432 



Fishery Bulletin 105(3) 



For fish that left the estuary, the last 

 detection was most frequent in the vicin- 

 ity of Little Egg Inlet where most detec- 

 tions occurred at hydrophones 2 (33%), 1 

 (23 %), and 4 (20%). Other final detec- 

 tions also occurred within the estuary at 

 hydrophones 6 (9%), 7 (6%), 13 ( 3%), 5 

 (3%), and 8 (<1%). The last detection at 

 relatively long distances from the inlet 

 (hydrophones 6, 7, 8) may have resulted 

 from departures during periods before 

 hydrophone 13 was deployed. 



Spatial and temporal patterns of 

 striped bass within the estuary 



0.6 

 0.5 

 0.4 

 0,3 

 0.2 

 0.1 



0.6 

 0.5 

 0,4 

 0,3 

 0.2 

 0.1 



Inlet hydrophones 1-4 



i OOOOOOOOOOOOO 



0,6 



0,5 

 0,4 

 0,3 

 0,2 

 0,1 



Fish moved, as evidenced by hydrophone 

 detections at selected gates, in a variable 

 manner with respect to areas in the study 

 site, seasons, and years (Figs. 4 and 5). 

 Fish were frequently detected in the poly- 

 haline portions near the inlet and in the 

 estuary and less consistently in the river. 

 The distribution of fish in the estuary 

 varied by season; fish were detected at 

 the inlet gate (hydrophones 1-4) during 

 all seasons, whereas fish detected in 

 spring were more frequently found far- 

 ther up at the estuary gate ( hydrophones 

 5-9, 13) or farther upstream at the river 

 gate (hydrophones 10-11). However, few 

 fish were detected during the winter 

 at any gate. These general patterns of 

 estuarine use varied between years. A strong peak in 

 estuarine users occurred in the spring (weeks 14-21) of 

 2003, but there were fewer users in 2004. Modest peaks 

 in inlet and estuarine users occurred in the fall (weeks 

 34-48) in both years. The sole peak in river use occurred 

 in spring (weeks 14-20) of 2003. 



The degree of residency and movements within the 

 estuary varied among individuals over time for a given 

 individual. Some individuals were resident in one por- 

 tion of the estuary for long periods of time. This finding 

 was substantiated by the long duration of detections 

 for some individuals in the vicinity of the inlet. For 

 example, two fish (/i=1273 contacts and 280 cumula- 

 tive hours of detection) spent 91% and 58% of their 

 time, respectively, at the inlet, even though they were 

 detected at two other gates. Together these types of 

 patterns account for the preponderance of detections in 

 the vicinity of the inlet and for the somewhat lower de- 

 tections upstream. Another fish, with one of the longer 

 time records (7i = 1190 hours of detection) was detected 

 at all gates in the study area. Alternatively, some fish 

 were consistently detected farther up the estuary. For 

 example, one fish (n=154.5 hours detected) was detected 

 frequently in the vicinity of Chestnut Neck (75% of the 

 time). 



Other individuals, although not detected as frequent- 

 ly, appeared to be resident for relatively long periods. 



8888888888??: ?"T?'?o<? 



River hydrophones 10-1 1 



o X ooooooooooo 



oooooooooooo 



dOOOfloOOOTD i 



000000000 



27 30 



Week 



33 36 39 42 45 4B 



Figure 5 



Annual variation in number of fish detected, by week in the inlet, by 

 estuary, and at river gates. See Figure 1 for locations of gates. 



For example, two fish were consistently found farther 

 up the estuary over several months and we interpreted 

 this period as residency. The lack of frequent detections 

 implies that this residency occurred in areas between 

 hydrophone gates. Active telemetry of individual fish 

 confirms this interpretation (Ng, 2006; Ng et al., in 

 press). Movements in the study area were often dy- 

 namic; individual fish moved large distances over short 

 periods. Several individuals moved quickly upstream af- 

 ter being tagged lower in the estuary during the spring. 

 Of six individuals tagged on 2 April 2003, five moved 

 upstream 7-10 km into the area of the freshwater-salt- 

 water interface (near Lower Bank, approximately 28.3 

 km from Little Egg Inlet) or farther into completely 

 freshwater in the vicinity of Sweetwater (approximately 

 38.1 km from Little Egg Inlet) (Fig. 4). These same 

 upstream movements occurred for 3 of 4 fish tagged at 

 Graveling Point on 2 May 2003. More extensive move- 

 ments were detected for all 3 fish tagged on 22 April 

 2004 at Little Egg Inlet. All of these fish moved 17-19 

 km upstream and were detected at the same locations 

 as those of the previous fish. 



Upstream movements were relatively quick. The speed 

 of fish passing upstream from Little Egg Inlet to Chest- 

 nut Neck ranged from 0.3 to 2.4 km/h (« = 10 fish) and 

 from Chestnut Neck to Lower Bank ranged from 0.09 to 

 0.5 km/h (h = 11 fish). The subsequent movement down- 



