Food habits of Atlantic white-sided dolphins (Lagenorhynchus acutus) off the coast of New England.
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.
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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%.
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.
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.
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) 
Pamela T. Polloni 
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(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
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|Author:||Craddock, James E.; Polloni, Pamela T.; Hayward, Brett; Wenzel, Frederick|
|Date:||Jul 1, 2009|
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