Manderson et al.: Residence time and habitat duration for predators in a small mid-Atlantic estuary 
149 
Number of days in the estuary 
Figure 3 
Kaplan-Meier analysis showing that (A) tagged Striped Bass ( Morone saxatilis) 
used the Navesink River for the fewest number of days, (B) Weakfish ( Cynoscion 
regalis) for the greatest number of days, and (C) age-l+ and (D) age-0 Bluefish 
( Pomatomus saltatrix) were resident in the estuary for intermediate durations 
in 2006 and 2007 for a study of residence times and habitat duration of these 3 
predators. Vertical lines crossing the horizontal line at 0.5 indicate the median 
number days (numbers above x-axis) each species used the small estuarine sys- 
tem in each year. 
individuals >500 mm TL were released in May and 
early June. We released age-0 Bluefish >175 mm TL 
in August and September. Weakfish were available for 
release from late June to mid-September. 
Release date and body size covaried for each age 
class of each species during at least one year (Table 
1). Smaller fishes were generally available for ear- 
lier release. However, in 2007, large age-l+ Blue- 
fish and Weakfish were released earlier than smaller 
individuals. 
Patterns of egress 
Although most of the tagged fishes remained in the 
Navesink River until final egress, several individuals 
of all age classes of tagged species made temporary ex- 
cursions out of the estuary for a period >3 d. More than 
half of the Striped Bass that we released in 2006 left 
the estuary temporarily and returned after absences of 
3-53 d (n=18; mean excursion [p] = 15.6 d). In 2007, only 
25% of the tagged Striped Bass made temporary excur- 
sions (n=3, m=15.6 d, max=33 d). Several Striped Bass 
made 2 or more excursions (n=7, max=6 d). Three fish 
that left the estuary in June or July 2006 returned in 
late August or September after absences >50 d. 
Weakfish and Bluefish showed stronger fidelity to the 
estuarine tributary than Striped Bass. More than 74% 
of the Weakfish and age-l+ Bluefish that we released 
remained in the estuary until final egress. Temporary 
excursions of these fishes (Bluefish n: 2006=4, 2007=5; 
Weakfish n\ 2006=5, 2007= 6) lasted 2-52 d (p=~15 d). 
In 2006, Bluefish and Weakfish left the estuary tempo- 
rarily during the period of late July-early August when 
temperatures exceeded 28°C and freshwater discharge 
was low (Fig. 2). In 2007, age-l+ Bluefish made excur- 
sions outside the estuary in late June-early July, and 
Weakfish made them throughout the summer. Age-0 
Bluefish rarely left the tributary before final egress (n: 
2006=1, 2007=3; m=10 d; range: 4-19 d). 
Duration of estuarine habitat use 
The species and size classes remained in the estuary 
for different lengths of time <x 2 =40.4, df=7, PcO.001; 
