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catadromy

/kəˈtædrəmi/

Downstream migration of fish to reproduce

From Greek kata- (down) + Greek drom- (running).

noun
kata-
Ancient Greek
κατά (katá)
Down, downward, or toward a lower place
Scientific English combining form
cata-
Used in zoological terms for downward or descending movement
drom-
Ancient Greek
δρόμος (drómos)
A running, course, or route
Scientific English combining form
-drom-
Relating to movement or a migratory course
Combined
καταδρομία (katadromía)
Greek-based formation meaning a downward course or movement
Scientific English
catadromy
The condition of being catadromous, especially migration from freshwater downstream to the sea for breeding
Modern English
catadromy

Picture a fish doing the aquatic equivalent of leaving home: it grows up in a river, heads downstream, and eventually reaches the sea to reproduce. The name combines Greek κατά, “down,” with δρόμος, “a course” or “running”—so catadromy is essentially a “downward course.” The second root has an unexpectedly busy family: a hippodrome was a track for horses, a palindrome is something that “runs back” the same way, and a dromedary is linked to the idea of running. Aristotle was already describing fish movements in the fourth century BCE, long before zoologists equipped the behavior with this tidy Greek label. Remember the image: anadromous fish climb the river like salmon going upstairs; catadromous fish take the downstream road to the sea.

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