Alewife (Alosa pseudoharengus)
AKA: Freshwater alewife, Sawbelly, Mooneye, Shad
Identifying characteristics: A small silvery fish with a darker, somewhat greenish-blue back. The eyes are large, and the mouth is small. The dorsal fin consists of one soft-rayed lobe and the tail is forked; both are usually dark in color. A dark spot (often called the shoulder spot) is present just behind the gills, above the lateral line. A serrated keel is present. The best way of differentiating a Blueback from an Alewife is to gut it; the Alewife’s interior lining is gray, the Blueback’s is black.
Size: Averaging 6 inches in length and weighing under a pound. Marine Alewife can grow twice as big.
New York State record: none kept.
Habitat: Marine Alewife school in the deep waters of the Atlantic and will run up the Hudson and its tributaries to spawn. Freshwater Alewife will inhabit the deep waters of New York’s larger lakes and rivers. They prefer cold, dark waters.
General range: The Great Lakes; Finger Lakes; a few Adirondack lakes; Hudson, Oswego and Delaware river systems. Atlantic Ocean.
Food: Primarily zooplankton; sometimes smaller fish or eggs.
Recommended baiting: Dip netting is often used near lake shores (freshwater Alewife) or in the deep, slow-moving areas of the Hudson during the spring spawning run. Use of a bright light at night may attract schools.
Predators: Pretty much all larger predatory fish. The Alewife is an important feeder fish in both the ocean and the Great Lakes. They are also important to commercial fisheries.
Stocked? Invasive. Most likely accidentally introduced to the Great Lakes and Finger Lakes, the Alewife has proliferated in fresh water.
Reproduction: Spawning occurs from late April to early June, when sea-run Alewives will run up the Hudson River and its tributaries. The freshwater variety will move closer to shore, with some migrating up larger tributaries to ponds. The females will begin the run first with males following shortly after. Spawning occurs at night, and the adults will leave after the eggs are deposited. The eggs hatch within a week and the young head back to deep waters in the fall.
Nesting: Females disperse eggs over the sand or gravel bottom. No nesting habits have been observed.
Other Info.: Although well established in the food chain of the Great Lakes and Finger Lakes, the Alewife is an invasive species that outnumbers native competitors, reducing their numbers and taking their place in the food chain. In the 1950s and 60s the Alewife population grew out of control (primarily due to large predators, such as the Lake Trout, being threatened), and spring die-offs littered Great Lakes beaches with millions of dead Alewives. The introduction and regular stocking of Atlantic Salmon has since reduced the Alewife numbers to an acceptable level.