Results tagged “right whales”

The Uncertain Future of Right Whales

The first time I saw a right whale surface, her broad shoulders and snout surged up through the foaming water looking like a gigantic hippopotamus. Aside from her immense size, it was hard to believe this was a whale. Then the enormous, lumbering filter feeder opened her permanently frowning maw, which was almost as long as our boat, and chugged slowly away, sieving water through her baleen, and leaving a burbling, foamy wake. 

I was lucky. Sightings like this are becoming rarer as the number of North Atlantic right whales declines, and their whereabouts are becoming ever more mysterious, especially off the shores of Maine. 

Just after the turn of this last millennium, scientists described the North Atlantic right whale as a species at a crossroads. There were only about 300 left in the world, and some experts laid out possible timelines for extinction. Two prominent right whale scientists, Scott Kraus and Rosalind Rolland, wrote, "Human decisions over the next few decades will decide the survival or extinction of the species."

...READ THE REST HERE

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A young right whale breaches in the Bay of Fundy in 2012. Photo courtesy Anderson Cabot Center, New England Aquarium.

Whale arrival date forecast validation, 2007 and 2008

Weather forecasters enjoy (or lament) the gratification of finding out how good their forecasts are just a few days after making them.  Ecosystem forecasters, on the other hand, often have to wait a long time before we know.  One of our forecasts is for the arrival date of right whales in the Great South Channel critical habitat.  Each year we try to predict when the whales will arrive in large numbers to feed there.  Then we wait, sometimes for years, for the data to come in, so that we can see which predictions are correct, and which need to be re-examined, and why.

We now have the right whale sightings data from 2007 and 2008, so the moment of truth is at hand.  I haven't dug into the analysis yet, but here is the first cut.  Our 2007 prediction was very close, falling just a few days from the actual arrival date, and falling well within the predicted window (see figure).  Our 2008 prediction was later than the arrival date.  This appears to be driven by a period in mid March when there were lots of whales, followed by a lull.  Use of the habitat picked up again in mid April, and persisted from there.  Our model appeared to pick up on this later arrival, missing the brief but intense party in mid March.  It'll be interesting to dig into this further when we start our analysis, and see if we can shed light on what was happening in mid March.

GSCarrival.jpg
Figure  Right whale sightings per unit effor in the Great South Channel for 1998-2008.  Black line indicates the arrival date computed from the data (day at which sightings per unit effort crosses 0.01).  Horizontal boxes indicate the arrival date forecast for each year.  Figure is preliminary.

Right whale forecasts

These results are Dan's, but he's indisposed and the results are too cool not to blog.  Dan fit a MaxEnt model for right whales in Cape Cod Bay based on hindcasts of Calanus and Pseudocalanus for 2003-2006 as well as SST, chlorophyll, and bathymetry.  He then applied the habitat model to the 2009 copepod estimates and satellite data to predict right whale habitat.  I extracted whale sightings from the PCCS reports and plotted over his images.  By and large, the PCCS sightings fall within areas of high habitat suitability (5/18/09 Note: figures with sightings have been removed).  The correspondence will probably (hopefully?) improve if we produce habitat maps for the specific survey time, rather than the nearest 8 day image.  Now, here's are forecasts for 5/9 and 5/17:
whalemaps8d_17.jpg
whalemaps8d_18.jpg
Note that the habitat area is predicted to shrink, and we expect that the whales should be moving to deeper, Calanus-dominated habitats like the Great South Channel

2010 Right Whale Prospectus

 While our crack economic team predicts a recovery in the "future", 2010 looks like a bleak year for stocks.  One stock that stands out is the North Atlantic right whale.  After taking a beating for the last 300 years, this year's  39 calves suggests that this stock may be poised for a slow recovery.  However, Seascape Investments is cautioning our short-term investors from jumping into right whales at this time. While stock prices do have some autocorrelation (explaining why past performance seems like a good indicator), the number of right whale births has a strong tendency for boom and bust cycles. While right whales may become a conservative long-term investment (that is, slow growing), the cyclic nature of this stock suggests taking the long view, especially in the highly speculative calving market.  Here's our reasoning:


The number of right whale births depends on the number of reproductively active females, better known as cows, in the population.  However, right whales require two, or more likely three or more, years between births.  This means that we need to remove the 39 mothers from this year from the available pool of females.  We should also remove most of the mothers from last year, which I believe was pretty good, say 25.  The wild card in this guess is how many new females will be added to the pool.  Since it takes at least 5 years for a female to become sexually mature (average is 11, see Ch. 6 in the Urban Whale), the high birth years from the early part of this decade are only now starting to enter the population.  Let's say that we've added 20 new females since 2005, then we have 112 total cows.  Subtracting this year's births and my guesstimate of last year's gives us 48 available females.  This provides an upper limit on the number of births for next year.  How many will actually give birth will depend on a lot of factors, with my favorite being food.  If Calanus is abundant this year, then our earlier modeling work suggests that as many as 63% could calve, producing 30 new whales.  Realistically, I think 50% is a better guess, giving 24 calves.  While Seascape Labs would never condone the practice, opportunities for short selling in 2010 could be lucrative.

Forecast: right whale arrival date in the Great South Channel

Our lab et al. published a series of papers in the latest issue of Marine Ecology Progress Series in which we explored linkages between copepod abundance and the migration patters of right whales.  Better knowledge of where and when right whales might show up can help prevent ship strikes and gear entanglements.  The full articles can be found here: 1 2 3.

One of our results was a strong correlation between the computed abundance of Calanus finmarchicus and the arrival date of right whales in the Great South Channel critical habitat.  Researchers have known for awhile that right whales use this habitat every year, but the factors that influence the timing of that usage are harder to pin down.  (Details on our computations, like how we calculate arrival date and C.fin. abundance, can be found in the papers.)

This correlation may have use as a forecasting tool.  The correlation spans the years 1998-2006.  By computing the C.fin. abundance for ensuing years, we can use a linear fit to produce a forecast for the arrival date in the Great South Channel (see figure).  Our prediction this year is for an early arrival date--right around now, in fact.  We also predicted an early arrival for 2007, and a late arrival for 2008.


ArrivalDate20090317.gif
Figure.  Top: correlation between computed C.fin. abundance and right
whale arrival day in the Great South Channel (R^2=0.7, p=0.01).  Red dots
show predicted values for 2009, with the most current prediction indicated
by text.  Bottom: our predictions for the 2009 arrival date.  As the year
progresses, we assimilate more data, and our prediction changes (see point
2 below).  The abrupt drop in late February is due to a modification in our
calculation (see point 4 below).



Caveats

There are a few caveats to this forecast.  I'll outline them here.

1) A linear regression is a simplification of the dynamics at play, and there is variability about the line.  Therefore, even though we give a specific arrival date, our forecasts should be taken as approximate.  It's better to think of them as "early", "average", or "late", rather than as occurring on a specific date.

2) Our models rely on satellite data, which is updated as the year progresses.  Therefore, our forecast changes as the year marches on (bottom plot in figure). It's similar to how the weather forecast gets better as next week gets closer.  This limits us somewhat, but our previous work has shown that satellite data from January and February generally provide enough data to get a significant correlation.

3) We check our forecasts against a whale arrival date that is calculated from survey data.  That is, real people looking for whales from boats and planes.  It takes a long time for that information to be processed and passed to us, so we haven't yet been able to check our 2007 and 2008 forecasts.  So, unlike the weather forecaster, we don't have the advantage of knowing what "today's weather" is.  Even though our 2009 forecasts tell us that right whales are arriving in the Great South Channel right around now, or possibly have arrived already, we may not be able to check that for awhile.

4) The nature of satellite data changes with technology.  For example, resolution has improved.  We've developed a new interpolation method that helps the satellite data to be consistent over many years.  The down side is that we had to re-run our experiment with all of the satellite data in this new format.  The good news is that the correlations persisted, though altered a little.

Record year for right whale births

Today the New York Times reported that a record number of right whales have been born this year - 39 so far!  That's about 10% of the total population size.  The last record was set in 2001 when 31 calves were born.  The NYT article lays out the challenges posed by shipping and fishing to the North Atlantic right whale population.  Check it out, and be sure to watch the videos (included below).

Estimating habitat suitability: Out of sample validation

The question of determining what is and what is not suitable habitat can be tackled from many angles.  My tool of choice is an empirical "species distribution model" (SDM), also known as an "ecological niche model", "environmental niche model", "habitat model", and by several other phrases.  The name of the game is to gather environmental data from the location (and in my case time) of known species occurrence.  By associating environmental data with species occurrence, one can build a characterization of the response of the species to its environment.  By applying this characterization to spatial environmental datasets, environmental "suitability" can be estimated over a broader area or in a different time than that of the species occurrences.  

I'm using several years of right whale sightings, along with satellite- and model-derived physical and biotic environmental data (e.g. previously posted copepod model output), to produce weekly estimates of right whale habitat suitability.  I'm in the model validating phase, in which I build a model with data from years 1,2,...,n-1, and test it with data from year n.  I refer to this as an "out of sample" test.  A common alternative to this method of model validation is to randomly select and remove a subset of occurrences from all n years, and test the model using these occurrence locations.  The former method is a considerably harder task for a model, but I think it is a better for my purposes because it measures the model's performance in the face of inter-annually varying response of a species to its environment.

roc.jpg
For certain years I can (using Maxent) build good models the springtime distribution of right whales in the Cape Cod Bay and Great South Channel critical habitats.  Pictured is a plot of the receiver operator characteristic curve, and the area underneath that curve (AUC).  AUC=0.5 indicates that the model is no better than random, AUC=1.0 indicates that the model is perfect (always placing species occurrences in "good" habitat). An AUC score greater than about 0.75 is generally considered to be the cut-off for a useful model.  I built this model with springtime data from 2002, 2003, 2004, 2006, and I tested it with data from 2005.  AUC=0.846.  Not bad.

Right whales, climate change, and the press

If you believe the old maxim that "all press is good press", then It's been a good couple of weeks for EMLab.  While I'm usually pretty happy to be the center of attention, I'm beginning to think that maybe all press is not so good.  

Last week, the Ellsworth American ran a story titled "Is Climate Change Keeping Whales in the Gulf of Maine?", that reported on a lecture I gave at the Marine Environmental Research Institute in Blue Hill.  The article did a good job describing many themes I discussed. Unfortunately, my talk did not address the question posed in the headline, namely whether climate change is keeping whales in the Gulf of Maine.  Given the strong feelings that right whales evoke along the coast of Maine, I was worried that this would create some negative feedback for our work, especially for some of my colleagues who are more actively engaged in the entanglement issues.  Thankfully, it didn't draw a lot of attention--no angry letters to the editor that I can find, but our local public radio station did pick up the story.  MPBN actually interviewed me and others to get the straight story.  My only complaint is that they only mentioned my GMRI affiliation.  

So what do we know about right whales and climate?  The Gulf of Maine, which extends from the coast of New England and Canada south to Georges Bank, is a special place for right whales.  All of the known right whale feeding grounds are found in this region, and all of the approximately 400 right whales in the North Atlantic spend some time in the Gulf during the spring and summer.  During the winter, pregnant females migrate to the calving grounds off of Florida.  We know very little about where males and nonpregnant females go during the winter.  This is why the recent sighting of 44 whales in the central Gulf of Maine in December was such big news.  While their presence was news to us, these animals were probably doing what right whales have done for thousands of years.  The fact that scientists only recently found them is more likely due to increased efforts to find whales than to a changing climate.  While it is unclear exactly how the Gulf of Maine will respond to a shifting climate, the coming changes will challenge the animals in the Gulf.  Scientists are learning more every year about how animals move in relation to environmental conditions.  Further research in this area will allow more precise predictions about how right whales and other animals will behave in a changing ocean.  

Mass Bay Forecasts--Coming Soon!

 The pervasive cold and darkness that characterizes winters in New England means that primary productivity in the Gulf of Maine shuts down during this time.  However, shallow waters along the coast limit how far below the surface the phytoplankton can be mixed.  For this reason, the spring bloom in the Gulf of Maine starts along the coast and in the south, so biology in Mass Bay tends to lead the rest of the Gulf.  If you're an animal, like a right whale, that can swim large distances, Mass Bay is likely your first stop in your annual tour of the Gulf. Autobuoys.jpg

From the point of view of a right whale, the downside to Mass Bay is that it is surrounded by Massachusetts.  This means that the Bay is one of the more industrial stretches of water in the world.  Large ships bring cargo to and from Boston.  Other ships are supporting the construction of liquified natural gas terminals in the Bay.  Smaller fishing boats move through the area, taking advantage of the same productivity that draws the right whales to the Bay.  Oh, and all those people in Massachusetts, they produce a lot of sewage, and a lot of it ends up in the Bay (after suitable processing, we hope).  The upside of all this activity, is that there is a lot of science going on.  Our colleagues at the Provincetown Center for Coastal Studies regularly collect zooplankton samples, partly to provide information relevant to right whales, and partly to monitor the impact of the sewage outfall.  Our colleagues at Cornell's Lab of Ornithology have installed a series of "autobuoys" that can detect the presence of right whales in the shipping lanes and near the LNG sites (see the image).  All this data creates the perfect environment to try some right whale forecasting.  If we can't do it in Mass Bay, we probably can't do it!

Here's what we plan to do
  1. Run SEASCAPE to estimate the abundance of the whales' favorite copepods: Calanus finmarchicus, Pseudocalanus, and Centropages typicus.
  2. Use the ensemble Kalman filter to assimilate PCCS's weekly zooplankton survey into our model.  This will give an improved estimate of the whale's prey-field and should improve the accuracy of the model over the following week.
  3. Use the model output, plus satellite data and other variables to estimate right whale habitat in the Bay.
  4. Use an assimilation procedure to refine our whale habitat estimates using the Cornell acoustic detections.
I have implemented the Kalman filter procedure and am currently testing it with previous years.  Hopefully, I'll have this working next week and we can start making some forecasts.
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