> The crevice spawning strategy of _Cyprinella_ is part
> of the reason that red shiners, _C. lutrensis_, are such aggressive exotics
> when introduced outside of their natural range.
Correct me if I'm wrong, but I think crevice spawning has nothing (or
exceedingly little) to do with red shiner aggressiveness and resilience
outside of their native range. Unlike most other Cyprinella, red shiner do
not need crevices to spawn; they will spawn over gravel riffles, gravelly
pools, beds of aquatic plants, and sunfish (Lepomis) nests. Johnston notes
this a couple of times in the paper you mentioned -- that red shiner can
revert to broadcasting.
In addition, several other factors help account for the red shiner's
reslience:
1) Red shiner are relatively short-lived, which means they mature quickly,
usually within a year, and produce large numbers of young.
2) As fractional spawners, they do not lose their reproductive "window"
should environmental conditions temporarily prevent spawning.
3) Red shiner is naturally tolerant of turbid waters and unusually adaptive;
it has a knack for exploiting habitats that are degraded and inhospitable
for more specialized fishes. They're extremely tolerant of high temperatures
-- having been collected from a warm spring in New Mexico at 103.1F -‹ and
can tolerate pH values of 4-11, salinities up 10 ppt, and sudden changes in
temperature of 50-70F. Red shiner can also survive dissolved oxygen
concentrations as low as 1.5 ppm by swimming near the surface and
respirating from the relatively oxygen-rich film at the water's surface.
Although not immune to extreme pollution, siltation, floods, and drought,
red shiner are noted for their ability to cling on in poor environmental
conditions, and to "bounce back" even after most of their numbers have been
wiped out. The book *Fishes of Kansas* mentions two examples: a few days
after a major oil spill in a Kansas river in 1974, the red shiner was the
only creature found living. And just a few weeks after pollution from
feedlots killed nearly every fish in a prairie stream, also in Kansas, red
shiner were once again common.
> stonerollers are holding their own for the most part because of their
> nest-building and guarding strategy.
Interesting. Where did you get this information? Does this account for all
stonerollers, or just, say, the central? I ask because the range and
abundance of the largescale stoneroller is shrinking, with the central
stoneroller supplanting it in many areas. The central stoneroller is a more
ecologically "plastic" species that's found in a wider array of stream
conditions; as such it may be better capable of modifying its breeding
behavior to successfully spawn when stream conditions (e.g., temperature)
change as a result of human modification. In contrast, the largescale
stoneroller is less tolerant of reduced flow, turbidity, and silt. In
agricultural areas of Iowa, Illinois and southern Wisconsin, where stream
modifications are often the most acute, the largescale stoneroller has been
or is likely to be extirpated from streams in which it sympatrically occurs
with its more adaptable cousin. In the Ozarks of Missouri and Arkansas,
where habitats are less disturbed and water quality is higher, the
largescale stoneroller thrives and is apparently secure.
Chris Scharpf
Baltimore
/-----------------------------------------------------------------------------
/"Unless stated otherwise, comments made on this list do not necessarily
/ reflect the beliefs or goals of the North American Native Fishes
/ Association"
/ This is the discussion list of the North American Native Fishes Association
/ nanfa_at_aquaria.net. To subscribe, unsubscribe, or get help, send the word
/ subscribe, unsubscribe, or help in the body (not subject) of an email to
/ nanfa-request_at_aquaria.net. For a digest version, send the command to
/ nanfa-digest-request_at_aquaria.net instead.
/ For more information about NANFA, visit our web page, http://www.nanfa.org