Assessing spawning habitat and natural recruitment in Green Bay muskellunge

The identification, and ultimately the protection, of critical spawning habitat for muskellunge (Esox masquinongy) in Green Bay is a vital step for re-establishing reproductive success in the Green Bay system.  This study was designed to document the extent of natural reproduction and locate spawning areas by oviduct insertion of radio transmitters into mature females prior to spawning.  The expelled transmitters were later located using radio telemetry to identify spawning sites.  In 2009, 20 transmitters were implanted in fish collected from lower Green Bay, a historic spawning area but one with considerable habitat degradation.  Spawning sites were located in sheltered areas of the bay and Fox River and displayed a strong correlation with shoreline absent of human development.  The average spawning location had a depth of 90 cm, contained a sand/silt substrate mixture, with minimal vegetation (0-25% total vegetative coverage) and shallow bottom slopes (0-3.0%).  The data collected this past year and in 2010 will help assess levels of natural recruitment and causes of poor reproductive success within the Green Bay muskellunge population.  Management implications of this project could include critical habitat designation to protect important spawning locations, as well as targeting areas for projects designed to rehabilitate muskellunge spawning habitat.