Male Yellow Labs get about 10"...females smaller. Typical Hericthys attitude. Pure Yellow Labs are hard to find as they are hybridizing with a H. Carpinte "Rio Verde" that's in the same water shed. The yellow labs are limited to Media Luna, Mexico and protected from collection by the Mexican government.
Here's a few pictures. The first is from Taninul...a small spring in Mexico. Blue Labridens...The blue labridens and Herichthys pantostictus are the same fish, blue labridens being a riverine variety of Herichthys pantostictus, which has its type locality in Laguna del Chairel (Lacustrine form). The Blue Labs from this collection locale are one of a kind:
Here's more...The fish pictured is a geographical variety of Herichthys pantostictus from Rio El Salto. Diagnostic features for H. pantostictus include the blotch behind the pectoral fins, red in H. pantostictus and purple in H. labridens. The body is more elongated and covered (partially sometimes) with red blotches over it, as you can see in the rear half of the pictured fish. Beautiful fish!
White Labridens fom Rio Tamasopo
The fish on the left hand side is a naturally occurring hybrid with Labridens and another larger predator fish called Hericthys Steindachneri.
Media Luna Yellow Labridens
Exact same fish under stress
To the best of my knowledge I'm one of two people in the country that have sucessfully bred the Yellow Labridens. I got rid of most of them a while back...and have five adults and about 20 smaller grow outs.