Can you say Anadromous, Catadromous, Amphidromous, Oceanodromous, or Potamodromous?

By Patrick Cooney

Can you say 'potamodromous' and can you guess what it means?

A) A mood disorder caused by eating too many potatoes.
B) A dinosaur that lived in water but could crawl across land.
C) A migration of fish entirely in freshwater.

A) B) C)

If you pronounced it like 'poe-tuh-moe-droe-miss', then you are off to a great start.   But what about the meaning?  For such a strange word, it simply signifies option C, a migration of fish entirely in freshwater.

Many fishes migrate long distances to spawn.   In order to better understand these movements, scientists have classified these migrations into several categories.

Anadromous fish are born in freshwater, then migrate to the ocean as juveniles where they grow into adults before migrating back into freshwater to spawn.

Examples: salmon, smelt, American shad, hickory shad, striped bass, lamprey, gulf sturgeon




Catadromous fish are born in saltwater, then migrate into freshwater as juveniles where they grow into adults before migrating back into the ocean to spawn.

Examples: American eel, European eel, inanga, shortfin eel, longfin eel



Amphidromous fish are born in freshwater/estuaries, then drift into the ocean as larvae before migrating back into freshwater to grow into adults and spawn.

Examples: bigmouth sleeper, mountain mullet, sirajo goby, river goby, torrentfish, Dolly Varden





Potamodromous fish are born in upstream freshwater habitats, then migrate downstream (still in freshwater) as juveniles to grow into adults before migrating back upstream to spawn.

Examples: sicklefin redhorse, lake sturgeon, robust redhorse, flathead catfish





Oceanodromous fish are born near spawning grounds, then drift on ocean currents as larvae before settling as juveniles to grow into adults before migrating back to spawning grounds.

Examples: black grouper, mutton snapper, goliath grouper






Although these different types of migration classifications may be difficult to pronounce, they are important to understand in order to help maintain connectivity between critical habitats.

Considering that many of these fishes use rivers as migration corridors:

1) What impacts might you expect dams to have on the ability of fish to get from one location to another?

2) Might impacts to riverine ecosystems propagate impacts on oceanic ecosystems, and vice versa?

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Also check out last week's post about why fish need floods.