This short observation shows a spawning aggregation containing seven species of fish in a Bluehead chub (Nocomis leptocephalus) nest in Toms Creek, New River Drainage in Blacksburg, Virginia. These species are Mountain redbelly dace (Chrosomus oreas), White shiner (Luxilus albeolus), Rosefin shiner (Lythrurus ardens), Rosyside dace (Clinostomus funduloides), Central stoneroller (Campostoma anomalum) and Crescent shiner (Luxilus cerasinus).
Bluehead chub with it’s impressive nesting behavior provides a rich natural history for ecologists. Brandon Peoples who recorded this short observation is a graduate student at Virginia Tech investigating the role of chubs in river landscapes.
External fertilization is a wasteful event. A large fraction of gametes is washed off without finding each other especially in fast moving waters like streams. In fact even in the oceans fish come together to spawn and increase the chances of sperms fertilizing eggs. Large groups of circling fish schools can create vortices that help fertilization. These spawning aggregations can be very large and in an ocean setting can even attract whale sharks.
Every spring, mature male chubs construct nesting mounds of gravel up to a meter wide in fast flowing water. In a single day, a hand sized male chub may transport approximately 7,000 pieces of stones from as far as 23 meters away.
Chub nests serve their purpose well. They not only attract females but also other species of fish. More than 30 minnow species are known to spawn on chub nests some with dazzling colors as seen in the featured video on top of this post. Multi-species spawning aggregations on chub nests show the importance of this species for the reproductive success of a whole fish community.
Many chub nest associating minnows are much more successful at colonizing degraded habitats. In degraded habitats with silt accumulation finding clean gravel to spawn is rather difficult. Chubs therefore can create patches of clean gravel in a stream full of silt and this may explain why most minnows don’t occur in the absence of chubs. Mound-building fish species including Bluehead chubs are considered as keystone species in biological communities.