Figure 5. Concepts of anadromy, amphidromy and potamodromy in acipenseriforms. These terms are defined and further explained in
the text. Patterns of spawning migrations used by fish employing these different life history patterns are indicated in text below each
condition. Once a spawning migrant enters a river, it typically follows one of three spawning migration patterns. These are keyed to the
drawing as follows: one step -short or long migration, spawning; shorttwo step -migration, overwintering, short migration, spawning;
long two step -migration, overwintering or oversummering (or both), long migration, spawning. See text for additional explanation.
ed with spawning activities, although in many cases,
anadromous sturgeons may re-enter estuaries or
even freshwater reaches of rivers during summer
months to feed and amphidromous sturgeons may
move from one riverine or estuarine foraging site to
another. Fish with mature gonads that migrate up-
stream during the spawning season are commonly
referred to as spawning fish orspawners,regardless
of whether they successfully complete spawning.
The age at first spawning migration is an important
life history parameter for all species of sturgeons,
although it is unknown in many cases. Emigration