Food habits of Atlantic white-sided dolphins (Lagenorhynchus acutus) off the coast of New England.

Abstract--Although the Atlantic white-sided dolphin (Lagenorhynchus acutus) is one of the most common dolphins off New England, little has been documented about its diet in the western North Atlantic Ocean. Current federal protection of marine mammals limits the supply of animals for investigation to those incidentally caught in the nets of commercial fishermen with observers aboard. Stomachs of 62 L. acutus were examined; of these 62 individuals, 28 of them were caught by net and 34 were animals stranded on Cape Cod. Most of the net-caught L. acutus were from the deeper waters of the Gulf of Maine. A single stomach was from the continental slope south of Georges Bank. At least twenty-six fish species and three cephalopod species were eaten. The predominant prey were silver hake (Merluccius bilinearis), spoonarm octopus (Bathypolypus bairdii), and haddock (Melanogrammus aeglefinus). The stomach from a net-caught L. acutus on the continental slope contained 7750 otoliths of the Madeira lanternfish (Ceratoscopelus maderensis). Sand lances (Ammodytes spp.) were the most abundant (541 otoliths) species in the stomachs of stranded L. acutus. Seasonal variation in diet was indicated; pelagic Atlantic herring (Clupea hareugus) was the most important prey in summer, but was rare in winter. The average length of fish prey was approximately 200 mm, and the average mantle length of cephalopod prey was approximately 50 mm.

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The Atlantic white-sided dolphin (Lagenorhynchus acutus) is restricted to the temperate and subpolar North Atlantic Ocean, ranging from west Greenland (approximately 64[degrees]N) to North Carolina (about 35[degrees]N) in the western North Atlantic, and from Norway to the Bay of Biscay in the eastern North Atlantic (Leopold and Couperus, 1995). There are thought to be three populations in the western North Atlantic--the Gulf of Maine, Gulf of St. Lawrence, and Labrador Sea populations (Palka et al., 1997). Seasonal shifts in the Gulf of Maine population have been reported; highest numbers are found in summer and fall and lowest numbers in winter (Northridge et al., 1997; Palka et al., 1997). Most of our animals, however, were obtained during the winter.

This study is the first detailed analysis of the food habits of the Atlantic white-sided dolphin in the western North Atlantic Ocean, hereafter referred to as L. acutus rather than the more cumbersome Atlantic white-sided dolphin. Previously, only three live-caught specimens from off New England have been examined for stomach contents and reported in the literature. A single specimen collected in 1954 (Schevill, 1956) and a second collected in 1976, likely a discarded incidental take from a gillnet set near Jeffreys Ledge (Katona et al., 1978), were taken in summer and contained the same species of fish and squid. These records indicated that Atlantic herring (Clupea harengus), silver hake (Merluccius bilinearis), and northern shortfin squid (Illex illecebrosus) could be significant components of the diet. A single animal driven ashore in Trinity Bay, Newfoundland, also contained Atlantic herring and northern shortfin squid (Sergeant and Fisher, 1957).

Other observations have reported a few more prey species for L. acutus. Stomachs of 14 of 40 stranded L. acutus examined from Cobscook Bay, Maine, contained one silver hake, nine shortfin squid, five rainbow smelt (Osmerus mordax), and fragments of unidentified decapod shrimp (St. Aubin and Geraci, 1979; Sergeant et al., 1980). Katona et al. (1978) reported probable feeding on sand lances (Ammodytes spp.) by L. acutus associated with feeding humpback (Megaptera novaeangliae) and fin whales (Balaenoptera physalus). The only L. acutus feeding incident recorded was on December 20, 1997, on Stellwagen Bank, southwestern Gulf of Maine, when a group was observed circling and feeding on a school of sand lance (Weinrich et al., 2001).

[FIGURE 1 OMITTED]

Materials and methods

This study records stomach contents from 28 incidentally caught and 34 stranded L. acutus from the Gulf of Maine population off the coast of New England (Fig. 1). The animals examined were collected between 1991 and 2006, most of them from 2004-5. The incidentally caught (hereafter referred to as net-caught) animals were taken either by otter trawl (22 stomachs) or by sink gillnet (six stomachs). Of these, 26 were from the Gulf of Maine, one was from deep water (500 m) on the continental slope south of Georges Bank near Munsen Canyon, and one was from the continental shelf south of Narragansett Bay. Thirty-four stomachs were from strandings: 33 from outer Cape Cod, Barnstable County, MA, and one from Naushon, Elizabeth Islands, Dukes County, MA (Table 1).

We have examined every available stomach of net-caught L. acutus. All were taken in the U.S. commercial fishery and sampled aboard ship by fisheries observers of the National Marine Fisheries Service (NMFS), Northeast Fisheries Science Center (NEFSC, Woods Hole, MA), Northeast Fisheries Observer Program (NEFOP). NEFOP is the permitting and monitoring agency of the commercial fishing fleet in compliance with the Marine Mammal Protection Act (MMPA) and the U.S. Endangered Species Act (ESA).

Stranded animals were obtained by volunteers of the Cape Cod Stranding Network, currently known as International Fund for Animal Welfare (IFAW), Yarmouth, MA. Most of the stomachs were initially frozen and curated by the NEFSC.

Contents from stomachs determined to be intact (reliable) were examined for frequency, relative abundance, and size (length, weight) of prey. Two net-caught dolphins examined and subsequently eliminated from the analysis were one partly decomposed female with a mud-filled stomach and thoracic cavity and virtually no food in the stomach, and a partially decomposed male with an almost empty stomach taken on the continental shelf south of Narragansett Bay.

Stomachs were weighed whole, divided into their three components (forestomach, main, and pyloric), emptied of contents, and weighed again to determine both the size of the stomach and the mass of its contents. Whole prey (termed "nontrace" prey because they were found relatively intact [not in traces]) were separated, identified, weighed, and measured directly (standard length for fishes and mantle length for cephalopods); well-digested prey (termed "trace prey" because they were found in traces as hard parts, e.g. skull bones, otoliths, jaws, prootic bones of clupeids, teeth and opercula of bony fishes, toothplates of hagfish, and cephalopod beaks and pens) were separated, identified, weighed, and original length measurements were estimated indirectly (standard length for fishes and mantle length for cephalopods). Otoliths were removed from skulls of both nontrace and trace fishes and then cleaned, dried, and measured. The remaining contents were soaked overnight in hot water, if necessary, or elutriated directly through a series of sieves to remove soft tissue and retain hard parts. All items found were identified to the lowest taxonomic level possible (usually to species) by using our own reference collection and published guides (Campana, 2004; Clarke, 1962, 1986; Collette and Klein-MacPhee, 2002; Gregory, 1933; Harkonen, 1986; Smale et al., 1995; Vecchione, 2002). Forestomach contents were then counted and measured and used in all further analyses (Table 2). All fish hard parts, including bones and otoliths, and hagfish toothplates, were stored dried. Cephalopod beaks were removed from buccal masses, cleaned, and stored in 70% ethanol. Crustacean remains and all parasites were counted and also stored in 70% ethanol.

Prey lengths and weights were calculated from otolith lengths for fishes, from lower rostral lengths for squids, and from lower hood lengths for octopods (Tables 3 and 4). Calculations of prey size were used to construct the frequency diagrams shown in Figure 2 for the most abundant species.

[FIGURE 2 OMITTED]

Results and discussion

Stomachs of immature and adult dolphins of both sexes were examined. The two calves were 119 cm and 139 cm in length and had milk but no solid prey in their stomachs. The smallest juvenile was 161 cm and contained solid prey but no milk in its stomach. Females longer than 200 cm and males longer than 230 cm were considered mature (Sergeant et al., 1980) (Table 1).

Altogether, the 62 L. acutus stomachs contained 5561 fishes of at least 26 species, and 304 cephalopods of one octopus and two squid species (Table 2). Most of the stomach contents were trace remains. The most commonly found prey species, in order of abundance, were: 1) Madeira lanternfish (Ceratoscopelus maderensis), 3876 individuals, all but one from a single stomach; 2) silver hake (Merluccius bilinearis), 945 individuals from 22 stomachs; 3) sand lance (Ammodytes spp.), 271 individuals from a single stranded dolphin; 4) spoonarm octopus (Bathypolypus bairdii), 212 individuals from 14 stomachs; 5) haddock (Melanogrammus aeglefinus), 107 individuals from eight stomachs; 6) Atlantic hagfish (Myxine glutinosa), 105 individuals from 17 stomachs; and 7) red hake (Urophycis chuss), 103 individuals from 14 stomachs.

Gulf of Maine, winter

The 20 stomachs containing prey from L. aeutus net-caught in winter in the Gulf of Maine provide our most complete data set for analysis (Table 3). These stomachs contained 1155 fishes of 17 species and 274 cephalopods of three species. Five species, three fishes and two cephalopods, silver hake (45.3%), spoonarm octopus (14.3%), haddock (15.3%), red hake (18.7%), and longfin inshore squid (1.1%) accounted for almost 95% of the mass of prey. We were unable to calculate the mass of hagfish; their toothplates (the only hard parts remaining in the stomachs) are not proportional to an individual's size.

In order of frequency of occurrence and numerical abundance 1) the demersal silver hake was found in 90% of the stomachs and accounted for 71% of the fishes eaten; 2) the benthic spoonarm octopus were found in 65% of the stomachs and accounted for 77% of cephalopods; 3) the demersal haddock were found in 35% of the stomachs and made up 8.9% of the fishes; 4) the demersal red hake were found in 65% of the stomachs and accounted for 7.7% of the fishes; 5) the benthic scavenger hagfish were found in 50% of the stomachs and accounted for 7.5% of the fishes; and 6) the pelagic longfin squid were found in 60% of the stomachs and accounted for 23% of the cephalopods. The four fish species constituted 96% of the fish prey eaten, and the two cephalopods made up nearly all of the cephalopods consumed. Fishes made up 81% of all prey, and cephalopods, the remainder (19%). Notable were the scarcity or absence in winter of pelagic fish species (e.g., herring, alewives, smelt, mackerel, and sand lance).

Gulf of Maine, summer

Only three stomachs were available from animals net-caught in the Gulf of Maine in summer. These three contained 150 fishes of six species and six squids of two species (Table 4). The most abundant prey were silver hake, Atlantic herring, and red hake, which numerically accounted for 63%, 19%, and 8% of total prey, respectively. These three species made up 29%, 64%, and less than 1% of total mass, respectively. Silver hake was numerically the most abundant species in both winter and summer stomachs. The pelagic Atlantic herring, which was almost absent in winter, was the most important species present in summer. The benthic spoonarm octopus, which was very abundant in the winter stomachs, was absent in summer.

Continental Slope south of Georges Bank

A single L.acutus was obtained south of Georges Bank near Munsen Canyon, in 500 m of water. This dolphin was a 252-cm lactating female. Its stomach contained over 3900 fishes of seven species (Table 4). Except for 37 silver hake and one white hake, this individual had been feeding on open-ocean pelagic fishes, of which 99% (3875) were Madeira lanternfish. Two other lanternfishes (the glacier lanternfish [Benthosema glaciale] and the soft lanternfish [Diaphus mollis]), the white barracudina (Arctozenus risso), and the boa dragonfish (Stomias boa) were also present. This stomach contained 9.6 kg of prey, the largest amount of any L. acutus in this study; Madeira lanternfish made up 58% of the prey mass, and silver hake 41%.

Strandings

Stomachs of the stranded dolphins contained little identifiable material (Table 1). No nontrace fish or cephalopods were present in any of these stomachs. About one-quarter of the otoliths (27%) were too digested to be identified or measured and therefore could not be used for further analysis. Of the identifiable otoliths, 87% were those of sand lance, all from one stomach (Table 2). The presence of these fish in that stomach was the only evidence indicating recent feeding.

Twenty-nine of the 34 strandings occurred in the winter. Stomachs of these dolphins contained eight fish species and three cephalopod species. Sand lance constituted 79% of all prey (both fishes and cephalopods) and made up 60% of the total mass. Silver hake and longfin squid made up 18% and 16% of the total mass, respectively. Five fish species present in the stomachs of stranded animals--cunner (Tautogolabrus adspersus), radiated shanny (Ulvaria subbifurcata), rainbow smelt, sand lance, and yellowtail flounder (Limanda ferruginea)--were not found in the stomachs of our net-caught dolphins. Of the five stomachs from nonwinter strandings, four were empty and the fifth (in September) contained only one identifiable fish, a silver hake.

Prey species

In the Gulf of Maine, silver hake was by far the most important prey species in the stomachs that we examined. A schooling, demersal fish, silver hake is found only along the Atlantic coast of North America, from Florida to Newfoundland, at a wide range of depths, from shallow waters to 900 m (Collette and Klein-MacPhee 2002; Iwamoto 2002). Previously, reports indicated the presence of silver hake in L. acutus diets but not as an important prey. Among the few otoliths found in stranded L. acutus stomachs, silver hake was the second most abundant prey species (Table 4).

Silver hake is also an important prey for other marine mammals in the Gulf of Maine. It was a primary prey for harbor porpoise (Phocoena phocoena) during summer in the Bay of Fundy (Recchia and Read, 1989) and in autumn near Jeffreys Ledge in the western Gulf of Maine (Gannon et al., 1998). It was also the predominant prey for net-caught young of the year harbor seals (Phoca vitulina) taken in shallow waters in the western Gulf of Maine (Williams, 1999).

Atlantic herring was present in stomachs of both winter and summer net-caught dolphins. It was of minor importance in the winter (only five individuals 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 summer 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 Georges 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 continental 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 United States and southeastern Canada, feed primarily on Madeira lanternfish. We found large numbers, often more than 1000 individuals, in common dolphin (Delphinus 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). Couperus 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 (Merlangius merlangus), haddock, gobies (Gobiidae), dragonet (Callionymidae), and argentine (Argentina sphyraena), (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 regurgitates 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 secondary consumption. There were no large red hake or haddock 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 inshore squid, were both important prey in our L. acutus. In winter stomachs, the benthic octopus was the second most abundant prey species, and the pelagic squid was the sixth most abundant (Table 3). Historical publications document northern shortfin squid in L. acutus diets, but give no record of spoonarm octopus or longfin inshore squid. Spoonarm octopus was rare (one individual in 95 stomachs) in harbor porpoise from the Gulf of Maine (Gannon et al., 1998).

Both Atlantic hagfish and spoonarm octopus are bottom-dwelling species associated with sandy to. muddy substrates on the continental shelf and upper slope. Spoonarm octopus is restricted to the western North Atlantic, and is found from Greenland to Florida (Muus, 2002). Atlantic hagfish is found on both sides of the North Atlantic and is bipolar, inhabiting comparable latitudes in the southern hemisphere (Collette and Klein-MacPhee, 2002). Lagenorhyncus acutus probably does not dive to the bottom to forage. It probably consumes benthic octopus and hagfish in several ways, namely 1) it may feed on catch unwanted and discarded by fishermen and 2) it may feed on animals that have been forced off the bottom by otter trawls or that have come off the bottom on their own, as with hagfish, to feed on fishes disturbed by otter trawls. Most of our net-caught dolphins (79%) were taken in bottom otter trawls. Spoonarm octopus and Atlantic hagfish were only found in dolphins caught in bottom otter trawls, not from those in sink or drift gillnets. Lagenorhyncus acutus feed in the vicinity of nets (Leopold and Couperus. 1995), as do bottlenose dolphin (Tursiops truncatus) (Corkeron et al., 1990) and other cetaceans (Fertl and Leatherwood, 1997). This would explain both the capture of L. acutus by otter trawls and the occurrence of benthic animals in their diet.

Acknowledgments

We thank M. Moore and D. Rana for assistance sorting stomach contents. We also acknowledge K. Touhey, K. Pugliares, S. Herzig, C. Harry, and the volunteers of the Cape Cod Stranding Network; K. Patchett and K. Matassa, Marine Science Education and Research Center, University of New England; D. Potter, B. Lentell, S. Wetmore, N. Gilles, and the Observers of the NOAA Fisheries Northeast Fisheries Science Center, Northeast Fisheries Observer Program (NEFOP); C. Potter, and M. Vecchione, Smithsonian Institution; R. Backus, M. Moore, A. Bogomolni, and R. Harbison, Woods Hole Oceanographic Institution; G. Early, Mote Marine Laboratory; K. Hartel and A. Williston, Museum of Comparative Zoology; J. Galbraith, J. Burnett, W. Duffy, B. Josephson, R. Merrick, F. Serchuk, S. Sutherland, G. Thornton, J. Kircun, and T. Vidal, Northeast Fisheries Science Center; C. Lea, Sea Education Association; M. Weinrich, Whale Center of New England; and one anonymous reviewer.

Manuscript submitted 18 September 2008. Manuscript accepted 5 May 2009.

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James E. Craddock (contact author) [1]

Pamela T. Polloni [1]

Brett Hayward [2]

Frederick Wenzel [3]

Email address for contact author: [e-mail]

[1] Biology Department Woods Hole Oceanographic Institution Woods Hole, Massachusetts 02543

[2] Integrated Statistics, Inc. 16 Sumner St. Woods Hole, Massachusetts 02543

[3] Protected Species Branch Northeast Fisheries Science Center National Marine Fisheries Service 166 Water Street, Woods Hole, Massachusetts 02543

(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.

Table 1
Summary comparison of numbers, sex, and stomach contents of
34 stranded vs. 28 net-caught Atlantic white-sided dolphins
(Lagenorhynchus acutus) collected in the western North
Atlantic Ocean off the coast of New England, between 1991
and 2006; and seasonality of the net-caught individuals.
Total net-caught includes two calves with empty stomachs;
seasonal net-caught excludes the two calves; S. of
Georges = South of Georges Bank. Nontrace = whole prey.

                             Strandings       Total net-caught

Number of dolphins           34               28
Depth where captured
  (m), mean (range)          0                189.8 (55-503)
Number of males              22               9
  Length of males (cm),
    mean (range)             227 (156-280)    208 (173-260)
  Adult males (>230cm)       10               2
Number of females            12               16
  Length of females
    (cm), mean (range)       205 (168-219)    199 (161-253)
  Adult females (>200cm)     10               6
Number unsexed               0                3
Number of stomachs
  containing fond            22%              25%
Number of empty stomachs     12%              3%
Number of otoliths           856              10287
  unidentified               231              54
Number of fish species       8                21
Number of cephalopod beaks   34               535
  Number of
    cephalopod species       3                3
Number of identified prey
  Nontrace fishes            0                50
  Near nontrace
    fishes (skulls)          7                56
  Total fishes               332              5179
  Nontrace cephalopods       0                2
  Near nontrace
    cephalopods              0                1
  Total cephalopods          20               282

                              Seasonal net-caught

                             Winter           Summer

Number of dolphins           22               3
Depth where captured
  (m), mean (range)          186.9 (71-265)   107.0 (55-187)
Number of males              9                0
  Length of males (cm),
    mean (range)             208 (173-260)    0
  Adult males (>230cm)       2                0
Number of females            12               3
  Length of females
    (cm), mean (range)       203 (171-253)    178 (161-203)
  Adult females (>200cm)     4                1
Number unsexed               1
Number of stomachs
  containing fond            20%              3%
Number of empty stomachs     2%               0
Number of otoliths           2157             287
  unidentified               51               2
Number of fish species       17               6
Number of cephalopod beaks   519              11
  Number of
    cephalopod species       3                2
Number of identified prey
  Nontrace fishes            35               15
  Near nontrace
    fishes (skulls)          38               4
  Total fishes               1120             135
  Nontrace cephalopods       0                2
  Near nontrace
    cephalopods              0                1
  Total cephalopods          274              4

                           Seasonal net-caught

                             S. of Georges

Number of dolphins           1
Depth where captured
  (m), mean (range)          503
Number of males              0
  Length of males (cm),
    mean (range)             0
  Adult males (>230cm)       0
Number of females            1
  Length of females
    (cm), mean (range)       252
  Adult females (>200cm)     1
Number unsexed
Number of stomachs
  containing fond            1%
Number of empty stomachs     0
Number of otoliths           7843
  unidentified               1
Number of fish species       7
Number of cephalopod beaks   5
  Number of
    cephalopod species       1
Number of identified prey
  Nontrace fishes            0
  Near nontrace
    fishes (skulls)          14
  Total fishes               3924
  Nontrace cephalopods       0
  Near nontrace
    cephalopods              0
  Total cephalopods          4

Table 2
Summary comparison of abundance of identified prey found
in the stomachs of both net-caught and stranded Atlantic
white-sided dolphins (Lagenorhynchus acutus) collected
between 1991 and 2006, in the western North Atlantic
Ocean off the coast of New England. n = number of stomachs;
S. of Georges = South of Georges Bank.

Prey species                   Common name              Family

Alosa pseudoharengus           alewife                  Clupeidae
Ammodytes spp.                 sand lance               Ammodytidae
Arctozenus risso               white barracudina        Paralepididae
Benthosema glaciale            glacier lanternfish      Myctophidae
Ceratoscopelus maderensis      Madeira lantern fish     Myctophidae
Clupea harengus                Atlantic herring         Clupeidae
Diaphus dumerilii              Dumeril's lanternfish    Myctophidae
Diaphus mollis                 soft lanternfish         Myctophidae
Enchelyopus cimbrius           fourbeard rockling       Phycidae
Gadus morhua                   Atlantic cod             Gadidae
Hippoglossoides platessoides   American plaice          Pleuronectidae
Limanda ferruginea             yellowtail flounder      Pleuronectidae
Maurolicus weitzmani           Atlantic pearlside       Sternoptychidae
Melanogrammus aeglefinus       haddock                  Gadidae
Merluccius bilinearis          silver hake              Merlucciidae
Myxine glutinosa               Atlantic hagfish         Myxinidae
Nezumia bairdii                marlin-spike             Macrouridae
Osmerus mordax                 rainbow smelt            Osmeridae
Scomber scombrus               Atlantic mackerel        Scombridae
Sebastes fasciatus             Acadian redfish          Scorpaenidae
Stomias boa                    boa dragonfish           Stomiidae
Tautogulabrus adspersus        cunner                   Labridae
Ulvaria subbifurcata           radiated shanny          Stichaeidae
Urophycis chuss                red hake                 Phycidae
Urophycis tenuis               white hake               Phycidae
Zoarces americanus             ocean pout               Zoarcidae
Bathypolypus bairdii           spoonarm octopus         Octopodidae
Illex illecebrosus             northern shortfin squid  Ommastrephidae
Loligo pealeii                 longfin inshore squid    Loliginidae
Total

                                Net-caught   Net-caught   Net-caught
                                  winter        summer      calves
Prey species                       n=20          n=3          n=2

Alosa pseudoharengus                 2
Ammodytes spp.
Arctozenus risso
Benthosema glaciale                  7
Ceratoscopelus maderensis            1
Clupea harengus                      5            29
Diaphus dumerilii                    1
Diaphus mollis
Enchelyopus cimbrius                18
Gadus morhua                         1             4
Hippoglossoides platessoides         4
Limanda ferruginea
Maurolicus weitzmani                 2
Melanogrammus aeglefinus           103
Merluccius bilinearis              823           99
Myxine glutinosa                    87            2
Nezumia bairdii                      4
Osmerus mordax
Scomber scombrus                     2
Sebastes fasciatus                                3
Stomias boa
Tautogulabrus adspersus
Ulvaria subbifurcata
Urophycis chuss                     90           13
Urophycis tenuis                     4
Zoarces americanus                   1
Bathypolypus bairdii               210
Illex illecebrosus                   1            5
Loligo pealeii                      63            1
Total                             1429          156           0

                                Net-caught
                                  S. of       Stranded
                                 Georges       winter
Prey species                       n=1          n=29

Alosa pseudoharengus
Ammodytes spp.                                 271
Arctozenus risso                      5
Benthosema glaciale                   3
Ceratoscopelus maderensis          3875
Clupea harengus
Diaphus dumerilii
Diaphus mollis                        2
Enchelyopus cimbrius
Gadus morhua
Hippoglossoides platessoides
Limanda ferruginea                                3
Maurolicus weitzmani
Melanogrammus aeglefinus                          4
Merluccius bilinearis                37          18
Myxine glutinosa                                 16
Nezumia bairdii
Osmerus mordax                                   10
Scomber scombrus
Sebastes fasciatus
Stomias boa                           1
Tautogulabrus adspersus                            9
Ulvaria subbifurcata                               1
Urophycis chuss
Urophycis tenuis                      1
Zoarces americanus
Bathypolypus bairdii                               2
Illex illecebrosus                                 2
Loligo pealeii                        4           16
Total                              3928          352

Table 3
Analysis of prey in 20 Atlantic white-sided dolphins
(Lagenorhynchus acutus) incidentally net-caught during
winter in the Gulf of Maine between 2001 and 2006.
NA = not applicable; * = Myzine glutinosa double
toothplates, 4 per individual; ** = may include a
few Urophycis tenuis.

                                      Prey species

                            Number       Number        Number
Fishes and                      of           of            of
cephalopods             occurrences       items    individuals

Alosa pseudoharengus              2            4             2
Benthosema glaciale               3           13             7
Ceratoscopelus
  maderensis                      1            1             1
Clupea harengus                   4            8             5
Diaphus dumerillii                2            2             1
Enchelyopus cimbrius              4           29            18
Gadus morhua                      1            2             1
Hippoglossoides
  platessoides                    2            7             4
Maurolicus weitzmani              2            2             2
Melanogrammus
  aeglefinus                      7          184           103
Merluccius bilinearis            18         1646           823
Myzine glutinosa                 10       332 *             87
Nezumia bairdii                   1            6             4
Scomber scombrus                  1            2             2
Urophycis chuss **               13          191            90
Urophycis tenuis                  3            7             4
Zoarces americanus                1            2             1
  Total otoliths                            2106
  Total fishes                                            1155
Bathypolypus bairdii             13          390           210
Illex illecebrosus                1            2             1
Loligo pealeii                   12          127            63
  Total cephalopod
    beaks                                    519
  Total cephalopods                                        274
  Total all prey                                          1429

                                    Otoliths or beaks

                                        Average        Length
Fishes and                  Number       length         range
cephalopods               measured         (mm)          (mm)

Alosa pseudoharengus              4          3.7      2.5-4.9
Benthosema glaciale               7          0.9      0.7-1.4
Ceratoscopelus
  maderensis                      1          2.3      2.3
Clupea harengus                   5          3.3      1.8-4.4
Diaphus dumerillii                2          2.8      2.6-2.9
Enchelyopus cimbrius             29          3.2      1.9-4.0
Gadus morhua                      2         11.0     11.0
Hippoglossoides
  platessoides                    7          3.1      2.5-3.7
Maurolicus weitzmani              2          1.6      1.5-1.8
Melanogrammus
  aeglefinus                    171         10.2      6.0-13.8
Merluccius bilinearis           306          9.9      3.0-22.4
Myzine glutinosa                NA
Nezumia bairdii                   6          5.6      4.0-6.2
Scomber scombrus                  2          3.8      2.5-5.0
Urophycis chuss **              111          8.9      1.6-19.1
Urophycis tenuis                  7         14.3     12.6-15.6
Zoarces americanus                2          3.0      3.0
  Total otoliths                664
  Total fishes
Bathypolypus bairdii             96          2.8      1.7-4.0
Illex illecebrosus                1          1.5      1.5
Loligo pealeii                   63          0.9      0.4-1.7
  Total cephalopod
    beaks
  Total cephalopods             160
  Total all prey                824

                                Prey length

                           Average       Length
Fishes and                  length        range
cephalopods                   (mm)    weight (g)

Alosa pseudoharengus
Benthosema glaciale
Ceratoscopelus
  maderensis
Clupea harengus               202.4   97.1-277.1
Diaphus dumerillii
Enchelyopus cimbrius         148.0   48.9-213.6
Gadus morhua
Hippoglossoides
  platessoides
Maurolicus weitzmani
Melanogrammus
  aeglefinus                  203.2   87.4-327.2
Merluccius bilinearis         202.5   58.6-464.1
Myzine glutinosa                 NA
Nezumia bairdii
Scomber scombrus
Urophycis chuss **            208.9   8.5-489.1
Urophycis tenuis
Zoarces americanus
  Total otoliths
  Total fishes
Bathypolypus bairdii           49.8   36.3-64.5
Illex illecebrosus
Loligo pealeii                 51.6   16.8-118.9
  Total cephalopod
    beaks
  Total cephalopods
  Total all prey

                                      Prey weight

                                       Weight           Total
Fishes and                 Average     range            weight
cephalopods                   (mm)       (g)             (kg)

Alosa pseudoharengus                                      0.27
Benthosema glaciale                                      <0.01
Ceratoscopelus
  maderensis                                             <0.01
Clupea harengus                88.2   7.4-177.8           0.44
Diaphus dumerillii                                       <0.01
Enchelyopus cimbrius          22.2    0.9-62.3           0.40
Gadus morhua                                              0.32
Hippoglossoides
  platessoides                                            0.35
Maurolicus weitzmani                                     <0.01
Melanogrammus
  aeglefinus                   91.7   5.9-341.2           9.44
Merluccius bilinearis          57.2   1.0-669.7          27.91
Myzine glutinosa                 NA                         NA
Nezumia bairdii                                             NA
Scomber scombrus                                          0.58
Urophycis chuss **            103.8   0.1-809.4          11.50
Urophycis tenuis                                          0.89
Zoarces americanus                                       <0.01
  Total otoliths
  Total fishes                                           52.10
Bathypolypus bairdii           42.6   11.2-99.0           8.78
Illex illecebrosus                                        0.01
Loligo pealeii                 10.9    0.8-52.8           0.69
  Total cephalopod
    beaks
  Total cephalopods                                       9.48
  Total all prey                                         61.58

Table 4
Analysis of prey in 33 Atlantic white-sided
dolphins (Lagerzorhynciaus acutus): 3 net-caught
in the Gulf of Maine in summer between 1992 and
2003; 1 net-caught south of Georges Bank in
summer 1993; and 29 stranded on Cape Cod in
winter between 1994 and 2006. NA = not applicable;
* = Myxine glutinosa double toothplates, 4 per
individual.

                                             Prey species

Fishes and cephalopods         Occurrences         Items   Individuals
Net-caught summer
Gulf of Maine (3 stomachs)
  Clupea harengus                        3            56            29
  Gadus morhua                           2             8             4
  Merluccius bilinearis                  2           193            99
  Myxine glutinosa                       1           7 *             2
  Sebastes fasciatus                     1             4             3
  Urophycis dross                        1            24            13
  Illex illecebrosus                     2             9             5
  Loligo pealeii                         1             2             1
  Total                                              303           156
Net-caught summer
south of Georges Bank
(1 stomach)
  Arctozenus risso                       1             9             5
  Benthosema glaciale                    1             5             3
  Ceratoscopelus maderensis              1          7750          3875
  Diaphus mollis                         1             2             2
  Merluccius bilinearis                  1            73            37
  Stomias boa                            1             2             1
  Urophycis tenuis                       1             1             1
  Loligo spp.                            1             5             4
  Total                                             7847          3928
Strandings winter
(29 stomachs)
  Ammodytes spp.                         1           541           271
  Limanda ferruginea                     1             6             3
  Melanogrammus aeglefinus               1             8             4
  Merluccius bilinearis                  2            31            18
  Myxine glutinosa                       6            53            16
  Osmerus mordax                         2            20            10
  Tautogolabrus adspersus                1            16             9
  Ulvaria subbifurcata                   1             2             1
  Bathypolypus bairdii                   2             2             2
  Illex illecebrosus                     1             4             2
  Loligo pealeii                         4            28            16
  Total                                              711           352

                                            Otoliths or beaks (mm)

                                                  Mean      Length
Fishes and cephalopods              Measured     length     range
Net-caught summer
Gulf of Maine (3 stomachs)
  Clupea harengus                         43       4.1     3.0-5.0
  Gadus morhua                             8       4.5     4.3-5.0
  Merluccius bilinearis                   79       6.9     2.6-12.0
  Myxine glutinosa                        NA
  Sebastes fasciatus                       4       1.7     1.1-2.1
  Urophycis dross                         23       2.2     1.5-4.7
  Illex illecebrosus                       5       2.8     1.8-3.5
  Loligo pealeii                           1       1.5     1.5
  Total
Net-caught summer
south of Georges Bank
(1 stomach)
  Arctozenus risso                         6       3.4     3.3-3.6
  Benthosema glaciale                      4       1.3     1.1-1.5
  Ceratoscopelus maderensis              100       2.9     2.2-3.7
  Diaphus mollis                           2       1.7     1.4-2.0
  Merluccius bilinearis                   32      12.9    11.0-15.4
  Stomias boa                              0
  Urophycis tenuis                         1      10.0    10.0
  Loligo spp.                              1       1.8
  Total
Strandings winter
(29 stomachs)
  Ammodytes spp.                          32       2.2     1.9-2.9
  Limanda ferruginea                       0
  Melanogrammus aeglefinus                 8      11.6    10.5-12.5
  Merluccius bilinearis                   15       5.2     3.9-6.3
  Myxine glutinosa                        NA
  Osmerus mordax                           0
  Tautogulabrus adspersus                 16       1.0     0.9-1.2
  Ulvaria subbifurcata                     2       2.5     2.5
  Bathypolypus bairdii                     2       2.1     1.4-2.8
  Illex illecebrosus                       2       3.7     3.7-3.8
  Loligo pealeii                          12       1.6     0.4-2.9
  Total

                                       Prey length (mm)     Prey Weight
                                                                Mean
                                       Mean        Length     weight
Fishes and cephalopods               length         range        (g)
Net-caught summer
Gulf of Maine (3 stomachs)
  Clupea harengus                      259.7   180.2-318.7      154.4
  Gadus morhua                          76.0    67.2-89.2         5.0
  Merluccius bilinearis                139.8    50.2-246.7       18.0
  Myxine glutinosa
  Sebastes fasciatus
  Urophycis dross                       25.0     5.7-93.6         0.4
  Illex illecebrosus                   145.2    96.3-179.4       70.9
  Loligo pealeii                       117.2                     40.5
  Total
Net-caught summer
south of Georges Bank
(1 stomach)
  Arctozenus risso
  Benthosema glaciale
  Ceratoscopelus maderensis             59.9    45.8-75.1         1.5
  Diaphus mollis
  Merluccius bilinearis               2692.0   229.5-321.5      120.0
  Stomias boa
  Urophycis tenuis
  Loligo spp.                          144.9                     67.4
  Total
Strandings winter
(29 stomachs)
  Ammodytes spp.                       140.9   124.8-172.2       15.1
  Limanda ferruginea
  Melanogrammus aeglefinus             249.7   212.2-279.7      152.1
  Merluccius bilinearis                107.3    81.1-131.3        7.0
  Myxine glutinosa
  Osmerus mordax
  Tautogulabrus adspersus
  Ulvaria subbifurcata
  Bathypolypus bairdii
  Illex illecebrosus                   191.7   189.2-194.1      135.1
  Loligo pealeii                       126.5    15.7-246.4       89.3
  Total

                                         Prey weight

                                                    Total
                                     Weight        weight
Fishes and cephalopods            range (g)          (kg)
Net-caught summer
Gulf of Maine (3 stomachs)
  Clupea harengus                 48.2-271.5         3.85
  Gadus morhua                    3.29-7.55          0.03
  Merluccius bilinearis            0.6-91.5          1.78
  Myxine glutinosa
  Sebastes fasciatus
  Urophycis dross                 0.05-4.1          -0.01
  Illex illecebrosus              18.3-115.9         0.35
  Loligo pealeii                                     0.04
  Total                                              6.05
Net-caught summer
south of Georges Bank
(1 stomach)
  Arctozenus risso
  Benthosema glaciale
  Ceratoscopelus maderensis        0.9-2.0           5.60
  Diaphus mollis
  Merluccius bilinearis           70.0-210.0         3.94
  Stomias boa
  Urophycis tenuis
  Loligo spp.                                        0.07
  Total                                              9.61
Strandings winter
(29 stomachs)
  Ammodytes spp.                  10.3-29.0          4.09
  Limanda ferruginea
  Melanogrammus aeglefinus        90.0-210.6         1.22
  Merluccius bilinearis            2.7-12.5          0.13
  Myxine glutinosa
  Osmerus mordax
  Tautogulabrus adspersus
  Ulvaria subbifurcata
  Bathypolypus bairdii
  Illex illecebrosus             130.3-139.8         0.27
  Loligo pealeii                   0.7-283.6         1.07
  Total                                              6.78