White perch Morone americana (Gmelin, 1789) habitat choice and movements: Comparisons between Phragmites-invaded and Spartina reference marsh creeks based on acoustic telemetry

An investigation of the effects of the Phragmites invasion on movements and habitat use focused on ultrasonic telemetry of white perch (Morone americana) throughout Alloway Creek, Delaware Bay, New Jersey. Of the individuals tracked (192-266 mm FL), there was high site fidelity (19 out of 30 individuals) but there was also variability in movement patterns, home range size, and habitat use. On average, individual fish spent most of their time stationary (67%), and substantially less time moving (22%) and tended to move up creek with flooding tides, and down creek with ebbing tides. Higher movement levels occurred at mid-ebb and mid-flood stages when water velocity was at its highest. Eighteen individuals had tidal excursions - either long distance movements with the tide or excursions onto the marsh surface or into shallow creeks at high tide. Individuals originally tagged in Spartina creeks tended to utilize only Spartina areas (12/13 tagged fish stayed in Spartina), whereas none of the individuals tagged in Phragmites creeks stayed in Phragmites areas (0 out of 5 tagged fish). These results suggest that the tagged individuals did not prefer Phragmites habitats. Further, this study indicates that it is important to consider animal behavior such as movement patterns, home range area and habitat use when evaluating the effectiveness of restoration programs. Such measures can provide insight into why altered habitats differ from reference sites in terms of quality, identify critical resources for animals and enhance our understanding of how animals contribute to ecosystem function.