- a Bridging the Watershed interactive lesson -

What is an anadromous fish? Anadromous fish are marine fish species that migrate each year to a spawning area. Each spring they leave the open ocean and travel into estuaries, coastal rivers, and freshwater rivers and creeks to release their eggs. The eggs are fertilized outside the female's body. If conditions are right, the fertilized eggs hatch within a few days. The tiny fish larvae will begin their lives in the upper estuary nurseries where marshlands and submerged aquatic vegetation (SAV) provide food and cover from predators. As the season moves into late summer and early fall, the juvenile fish leave the shelter of the upper estuary and begin a journey to the open ocean from which their parents came. During their life cycle, the fish encounter many perils and not all of them will survive to reproductive maturity. The survivors will complete the cycle by taking the same journey their parents took years earlier. The full-grown adults are greatly valued by animals and humans as a food source.

Fish history: Typical anadromous fish species were herring, alewives, sturgeon, and several species of shad. Early explorers in the Potomac watershed noted that these fish were in great abundance. Fisheries were to become an important part of the early American colonial economy. These fish provided an inexpensive and plentiful source of protein for colonists and their laborers. The fish were harvested annually and were preserved for year-long use as food in brine held in wooden casks and ceramic crocks. Harvesting continued well into the twentieth century for use in new products derived from the fish. Fish oils were needed for paints, medicine, and cosmetics. Whole fish and fish wastes were used to produce fertilizer and livestock feed or as bait in crab traps. Fish scales were once used in the manufacture of costume jewelry.

Over the course of time, some once common species of anadromous fish have all but disappeared. Atlantic sturgeon is one such species. Today there is a moratorium on harvesting American shad. There are many causes for the decline of these species. Over-harvesting has certainly affected fish populations. However, most fisheries biologists agree that the steady decline in water quality and resulting loss of spawning and wetland habitats during the early and middle part of the last century has had the most dramatic impact. The annual migration or run is still significant for the herring and alewife. One can still see people gathering at bridges over creeks and along waterways in the early spring when the fish make their move upstream to begin again this timeless cycle of life.

About the game: The game traces the natural history of the anadromous fish. In the game, they begin their lives as developing fish embryos contained within the egg, then larval fish living and feeding in marshland nurseries. Later they move into the river and estuary to begin their journey to the ocean. Once in the ocean, they will require three or four years of growth to reach sexual maturity, whereupon they will begin the same migration their parents made, leaving the open ocean and entering coastal estuaries and rivers. Their upstream journey will eventually take them to the watersheds from which they originated. Once there, they will leave the spawn for a future generation and continuation of the cycle.