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Chapter six: Diet and nutrition
The diet of the narwhal (Monodon monoceros) includes fish (such as Greenland halibut and polar cod), muscular squid, and shrimp. Belugas (Delphinapterus leucas) feed on
fish such as capelin and sand lance, as well as larger species (cod and flounder). Sand
and bottom-living worms show that they probably feed on the bottom as well as in
midwater.
Sperm whales (Physeter macrocephalus) are the largest odontocete species. They feed
primarily on squid, although a few fish are taken as well (including sharks). Sperm whales
dive deep in the water column to feed on deep-living oceanic squid, most of which are
soft-bodied or gelatinous, luminous, and weak swimmers. Some sperm whales consume
squid over 15 m in length, but most of the species they consume are remarkably small
(0.5–7.0 kg). Pygmy and dwarf sperm whales (Kogia breviceps and Kogia sima) eat some of
the same species as their larger counterparts, but their diet also includes muscular squids
and octopods in continental shelf waters.
River dolphins (families Inidae, Pontoporiidae, Lipotidae, Platanistidae) inhabit freshwater systems of major rivers in South America, China, and the Indian subcontinent. The
Franciscana dolphin (Pontoporia blainvillei) has a marine distribution and is endemic to the
southwestern Atlantic where it is found in coastal and estuarine waters. Species found in
river systems feed on a variety of freshwater fish (including sharks) and prawns, and occasionally freshwater turtles. Franciscanas eat mainly bottom-dwelling fish, coastal cephalopods, and several species of shrimp.
Pinnipeds are made up of 19 species of true, earless seals (Phocidae), 16 species of fur
seals and sea lions (Otariidae) and walruses (Odobenus rosmarus), and the vast majority
of these species use pierce feeding. Fish and cephalopods are the most common prey
of pinnipeds. In the Southern Ocean, mesopelagic fish (e.g., myctophids, particularly
Gymnoscopelus and Electrona spp.) and squid are important prey for many pinniped species, including southern elephant seals and Ross seals (Ommatophoca rossi). Although shelf
and deep-sea squid are also an important part of the diet of adult southern elephant seals,
which exhibit a range of feeding strategies from pelagic dives within the open waters of
the Antarctic Circumpolar Current to demersal foraging over Antarctic continental shelves
(Hindell et al. 1991; Biuw et al. 2007).
Mesopelgic fish and squid are an important part of the diet of several species of
fur seals in the Arctocephalus genus, including Antarctic and subantarctic fur seals
(A. gazella and A. tropicalis) in the southern Indian Ocean sector of the Southern Ocean
(Lea et al. 2002; Makhado et al. 2008; Makhado et al. 2013). Other temperate species,
such as New Zealand fur seals (Arctocephalus forsteri), feed on mesoplegic prey (myctophids) in oceanic (offshore) waters, in addition to arrow squid (Nototodarus sloanii) and
other benthic fish species in continental shelf/slope waters (Harcourt et al. 2002). In the
North Pacific, between California and Alaska, the northern fur seal (Callorhinus ursinus)
eats primarily small shoaling fish (northern anchovy), Pacific herring, capelin, Pacific
sandlance and whiting, salmon and muscular squids; while in the Bering Sea, the species feeds largely on walleye pollock, salmon, Pacific herring and sandlance, northern
smooth tongue, and squid.
All species of sea lions include cephalopods in their diet, but only some eat fish.
California, Galapagos, and Japanese sea lions (Zalophus californianus, Zalophus wollebaeki,
and Zalophus japonicas) feed on shelf-living muscular squid and octopods, as well as oceanic, muscular squids; while Australian sea lions eat shelf octopods and cuttlefish. Steller
sea lions (Eumetopias jubatus), which range throughout the North Pacific, consume a wide
variety of fish such as walleye pollock, Atka mackerel, salmon, Pacific cod, hake, and herring, in addition to squid and octopod.
Chapter six: Diet and nutrition
The diet of the narwhal (Monodon monoceros) includes fish (such as Greenland halibut and polar cod), muscular squid, and shrimp. Belugas (Delphinapterus leucas) feed on
fish such as capelin and sand lance, as well as larger species (cod and flounder). Sand
and bottom-living worms show that they probably feed on the bottom as well as in
midwater.
Sperm whales (Physeter macrocephalus) are the largest odontocete species. They feed
primarily on squid, although a few fish are taken as well (including sharks). Sperm whales
dive deep in the water column to feed on deep-living oceanic squid, most of which are
soft-bodied or gelatinous, luminous, and weak swimmers. Some sperm whales consume
squid over 15 m in length, but most of the species they consume are remarkably small
(0.5–7.0 kg). Pygmy and dwarf sperm whales (Kogia breviceps and Kogia sima) eat some of
the same species as their larger counterparts, but their diet also includes muscular squids
and octopods in continental shelf waters.
River dolphins (families Inidae, Pontoporiidae, Lipotidae, Platanistidae) inhabit freshwater systems of major rivers in South America, China, and the Indian subcontinent. The
Franciscana dolphin (Pontoporia blainvillei) has a marine distribution and is endemic to the
southwestern Atlantic where it is found in coastal and estuarine waters. Species found in
river systems feed on a variety of freshwater fish (including sharks) and prawns, and occasionally freshwater turtles. Franciscanas eat mainly bottom-dwelling fish, coastal cephalopods, and several species of shrimp.
Pinnipeds are made up of 19 species of true, earless seals (Phocidae), 16 species of fur
seals and sea lions (Otariidae) and walruses (Odobenus rosmarus), and the vast majority
of these species use pierce feeding. Fish and cephalopods are the most common prey
of pinnipeds. In the Southern Ocean, mesopelagic fish (e.g., myctophids, particularly
Gymnoscopelus and Electrona spp.) and squid are important prey for many pinniped species, including southern elephant seals and Ross seals (Ommatophoca rossi). Although shelf
and deep-sea squid are also an important part of the diet of adult southern elephant seals,
which exhibit a range of feeding strategies from pelagic dives within the open waters of
the Antarctic Circumpolar Current to demersal foraging over Antarctic continental shelves
(Hindell et al. 1991; Biuw et al. 2007).
Mesopelgic fish and squid are an important part of the diet of several species of
fur seals in the Arctocephalus genus, including Antarctic and subantarctic fur seals
(A. gazella and A. tropicalis) in the southern Indian Ocean sector of the Southern Ocean
(Lea et al. 2002; Makhado et al. 2008; Makhado et al. 2013). Other temperate species,
such as New Zealand fur seals (Arctocephalus forsteri), feed on mesoplegic prey (myctophids) in oceanic (offshore) waters, in addition to arrow squid (Nototodarus sloanii) and
other benthic fish species in continental shelf/slope waters (Harcourt et al. 2002). In the
North Pacific, between California and Alaska, the northern fur seal (Callorhinus ursinus)
eats primarily small shoaling fish (northern anchovy), Pacific herring, capelin, Pacific
sandlance and whiting, salmon and muscular squids; while in the Bering Sea, the species feeds largely on walleye pollock, salmon, Pacific herring and sandlance, northern
smooth tongue, and squid.
All species of sea lions include cephalopods in their diet, but only some eat fish.
California, Galapagos, and Japanese sea lions (Zalophus californianus, Zalophus wollebaeki,
and Zalophus japonicas) feed on shelf-living muscular squid and octopods, as well as oceanic, muscular squids; while Australian sea lions eat shelf octopods and cuttlefish. Steller
sea lions (Eumetopias jubatus), which range throughout the North Pacific, consume a wide
variety of fish such as walleye pollock, Atka mackerel, salmon, Pacific cod, hake, and herring, in addition to squid and octopod.