Some fish live in two different habitats: Fresh and salt water. American shad, herring, striped bass, and American eels do that. These fish are found in the Delaware River. American shad and herring are also found in Pennsylvania's section of the Susquehanna River. Shad, herring, and striped bass are anadromous (eh-nad-ro-muss) fish. They are born in fresh water and grow up in the ocean. Adults return to fresh water to lay eggs. Eels are born in salt water and grow up in fresh water. They are catadromous (cat-ad-ro-muss).
When the leaves turn colors and begin to fall, these groups of fish begin their travels to the sea. It's like a parade of fish marching back to the ocean. On the Susquehanna, adult and young American shad and herring make the move. On the Delaware River, striped bass of all ages, shad, and eels migrate out to sea. Scientists tell us that these fish move when river flows increase. They "ride the wave" made by rain in October and November.
Unfortunately, they run into some hazards before reaching the sea. Dams slow their journey. Scientists have conducted many studies to find out how fish make it through dams. On some dams, they make it through the turbines safely. Some turbines are not so good for fish. These dams have ways to help fish around the turbines.
Once at sea, the fish travel in large schools, just as you do on school buses. The fish in these schools are from many different rivers. They follow warm water up and down the Atlantic Coast. American shad and herring do this for three to five years until they are adults. Stripers also do this until they become adults.
Then, as they are swim-ming up the coast, they pass the different rivers where they were born. The fish born in that river break off from the school and move into fresh water. This is like your getting off the school bus at your stop. The adults move up those rivers and have their young. Then, in the fall, the parade happens all over again.
Eels are a little different. Young eels spend their time in the Delaware River and its tributaries. Each fall, the adults move out to sea to spawn. In the spring, young eels migrate up the rivers their parents came from.
This is the cycle of fish migration!
September/October 1998 Angler & Boater
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