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Fallfish build stone-pile nests in Massachusetts streams

May

The fallfish, the biggest minnow in Massachusetts, builds its nest by carrying small stones in its mouth and piling them into a mound. MassWildlife says some of the mounds are nearly a foot tall, and other kinds of fish lay their eggs in them too.

Why this time of year

MassWildlife says that during the spring breeding season in May, adults move to gravel areas in tributary streams with moderate flow and clear water, and build pyramid-shaped nests.

How to notice it

  1. Pick a clear, gravel-bottomed stream with a moderate current and look from the bank for a rounded heap of clean stones on the bottom that stands out from the flat gravel around it.
  2. Watch the mound for a few minutes. MassWildlife says fallfish often spawn in communal groups, and several kinds of fish may use the same nest.
  3. Look for males with bumps on their heads. MassWildlife says breeding males grow these and use them to defend their territory.
  4. Leave the stones where they are. The mound holds eggs, and the eggs hatch in about six days.

Try this with kids: If you had to build a pile of stones using only your mouth, how many trips would it take? Look for a mound a fish built that way.

Safety

  • Watch from the bank. Spring streams can run high and fast, and the rocks are slippery.

Sources

  • web.archive.orgRead 2026-11-10 (archived MassWildlife page). 'This minnow is the largest found in Massachusetts.' 'During the spring breeding season in May, adults migrate to areas with gravel and create a pyramidal nest by moving small stones with their mouths. Some of these nests can be nearly a foot tall and are often used by several species of fish for spawning.' 'Spawning aggregations are often communal'. Breeding males develop 'large tubercles (protruding bumps) on their heads that are used for territory defense'. 'Fish hatch within about six days'. 'rare in the eastern part of the state but is very common in the Connecticut River Basin and can be readily captured in the central and western parts'. Spawns in 'tributaries containing moderate flow, clear water, and rock and gravel'.
  • nj.govRead 2026-11-10 (New Jersey Division of Fish and Wildlife fact sheet, primary state agency). 'males construct nests of gravel by carrying stones in their mouths: nests can be 4 feet wide and 1.5 feet tall'; 'largest minnow native to eastern North America'; 'clear streams... with gravel bottom'.

Checked against these sources on November 10, 2026.

In the guide for May

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