amphidromie

Amphidromy is a form of diadromy in aquatic organisms in which migration between freshwater and marine environments occurs, but the migratory movements are not primarily driven by reproduction. The term derives from Greek roots meaning “both ways running,” reflecting the alternating habitats used during life cycles.

In amphidromous species, the life cycle typically involves a larval or juvenile stage that moves between the sea and freshwater environments, often for dispersal rather than to reach a breeding site. A common pattern is that adults inhabit one habitat (often freshwater), reproduce there, and after hatching, the offspring migrate to the coastal or open-sea zone to develop before returning to the freshwater habitat as juveniles. The exact timing and direction of migrations can vary among species and populations, and some species may exhibit deviations from the typical pattern.

Amphidromy is distinct from anadromy and catadromy, where movements between habitats are tightly linked to reproduction (spawning in one habitat with juveniles maturing in the other). Amphidromous migrations may serve colonization, gene flow, and larval dispersal rather than a reproductive strategy. The pattern is common in tropical and subtropical river systems with accessible estuarine zones and is particularly noted among certain gobies, freshwater prawns, and related groups.

Ecological and conservation concerns for amphidromous species include habitat fragmentation, dam construction, water quality changes, and barriers that disrupt larval dispersal and juvenile recruitment. Maintaining connectivity between rivers and coastal habitats is important for sustaining these life histories.