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Fishery Bulletin 107(3) 
Atlantic herring was present in stomachs of both 
winter and summer net-caught dolphins. It was of 
minor importance in the winter (only five individu- 
als identified in 20 stomachs analyzed), but was of 
primary importance (the largest biomass of all prey) 
in the summer; 29 individuals were present in the 
three stomachs analyzed. Lagenorhynchus acutus feeds 
on Atlantic herring in the summer months when the 
lipid content of herring is highest (Yasui and Gaskin, 
1986). Even though only three stomachs from the sum- 
mer were analyzed, our findings are similar to those 
reported in the literature. 
Lagenorhynchus acutus is rarely observed in the 
deeper waters of the continental slope south and east 
of New England (Selzer and Payne, 1988; Waring et 
al., 2008). The stomach contents of our single L. acutus 
taken incidentally in water 500 m deep, south of Georg- 
es Bank, were unlike those from the Gulf of Maine. 
The primary prey of this dolphin was the Madeira 
lanternfish, a myctophid living between 330 and 600 
m during the day in slope water and on the continen- 
tal slope (Backus et al., 1968). This indicates that L. 
acutus is not limited to feeding on shallow-water and 
epipelagic species. 
We have found that other species of cetaceans, when 
on the continental slope off the east coast of the Unit- 
ed States and southeastern Canada, feed primarily on 
Madeira lanternfish. We found large numbers, often 
more than 1000 individuals, in common dolphin (Del- 
phinus delphis), Atlantic spotted dolphin ( Stenella 
frontalis ), and pantropical spotted dolphin ( Stenella 
attenuata ), which had maximum numbers of 3646, 
568, and 870 Madeira lanternfish, respectively. A 
single harbor porpoise (Phocoena phocoena) taken 
incidentally off Cape Hatteras in winter had nearly 
500 Madeira lanternfish in its stomach (Read et al., 
1996). 
In the eastern North Atlantic Ocean, L. acutus feeds 
for the most part on oceanic fishes, primarily silvery 
pout ( Gadiculus argenteus ), lanternfishes, and pearl- 
sides (Maurolicus muelleri) (Couperus, 1997). Coupe- 
rus found that, in certain years, southwest of Ireland, 
L. acutus follow the spawning migration of mackerel 
( Scomber scombrus) inshore in the late winter and 
spring and are caught by net in the mackerel fishery. A 
comparison of trace and nontrace prey in their stomachs 
indicated that although mackerel represented 88% of 
the fresh prey, the dolphins’ prior meals had comprised 
88% mid-water fishes. Lagenorhynchus acutus feeds on 
herring when in shallow water off Norway (Jonsgard 
and Nordlii, 1952). 
In addition to the above mentioned species, stomachs 
of L. acutus stranded on the coast of northern Europe 
have contained otoliths of blue whiting ( Micromesistius 
poutassou), tacauds (Trisopterus spp.), horse mackerel 
( Trachurus trachurus), pilchard ( Sardina pilchardus), 
sand lances, pollock (Pollachius virens), whiting (Mer- 
langius merlangus), haddock, gobies (Gobiidae), drag- 
onet (Callionymidae), and argentine ( Argentina sphy- 
raena), (Desportes, 1985; Rogan et al., 1997; Santos et 
al., 1995 1 , 1996 2 ). Santos et al. (1995) also identified 
four species of cephalopods in the stomachs of L. acutus 
stranded in Scotland. 
Despite previous observations of L. acutus feeding 
on sand lance (Weinrich et al., 2001), in this study 
we found sand lance in only one stomach, that of a 
stranded dolphin. Although approximately 50% of the 
stranded animals in our study had virtually empty 
stomachs, this one stomach contained 549 sand lance 
otoliths. The relatively empty stomachs indicate a lack 
of feeding before stranding. Little information exists 
on the digestion and egestion rates for cephalopod and 
teleost prey in cetaceans; therefore, it is impossible to 
accurately estimate how long a period elapsed between 
the last feeding and the stranding event (Mintzer et 
al., 2008). It is also possible that L. acutus regurgi- 
tates food because of the stress of a stranding event, 
leaving its stomach virtually empty. The trace sand 
lance otoliths found in the one stomach could have 
been trapped in the stomach rugae, giving a false 
impression of a recent meal. Regardless of when the 
sand lances were eaten, their presence in the stomach 
corroborates historic observations of L. acutus feeding 
on sand lance (Katona et al., 1978; Weinrich et al., 
2001 ). 
Lagenorhyncus acutus appears to exhibit size-selective 
predation; the average fish prey length is approximately 
200 mm and cephalopod prey mantle length is about 50 
mm during the winter (Fig. 2). The total lengths of the 
cephalopods (tentacle length plus the mantle length) 
are little more than half the length of the fishes. One 
large 464-mm silver hake, whose size was determined 
from a 22.4-mm otolith and two 100 mm dentaries, was 
found in the stomach of a winter net-caught dolphin. 
We assume that the dolphin ate only the head of this 
fish, which would itself have been approximately 200 
mm. It is possible that the head had been cut off and 
discarded by fishermen. 
Some very small red hake (less than 90 mm) were 
found in the stomachs of two L. acutus (Fig. 2A). These 
were smaller than the smallest silver hake, haddock, 
and herring eaten, and are therefore evidence of second- 
ary consumption. There were no large red hake or had- 
dock in either of the two stomachs. Large silver hake, 
the only predatory fish in each of the two L. acutus 
stomachs, was therefore the likely primary consumer 
of the small red hake. 
Two cephalopods, spoonarm octopus and longfin in- 
shore squid, were both important prey in our L. acu- 
tus. In winter stomachs, the benthic octopus was the 
second most abundant prey species, and the pelagic 
squid was the sixth most abundant (Table 3). Histori- 
cal publications document northern shortfin squid in L. 
1 Santos, M. B., G. J. Pierce, G. Wijnsma, H. M. Ross, and R. J. 
Reid. 1995. Diets of small cetaceans stranded in Scotland 
1993-1995. ICES Council Meeting (C.M.). 1995/N:6, 9 p. 
2 Santos, M. B., G. J. Pierce, A. Lopez, A. Barreiro, and A. 
Guerra. 1996. Diets of small cetaceans stranded in NW 
Spain 1994-95. ICES Council Meeting (C.M.). 1996/N:11, 6 p. 
