marine and fresh water

Catadromous

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Eels have a unique larval form, leptocephali, which can utilize marine currents to travel long distances.

Eels have a unique larval form, leptocephali, which can utilize marine currents to travel long distances.

A catadromous fish hatches and spawns in salt water but spends most of its life in fresh water.  Catadromous life cycles are much less common than anadromous life cycles.  American and European Eels (Anguilla rostrate and A. anguilla, respectively) are among the more famous fish that utilize this unusual migration pattern.  They have a highly specialized larvae, leptocephali, which resemble a transparent leaf.  Their specialized shape allows leptocephali to ride marine currents to the continental shelf using relatively low amounts of energy.  In coastal waters, they metamorphose into glass eels.  As they continue to grow and start developing pigmentation, they enter the yellow eel phase.  Yellow eels migrate into estuaries and onto fresh water where they will remain until they reach sexual maturity as a silver eel and return out to sea to spawn.

For more information, check out the “CAN YOU SAY ANADROMOUS, CATADROMOUS, AMPHIDROMOUS, OCEANODROMOUS, OR POTAMODROMOUS?” post on The Fisheries Blog!

Anadromous

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Pacific salmons are well-known examples of anadromy. They live most of their lives at sea but spawn in fresh water

Pacific salmons are well-known examples of anadromy. They live most of their lives at sea but spawn in fresh water

An anadromous fish hatches and spawns in fresh water but spends most of its life in the salt water.  This dual life cycle allows the younger fish to grow and feed in the less perilous fresh water habitats (fewer predators in the smaller systems) and the older, larger fish to grow and feed in the marine systems, where there is a greater prey base.  Migrating between fresh and salt water requires complex osmoregulatory adaptations.  Some species, such as Pacific salmons, only transition between fresh and salt water twice, migrating to salt water early in life and then migrating back to freshwater to spawn once and die (a semelparous reproductive strategy).  Other species, such as Striped Bass (Morone saxatilis) will migrate between fresh and salt water every year to spawn (an iteroparous reproductive strategy).

For more information, check out the “CAN YOU SAY ANADROMOUS, CATADROMOUS, AMPHIDROMOUS, OCEANODROMOUS, OR POTAMODROMOUS?” post on The Fisheries Blog!

Striped bass are anadromous fish that migrate between fresh and salt water every year to spawn

Striped bass are anadromous fish that migrate between fresh and salt water every year to spawn