Subject: whale populations

Nancy Stevick (Nancy.Stevick@btinternet.com)
Tue, 25 May 1999 14:24:32 +0100

On 24 May 1999 02:05, Stephanie Wooley wrote:

>Hi Nancy,
>
>I am a 7th grade math teacher at H.M.S.  I am looking for various whale
>population estimates over the last few decades.  I would like students to
>use this information to create line graphs.  If you do not has this
>information, any suggestions on where I might find it?
>
>Thanks for your help.

Dear Stephanie,

It is difficult to provide you with data on population estimates over the
past few decades which would be meaningful to compare.  In an ideal world,
abundance estimates would be calculated using the same survey and analysis
methods over a long period of time, and would sample a species over its
entire range.  In reality, this is impossible. In some cases, scientists are
able to modify available data to correct for varying sampling techniques.
This gives them
abundance indexes to compare over time.

It is important to stress to your students that these indexes are only
estimates,
best
guesses, based on the data available.  To show your students how difficult
collecting data on marine mammals is, check out Activity 2e of the On-line
Humpback Whale Catalog Curriculum Unit at
http://whale.wheelock.edu/whalenet-stuff/CDROMcurr/CDROM_lesson2.html.
After working on this activity, I
hope your students will treat all marine mammal abundance estimates with the
suspicion they deserve.

Here are some excellent whale studies which provide interesting data for
your students to graph.  Along with these various estimates are citations
for the journal articles, so you can do some further reading if you wish.
If you require further abundance estimates, I would encourage you to find
issues of the International Whaling Commission's annual reports and special
issues.


***
Belugas in the St. Lawrence estuary were hunted extensively until they were
protected in 1979.  Scientists were concerned that this hunting pressure
combined with the effects of pollution posed a distinct threat to the
survival of this population.  Nine surveys were conducted of the St.
Lawrence belugas between 1973 and 1995.  Corrections were made for slight
variation in survey methods and in the area covered by the different
surveys, and population index estimates were calculated as follows.

YEAR:POPULATION INDEX ESTIMATES
1973:  475 (-112 subsequently hunted) for a total of 363
1977:  412 (-48 subsequently hunted) for a total of 364
1982:  512
1984:  441
1985:  601
1988:  519
1990:  641
1992:  532
1995:  713

from:  Kingsley, M.C.S.  1998.  Population index estimates for the St.
Lawrence belugas, 1973-1995.  Marine Mammal Science, 14(3):508-530 July
1998).

***
Bowhead whales were counted annually at Point Barrow, Alaska during spring
migrations from 1978 to 1988.  These counts were corrected for various
factors and an index of whale abundance was calculated which showed a trend
of 3.1% annual rate of increase.  This graph is a little messier than that
of the belugas.

YEAR: INDEX OF WHALE ABUNDANCE
1978:  3,383
1979;  no index listed
1980:  2,737
1981:  3,231
1982:  4,612
1983:  4,399
1984:  no index listed
1985:  3,134
1986:  4,006
1987:  3,615
1988:  4,862

from:  Zeh, J.E., J.C. George, A.E. Raftery, and G.M Carroll.  1991.  Rate
of increase, 1978-1988, of bowhead whales, balaena mysticetus, estimated
from ice-based census data.  Marine Mammal Science, 7(2):105-122 (April
1991).  I think that Judith Zeh has a more recent paper, but I could not
find it
today.

***
Aerial surveys of humpback whales off Shark Bay, Western Australia indicate
an increase in this population.

YEAR:  MONTH, WHALES SEEN

1963:  July, 95
              Aug, 6
1976:    June, 0
               July, 9
               Aug, 0
1977    July, 30
1978    July, 17
1980    Aug, 86
1982    July, 113
1986    July, 169
1988    July, 170
1991    July, 279

The 1963 surveys were performed by a whaling company spotter during the last
year of humpback whaling.  From these sightings, population estimates were
calculated for 568 humpbacks in 1963 and 3,302 for 1991.

from:  Bannister, J.L.  1994.  Continued Increase in Humpback Whales off
Western Australia.  Report of the International Whaling Commission.

***
North Atlantic humpback whales are one of the most studied cetacean.  For
over twenty years, Allied Whale, the marine mammal laboratory at College of
the Atlantic has studied this population using photo-identification.  Over
350 contributors have submitted fluke photographs and sighting data to the
North Atlantic Humpback Catalog.  You can access these fluke photographs and
sighting data at http://whale.wheelock.edu/whalenet-stuff/humpcat.html .Each
fluke pattern is as unique as a fingerprint, and
individuals can be tracked over time.  Using resightings based on fluke
photographs, the following population estimates were calculated for the
North Atlantic humpback population.

YEAR    ESTIMATE
1979:  3,528
1980:  5,362
1981:  5,444
1982:  5,590
1983:  17,925
1984:  7,000
1985:  12,647
1986:  5,198

from:  Katona, S.K., and J.A. Beard.  1990.  Population size, migrations and
feeding aggregations of the humpback whale (Megaptera novaeangliae) in the
western North Atlantic Ocean.  Report of the International Whale Commission
(Special issue 12):295-305.

An abundance estimate of 10,600 North Atlantic humpbacks was recently
calculated.  This estimate is based on extensive field work done by a
collaboration of scientists from seven different countries sampling all
areas of the humpback range, using the same protocol, during 1992 and 1993.
This is the most accurate estimate every calculated for this population.
While part of the increase in population size is probably due to better
methodology, the North Atlantic humpback population does appear to be
increasing.

from:  Smith, T.D., J. Allen, P.J. Clapham, P.S. Hammond, S. Katona, F.
Larsen, J. Lien, D. Mattila, P.J. Palsboll, J. Sigurjonsson, P.T. Stevick,
and N. Oien.  1999.  An ocean-basin-wide mark-recapture study of the North
Atlantic humpback whale (Megaptera novaeangliae).

I hope that provides you with the information you were wanting.  It should
keep your students busy for a while!

Nancy