This is what I was talking about:
Breeding: Herichthys tamasopoensis starts breeding activity as the rainy season stops in the Pánuco area and the level of the river decreases. This could be as early as mid December, when the water temperature and transparency increase. Areas of bigger reproductive concentrations are found below waterfalls. Around that time H. tamasopoensis males commonly develop a big nuchal hump, which remains on their foreheads until spawning takes place, making it a feature either designed to impress females or other competing males. Males then protect territories, the areas with higher oxygen content below falls, which are also shallow enough to permit algae growth are the favorite zones, and pair concentrations in those areas are much bigger, and territories smaller. Females are attracted to established territories, primarily to those found in the mentioned areas. The price of having real estate in these highly desirable zones is a greater expense of energy that pairs once established have to devote to protect their borders against neighboring pairs. Males as small as eight centimeters TL participate in pair formation, although they normally just procure the peripheral areas of the colonies, or are forced to breed in isolated zones.