Gannon et a I.: Food habits of Phocoena phocoena 
433 
Table 4 
Relative food importance, measured by frequency of occurrence (%FO), numerical proportion (%Num), and proportion of total 
mass (%Mass), in the autumn harbor porpoise diet. Numbers in parentheses refer to frequency of occurrence values found by 
Smith and Read (1992) for the summer calf diet of the same population in the Bay of Fundy portion of their range. 
Calves Juvenile males Juvenile females Mature males Mature females 
(n=13) (rc=18) (n=12) (rc=34) (n=10) 
Food items 
%F0 
%Num 
%Mass 
%F0 
%Num 
%Mass 
%F0 
%Num 
%Mass 
%FQ 
%Num 
%Mass 
%FO 
%Num 
%Mass 
Bathypolypus arcticus 
0(0) 
0 
0 
0 
0 
0 
0 
0 
0 
3 
<1 
<1 
0 
0 
0 
Clupea harengus 
15(4) 
<1 
11 
89 
8 
44 
75 
38 
66 
79 
6 
66 
70 
20 
35 
Gadus morhua 
0(0) 
0 
0 
0 
0 
0 
0 
0 
0 
6 
<1 
1 
10 
1 
1 
Illex illecebrosus 
0(0) 
0 
0 
0 
0 
0 
17 
1 
<1 
3 
<1 
<1 
20 
1 
<1 
Loligo pealei 
0(0) 
0 
0 
11 
<1 
1 
0 
0 
0 
3 
<1 
1 
0 
0 
0 
Maurolicus weitzmam 
54 (0) 
72 
53 
39 
42 
1 
17 
3 
<1 
41 
87 
7 
30 
7 
<1 
Meganyctiphanes 
norvegica 
54 (63) 


22 


17 


9 
_ 

0 


Merluccius bilinearis 
54 (0) 
26 
27 
78 
38 
31 
67 
50 
32 
62 
4 
19 
70 
65 
37 
Myxine glutinosa 
8(0) 
— 
— 
0 
0 
0 
8 
— 
— 
3 
— 
— 
40 
— 
— 
Pandalus montagui 
0(4) 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
Peprilus triacanthus 
15(0) 
<1 
2 
11 
1 
1 
8 
1 
<1 
21 
1 
1 
0 
0 
0 
Pollachius virens 
0(0) 
0 
0 
6 
<1 
1 
0 
0 
0 
9 
1 
2 
20 
4 
10 
Scomber scombrus 
0(0) 
0 
0 
6 
<1 
1 
8 
1 
<1 
15 
<1 
2 
0 
0 
0 
Sebastes spp. 
23 (0) 
1 
<1 
17 
3 
<1 
25 
1 
<1 
6 
<1 
<1 
0 
0 
0 
Urophycis spp. 
15(0) 
1 
7 
39 
7 
21 
33 
6 
1 
24 
1 
1 
20 
2 
18 
Unknown fish 
0(8) 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
10 
2 
— 
Milk 
23(29) 
— 
— 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
numerical and mass proportions because it was not 
possible to quantify their contributions. To facilitate 
comparisons between seasons, Table 4 also contains 
data from Smith and Read (1992) on the summer 
diet of calves from the Bay of Fundy. 
Significant differences in stomach contents existed 
among the five sex and maturity groups regarding 
the mass proportion of Atlantic herring (no. of 
cases=87, df=4, K [the Kruskal-Wallis test statistic] 
= 16.077, P=0.003), the number of Atlantic herring 
present (Table 5; A=18.313, P=0.001), and the exist- 
ing mass of all stomach contents (K=l 1.594, P=0. 021). 
The stomach contents of calves were the most diver- 
gent of these three categories and when the Kruskal- 
Wallis tests were repeated with calves excluded, none 
of the results were significant (Atlantic herring mass 
proportion: no. of cases=74, df=3, K= 4.284, P= 0.232; 
number of herring: K= 1.739, P=0.628; existing mass 
of stomach contents: A=0.27Q, P= 0.855). No other 
significant dietary differences were noted between 
any of the sex and maturity groups at the a = 0.05 
level. 
Qualitative comparisons between lactating and 
nonlactating mature females revealed that the 
former had higher frequencies of occurrence for most 
prey (Table 6). The proportion of total reconstituted 
mass represented by herring was much higher in 
nonlactating females. The mass proportions of sil- 
ver hake and red and white hake were higher in lac- 
tating females. It is also interesting to note that three 
of five lactating females ate hagfish, a frequency far 
greater than that of any other sex and maturity group. 
Discussion 
Atlantic herring was the most important prey of har- 
bor porpoises in the Gulf of Maine during autumn; 
silver hake, red and white hake, and pearlsides were 
of secondary importance. Although herring was the 
most significant prey for porpoises in autumn, it was 
not as dominant as in the summer diet in the Bay of 
Fundy (Recchia and Read, 1989). Recchia and Read 
( 1989) found Atlantic herring in 88% of noncalf por- 
poise stomachs, contributing 64% of ingested prey 
mass; we found herring in 78% of stomachs from 
noncalves, contributing 44% of prey mass. The rela- 
tive importance of silver hake, of red and white hake, 
and of pearlsides was greater in the autumn than in 
the summer. For example, pearlsides occurred in 38% 
