The Saugus River and its tributaries are home to many species of fish.  Some are true freshwater species, such as redfin pickerel, white sucker, yellow perch, and bluegill.  Other species may be found throughout the year in brackish water estuaries (mixture of freshwater and saltwater) , such as sticklebacks and mummichogs.

Several fish species spend a part of their lives in the ocean.  The alewife, blueback herring, and rainbow smelt are anadromous fish. They swim up rivers and streams from saltwater to freshwater from late winter through spring to spawn.  In the fall, young fish swim back to the ocean where they mature. The American eel is known as a catadromous fish.  They spawn in oceans and their young migrate towards freshwater to feed and mature. 

Alewives and other anadromous fish species were an important food source for Native Americans and early European settlers.  Early fishermen built weirs or small dams in the river using nearby stones.  These weirs helped fishermen capture alewives by the thousands.  Fishing quickly grew as a profitable industry from the 17^th century through the middle part of the 19^th century.  Fisherman caught and sold bass, shad, alewives, perch, smelt, and eels.  There were so many fish in the river during this time that large quantities were collected in scoop nets.  During the early part of the 19^th century, fish were routinely caught on the “Cinder Banks” at the head of the tidewater of the Saugus River.  The “Cinder Banks” area is now known as the slag pile, a primary feature of the historic landscape at Saugus Iron Works National Historic Site.

Within the last twenty years, two major fish inventories were conducted within Saugus Iron Works National Historic Site.  The first major inventory was completed by Hudsonia, an environmental research institute, in 1989.  Hudsonia found four species of fish, including American eel (Anguilla rostrata), four-spine stickleback (Apeltes quadracus), white sucker (Catostomus commersoni), and mummichog (Fundulus heteroclitus).  The second major fish inventory was conducted in 2004 by the University of Rhode Island.  This study listed eleven species of fish.  In addition to the four species previously surveyed by Hudsonia, the University of Rhode Island discovered alewife (Alosa pseudoharengus), brook stickleback (Culaea inconstans), redfin pickerel (Esox americana), three-spine stickleback (Gasterosteus aculeatus), large mouth bass (Micropterus salmoides), white perch (Morone americana), and nine-spine stickleback (Pungitius pungitius).  The data provided by these surveys enables the National Park Service staff at Saugus Iron Works to better understand, manage, and protect the various fish species found within the Saugus River watershed.

Additional fish inventory and monitoring projects will continue in the near future.  Beginning in the spring of 2005, the National Park Service will partner with the Saugus River Watershed Council, the Corporate Wetlands Restoration Partnership, and the Massachusetts Division of Marine Fisheries to conduct a rainbow smelt (Osmerus mordax) and American eel spawning survey within the river.  This project will provide new smelt and eel population and habitat information to state and federal fisheries biologists.