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Fishery Bulletin 95(4), 1997 
Time (h) 
Figure 3 
Gut-fullness values (mean ± SE) of spring-spawned bluefish, Pomatomus saltatrix, 
versus time of capture during 1992 diel beach-seine collections. (A) Mean gut fullness 
(± SE) averaged across all dates of collection: (B) 16-17 July, (C) 28-29 July, <D) 13- 
14 August, (E) 26-27 August, and (F) spring-spawned (closed circles) and summer- 
spawned (open squares) bluefish versus time of capture during diel beach-seine col- 
lections on 19-20 September. The time periods from sunset to sunrise are indicated 
by dark horizontal bars. Numbers above (or near, for summer-spawned) each gut- 
fullness estimate represent bluefish sample size. Upward and downward facing ar- 
rows represent the time of high and low tide, respectively. 
One potential problem in the above analysis is the 
potential lack of independence of gut-fullness esti- 
mates between time points. This lack of independence 
is mainly a concern with adjacent time points (spaced 
3 hours apart) because gastric evacuation in blue- 
fish is ~6-8 hours ( Juanes and Conover, 1994; Buckel 
and Conover, 1996). Therefore, 
gut-fullness estimates at time 
points that are separated by at 
least six hours are more likely 
to be independent of each other. 
We used post-hoc comparisons 
to examine for statistical differ- 
ences between such pairs. 
The gut-fullness value at 
1800 was significantly higher 
(nonparametric multiple-com- 
parison test, P<0.001) than the 
gut-fullness value at 1200, 
2400, and 0300. A similar pat- 
tern was seen for summer- 
spawned fish (Fig. 3F). The 
gut-fullness values of 1993 
beach-seine-collected bluefish 
differed from those seen in 
1992 (Fig. 4A); decline in gut 
fullness at night was not as 
dramatic. Gut-fullness values 
at 1200 were significantly 
lower (P<0.01) than values 
from morning (0600 and 0900) 
and evening (2100) collections. 
However, the lowest night gut- 
fullness value (0300) was not 
significantly different from the 
highest day (0600) gut-fullness 
value (P>0.05). 
Daily ration estimates 
Daily ration estimates for YOY 
spring-spawned bluefish dur- 
ing 1992 beach-seine collec- 
tions were highest on our first 
sampling date 16-17 July at 
22.2% body weight/d (95% con- 
fidence interval (Cl) 13.3-32.3) 
and dropped to 7.3% body 
weight/d (1.7-13.6) by 19-20 
September (Fig. 5A). Although 
there was a decline in daily ra- 
tion, these values had overlap- 
ping CFs and were therefore 
not statistically different. In 
1993, daily ration values from 
beach-seine-captured spring-spawned bluefish were 
highest on 20-21 July at 14.7% body weight/d (8.5- 
21.6) and lowest on 7-8 July at 10.1% body weight/d 
(6.7-14.0) (Fig. 5B). The diel collection made with 
surface trawls on 15-16 July 1993 yielded a daily 
ration estimate of 8.6% body weight/d (4.7-12.8). 
