Counting
Gray Whales: Why Different Results?
Michael H. Smith, Project Director
of Gray Whales Count
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Mr.
Smith with his binoculars at Coal Oil Point ("Counter Point") |
Q. What can't the counts tell us? What can they tell us?
A. Neither Gray Whales Count nor the ACS-LA Census are capable of estimating the size of the overall migration. Both are capable only of estimating the number of whales that use the respective "corridors" by each of our survey stations. As such, the data from Gray Whales Count in Goleta, California, reflect what is happening locally. Since, however, we are all sampling, and we are in a sense connected as a network, we (along with other stations such as Piedras Blancas) can together provide a bigger picture of what is going on for the greater migration.
Q.
Why are numbers so different at the California counting sites?
A. The numbers at all the
counting sites will be different. Some reasons are:
the
hours
and days in the survey, the weather and sea conditions,
the ability of the observers, and most importantly, the number of whales
going by the survey area that could potentially be counted. (Whales
travel around the clock and in all types of weather, so not all whales
are seen!)
Q.
Why don't you count the southbound migration from Coal Oil Point?
A. Most of the southbound
migration does not go by Coal Oil Point. Most of the whales go from
Point Conception out through the Channel
Islands. The whales are riding the very strong California Current in
a more
direct
line
to Mexico. Any whales that do go by
Coal Oil Point are mostly juveniles who are, perhaps, following the
route
taught
to
them
by their
mothers. The
ACS-LA site (#6 on
the globe showing Journey North's observation posts)) is
a much better place for seeing the southbound migration.
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Find:
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Q. What makes Coal Oil Point a good place for counting northbound whales?
A. We do have many mature whales coming through the nearshore of the Channel. As they head north, they are riding a small gyre-current created by the passing California Current. The large majority of mothers and calves choose the nearshore corridor through the Santa Barbara Channel.
Q. How do counts from different places help scientists find answers?
A. Our location in the Channel puts us in a good position to provide a check for Wayne Perryman's counting station at Piedras Blancas (#8 on the globe showing Journey North's observation posts). Mr. Perryman's count estimates successful calf production for NOAA. Mr. Perryman sees more mothers and babies than we do because of his location. He also spends more hours per day counting. However, our sampled numbers should graph in a similar manner. for example, in 2007, we all graphed similar pictures of the decline in calves; and so, with our combined samples, we were able to state with confidence that there was, indeed, a problem with low calf numbers. We look forward to seeing what each year's counts will reveal!
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