The blueback herring, also known by its scientific name Alosa aestivalis, is a migratory fish species belonging to the Clupeidae family. It is primarily observed in freshwater and brackish waters but can also be found in coastal waters of the Northwest Atlantic. In Quebec, the blueback herring is less popular among sport fishermen due to its relatively modest size and less vigorous fight compared to other species like salmon or muskellunge. However, it can offer an interesting challenge for those who enjoy fishing for less common species. Its distribution in Quebec is mainly limited to rivers that flow into the Saint Lawrence River and its tributaries. The blueback herring is known for its annual migration to freshwater to spawn, making it a species of interest for studies on fish migrations.

The blueback herring is a moderately sized fish, generally measuring between 10 and 14 inches, with an elongated and laterally compressed body. Its coloration is silvery with a metallic blue-green back, giving it a particular sheen in the water. The sides are lighter, almost white, and the belly is silvery. A distinctive feature of the blueback herring is a series of dark spots on the upper part of its sides, often present behind the gill cover. Its mouth is terminal and slightly oblique, adapted for capturing small prey. The fins are generally clear, and the caudal fin is forked, which is typical of fast-swimming fish. The scales are large and easily detachable. Juveniles resemble adults but are often more slender. During the spawning season, males and females do not exhibit marked sexual dimorphism, but females may be slightly larger and more robust.

In Quebec, the blueback herring is mainly present in rivers that flow into the Saint Lawrence River and its tributaries. Notably, it is found in the watersheds of the Richelieu, Yamaska, and Châteauguay rivers. It is less frequent in regions further from the river, where it may be absent due to natural or anthropogenic barriers limiting its migration. The blueback herring is a migratory species that makes seasonal movements to spawn, explaining its variable presence depending on the time of year. Outside Quebec, it is common along the Atlantic coast of Canada and the United States, where it migrates between coastal waters and rivers.

The blueback herring prefers freshwater and brackish waters to spawn and feed. It frequents rivers with moderate currents and estuaries, where it finds optimal conditions for reproduction and growth. During migrations, it can also be observed in shallow coastal waters. The blueback herring is often found at depths ranging from 3 to 33 feet, although it can go deeper in brackish waters. It favors areas with sandy or silty bottoms, where it can feed on small invertebrates and zooplankton. Ideal temperatures for the blueback herring range from 59 to 68 °F, influencing its seasonal distribution.

The life cycle of the blueback herring begins with a migration to freshwater rivers to spawn in the spring, generally between April and June. Females lay several thousand floating eggs in shallow areas, often near banks or in sheltered bays. After hatching, the fry remain in freshwater to feed and grow until the end of summer. In the fall, young herrings migrate to brackish or coastal waters where they spend the winter. The blueback herring reaches sexual maturity at the age of 2 to 3 years. Its lifespan is generally 6 to 8 years, although some individuals may live longer. Spring → Spawning → Summer → Growth → Fall → Migration → Winter → Rest.

The blueback herring is a gregarious fish that forms large schools, especially during migration periods. It is not particularly territorial and often shares its habitat with other migratory fish species. Sensitive to light variations, the blueback herring prefers low-light periods for movement, such as early morning or late in the day. It reacts moderately to noise and water disturbances, which can influence its location in the water column. Winds and weather conditions can also affect its movements, particularly during migrations.

The diet of the blueback herring varies according to its developmental stage. Fry primarily feed on zooplankton, capturing small prey such as copepods and aquatic insect larvae. As it grows, the blueback herring expands its diet to include small crustaceans, fish larvae, and benthic invertebrates. Adults continue to consume zooplankton but can also feed on small fish when available. The diet is opportunistic and may vary depending on prey availability in the habitat.

In the spring, the blueback herring migrates to rivers to spawn, making it an ideal time to observe in freshwater. The best times for fishing are early morning or late in the day when the light is softer. In summer, the blueback herring remains in rivers or estuaries but may be more dispersed due to high temperatures. Fall marks the beginning of its migration to deeper and brackish waters, where it prepares for winter. Weather conditions influence its activity, notably atmospheric pressure and wind. In overcast or rainy weather, it is often more active.

For blueback herring, lures in silver or gold colors are often the most effective, as they mimic the small fish it feeds on. In clear waters, favor natural and translucent colors. In murky water, bright colors like chartreuse or pink can help attract attention. In sunny weather, reflective metallic lures are ideal, while in overcast weather, darker colors may stand out better. Also, adapt the lure size to the depth you're fishing, choosing heavier models to reach deeper water layers.

To fish for blueback herring, a light to medium fishing rod, 6 to 7 feet long, is recommended. A rod with a fast action allows detecting subtle bites. An open-face reel size 1000 to 2500 is ideal, paired with a 6 to 10 lb monofilament line. Hook sizes 6 to 10 are appropriate, depending on the bait or lure used. For leaders, a 6 to 8 lb fluorocarbon can be used for its discretion in water.

The blueback herring should be handled with care to avoid removing its fragile scales. Use a wet cloth or wet hands to hold it. If you plan to release it, minimize the time out of the water and release it gently, ensuring it has fully recovered. For a photo, support the fish under the belly and take it quickly.

Predators of the blueback herring in Quebec include fish such as pike and walleye. Among birds, herons and ospreys are known to capture herrings, especially young individuals. Cormorants can also be effective predators in estuaries.

The blueback herring is not currently considered an endangered species in Quebec, but it is subject to environmental pressures such as pollution and dam construction that can affect its migratory routes. Sport fishing regulations often impose catch limits to ensure population sustainability. The release of captured individuals is encouraged to preserve stocks.