Buckel and Conover. Movements, feeding, and daily ration of Pomatomus saltatrix 
675 
Table 3 
Stomach contents of spring-spawned bluefish captured during surface trawl and gill-net collections in the Hudson River estuary 
in 1993. %F = frequency of occurence, %W = percent wet weight. 
Date 
Prey type 
Surface trawl 
Gill net 
15-16 July 
20 July-4 Aug 
11-12 Aug 
18-19 Aug 
Species 
Common name 
%F 
%W 
%F 
%W 
%F 
%W 
%F 
%W 
Anchoa mitchilli 
bay anchovy 
56.3 
51.7 
3.0 
5.9 
6.3 
10.1 
2.6 
0.6 
Morone saxatilis 
striped bass 
7.0 
20.4 
18.2 
47.6 
25.0 
33.9 
18.4 
33.3 
Morone spp. 
6.1 
5.1 
Alosa sapidissima 
American shad 
3.0 
5.1 
12.5 
19.8 
Alosa aestivalis 
blueback herring 
2.6 
3.5 
Alosa pseudoharengus 
alewife 
6.3 
8.7 
Alosa spp. 
1.4 
2.5 
15.2 
8.5 
5.3 
2.8 
Menidia menidia 
Atlantic silverside 
6.1 
2.9 
18.8 
9.0 
31.6 
39.1 
Other fish 7 
1.4 
10.2 
3.0 
8.7 
6.3 
15.2 
2.6 
1.2 
Unidentified fish remains 
43.7 
13.9 
51.5 
15.3 
25.0 
1.4 
44.7 
19.2 
Total fish 
98.7 
99.2 
97.9 
99.7 
Crangon spp. 
sand shrimp 
3.0 
0.8 
12.5 
2.1 
2.6 
0.3 
Zoeae and copepods 
4.2 
0.5 
Total stomachs analyzed 
94 
83 
29 
71 
Number containing prey 
71 
33 
16 
38 
Mean bluefish size (g) (SE) 
6.83 (0.65) 
50.93 (1.81) 
55.25 (3.68) 
52.95 (2.44) 
1 “Other fish” are bluefish, Atlantic menhaden, unidentified sciaenid, and American eel. 
Declining gut-fullness values probably represent 
periods when fish do not feed. In 1992, these periods 
occurred mostly after sunset during nocturnal hours 
for both spring- and summer-spawned bluefish (Fig. 
3, B-F). In 1993, declining gut-fullness values were 
more variable and followed sunset or sunrise peaks 
in gut fullness, or else not at all (Fig. 4, B-E). Blue- 
fish that Juanes and Conover (1994) captured dur- 
ing diel sampling showed peaks in gut-fullness val- 
ues during crepuscular periods and a subsequent 
decline in gut-fullness values and a higher percent- 
age of empty guts at night. 
Many freshwater, estuarine, and marine fish spe- 
cies show periodicity in their daily feeding (Helfman, 
1979; Miller and Dunn, 1980; Reis and Dean, 1981; 
Popova and Sierra, 1985; Wurtsbaugh and Li, 1985; 
Nico, 1990; Jansen and Mackay, 1992). This period- 
icity is exhibited in fish that feed either diurnally, 
nocturnally, or during crepuscular periods. Young- 
of-the-year bluefish appear to be mainly diurnal 
and crepuscular foragers but are also able to feed at 
night. 
Daily ration estimates 
Daily ration estimates from this study are consis- 
tent with prior laboratory and field studies in which 
YOY bluefish were shown to have relatively high 
consumption rates for a temperate fish (Juanes and 
Conover, 1994; Buckel et al., 1995). Field estimates 
of bluefish consumption rates in the Hudson River 
estuary in early 1992 approached 25% body wt/d. In 
1992, daily rations declined as fish grew. Largest 
values for consumption-rate rations occurred in mid- 
July (22.2%) and dropped to a low in mid-September 
(7.3%) (Fig. 5A). The pattern and magnitude of field 
estimates of consumption rate were similar to val- 
ues of consumption rate from laboratory-mesocosm 
experiments made at the same time on similar-size 
fish (Buckel et al., 1995). In 1993, however, the early 
(10.1 %) and mid-July (8.6%) estimates of daily ra- 
tion from 24-hour collections made with beach seines 
( 7-8 July) and surface trawls (15-16 July) were lower 
than the mid-July beach-seine estimate in 1992 ( lb- 
17 July). The last three daily ration estimates in 1993 
