This project is in its second year of funding from Public Service Enterprise Group (PSEG). The objective of this study is to provide another discrete evaluation of the success of the restoration of marsh dominated by Phragmites in Delaware Bay by comparing the role of predators in a treated marsh (Phragmites exposed to herbicides and burning) and in adjacent reference (Phragmites-dominated but not treated and Spartina alterniflora) marshes. This study is being conducted in Alloway Creek, Salem County, New Jersey, where the close proximity of the different marsh vegetation types increases the likelihood that environmental factors are similar. Specifically, we are investigating the seasonal occurrence, relative abundance, relative movement, and size composition of white perch (Morone americana) and other predators (including white catfish (Ameiurus catus), brown bullhead (Ameiurus nebulosus), channel catfish (Ictalurus punctatus), striped bass (Morone saxatilis), black drum (Pogonias cromis), bluefish (Pomatomus saltatrix), and weakfish (Cynoscion regalis). We are also investigating the food habits for these piscivorous fishes. Additionally, we are assessing the movement patterns of white perch, which is the dominant fish predator in Alloway Creek.

Field sampling involves extensive gill netting in intertidal and subtidal creeks. We sample throughout a 24-hour period to determine the influence of tide and day/night on fish predator distribution, abundance, and diet. All fishes, crabs, and turtles caught in the nets are measured and released with the exception of piscivorous fishes. All piscivorous fishes have their stomachs removed immediately after collection for diet analysis. Stomachs are preserved in the field for extraction and identification of contents at a later date.

For the movement component of our study, we surgically implant ultrasonic tags (IBT-96, Sonotronics) into the body cavity of large (200 mm FL) adult white perch. We track the movements of these fish in marsh creeks using hydrophones and receivers. We follow some of the perch by kayaks to minimize disturbance from an outboard engine, and also to increase our ability to maneuver in small marsh creeks and shallow areas. We track individual fish for up to 6 hours at a time, recording their spatial location with GPS. We are investigating movement through restored and reference marsh areas, as well as tidal and diurnal/nocturnal activity patterns.

To date, we have learned that white perch show a high degree of individual variation in habitat use and movement patterns. Some individuals cover very small areas (~0.2 km²), whereas others cover much larger areas (~ 1 km²). Activity levels change throughout the tidal cycle, with higher movements during the flooding tides, and peaks in movement during mid-flood. Activity levels are more influenced by tides than by diurnal/nocturnal changes; white perch show as much movement during nighttime hours than daytime hours. Most individuals go through periods or bursts of continuous movement followed by periods of inactivity. An intensive tracking program is underway again during the 2002 field season.

Principal investigators:
   Ken Able (able@imcs.rutgers.edu)
   Martha Jones (mjones@imcs.rutgers.edu)