A Review of Northern Pike Population Genetics Research andIts Implications for Management

Conserving genetic diversity within and among populations of northern pike Esox lucius is important for maintaining their short‐term fitness and long‐term evolutionary potential. Northern pike have consistently shown low within‐population variation, as detected by allozymes, mitochondrial DNA, and randomly amplified polymorphic DNA. Microsatellite DNA loci reveal considerably greater variation in northern pike, yet microsatellite variation tends to be less than that in other fish species. Low genetic variation within populations may result from compounding factors of low effective population size and bottlenecks. Allozyme, randomly amplified polymorphic DNA, and microsatellite markers have revealed significant differentiation of populations located in different continents and major drainages, but only microsatellites have differentiated populations on finer geographic scales. Within the north‐central United States, analyses with microsatellites have detected genetic differences among most populations but have inconsistently detected structure, or genetic relationships, among populations. Microsatellites did reveal fine‐scale structure between freshwater and brackish‐water populations in Finland, showing that population structure does develop in this species. The lack of structure in the north‐central United States may be the result of repopulation from a common glacial refugium, but stock transfers also may have played a role in obscuring past structure. Allozyme studies indicated that western North American populations might have recolonized from a second glacial refugium. Northern pike biologists should consider how management actions affect within‐ and among‐population variation. Stock transfers are the most common means by which genetically differentiated populations are mixed. Genetic data support avoiding transfers of northern pike across continents and between populations in western and central North America. Management actions such as harvest and habitat manipulations can also reduce genetic variation within populations by altering demographic factors that determine effective population size.