Spawning Habitats for American Shad at the St. Johns River, Florida: Potential for Use in Establishing MFLs. Final Report

摘要

The St. Johns River, Florida contains the southernmost population of anadromous American shad Alosa sapidissma. Given increasing demands for freshwater resources in Florida, variation in water levels within the St. Johns River could increase in the near future potentially altering access to spawning habitat for American shad. To help inform water and resource management decisions, a collaborative research effort between the St. Johns River Water Management District (SJRWMD), Florida Fish and Wildlife Conservation Commission (FWC), and University of Florida was initiated to expand on earlier research suggesting that spawning habitat use of migrating shad could be influenced by variation in water levels. This report presents the conclusions of this collaboration. We assessed spawning habitat use of American shad over a three-year period using active and passive tracking of telemetered adult American shad. We then compared these movement patterns with habitat available in areas of high and low use to assess whether specific habitat characteristics (i.e., depth, substrate, flow) were selected. We assumed that during late winter and early spring American shad would migrate to areas in the St. Johns River favorable for staging prior to, or for spawning. We also assumed that areas of repeated occurrence for telemetered shad represented important habitat for spawning.