Chub Mound

Our stream ecology research team took to the water for an afternoon snorkel trip down 2 miles of Bull Creek.  One cool find was these under water gravel edifices created by a male chub.  The species I have seen and caught in our swimming hole is the hornyhead chub (HHC)  Our common Missouri chubs are 5 to 7" long members of the minnow family.

Horneyhead Chub on Bull Creek - Dave Fleshman

Like males of some other species including us, when looking for love the HHC gets dressed up to attract a lady chub.  In this case he develops large pointed tubercles on the top of the head and a red or orange spot on the upper opercle behind the eyes.

HHC - Dave Fleshman

Like bower birds and other love-struck males that build a love nest to attract a female, the river chub creates a mound nest of gravel for mating.  He does it one piece at a time, first picking up pebbles in his mouth and moving them to the side, creating a shallow pit with a rock rim.  Next he picks up uniform 1cm pebbles from up and down stream, creating a mound.  This can have up to 10,000 pebbles!  Talk about chapped lips!

The mound will have a trough on top and when she enters it he will hold her down as she releases some of her 500-1000 ova.  From then on, the male will fiercely guard the nest, head butting intruders.

Ovisac with several hundred glochidia *

Chubs are an indicator of high quality water and are intolerant of pollution.  They are a valuable member of stream species and food for other fish.  Their diet includes insects, filamentous algae and even the eggs of mussels. 

"Fresh-water mussels release small masses of microscopic larvae known as glochidia in a loose gelatinous matrix or ovisac. The glochidia encyst on the gills of river chubs where they metamorphose into juveniles and then drop off. It is suspected that the river chub feeds on the gelatinous masses as it does drifting insects." Wikipedia

* Barnhart, M. C.  2008. Unio Gallery:  http://unionid.missouristate.edu.