Where Have the Blue Whales Gone?

While planning an upcoming trip to Southern California I ran across various sites advertising whale watching excursions and noticed that several companies actually post logs of sightings. If you have read more than a couple posts on this site, you know I’m not one to turn down an opportunity to scrape and analyze data! After merging the logs with water temperature data from the NOAA, I uncovered an interesting story behind the numbers.

The Data

First, a look at the water temperature data. The National Oceanic and Atmospheric Administration’s National Ocean Service provides real-time data via the Center for Operational Oceanographic Products and Services. The whale watching companies I found with data are in Long Beach and Newport Beach, so the closest NOAA/NOS/CO-OPS station is in Los Angeles off the coast of San Pedro. The sightings logs go back to 2011, so I only looked at water temperature data from 2011 to 2016. Via the site, you can only pull 31 days of data at a time, but I wrote an R script that repeatedly pinged the API. The plot below is the result.

The plot lines up with what NOAA and NASA have been saying for a while now: The current decade has seen some of the warmest years on record. But this post is about whales.

Data on whale sightings were taken from two companies, Harbor Breeze Cruises, based out of Long Beach, and Newport Landing Sportfishing, based out of Newport Beach. This is where I warn you that these numbers should not be taken as incredibly accurate measurements. (In fact, I wrote an entire post on the problem with counting and human error). Until we live in a world where whales surface and introduce themselves, adding “By the way, I swam by earlier and you may have counted me twice,” we’ll have to settle for these numbers.

One other potential complication is that it may be in the best interest of whale-watching companies to boost their sightings numbers in order to attract tourists. I’m not saying either of these companies did that, and in fact, both sets of data reflect trends that I’ll elaborate on later, which makes it unlikely the numbers were completely made up.

A Whale of a Tale

A first glance at the data shows that whale sightings have been on the rise in Southern California.

Separating the data by type of whale and including the temperature data, however, reveals a different story.

In statistics, this is called Simpson’s paradox, and you know me, I love a good paradox. While the overall data show an increase in whale sightings, we actually see that the increases are being driven by a couple types of whale and that sightings of some, particularly blue whales, are decreasing [1]. Moreover, the blue whale sightings appear to be correlated with increasing average temperatures, as the plot below shows.

Remember my comment above about data from both companies reflecting trends that would make it unlikely they were making up numbers?

Correlation Does Not Equal Causation

While there appears to be a correlation between less blue whale sightings and higher average temperatures, some caution is necessary. First, I’m basing these assumptions off of data from two companies. The distance between Long Beach and Newport Beach is approximately 32 miles, so we’re only talking about a small portion of the Southern California coastline. I searched for similar companies in the San Diego area, but they didn’t include sightings logs like the two companies in the data.

So far I can only assume that blue whale sightings in specifically the Los Angeles/Orange County area have declined.

Second, what is it about higher average temperatures that would lead to less sightings? A couple of potential clues can be found in this 2010 article from the Los Angeles Times, which talks about a spike in blue whale sightings (also reflected in 2011 in the plot above):

“A year ago, we were lucky to see three or four blue whales per trip,” said Michele Sousa, senior mammal biologist at the Aquarium of the Pacific. “Now we’re seeing up to 15 per trip, along with a few fin whales thrown in for good measure.”

Sousa believes the whales are following vast clouds of krill — tiny, shrimplike crustaceans that are a mainstay of their diet — into relatively shallow waters just a few miles offshore.

Could the warmer waters be affecting the growth of krill in the eastern Pacific much like increasing Southern Ocean temperatures are affecting the Antarctic krill? That’s a hypothesis I can’t answer. Krill also face other issues, like overfishing, but that doesn’t appear to be an issue in this particular region. [2]

Another potential clue: The Los Angeles Times also notes that the blue whales were being sighted increasingly in the shipping lanes, a dangerous place for cetaceans to hang out. It’s possible that the blue whales simply learned to avoid the area.

And what about the increase in grey whale sightings? A couple of ideas there. Blue whales are an endangered species. It’s believed there are only about 2,800 feeding off the California coast. Eastern Pacific grey whales, on the other hand, were actually taken off the endangered species list in the 90s.

Also, while grey whales share blue whales’ love of krill, they also suck up a variety of bottom-dwelling animals, primarily in the Arctic.

Do You Speak Whale?

If so, you know more about what’s going on then I do. There’s not much I can say other than based on a sample of sightings from whale watching companies in Southern California, there have been less blue whale sightings in recent years, which is highly correlated with warmer average water temperatures.

There’s an interesting story there, but it doesn’t have an ending or much of an explanation in terms of the central mystery. So it’s kind of like Lost.

Are you a marine biologist? Feel free to leave a comment and help me out here.

[1] It should be noted that Harbor Breeze Cruises lists blue whale sightings dating back to 2005. There was a definite spike in 2010 and 2011. Sightings from 2007-2009 averaged around 600 per year. Prior to 2007, however, sightings were less frequent. This can at least be explained by their status on the endangered species list. The population of the eastern Pacific blue whale hasn’t actually rebounded until recently, which introduces more questions as to why sightings have become less frequent in Southern California.

[2] Krill are used for Omega-3 (aka “krill-oil”) supplements, however, the NOAA banned krill fishing off the West Coast in 2009.