NANFA-- fish distributions

Dave Neely (rheopresbe_at_hotmail.com)
Wed, 08 Oct 2003 16:48:56 -0500

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A while back there was a thread on what native fish taxa had the largest
distribution in North America. Well, I couldn't get this one out of my
skull, so I started playing around on my free time... and happened to
re-read the opening chapter of Hocutt and Wiley (1986), Ichthyofaunal
Patterns on a Geographic Grid, and it hit me...

I started poking around and found a Lambert azimuthal equal-area projection
of North America with river basins on it . This projection is scaled so it
should portray areas as equivalent across the map. I overlaid a grid scaled
at approximately 100km on each side (so each cell has a total area of
roughly 10,000 km2) onto the map, made a whole bunch of photocopies, and
then reconstructed ranges of several of the candidates for "most broadly
distributed" onto these maps, leaving out introduced populations. I
generally used ranges as depicted in Lee et al. (1980) and Scott and
Crossman (1973), although where I knew of additional range extensions, I
included these as well. For taxa with ranges extending into Eurasia, I did
not include the Eurasian portion in the estimate.

Grids were scored for presence/absence, and the number of grids occupied
summed to give a very rough , first-order approximation of range size, in
km2 (and no, I'm not even going to try and derive an error measurement!)

Drum roll, please...

The winner is...

Esox lucius, range 11,130,000 km2.

Close runners-up were Lota lota, 10,560,000 km2 and Catostomus catostomus,
10,410,000 km2.

Other widely-distributed fishes weren't even in the same ballpark.
Rhinichthys cataractae 811,000 km2
Semotilus atromaculatus 513,000 km2
Aplodinotus grunniens, 440,000 km2

As a frame of reference, the total land area of Canada, Mexico, and the US
is approximately 21,600,000 km2.

Hope this satisfies the curiosity of the rest of you folks who lost sleep
over this...

cheers,
Dave
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