Blue whale portraits: pieces of the puzzle

By Dawn Barlow, MSc Student, Oregon State University

Perhaps you’ve read some posts about New Zealand blue whales on this blog from the past field season in the South Taranaki Bight (STB). I know I eagerly awaited updates from the field while the team was in New Zealand and I was in Southern California, finishing undergrad and writing funding proposals and grad school applications. Now that undergrad is done and dusted, I’ve arrived in Newport and begun to settle in to my next chapter as the newest member of the GEMM Lab, joining the blue whale research team as a MSc student in OSU’s Department of Fisheries and Wildlife. Since no blue whale news has made it onto this blog in some time, I’m excited to share what has happened since the team returned from the field!

As you may have heard from Leigh, Callum, and Kristin, 2016 was a fruitful field season. In nearly 1,500 miles of vessel surveys, the team documented blue whale foraging behavior, a pair of racing whales, four mother-calf pairs, what may be the first aerial footage of nursing behavior in baleen whales (video below), and a whale with apparent deformities. Five hydrophones units were deployed, fecal and biopsy samples were collected, oceanographic conditions were measured, and photos were taken.

I was welcomed into the GEMM Lab in early July, and presented with a workspace, a hard drive with thousands of photos, new software programs to learn, wonderfully accessible tea and coffee, and tasked with creating a photo-ID catalog of all the blue whales our team photographed this past field season. Here’s a great thing about blue whales: while they may be tricky to study, when someone sees a blue whale they are often excited to report it. In addition to the data collected by our team during the 2016 season and the 2014 pilot season, we are incorporating many photo-documented sightings of blue whales from all around New Zealand that we have received from collaborative researchers, whale watch organizations, and fishing vessels alike captured between 2004 and 2016. All these photos are precious data to us, as we can use them to better understand their ecology.

There are many unanswered questions about this population of blue whales in New Zealand — How many are there? Just how big are they? Do they stay in New Zealand year-round or are they migratory? Through the photo-ID analysis that I’ve done, we are just beginning to piece together some answers. We have now compiled records of sightings in New Zealand from every month of the year. I’ve identified 94 unique individual blue whales, 26 of which were sighted in the STB during the 2016 season. Five whales were seen in multiple years (Figure 1), including one whale that was seen in three different years, in three different places, and with three different calves! And what might all of this mean? At this point it’s still speculative, but these findings hint at year-round residency and seasonal movement patterns within New Zealand waters… with more data and more analysis I will be able to say these things more conclusively.

New Zealand Blue Whale Photo-ID

NZ Blue Whale Photo-ID
Figure 1. Blue whale photographed off of Westport on 31 January 2013 (above) by the Australian Antarctic Division (data provided by Mike Double), and in the South Taranaki Bight on 2 February 2016 (below). Note how the tear in the dorsal fin has healed over the three-year period.

Perhaps you’ve read Leila’s post about photogrammetry, and how she is able to make measurements using aerial photographs captured using an Unmanned Aerial System (UAS, aka ‘drone’). Using the same method, I will soon be able to tell you how long these whales really are (Figure 2).

sighting 22 UAS reduced
Figure 2. An aerial photograph captured with the UAS during the 2016 season, which will be used to measure the length of these whales using photogrammetry.

How many of them are there? Well, that’s a trickier question. Using a straightforward abundance calculation based on our rate of re-sightings, the estimate I came up with is 594 ± 438. In other words, I can say with 95% confidence that there are between 156 and 1031 blue whales in New Zealand. How helpful is this? Well, not very! The wide confidence intervals in this estimate are problematic, and it is difficult to draw any conclusions when the range of possible numbers is so large. So stay tuned as I will be learning more about modeling population abundance estimates in order to provide a more precise and descriptive answer.

But stepping back for a minute, what does it matter how many whales there are and what they’re doing? In 2014, Leigh demonstrated that the STB is an important foraging ground for these blue whales. However, the STB is also a region heavily used by industry, experiencing active oil and gas extraction (Figure 3), seismic surveying, shipping traffic, and proposed seafloor mining. If we don’t know how the blue whales are using this space, then how can we know what effect the presence of industry will have on their ecology? It is our hope that findings from this study can guide effective conservation and management of these ocean giants as well as the ecosystem they are part of.

Figure 2. A blue whale surfaces in front of an oil rig in the South Taranaki Bight, New Zealand. Photo by Deanna Elvines.
Figure 3. A blue whale surfaces in front of an oil rig. Photo by Deanna Elvines.

Keeping these goals in mind, I’m eagerly awaiting the start of our 2017 field season in the STB. As I look through all these photos I feel like I’m getting to know this group of whales just a little bit and I look forward to being on the water seeing them myself, maybe even recognizing some from the 2016 photos. More time on the water and more data will bring us closer to the piecing together the story of these whales, and inevitably open doors to more questions than we started with. And in the meantime, I’m grateful for the community I’ve found here in the GEMM Lab, at Hatfield Marine Science Center, and in Newport.

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