Scharf et al.: Diet analysis of piscivorous fishes 
585 
dentary of silver hake are much smaller relative to 
the same ratios for the red hake dentary. In addi- 
tion, the teeth of red hake are much less prominent, 
and the ventral process of the dentary of red hake is 
considerably broader than that of silver hake. Simi- 
lar to the dentaries of the hakes, the dentaries of 
Atlantic cod and haddock also possess a row of sepa- 
rate conical teeth that extend slightly farther onto 
the dorsal process (Fig. 3, C and D). The length of 
the dorsal process of the dentaries of Atlantic cod 
and haddock is much smaller than the length of the 
Table 6 
Independent variables included in stepwise multiple re- 
gression models estimating original fish weight. Abbrevia- 
tions for independent variables are those given in Tables 2 
and 3. * indicates that forward and backward models were 
not identical. 
Variables 
Variables 
included in 
included in 
forward 
backward 
Species 
stepwise model 
stepwise model 
Alewife 
BD, CP, CL 
BD, CP, CL 
Blueback herring 
BD, CP, PF, CL 
BD, CP, PF, CL 
Atlantic herring 
BD, CP, OP 
BD, CP, OP 
Atlantic mackerel 
OP, CL 
OP, CL 
Butterfish 
BD, CP, PF, CL 
BD, CP, PF, CL 
Sand Lance 
BD, CP, CL, DN 
BD, CP, CL, DN 
Red hake 
CP, PF, CL 
CP, PF, CL 
Silver hake* 
BD, CP, PF, OP 
BD, ED, CP, PF, 
OP, DN 
Haddock 
BD, CP, CL 
BD, CP, CL 
Atlantic cod 
BD, CP, PF, CL 
BD, CP, PF, CL 
ventral process, which contrasts with the dentaries 
of the hakes. The dentaries of Atlantic cod and had- 
dock can be distiguished by the teeth located just 
posterior to the mandibular symphysis; the teeth are 
longer in haddock than in Atlantic cod. Further, the 
ventral process is considerably broader in haddock 
than in Atlantic cod. The dentaries of alewife and 
Atlantic herring each consist of a long, slender ven- 
tral process that is considerably longer than the 
broadly expanded dorsal process, and are toothless 
(Fig. 3, E and F). The only noticeable difference be- 
tween the dentaries of the alewife and Atlantic her- 
ring is a more gradual incline along the dorsal mar- 
gin of the dorsal process and a slight hump located 
anteriorly in Atlantic herring. Similar to the 
dentaries of the gadids, Atlantic mackerel dentaries 
possess a row of separate conical teeth (Fig. 3G). 
However, the teeth of Atlantic mackerel extend well 
onto the dorsal process, are spaced relatively uni- 
form distances apart, and are not curved inwards. 
The dentaries of butterfish possess a continuous row 
of separate teeth that are squared off at the tips, 
which is a unique feature among the fishes exam- 
ined here (Fig. 3H). The ventral process of the but- 
terfish dentary extends from the body of the dentary 
at a considerable angle. In sand lance, the dentaries 
have a long, thin ventral process that ends sharply 
and is much longer than the dorsal process, and are 
toothless (Fig. 31). The dorsal process of the dentary 
of sand lance is curved along its margin, similar to 
the dorsal processes of the dentaries of alewife and 
Atlantic herring. However, the dorsal process of the 
dentary of sand lance is much less broad than that 
found in the dentaries of alewife and Atlantic herring. 
Table 7 
Least squares regression equations relating measurements (in millimeters) of total length (TL) and fork length (FL) to total 
weight (W) in grams for ten prey species in the Northwest Atlantic. s fc = standard error of the regression coefficient; r 2 = coeffi- 
cient of determination; %PE = mean percent prediction error; n = number of fish measured; Range = size range in total length. 
Fork lengths were not measured for red hake, silver hake, or Atlantic cod. 
Total length Fork length 
Species 
Equation 
s b 
r 2 
%PE 
Equation 
h 
r 2 
%PE 
n 
Range 
Alewife 
W= 2.74 xlO^TL 3 213 
0.031 
0.99 
7.12 
W = 3.29xlQ- 6 FL 3 - 254 
0.035 
0.99 
7.82 
137 
73-282 
Blueback herring 
W = 6.24 xlO- 6 TL 2 " 3 
0.101 
0.96 
6.78 
W = 13.78 xlO _6 FL 2 ' 887 
0.113 
0.95 
7.16 
38 
83-134 
Atlantic herring 
W = 4.10 xHHTL 3 111 
0.037 
0.99 
8.10 
W = 4.53 xlO _6 FL 3 - 156 
0.040 
0.99 
8.33 
84 
97-295 
Atlantic mackerel 
W= 1.09x10 -6TL 3 - 354 
0.039 
0.99 
5.86 
W = 0.85 xlO _6 FL 3 - 451 
0.041 
0.99 
5.84 
56 
158-330 
Butterfish 
W= 8.14 xlO^TL 3 094 
0.024 
0.99 
6.78 
W = 8.43 xlO _6 FL 3180 
0.032 
0.99 
8.36 
108 
54-193 
Sand lance 
W = 0.32 xlO- 6 TL 3 - 449 
0.112 
0.93 
12.74 
W = 0.41 xlO _6 FL 3 421 
0.119 
0.92 
13.63 
75 
109-209 
Red hake 
W = 4.41 xlO^TL 3 053 
0.034 
0.99 
5.75 
45 
108-340 
Silver hake 
W = 1.91 xlO^TL 3213 
0.027 
0.99 
8.96 
95 
75-300 
Haddock 
W = 3.44 xlO^TL 3186 
0.063 
0.98 
7.50 
W = 3.78 xlOAFL 3 196 
0.080 
0.97 
9.12 
47 
79-202 
Atlantic cod 
W = 1.99 xlO^TL 3 - 308 
0.090 
0.99 
5.53 
31 
52-140 
