# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DeC8jllyx8Z
- **Gondola URL:** https://gondola.cc/posts/71131427-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/6696d965ce.jpg
- **Posted:** 2026-10-03T20:45:51.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

A dead fish can swim upstream. It has been measured in a lab.

In 2006, researchers from MIT and Harvard (Beal, Hover, Triantafyllou, Liao, Lauder) placed a dead trout behind a cylinder in a flow tank. The cylinder shed a Karman vortex street: vortices peeling off alternately from each side, producing a sinusoidal pattern of rotating flow downstream. The lifeless body resonated with those vortices, flexed passively, and moved forward against the current.

How it works:
- Each vortex creates a local low-pressure region and a sideways velocity component
- A flexible body tilts into that pressure gradient, much like a sail tacking upwind
- When the body’s natural bending frequency matches the shedding frequency, it extracts energy from the flow
- Net thrust can exceed drag, so the body moves upstream with zero metabolic input

Live trout use the same physics. Liao’s 2003 work showed fish slaloming between vortices, a behavior called Karman gaiting, with sharply reduced muscle activity.

Why this matters for finding fish:
Every fish is solving an optimization problem with three variables:
- Safety: cover from predators (weeds, rock, timber, depth, shade)
- Energy: low swimming cost (current breaks, eddies, seams, stable temperature)
- Food: access to prey with minimal search effort

Where those three overlap is where fish hold. In a river, check behind boulders and bridge pilings, right where vortex wakes form. In a lake, look for edges: drop-offs, weed lines, points, and transitions between structure and open water. Predators wait where cover meets food.

Temperature and dissolved oxygen add constraints. In summer, many lakes stratify, and fish often hold near the thermocline boundary.

Good fishing is applied fluid dynamics and ecology.

#stemantics #fluiddynamics #biomechanics #fishing #ecology

## Stats

- **Views:** 5,652
- **Likes:** 238
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- **Comments:** 1

## Tags

biomechanics, fishing, fluiddynamics, ecology, stemantics

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