Million Minnow March

At about 6:15 p.m. today, Grandpa and I noticed some lake weed floating in toward shore.

Ken observes the strange phenomenon

The funny thing was, that clump of weed seemed to be moving toward shore a bit faster than you'd think, given the stillness of the lake. And we really knew something was up when the clump suddenly disappeared under the water near shore.

When I went out to the dock to investigate, I saw hundreds of tiny minnows moving from east to west along the shore. We do see minnows from time to time, but never so many and never moving with such purpose in one particular direction.

Peering over the edge of the dock with camera. Bottom to top of frame is east to west.

This went on for so long I finally went inside and had Pa come out. And even though he doesn't move fast, he was fast enough. He stood and watched till his legs complained, and when he got back inside the minnows were still coming.

Every so often, the column would react to sound, movement, or tiny bugs hitting water's surface. But within seconds they would reorganize and resume their migration. This went on for over an hour maybe longer if it started before we noticed.

What gives? Must Google.

Found this poem by Richard Brautigan.

And this journal article, which describes shoaling behavior in response to predation.

Another journal article, this one about shoaling as a defense against parasites.

It is apparently not related to spawning, which occurs in early summer.