anadromous

American  

[uh-nad-ruh-muhs] / əˈnæd rə məs /

adjective

1. (of fish) migrating from salt water to spawn in fresh water, as salmon of the genera Salmo and Oncorhynchus (distinguished from catadromous).

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anadromous British  

/ əˈnædrəməs /

adjective

1. (of fishes such as the salmon) migrating up rivers from the sea in order to breed Compare catadromous

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anadromous Scientific  

/ ə-năd′rə-məs /

1. Relating to fish, such as salmon or shad, that migrate up rivers from the sea to breed in fresh water.

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Etymology

Origin of anadromous

First recorded in 1745–55, anadromous is from the Greek word anádromos running upward. See ana-, -drome, -ous

Explanation

Anadromous is used to describe animals, usually fish, that live in the ocean but travel back up through rivers so they can breed in fresh water. The word anadromous comes from Greek, and means "running upward." When fish swim from the oceans up to the rivers, it's called a run. The most famous version of this is a salmon run, where salmon, an anadromous species, swim all the way from the ocean up to the creek they hatched in. They lay eggs there so that a new generation of salmon will hatch and complete the cycle all over again.

Example Sentences

Salmon are anadromous, meaning they spend much of their lives in the ocean but return to freshwater rivers to spawn.

From BBC • Apr. 3, 2024

“These would represent extraordinary and unprecedented levels of anadromous fish habitat losses and degradation, dramatically expanding the unacceptable adverse effects identified in the 2020 plan,” the document stated.

From Seattle Times • Jan. 31, 2023

They interfere with, or block altogether, the migration of anadromous fish such as salmon and steelhead.

From Washington Times • Nov. 15, 2017

Even though officials have made it easier for the anadromous fish to migrate from the ocean to freshwater rivers where they are born, “the fish aren’t coming back,” he said.

From Washington Post

Upstream passage of anadromous fish through navigation locks and use of the stream for spawning and nursery habitat, Cape Fear River, N.C., 1962-66.

From Whales, Dolphins, and Porpoises of the Western North Atlantic A Guide to Their Identification by Caldwell, David