Alewife
In Canada, alewives live two very different lives. Along the Atlantic coast — from Labrador through the Gulf of St.
Lawrence and into Maritime rivers — they're a native, anadromous forage fish that runs upstream each spring to spawn, feeding everything from striped bass to ospreys.
In the Great Lakes, they're an introduced species that colonized via the Welland Canal, where they became the dominant forage base underpinning the salmon and trout fishery.
Anglers rarely target alewives directly; they matter most as bait and as the prey that drives bigger fish.
Scientific Name: Alosa pseudoharengus
Also known as Gaspereau, bigeye herring, branch herring, freshwater herring, gray herring, grayback, sawbelly, kyak, white herring, river herring
- Slender, silvery body with a greyish-green back, forked tail, and a single dark spot just behind the eye on the shoulder — the clearest field mark.
- Belly has a row of sharp, keel-like scutes (modified scales) that feel rough to the touch — a quick way to confirm ID in hand.
- Large eyes relative to head size; broader, deeper body than the closely related blueback herring, which also has a darker (black to dusky) belly lining versus the alewife's white one.
- Sea-run fish typically under 30 cm and around 400 g; landlocked Great Lakes fish run noticeably smaller, usually under 25 cm.
What to know
Habitat Distribution
- Native along Canada's Atlantic coast from Red Bay, Labrador, south through the Gulf of St. Lawrence; common in larger rivers of New Brunswick, Nova Scotia, and PEI during spring spawning runs.
- Native to Lake Ontario; introduced into Lake Erie via the Welland Canal by 1931, then spread through Lake Huron, Michigan, and Superior over the following decades.
- Sea-run fish use the full range — open ocean, estuaries, and freshwater rivers — while Great Lakes populations are fully landlocked in large, deep lakes.
- Spawn in lakes or slow-moving river sections; juveniles rear in freshwater before migrating to salt or open lake.
Key Locations
- Gulf of St. Lawrence and Maritime rivers (New Brunswick, Nova Scotia, PEI) — core Canadian range for native, sea-run gaspereau runs.
- Lake Ontario — the entry point for Great Lakes colonization and still the lake most closely monitored for alewife population health; annual spring trawl surveys track abundance.
- Lake Huron, Michigan, and Superior — landlocked populations that form the forage base for those lakes' salmon and trout fisheries.
Specific Spots
- During Atlantic spring runs, concentrate at river mouths, pool tails, and the base of falls or dams where upstream passage is blocked — that's where nets and dip nets are most effective.
- In the Great Lakes, alewives school in open, pelagic water and move deeper as summer warms the surface — the same depth bands where salmon and lake trout are found chasing them.
- In rivers, slow backwater pools and lake shallows draw spawning fish; look for surface dimpling and visible schools in clear water.
Alewife FAQ
Answers from onWater's species guide.
What are the best lures and bait for Alewife?
Alewives are harvested as bait rather than fished as a sport target; small-mesh dip nets and gill nets (where regulations permit) are the primary tools during spring river runs. Fresh or frozen alewives are widely used as cut bait or whole bait for Great Lakes salmon and lake trout trolling rigs.
When is the best time to fish for Alewife?
Spring, peak season for Atlantic gaspereau runs; fish move into rivers as water warms, making them accessible at river mouths and pool tails. Summer, Great Lakes alewives move deeper as surface temperatures rise, pulling predator fish to deeper water and shaping where salmon trollers set their gear.
How do you catch Alewife?
In Atlantic Canada, gaspereau are harvested during spring spawning runs using dip nets or small gill nets at river mouths and below dams, primarily for use as lobster bait or personal food.
What do Alewife eat?
Filter-feed on zooplankton, tiny crustaceans like copepods and cladocerans, which is why they don't take conventional lures or flies; they're caught by net, not rod.
Where do Alewife live?
Native along Canada's Atlantic coast from Red Bay, Labrador, south through the Gulf of St. Lawrence; common in larger rivers of New Brunswick, Nova Scotia, and PEI during spring spawning runs.
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