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Fishery Bulletin 105(3) 



36 42 



Week 



Week 



Figure 2 



Arrivals and departures of tagged striped bass {Morone saxatilis). number of active hydrophones, and number of fish 

 tagged (available) and detected in the system during 2003 and 2004. Number offish detected in the system and number 

 of active hydrophones included all data combined within each week. Temperature data were collected at a Jacques Cous- 

 teau National Estuarine Research Reserve data logger in lower Great Bay (Fig. 1). 



at km) were arranged to take advantage of local top- 

 ography, such as at sand bars, channels, etc. to detect 

 fish moving along several passages. The entrance to 

 Little Egg Harbor was monitored by hydrophone 1 (con- 

 sidered to be km from the inlet for the purposes of this 

 study). This same hydrophone, along with no. 5, also 

 served to identify fish moving through a deep (to 7 m) 

 channel (Little Sheepshead Creek) between Little Egg 

 Harbor and Great Bay. The channel exiting Great Bay 

 to the south (Main Marsh Thorofare) was monitored by 

 hydrophone 13 (4.5 km from the inlet), although this 

 hydrophone was deployed later than the others. Hydro- 

 phone 5 (4.5 km from the inlet) also served to monitor 

 fish passing through the deepest channel in Great Bay 

 (Newmans Thorofare). The next gate upstream was 

 located in the Mullica River (hydrophones 6, 7, 8, 9; 

 approximately 18 km from the inlet). Hydrophones 6 

 and 8 were removed after a test period because they 

 were largely redundant. Farther upstream the next gate 

 consisted of a single hydrophone (no. 10; 28.3 km from 

 the inlet) just above the saltwater-freshwater interface. 

 On occasion, another hydrophone (no. 11; 38.1 km from 

 the inlet) was deployed farther upstream in tidal fresh- 

 water. The total number of hydrophones deployed over 

 the period of the study is indicated in Figure 2. Addi- 

 tional details of this estuarine system (referred to as an 

 "observatory") are provided in Grothues et al. (2005). 

 Our ability to detect tagged fish in certain portions of 



the estuary was affected by the times of hydrophone 

 deployment and, occasionally, by aperiodic retrieval of 

 the hydrophones because of poor weather conditions 

 (ice formation in the winter of 2003-04) or equipment 

 malfunction (Fig. 2). 



Striped bass bearing surgically implanted acoustic 

 transmitters (76.8 KHz) with an individual identifica- 

 tion code were detected when they came within range 

 (approximately 500 m; Grothues et al., 2005) of moored 

 wireless hydrophones (WHS-1100, Lotek Wireless, Inc., 

 St. Johns, Newfoundland, Canada), which were suspend- 

 ed at a depth of 3.2 m where surrounding total water 

 depth reached a depth of 10 m. Wireless hydrophones 

 transmitted received sound in the 76.8 KHz band by a 

 VHF radio frequency unique to the unit (between 148 

 and 152 MHz) to shore-based receivers for the interpre- 

 tation and logging of the data in real time (see Grothues 

 et al., 2005, for additional details). The JCNERR study 

 area also provided useful infrastructure for routine en- 

 vironmental monitoring. Permanent instrumentation in- 

 cluded data loggers used to record salinity, temperature, 

 pH, and water depth (Kennish and O'Donnell, 2002) 

 along the estuarine gradient (Fig. 1). 



Tagging technique 



Fish were collected by hook and line from 2 November 

 2002 to 2 November 2004 in the study area. Immedi- 



