Re: NANFA-- RE: Speckled Chub fish

Christopher Scharpf (
Wed, 04 Feb 2004 22:16:22 -0400

> Other species within the genus- others endangered or not?

Macrhybopsis aestivalis -- speckled chub
Macrhybopsis australis -- prairie chub
Macrhybopsis gelida -- sturgeon chub (listed in IL, KS)
Macrhybopsis hyostoma -- shoal chub
Macrhybopsis marconis -- burrhead chub (threatened in Mexico)
Macrhybopsis meeki -- sicklefin chub (listed in KS)
Macrhybopsis storeriana -- silver chub
Macrhybopsis tetranema -- peppered chub (listed in KS, NM)
Macrhybopsis sp. -- Fall Line chub
Macrhybopsis sp. -- Florida chub
Macrhybopsis sp. -- Pine Hills chub

> what makes species more vulnerable? Known factors contributing to its
> population status-habitat destruction, human population encroachment, etc.?
> -Outlook for the future of this species population numbers- reason for
> optimism or concern? -Management plan-any programs underway to bolster
> populations or reserve habitat?

Big rivers attract big dams and big irrigation projects. So it should come
as no surprise that dams and their associated irrigation diversions are the
biggest threats facing Macrhybopsis species. The peppered chub has been
extirpated from approximately 90% of its historic range and persists only in
two widely disjunct areas, one in Kansas and the other in a stretch of river
between New Mexico and Texas.

The shoal chub has been extirpated from approximately 55% of it historic
range in the Arkansas River Basin, but remains widespread in the Mississippi
River Basin.

While the direct causes of these extirpations cannot be assigned with
certainty, dams play a major role by altering the natural flow and
temperature cues these chubs need to spawn, and by blocking the upstream
migration of chub larvae and the downstream dispersal of adults. Another
hazard is that reservoirs are stocked with sight-feeding fishes that eat
Macrhybopsis chubs and/or out-compete them for food.

In arid and drought-prone regions of the Great Plains, reservoirs,
irrigation diversions, and groundwater depletions have caused some peppered
chub streams to run dry. The stocking of peppered chub into suitable habitat
where it formerly occurred has been recommended, but consistent monitoring
and repeated stockings may be necessary given the harsh environment of
prairie streams and the formidable barriers that stand in the way.

Luckily, despite 35 years of dams, sicklefin and sturgeon chubs remain
present in substantial numbers where turbidity levels and flow regimes still
provide some semblance of their natural characteristics. This is not to say
that the two species haven't seriously declined over the years. Indeed they
have. Sicklefin chub currently occupy just 54% of their historic range,
while sturgeon chub occupy 55% of theirs. These numbers are good enough to
keep sicklefin and sturgeon chubs off the federal endangered species list,
but careful monitoring and management will be necessary to make sure they
stay off.

The silver chub is staging a promising comeback in Lake Erie. Last seen in
the lake in 1953, the silver chub was killed off by industrial waste and
other toxic substances that caused excessive algae blooms. When the algae
died and decayed, they used up all the oxygen near the lake9s bottom, where
silver chub live and feed. Stricter pollution controls mandated by the Clean
Water Act and, ironically, the introduction and spread of the exotic zebra
mussel, have helped clean Lake Erie's waters. The silver chub are now
finding their way back to the lake from tributary streams. And although most
of the native mollusks that were the staple of the chub's diet have been
squeezed out by the zebra mussel, the chub are finding that the zebra mussel
suit their palate just fine. Wildlife officials are hoping that if the
silver chub continue to increase in numbers, sportfish that like to eat
them, especially pike and muskies, will increase in numbers too.

Literature references available upon request.

Chris Scharpf
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