catadromous

Amphidromous

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‘O’opu nakea (Awaous stamineus) is an important cultural resource for Indigenous Hawaiians.  All five Hawaiian gobies exhibit amphidromous life cycles.

An amphidromous fish is a type of diadromous fish which migrates between fresh and saltwater.  Unlike anadromous and catadromous fish, which migrate explicitly for the purposes of breeding, amphidromous fish migrate for other purposes.  A typical cycle of amphidromy includes eggs hatching in freshwater or estuaries, larvae drifting out into the open ocean to feed and grow, juveniles returning to freshwater to feed and grow, and adults reproducing in freshwater.  Gobies, such as those found on volcanic islands in the Pacific, exhibit an amphidromous life cycle.

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

Diadromous

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George S. Myers defined the term diadromous to refer to fish that migrate between fresh and salt water.

George S. Myers defined the term diadromous to refer to fish that migrate between fresh and salt water.

Diadromous fish migrate between fresh and salt water.  This term, coined by George S. Myers in 1949, refers to both anadromous and catadromous fishes.  Diadromous life history strategies have evolved in numerous fish taxa.  The complex life cycles do require complex osmoregulatory adaptation but the advantages of the given environments for specific life stages of the fish outweigh the costs.

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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!