Able and Grothues: Diversity of the estuarine movements of Morone saxatilis 



429 



ately after capture, each individual was anesthetized in 

 a cooler containing 0.4-0.6 g/liter of MS-222 (Sigma- 

 Aldrich Corporation, St. Louis, MO). A transmitter 

 (CAFT 16-3, Lotek Wireless Inc., St. Johns, Newfound- 

 land, Canada) was then surgically implanted in the body 

 cavity. The incision was closed with absorbable ethalon 

 monofilament sutures and treated with antibiotic oint- 

 ment. An external tag (Floy Tag, Inc., Seattle, WA), with 

 printed contact information, was anchored into the flesh 

 to allow fishermen to report capture later to the study 

 crew. While still anesthetized, the fish was measured 

 (mm total length, TL), injected with Liquamyacin®Pfizer 

 at 0.1 mg/kg fish weight as a prophylactic against latent 

 infection. Each fish was then placed in clean, ambient 

 water until it showed normal swimming ability at which 

 time it was released at the capture site. On occasion, 

 fish were held for short periods of time (two hours) 

 before release. However, one fish was held for four days 

 at Rutgers University Marine Field Station (RUMFS) 

 before surgery and then taken to the site of capture 

 and released. 



Data analyses 



The sampling unit in) used in the analyses of telemetry 

 data was an individual tagged fish because this approach 

 places equal importance on the movements of each fish 

 (Rogers and White, in press). For the purpose of this 

 study, immigration of a tagged fish occurred when the 

 first detection of a fish tagged in 2002 was recorded 

 after January 2003 at or near an entrance to the estu- 

 ary. Emigration was determined by detection at one of 

 the entrances to the estuary followed by no detections of 

 that individual for two consecutive weeks, presumably 

 because it left the estuary for the ocean or an adjacent 

 bay. In order to measure swimming speed, we used the 

 last detection at a hydrophone at one gate and the first 

 detection at the next gate to determine time of travel 

 and distance between hydrophones. 



Results 



Environmental parameters 



Pronounced seasonal changes in temperature and dis- 

 solved oxygen occurred consistently throughout the estu- 

 ary, and salinity and pH decreased in the river (Fig. 3). 

 Temperatures approached, and probably reached, 0°C 

 during both winters but reached maximum tempera- 

 tures of approximately 25°C farther up the estuary 

 during summer. Temperatures near Little Egg Inlet 

 were consistently cooler than elsewhere in the estuary 

 during both years. Dissolved oxygen values followed the 

 same seasonal trend, except that values were highest in 

 the winter, near 14 mg/L, and lowest in the summer, at 

 4-6 mg/L, but in both years values at Little Egg Inlet 

 were higher than farther up the estuary. The salinity 

 varied distinctly with distance up the estuary. The 

 values at Little Egg Inlet averaged 28.6 (16.8-32.7) 



during both years, whereas those upstream at Chestnut 

 Neck (mean = 13.8, range 0.9-24.4) and Lower Bank 

 (mean=2.1, range 0-13.4) were much lower. Although 

 there were no data collected at Sweetwater during the 

 2005 study period, the salinity values averaged 0.1 

 (range: 0.02-5.1). The estuary differs from many others 

 in the Middle Atlantic Bight in that pH values in the 

 upper portions of the study area are naturally low (Lower 

 Bank, mean 5.9, range=4-7.4). These values tended to 

 be lowest in the spring and winter, presumably because 

 of higher runoff associated with more precipitation and 

 because of lower salinities at that time of the year. 



General characteristics of ultrasonicaiiy tagged fish 



During the study period, 68 striped bass (range 483-978 

 mm TL) were tagged and tracked through the Mullica 

 River-Great Bay study area. Most of these fish were 

 tagged in Great Bay (?! = 61), especially in the lower bay 

 near Little Egg Inlet and Shooting Thorofare, although a 

 number were also tagged at Graveling Point and Pebble 

 Beach (Fig. IB). Most fish were tagged in the fall and 

 spring of 2003 and spring of 2004. The duration of 

 detection of these tagged fish varied greatly among 

 individuals. Some individuals (?! = 3) were detected only 

 immediately after tagging and not again. Some were 

 detected only during one season or one year (n = 3), 

 others l7! = 5) were detected in both years, and two indi- 

 viduals were detected for almost the entire duration of 

 this study. The mean duration in the study area for fish 

 tagged in 2003 was 43.5 days and in 2004 was 20.0 days. 

 Several fish were captured by anglers within the estu- 

 ary (/z = 4), outside the estuary elsewhere in New Jersey 

 (n = 5), on the south shore of Long Island (n = l), coastal 

 New Hampshire (/i=l) and one was detected by similar 

 hydrophones in the Saco River, Maine (CarterM. 



The overlap in time between hydrophone deployment 

 and the time of initial tagging of each fish and their 

 exit and re-entry into the estuary determined the fre- 

 quency and duration of tag detections (Fig. 2). Overall 

 the rate of detection was high; over 97% of all tagged 

 fish were detected after tagging. The number of detec- 

 tions for each individual varied markedly and ranged 

 from 22 to 75,603 contacts; the total number of contacts 

 for all fish was 501,760 over the course of the study. 

 Of the fish tagged and subsequently detected, duration 

 at liberty varied from 15 to 731 days. Most fish were 

 detected by more than one hydrophone and numerous 

 individuals were detected by 2-10 hydrophones. 



Annual and seasonal visits to the estuary 



The patterns of estuarine use by tagged striped bass 

 were diverse and varied by individual, season, and year. 

 We characterized individual tagged fish by their use 

 of the estuary, either as resident fish (never detected 



^ Carter, J. 2005. Personal observ. Department of Life Sci- 

 ences, Univ. New England, 11 Hills Beach Road. Biddeford, 

 ME 04005. 



