Saturday morning I stopped at the Mashpee River fish ladder by the Mashpee Wampanoag Indian Museum on Route 130 to see if the herring were running yet. To my delight, they were. The Mashpee River is approximately four miles long and flows from Mashpee-Wakeby Pond to Popponesset Bay, and then out into the Atlantic Ocean. Each spring, two species of river herring, alewives (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), make their way from the sea back to Mashpee Pond en masse to spawn. Although difficult to distinguish between these two species, based on the time of year, their size (alwives are slightly smaller than bluebacks) and their eye size and position, the fish pictured here are likely alewives (Alosa pseudoharengus). Fittingly, the name “Mashpee” means “a great river coming from a pond bearing many fish” in the Massachuset Algonkian language. 

Mashpee River fish ladder.

Each female can lay between 100,000 and 150,000 amber, translucent eggs, which take 3 to 6 days to hatch. By late summer or early fall, the juvenile fish are approximately 1 to 3 inches long and will swim down the Mashpee River to the Atlantic Ocean, where they will then migrate to more southern waters to feed, grow and mature. In general, river herring have extremely high fidelity to their natal pond, and after they are reproductively mature 3 to 4 years later, river herring born in Mashpee-Wakeby pond will return to this same location to spawn. 

While in the River’s shallow waters, the herring are vulnerable to many predators. In the 15 minutes I was at the fish ladder, I watched at least 7 different osprey (Pandion haliaetus) dive into the water over and over retrieving fish. In fact, the fish are so densely packed that on one occasion I actually witnessed an osprey come up with two fish – one in each foot! Although many will be taken by osprey, as well as other fish-eating birds such as belted kingfishers, herring gulls, double-crested cormorants and herons, the river herring are a vital food supply for these birds at a time when they are preparing to nest and raise young of their own.