Chemical tracking of northern pike migrations: If we restore access to breeding habitat, will they come?

Abstract

Landscape alterations can obstruct movement corridors and degrade spawning habitats for migratoryfishes,requiring expensive restoration efforts. To assess use of natural and artificial waterways for spawning migrations,we monitored adult migrations and young-of-year production of northern pike (Esox lucius) for two years in sixadjacent tributaries of southern Green Bay on Lake Michigan, USA. Field observations were compared with natalorigins of young-of-year and adults inferred from otolith microchemistry. Individual tributaries varied widely intheir production of young-of-year pike. Microchemical differences were apparent only among tributaries whosewatersheds differ in land use, and adult pike showed no evidence of homing even to the same tributary land useclass where they were born. Though otolith microchemistry suggests a lack offidelity to natal streams, carbonstable isotope ratios of adult pike showed a latitudinal gradient across tributaries, suggesting that adult pike donot mix freely outside of the breeding season. Bothfield observations and microchemical tracing suggest thatpike can potentially recolonize historical or newly-created breeding habitats after restoration efforts makethem accessible.