Amphidromy is one kind of diadromy (meaning two migrations) in which newly hatched larvae (sometimes referred to as free-living embryos) are swept downstream into the ocean where they live for a period of time (as much as six months in one Hawaiian fish species) before migrating back into fresh water where they eventually mature, reproduce, and complete the life cycle (Figure 1). Amphidromy is a boon to stream restoration because, once a problem is corrected, the recruitment of native animals into the stream will occur naturally. No biologist is needed to restock formerly altered streams.
Figure 1. Amphidromous life cycle of indigenous stream animals.