150 
Fishery Bulletin 112(2-3) 
Table 2 
Results from log-rank tests in the Grho family of statistics used to examine differences between “residency 
curves” derived from Kaplan-Meier survival analysis (j( 2 =40.4, df=7, P=1.07e06; see Fig. 3) for fishes tagged 
with acoustic transmitters and released in the Navesink River, New Jersey, in 2006 and 2007 for a study of 
residence times and duration of habitat suitability for 3 predators: age-l+ Striped Bass (Morone saxatilis), 
age-0 and age-l+ Bluefish ( Pomatomus saltatrix), and age-l+ Weakfish (Cynoscion regalis). Analysis used 
year and species-and-age class as predictors. V=Variance. 
Species 
Year 
N umber 
Observed (O) 
Expected (E) 
(0-E) 2 /E 
(OE)W 
Age-0 Bluefish 
2006 
15 
11 
10.21 
0.0606 
0.0688 
2007 
30 
29 
25.32 
0.5350 
0.6775 
Age-1+ Bluefish 
2006 
14 
14 
9.90 
1.6978 
1.9043 
2007 
21 
21 
22.39 
0.0869 
0.1109 
Striped Bass 
2006 
34 
33 
21.05 
6.7900 
8.2661 
2007 
12 
12 
4.41 
13.0586 
14.1044 
Weakfish 
2006 
15 
14 
16.64 
0.4175 
0.4900 
2007 
26 
26 
50.08 
11.5787 
20.9341 
Fig. 3, A-D, Tables 1 and 2). Smaller individuals (300- 
500 mm TL) of all species were more likely to have 
longer residence times than larger fishes. Striped Bass 
typically used the system for the fewest number of 
days. Weakfish had the longest residencies. 
Striped Bass used the estuary for a median of 16 
d in 2006 and of 8 d in 2007. This difference was not, 
however, statistically significant because of the small 
sample size in 2007 (%' 2 =2.5, df=l, P=0.1120). All 
Striped Bass >485 mm TL used the estuary less than 
24 d. Many smaller fish had longer residencies (n= 24) 
and some of them (n= 4) used the estuary >50 d. 
Median residency periods for age-l+ Bluefish were 
19 d in 2006 and 29 d in 2007, but the interannual 
difference was not significant (% 2 =1.3, df=l, P=0.248). 
Several age-l+ Bluefish <500 mm TL (n= 8) used the 
estuary >40 d. Age-0 Bluefish used the system for a 
median of 29 d, and distributions of residencies were 
nearly identical in the 2 years of this study (% 2 =0.2, 
df=l, P~ 0.651). Age-0 fish remained in the river for 
as long as 52 d (n=2). Residencies of tagged age-0 and 
age-l+ Bluefish were not statistically different (x 2 =1.8, 
df=3, P= 0.625). However, we were unable to tag age-0 
fish <175 mm TL that occurred in the Navesink River 
as early as June (senior author, unpubl. data), and re- 
ceivers were removed before the final egress of several 
tagged age-0 individuals ( n : 2006=4, 2007=1). There- 
fore, age-0 Bluefish probably used the system much 
longer than age-l-i- fish. 
Weakfish remained in the estuary for a median of 33 
d in 2006 and 47 d in 2007 (/ 2 =5.6, df=l, P=0.02). Resi- 
dencies may have been longer in 2007 because, during 
that year, Weakfish were released earlier and the ob- 
servation period was longer. All Weakfish <400 mm TL 
(n=18) used the estuary >40 d and 10 individuals were 
resident >60 d. 
Effects of environmental variables and body size on 
residence and egress 
Smaller individuals of all 3 species tended to re- 
main in the estuary at warmer temperatures than 
those preferred by larger individuals (Table 3, Fig. 
4). Size-dependent temperature responses were con- 
tinuous for Striped Bass and Weakfish but discontinu- 
ous for Bluefish. On average, Striped Bass were more 
likely to leave the system when temperatures ex- 
ceeded 23°C than when cooler temperatures occurred 
(Fig. 4A). However, temperature effects were greater 
for larger Striped Bass, which left rapidly as tem- 
peratures warmed in the early summer. In contrast, 
smaller fish were more likely to remain in the sys- 
tem into the summer when temperatures were rela- 
tively warm. Large Bluefish released in early summer 
were also likely to emigrate from the estuary when 
temperatures increased above 23°C (Fig. 40. In con- 
trast, smaller age-l-i- Bluefish were likely to be pres- 
ent when temperatures were warmer (Fig. 4D). Age- 
0 Bluefish were likely to remain in the estuary when 
temperatures were warmest. It was unlikely for age-0 
Bluefish to leave until autumn temperatures fell be- 
low ~20.5°C (Fig. 4E). Weakfish were resident in the 
estuary at the warmest temperatures and were likely 
to leave the estuary when temperatures cooled below 
23°C (Fig. 4B). Larger Weakfish emigrated at slightly 
higher temperatures than smaller fish. 
All 4 species-and-age classes were more likely 
to leave the estuary when the Swimming River dis- 
