Understanding the role of origin and release location in behavior and habitat use of pre-spawning alewives to improve the efficiency of restoration

Conserving and restoring anadromous fish is an important research and management priority.  Along most of the Atlantic coast, anadromous alewives (Alosa pseudoharengus) are declining. An understanding of alewife reproductive behavior is critical for interpreting distributional patterns and improving management efforts to restore populations. Out-of-basin trap and transfer, in which pre-spawned adult fish are taken from a healthy population and stocked to a depleted system, is a common restoration tool. Using radiotelemetry, we evaluated the movements of spawning adult alewives in the Ipswich River, MA, and examined how origin (native or stocked) and release location (upstream or downstream sites) affected alewife distribution and movement. Native fish remained in the river significantly longer than stocked fish, regardless of release location. Duration of time in upper and lower areas of the river was related to release location. Although assumed to be generalists, these schooling fish exhibited complex behaviors that may help them locate appropriate habitats, navigate obstructions, and aggregate with other spawners. Restocking of rivers must be performed within the context of understanding fish behavior, protecting habitat, and providing regulatory restrictions on the fishery, in order for it to effectively contribute to broader management and restoration goals.