The term gaspereau is the most common name used for two species of the herring family. Depending where you live they are also called river herring, alewives, grey backs, blue backs, kiacks and sawbellies. The correct names for the two species in our waters are alewife and blueback although they are so similar in appearance that most people refer to them collectively as gaspereau.
Nova Scotia anglers are familiar with seeing gaspereau in lakes and rivers when they spawn in May and June. They are a diadromous species which spends most of its life cycle in the sea, returning to fresh water to spawn.
Spawning occurs over a six-week period as the water warms up. No nest is built. Gaspereau eggs are tiny, about one millimetre in diametre and, depending on water temperature, will hatch in about a week. The young fish spend the summer feeding in fresh water and, beginning in August, they begin their downstream migration to the sea. This fresh water growth is very rapid and some fish will be up 15 cm long at the end of the summer. Gaspereau first spawn after two years at sea and many survive spawning to return several times. Gaspereau up to 20 years old have been recorded from Nova Scotia.
Prior to spawning gaspereau do not feed and as a result they are very difficult to catch. After spawning they resume feeding and some anglers have had luck with small lures or white and yellow flies.
Not highly prized on the table, gaspereau have sometimes been referred to as the Sunday fish, as it would take you all day Sunday to remove the bones. At one time most of the commercial catch was salted and shipped to the Caribbean but today most gaspereau are used locally as lobster bait.

On the South Shore of Nova Scotia they smoke gaspereau, or as they call them down there, kiacks. I have eaten them that way and they are delicious, as long as you have all day Sunday to take out the bones.
Description taken from The Cape Breton Post