The alewife, of the species Alosa, is a fish belonging to the herring species, and is also known as the sawbelly, gaspereau, and kiack. These fish are native to the Atlantic coast along the eastern United States and Canada. The fish became well known in the 1950s and 1960s for their rapid invasion of the Great Lakes, particularly Lake Michigan and Lake Huron. Their population has since been controlled due to predators such as salmon being released in the lakes.
The average adult alewife grows to 10-11 inches (25-28 cm) and generally weighs no more than 9 ounces (255 grams). The alewives found on the Atlantic coast tend to be larger than those found in the freshwater lakes. The typical life span of this fish is six years. These fish range in color from silver to a metallic blue-green, with their darkest color found on their backs. They also have a characteristic line down their belly that resembles a line of saw blades, hence one of their common names. Alewife scales were once a hot commodity due to their role in the production of fake pearls.
Though they are closely related, alewives differ from the sea herring in appearance — they have a broader body, a spot behind the gills and the dorsal fin is closer to the nose than to the tail. When filleted, their abdominal cavity lining is often much lighter than that of the herring. For human consumption, they are often chosen over the herring due to a better taste and more meat per fish.
The alewife tends to reach sexual maturity between three and four years of life. They are anadromous, meaning they migrate for spawning. They typically mature in saltwater oceans before venturing to freshwater to spawn. Once the female has laid approximately 60,000-100,000 eggs, the fish return to the ocean. This journey from varying waters is difficult for the fish, and they tend to lose weight and act sluggish during these trips. Repeated journeys often lead to death.
The alewife tend to feed on plankton, but some will also consume small fish such as herring, cunners, and eels. They usually do not eat while traveling to spawn, but typically devour shrimp on their return trip to the sea. Bait is often not necessary to catch alewives, as they can be scooped up using large dip nets as they are venturing down stream after spawning. They can be caught for human consumption, or to use as bait for other fish, particularly pollock, lobster, and cod.