Beluga Notebook--Beluga By the Numbers, Part Two

Many folks familiar with my volunteer work as a Cook Inlet beluga whale monitor usually ask me two questions: “How many beluga whales do you see?” and “How many beluga whales are there?” 

In a previous blog entry, I addressed the first question.  In this blog entry, I address the second.

The latest stock assessment estimated the abundance of Cook Inlet beluga whales at 328 whales in 2016, down from an estimate of 340 whales just two years earlier.  To place these two numbers into context, the best available historic abundance estimate is 1,293 beluga whales obtained from 1979 surveys.  Within two decades, in 1998, this estimate stood at 347 beluga whales.  While the large reduction was attributed to an unsustainable harvest by Alaska Native hunters in the 1990s, the numbers have not rebounded as expected after the cessation of hunting.  In fact, the decline continues.

While the estimates of abundance in the accompanying figure show year-to-year fluctuatations, the trend is definitely downward. So when asked how many beluga there are in Cook Inlet perhaps the best response is "328 whales, but they continue to decline rather than increase which is why I and others are doing monitoring."  Hopefully, we are not witnessing a gradual countdown to beluga whales' extirpation (local extinction).

Whenever I discuss wildlife abundance estimates, I recall a conversation I had in 1988 with an official from the California Department of Fish and Game's Marine Resources Division.  "It's not like counting cattle on a hillside to get an estimate of herd size.  In the marine enviromnent you have a great deal of uncertainty.  Many different factors contribute to this uncertainty."  We see this with beluga abundance estimates.  How one counts a thing is as important as how many of a thing one counts.  Numbers play the role of indicating whether things are getting better or worse.  They motivate us to stop keeping score and start refereeing.

One of the earliest estimates of beluga whale abundance in Cook Inlet comes from a 1972 University of Alaska, Fairbanks Institute of Marine Science Report R72-23, A Review of the Oceanography and Marine Resources of the Northern Gulf of Alaska, one chapter of which discusses marine mammals. The section reports that "aerial surveys of Cook Inlet ...made in 1963 and 1964, indicated a summer population of 300 to 400 animals." This statement, if not examined critically, could lead to the conclusion that with a point estimate of abundance of 328 whales today, the population has remained relatively stable of 60 years.    The conclusion is erroneous. 

As noted in the National Marine Fisheries Service Cook Inlet Beluga Whale Recovery Plan (December 2016) "aerial surveys in the 1960s, 1970s and early 1980s counted belugas in the Cook Inlet but only a few of these had sufficient coverage to estimate the population size...The survey in 1979 resulted in an estimate of 1,293 whales using a correction factor of 2.7 developed to account for submerged whales ....This is the best available estimate of historical beluga abundance in Cook Inlet, and represents the maximum observed size of this population."

The trend in abundance estimates since 1993 is shown graphically in figure 2, which is from the Marine Mammal Commission 2018 Cook Inlet Beluga Stock Assessment.  At certain points, the number of beluga whales got the stock declared "depleted" under the Marine Mammal Protection Act and "endangered" under the Endangered Species Act.  In the future, the stock may be "downlisted" from "endangered" to "threatened" when the abundance estimate equals or exceeds to 520 individuals.  "Delisting" from "threatened" to "recovered" may occur then the population reaches 780 individuals.  Other criterial will have to be satisified as well.  The number alone will not suffice.

We have a long way to go to acheiving either number.  As a monitor, I make a small contribution to achieving the goal--a topic that will be covered in a future blog entry.

Beluga Notebook--Belugas by the Number Part One

Many folks familiar with my volunteer work as a Cook Inlet beluga whale volunteer monitor usually ask me two questions: “How many beluga whales do you see?” and “How many beluga whales are there?” 

In this blog entry, I address the first question.

In my recent sessions at Ship Creek, my typical response to “how many did you see” response is “none-zero-nada.”  I encountered beluga whales in only one of my seven sessions at Ship Creek in September. In the one session, my team counted three beluga whales--an adult, a juvenile, and a calf.  In the other six sessions, I saw none—a “batting average” of .142.  Not bad considering the Ship Creek is the station with the least number of sessions where beluga were sighted as a percentage of total observation sessions for the month of September.   

Monitoring Station Data for Beluga Whales, September 1 to 30, 2019
Station/Location	Number of Sessions	Number Session Where Beluga Were Seen	Total Number of Beluga Whale Reported
Ship Creek—Knik Arm	32	12   (37.5%)	50
Bird Point/MM 95.2 Pullout—Turnagain Arm	26	24  (92.)%)	392
Twenty Mile River Turnagain Arm	11	7  (63.7%)	76

Data from Alaska Beluga Monitoring Partnership Siting Log Webpage (accessed  on October 12, 2019,  https://akbmp.org/beluga-observation-log/)

Two necessary conditions determine whether we observe beluga whales during a session.  The first factor—presence of beluga whale--seems obvious.  If the whales don’t show up, they can’t be counted.  The second factor—did the observers see the whales--seems equally as obvious. You can’t count what you can’t see.  Of course, you have to know what to look.  Our training and experience help with that aspect.  

To address the first condition, the research protocol locates observation stations near anadromous streams where the beluga’s prey species, salmon, are likely to be present.  The protocol sets the timing of the sessions around the time of high tide when beluga may safely navigate the shoals and flats of Knik and Turnagain Arms in order to feed on their prey.   Biology and oceanography largely satisfy this condition.

The second condition is more variable.  A number of factors influence whether the volunteers observe and record the beluga whales.  The physical environment--glare, sea state, weather conditions--all could affect the ability of an observer to see the beluga whales.  

Rain and reduced visibility are environmental factors.  We note
the conditions for each session and if they change during the session.

Other factors are related to the individual observer and include scanning technique; the expanse of the area scanned; visual acuity; attentiveness, and so on.  The number of observers has an effect—the more eyes looking for something the more likely it is seen.  A final factor might be the frequency of observers during a session and the number of beluga whales in each encounter.  That is, the number of pods passing by the observation point and the number of beluga in each pod increase the likelihood they will be seen.  The protocol can control some of potential observation errors to some degree.  

October is pretty much shaping up to be a repeat of September for me.  I am comforted by the knowledge that negative observations (no beluga seen) provide important data.  I describe beluga whale counting as “hours of scanning, punctuated by minutes of intense observation and data recording.”  I will keep on going to Ship Creek.  You can’t see them if you are not there to see them.