340 
Fishery Bulletin 95(2), 1997 
ber and represented 9.2% of all prey consumed. How- 
ever, the family Ommastrephidae had the highest 
percent frequency of occurrence at 65.2%, followed 
by the family Enoploteuthidae at 54.9%. Octopus 
accounted for only 0.23% of cephalopod prey and oc- 
curred in 4.4% of the stomachs examined (Table 1). 
Prey size 
The beaks of 18 out of 32 squid species could be con- 
verted to mantle length and weight (Table 2). The 
average mantle length of squid was 75.8 mm 
(SE=0.54) and ranged in size from 2.4 to 321 mm. 
The largest species of squid, on average, was 
Dosidicus gigas at 181 mm (SE=2.9), and the smallest 
species of squid was Pterygioteuthis giardi (mean=22 
mm, SE=0.41). The otoliths of only eight fish species 
could be converted to total length (TL) (Table 3). The 
average size fish consumed was 92.9 mm TL (SE=L41) 
with a range of 34-260 mm TL. The largest species of 
fish, on average, was A. thazard (mean =2 11. 5 mm TL, 
SE=8.08) and the smallest was Ceratoscopelus 
warmingii (mean=49.3 mm TL, SE=0.45). 
We found that the size of fish and squid consumed 
increased significantly with dolphin length (Fig. 2; 
fish: r 2 =0.648, PcO.QQl; squid: r 2 = 0.791, PcO.OOOl). 
We also found that the number of prey consumed was 
negatively correlated with the size of prey (squid: r 2 = 
-0.555, PcO.001; fish: ^=-0.624, ,P<0. 003). If a prey 
species was small, more were consumed by the dolphins. 
Geographic and seasonal variability 
To test the hypotheses of variability in prey compo- 
sition between areas and seasons, 10 species that 
accounted for 55% of the sample by number were 
selected for the analyses (Table 1). These included 
five species offish: Symbolophorus spp., Myctophum 
aurolaternatum, Lampanyctus parvicauda, Diaphus 
splendidus, Cubiceps pauciradiatus, and five species 
of squid: Ommastrephes bartrami, Onychoteuthis 
banksii, Abraliopsis affinis, Mastigoteuthis dentata, 
and Leachia dislocata. A significant difference was 
found in the prey composition by area and season 
(X 2 =13,373, df=45, PcO.OOOl). 
Fish were the dominant prey species of S. attenuata 
in the winter: L. parvicauda was found in the high- 
est numbers in the northeast, M. aurolaternatum in 
the south, and Symbolophorus spp. in the west. Squid 
were the dominant prey species in the summer; A. 
affinis was found in highest numbers in both the north- 
east and west, and O. bartrami in the south (Fig. 3). 
Table 2 
Mean, standard deviation, and range of mantle length and weight of cephalopod species consumed by spotted dolphin, calculated 
with regression equations (Clarke, 1986a; Wolff*). ‘Number’ represents the total number of cephalopod beaks that were measur- 
able, without being broken or worn. 
Estimated prey length Estimated prey weight (g) 
Species of prey 
Number 
Mean ±SD 
Range 
Mean +SD 
Range 
Total 
% weight 
Cephalopods 
Ommastrephes bartrami 
1,158 
129.2 ±35.3 
69.7-273.5 
63.9 ±69.6 
2.3-463.0 
74,048 
31.90 
Eucleoteuthis luminosa 
475 
112.7 ±33.9 
51.6-219.4 
40.4 ±38.5 
2.5-226.9 
19,186 
8.30 
Sthenoteuthis oualaniensis 
287 
144.2 ±42.1 
73.4-320.9 
136.5 ±147.1 
11.8-1,248.2 
39,165 
16.90 
Dosidicus gigas 
207 
180.8 ±43.1 
99.2-319.4 
177.9 ±134.3 
15.7-853.2 
36,822 
15.90 
Hyaloteuthis pelagica 
141 
75.3 ±12.7 
50.6-117.9 
11.9 ±5.3 
3.7-34.0 
1,688 
0.70 
Nototodarus hawaiiensis 
5 
70.8 ±9.9 
65.0-87.9 
16.3 ±9.9 
10.9-33.6 
82 
0.03 
Onychoteuthis banksii 
646 
74.3 ±20.0 
8.6-139.9 
14.9 ±11.3 
0.2-77.3 
9,676 
4.20 
Abraliopsis affinis 
3,671 
30.0 ±4.9 
18.7-45.4 
2.3 ±1.2 
0. 4-7.0 
8,424 
3.60 
Ancistrocheirus lesueuri 
139 
46.9 ±29.6 
8.8-203,1 
21.9 ±50.7 
0.3-484.7 
3,043 
1.30 
Pterygioteuthis giardi 
65 
21.8 ±3.4 
16.4-31.7 
0.7 ±0.4 
0.2-2. 5 
50 
0.02 
Mastigoteuthis dentata 
870 
69.1 ±14.2 
20.6-132.4 
17.4 ±10.7 
0.6-98.3 
15,166 
6.50 
Leachia dislocata 
628 
127.9 ±33.4 
49.6-248.1 
12.4 ±7.6 
0.8-52.3 
7,782 
3.40 
Liocranchia reinhardti 
238 
125.4 ±34.4 
42.2-199.6 
18.3 ±10.6 
1.2-48.0 
4,363 
1.90 
Megalocranchia sp. 
479 
109.1 ±54.2 
2.4-253.9 
15.4 ±12.2 
0.4-63.8 
7,296 
3.10 
Pholidoteuthis boschmai 
150 
97.3 ±25.5 
42.9-181.9 
26.5 ±23.0 
1.3-149.2 
3,978 
1.70 
Octopoteuthis deletron 
63 
45.6 ±23.5 
10.3-130.2 
15.8 ±20.2 
0.4-125.4 
996 
0.40 
Ctenopteryx sicula 
39 
34.7 ±6.3 
21.7-51.6 
3.9 ±2.5 
0.5-12.5 
153 
0.06 
Architeuthis sp. 
2 
62.9 ±25.8 
44.7-81.2 
4.8 ±4.2 
1.9-7. 7 
10 
<0.01 
