Habitat requirements of northern pike (Esox lucius)

Over the past half century, habitat changes have significantly affected production of northern pike (Esox lucius), especially in the Great Lakes Basin. Loss of wetlands, reduction of shoreline cover and structure, cultural eutrophication, and siltation have negatively affected water transparency, abundance of macrophyte habitat, and even body condition. We review recent habitat restoration programs conducted in the Great Lakes Basin to reverse this trend. However, assessment has usually been inadequate to evaluate their success. Spawning and nursery requirements (first year of life) are examined, using a system for classifying and ranking major physical characteristics and requirements. Depth of nursery habitat is directly correlated with fish size and age. Spawning habitat is usually less critical or limiting but more easily manipulated and restored than nursery or juvenile-adult habitats. Year-class strength over 22 yr in eastern Lake Ontario was correlated positively with midsummer temperature and negatively with late summer-early fall water elevation; also, the largest year-class appeared immediately after catastrophic winterkill of a predator, white perch (Morone americana). Both implicate nursery rather than spawning associations. Adult abundance is related to the extent of macrophyte cover, which is optimal from 35 to 80% but inversely related to body size.