what is the estimated number of dolphins on the planet?

Hello frycek-ga,

Perhaps this will interest you, although it's from 1995 publication. 

"According to OLDEPESCA, in 1992 the dolphin mortality rate as a
result of tuna fishing was 15,000, equivalent to 0.16% of the total
global dolphin population of 9.5 million."

"But by 1993, the mortality rate had dropped to 3,600 dolphins, or
just 0.04% of the total population, meaning that the region is now
complying with internationally recognized standards."

LATIN AMERICA DATA BASE
Chronicle of Latin American Economic Affairs
ISSN 1054-8874      
Volume 10, Number 31   
August 17, 1995

http://ssdc.ucsd.edu/news/claea/h95/claea.19950817.html

--Bobbie7

Hi Frycek,
I don't think you are going to get anything close to an accurate
answer for this question. There are at least 40 species of dolphin and
porpoise (there is some argument about whether some species are
subspecies of another), and very little is known about most of these.
Population estimates range from several million (and no more accurate
than that) for some species such as the common dolphin, delphinus
delphis, to as few as 50 for the Yangtze river dolphin, Lipotes
vexillifer.

http://ourworld.compuserve.com/homepages/jaap/lag-acut.htm
"In the eastern North Atlantic the Atlantic white-sided dolphin
population size is estimated to be about 40% of the size of the
white-beaked dolphin population (relative estimate based on sightings.
There is no absolute size estimate for either species)"
The above are two regularly see oceanic dolphins, yet there is no size
estimate available.
Even taking taking the best known species, the bottlenose dolphin
(Tursiops truncatus) of Flipper fame, while there are many studies
which give local populations, eg. The Shannon dolphins in Ireland, the
Moray Firth dolphins in Scotland, there is no global assessment other
than "No longer endangered".

http://www.shannondolphins.ie/sdwf/research.htm
http://www.morayfirth-partnership.org/Dolph2.html
http://www.enchantedlearning.com/subjects/whales/species/Bottledolphin.shtml

Finally, just as a matter of opinion, I would think that the figure
quoted in the comment above is a gross underestimate, which I suspect
refers to just one species.


Sources:
Search terms:
"dolphin population"
"Bottlenose dolphin population"

Some reference books of mine and personal knowledge of the subject

Hi!

"Various dolphin species are abundant in the North Pacific, examples
of population estimates are: the common dolphin at 3,179,000, the
striped dolphin at 1,485,000, the spotted dolphin at 1,782,000 and the
spinner dolphin at 1,582,000 (Source: Tsutomu Tamura and Seiji Ohsumi,
Estimation of total food consumption by cetaceans in the world’s
oceans, Tokyo: ICR, 1999)."

http://www.highnorth.no/iwc2000/briefings/Numbers.htm