWJ-2013-04-2718-09-57-1.jpg[/photo]

This was not solely for my own enjoyment, but for the sake of research because having the additional height greatly increases the distance at which whales can be detected.  Case in point, I spotted some killer whales out in the middle of Chatham straight miles away.  Too bad our fearless leader Jan Straley said “killer whales are a huge time suck” and made the (very wise) decision to stay focused on our task at hand (find humpbacks) rather than go for the distraction.  We did find a humpback, number 2227, who has been documented feeding on hatchery release smolt before (a known “perpetrator”).  This humpback, “the perpetrator”, also termed “bionic whale” by Ari for its ability to repel Ellen’s (accurate) biopsy attempts (for genetic samples) was very elusive and also managed to avoid all tagging attempts by Dave and Jan (some during a snowstorm).   Despite our lack of tagging success on this leg of the trip, Ellen was beside herself with delight that the timing of our trip coincided with some early hatchery releases and whale activity, both of which can be unpredictable.  I think it’s safe to say that this leg of the trip was also a success!  If you are interested in learning more about Ellen’s research, check out the video she made.

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ACKNOWLEDGEMENTS

I’d like to extend a special thank you to our awesome field assistants: Kelly Newton, Heather Riley, Madison Kosma, our Principle Investigators: Ari Friedlaender, Dave Johnston, and Jan Straley, fellow PhD student and partner in crime Ellen Chenoweth, the captain and crew of the Northern Song: Dennis Rogers, Angie Battaglia, and Johann Rousseau, and the captain and crew of the BOB: Blain and Monique Anderson.  Everyone helped make it a successful and very special trip.

PERMITS

All our research was conducted under the appropriate NMFS (14122), ADFG (CF-13-053), and IACUC permits.