I can think of only one place where hybrid minnows were really abundant, more than 20% of fish. South Stanley Creek in eastern Gaston Co NC, where redlip shiners were introduced into native greenhead shiner habitat. I recall lots of redlips and hybrids, and very few pure-looking greenheads. That was 15 yrs ago. I oughta go back and see whats there now. It was an agricultural watershed beginning to urbanize back then (i was surveying for a new sewerline) so it may now be shiner-less. (Redlips, greenheads and yellowfins are all closely related and I'd guess their hybrids are pretty "fit" and fecund).
And in captivity greenhead can definitely cross with redlip [so do not keep them together if you don't want hybrid].
Edited by tricolor, 16 February 2012 - 05:19 PM.