[Odonata-l] what a difference a wing makes

[Dennis Paulson]

A recent paper published in the journal Fisheries concludes that  
nearly 40 percent of all species of freshwater and anadromous fishes  
in North America (Canada, US, Mexico) are in jeopardy.

Details here: http://www.ens-newswire.com/ens/sep2008/2008-09-09-02.asp

There is a link to an interactive map of North America with  
ecoregions. Click on any of them, and a list of species that are  
vulnerable will pop up.

The report shows that 61 fishes are presumed extinct, and 280 species  
are classed as endangered. In addition 190 are considered threatened,  
and 230 are listed as vulnerable to extinction. The fishes are  
analyzed down to the level of subspecies and even populations, and in  
many case it is only particular populations that have become rare,  
not the entire species, but nevertheless it is obvious that the  
situation is dire.

Regions with the greatest levels of endangerment include river  
systems such as the Tennessee and Mobile and many of those along the  
southeastern coastal plain of the US. The California Central Valley,  
western Great Basin, Rio Grande, and rivers of central Mexico also  
support a high diversity of species and have many of them at risk of  
extinction.

I assume odonate enthusiasts are interested in this information, as  
our dragonflies share the waters with those fishes. The interesting  
thing is that dragonflies do not seem to be similarly endangered.  
Only a few species in Canada and the US are of special concern  
(information much more sketchy for Mexico). This is presumably  
because they can fly, so the adults can disperse to new habitats as  
they appear or from declining to improving habitats, when those are  
available. On the average, odonates have much larger ranges than  
freshwater fishes. Fish are pretty much limited to where they are,  
with no recourse when wetlands over their entire range have declined.

On the other hand, it is possible that odonates are also more  
resistant to the numerous environmental problems encountered by fish.  
One I can think of is fishing pressure. There isn't much of a fishery  
revolving around any species of odonate! Dragonfly larvae could also  
be more resistant to pollution, siltation, reduced oxygen levels, and/ 
or temperature fluctuation. They could have greater habitat breadths  
than fishes, species for species. Or does it all come down to those  
two pairs of wings?

We know a lot about the fishes that are in trouble, and it would be  
interesting to assess odonate faunas in areas that support the  
greatest number of these species.

-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson at comcast.net



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