Movers and Shakers: River Chub

Meet the male river chub, an aquatic mover and shaker par excellence. In spring these robust minnows carry stones in their mouths to create nests, aka “redds,” that can span a metre wide and rise 30 cm or so. Truly herculean labour for creatures the length of ballpoint pens.

These aquatic stonemasons scour the streambed for the materials they need. Watching them lift large rocks recalls the effort of human weightlifters hoisting dumbbells.

After toiling for a day or more, the nests are complete, and the females arrive to inspect the quality of the males’ work. Big nests may signal males with the chops to father healthy, vigorous young. Larger nests also offer more nooks and crannies for the females to hide their eggs.

River chub male on his nest. Photo by Don Scallen.

River chub male carrying a stone. Photo by Don Scallen.

River chub male surrounded by smaller females, rosyface shiners also present. Photo by Don Scallen.

Perhaps the females are also charmed by the winsome bumps or tubercles, that adorn male river chub heads during breeding season. The males further heighten their appeal by engaging in a sort of piscine tango, enticing females to join them on the redds by shaking their bodies.

Other minnow species, including common shiners and rosyface dace breed on river chub redds. Why do the hard work of nest making if another species can do it for you?

Then there are the aquatic brigands, like longnose dace, that arrive at river chub nests with nefarious intent. They scarf down the eggs laid by the chub and the other spawning minnows.

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The breeders and the egg stealers make a river chub nest a happening place in springtime. Fish of several species swarm above the nests. For observant naturalists it’s a treat to watch.

Male river chub are ecosystem engineers, creating crucial nesting habitat for themselves and other minnow species. That they do this by carrying thousands of stones in their mouths is another great example of the endless wonders of nature.

River chub breeding

A male river chub building his nest