The real point of this article, though, is an examination of why many of
these species have gone from being common in parts of the Rio Grande and
Pecos Rivers to being locally extinct or Federally listed. Their working
hypothesis is that because the rivers are largely dammed, the downstream
transport of eggs and larval fish is blocked. Eggs and larvae can be
transported as far as 350 km. It appears that the reproductive strategy of
these fishes is to produce these mobile larvae, which can grow downstream
and then move upstream as adults, and also that as long as adults survive in
an upstream area, with better water flow and steady temperatures, they can
recolonize downstream areas if they become depopulated from drought or high
temperatures. Dams interefere with this strategy, and examination shows that
the extirpated or endangered populations are those downstream from dams.
Dams also interfere with normal riverine water flow, affecting for instance
temperature and current flow.
The primary focus of why dams are bad has been on salmonids, a commecially
important and fairly charismatic group. But dams can also affect other
species in ways that we don't immediately consider. Sherwin Williams wants
to cover the world with its paint; it seems that river management practices
in this country want to cover the US with Gambusia and largemouth bass (I
apologize for preaching to the converted).
"situated on the less-than-free-flowing Tennessee"
>In Kansas, there are two strains of Speckled Chub. One sub-species lives
>in the Kansas River and it's tributaries in the northern half of the
>state. The Kansas or "Kaw" river is a tributary of the Missouri. To the
>south lives the other sub-species. This one is listed as endangered. I
>don't remember if that is a state or federal listing though. It is found
>in the drainages of the Arkansas River (or was anyway). The Arkansas has
>suffered greatly over the past century from too many people taking too
>much water out of it. The Arkansas River Shiner (Notropis girardi <I
>think is it's scientific name>) is probably gone or close to it in Kansas
>now. The Kaw is in trouble in a different way. Federal reservoirs,
>channelization and "modern" agricultural and industrial interestes have
>been at war with the river for decades now. The Kaw is the river system
>in which Topeka Shiners, Pallid Sturgeons and other species once thrived.
>Sadly, no more. Clean up efforts are underway or being discussed,
>unfortunately it may be too late for some species.
>Just airing a few thoughts this morning...
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