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Order Pinniped (seals, sea lions, & walruses) Family Phocidae- true, earless seals. Family ... Family Odobenidae- walruses. 34 known species. Evolved 20 mya from Order Carnivora ...

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  • Organisms capable of swimming against a current
    • Fishes
    • Marine mammals
    • Marine reptiles
    • Cephalopods
    • Some crustaceans
    • Sea birds

Importance of Nekton

  • Large nekton can profoundly influence marine communities
  • Important in current or historical harvests
  • Fishes of critical importance to world food supply

Nektonic Crustacea

  • Pelagic crabs and shrimp
  • Larger euphausiids
  • Antarctic Krill (Euphausia superba)
    • 5-6 cm long
    • Dominant food of baleen whales
    • Increased fishery for livestock and poultry feeds

Krill & the Antarctic Food Web

Critical components of Antarctic food webs


Krill Fishery

  • Annual consumption by natural predators = 470 million MT
  • 1972: Japan and Russia began harvesting krill

Krill Fishery…

  • Potential harvest = 25-30 million MT/yr
  • Economic cost of fishery high
  • Patchy distribution complicates location
  • Depths may be 150-200m
  • Single net haul may collect 10 MT
  • Ecological consequences of removal poorly understood


  • Large size range: cm … > 20 m
  • Giant squid (Architeuthis): largest invertebrate
  • Water jet propulsion
  • Highly maneuverable and agile
  • Up to 10 m/s
  • Predators consuming 15-20% body mass per day

Giant Squid (Architeuthis dux)

  • One of the largest marine predators
  • Little is known about their ecology
  • Diet: deep-sea fishes, orange roughy, hokie
  • Rapid growth: full size in 3-5 years with a life span of ~7 years
  • Predators: fishes when squid are young, then sperm whales


Squid Fisheries

  • ~70% of present catch of cephalopods
  • Major source of human food
  • Driftnet fishery began in N. Pacific in 1981
    • Driftnets: monofilament panels 8-10 m tall and up to 50 km long
    • Set at night and allowed to drift while entangling prey


  • 1989: Japan, Korea, & Taiwan were deploying 800 driftnet vessels in N. Pacific
  • Harvested 300,000 T squid annually
  • Salmon and tuna also captured as by-catch
  • 750,000-1,000,000 seabirds killed annually
  • 20,000-40,000 marine mammal deaths
  • Destruction to zooplankton not quantified


  • 1993: UN General Assembly accepted a resolution calling for a moratorium on all high-seas drift-netting
  • Some illegal drift-netting continues

Marine Reptiles

Saltwater crocodile

Marine iguana

Sea snake

Marine turtle


Sea Snakes

  • Diversity:
  • Laticodtidae- krates- 5 species (1 is fw in Solomon Islands)
  • Hydrophidae- 54 different species
  • All derived from Colubrid ancestor; colubrids evolved 40 mya; Laticotids evolved from colubrids 30 mya
  • Location:
  • Laticotids- live from east coast India to Japan and come to the tip of Cape York (Australia)
  • Hydrophiids- found from south tip of Africa to India to South East Asian Islands to Japan to north half of Australia
  • Habitat:
  • Primarily tropical; coastalestuaries, coral reefs, open sea; 33-36oC

Sea Snakes

  • Behavior: Often schooling in aggregations; Not aggressive but human fatalities have occurred
  • Prey: Feed on small fish or squid, which are killed with powerful venom
  • Predators (few): sharks, snapper, grouper, crabs, saltwater crocodiles, raptors; they descend to escape
  • Venom: 2-10 times as toxic as that of a cobras

Sea Snakes

  • Adaptations to life in the sea
  • Osmoregulation: skin is impermeable to salts; salts eliminated by sublingual gland
  • Developing a flattened paddle-shaped tail and a laterally compressed body.
  • Reduced metabolic rate and increased tolerance for low oxygen levels
  • Lungs- greatly enlarged; hydrostatic organ
  • Gaseous exchange - lungs and the skin.

Sea Snakes

  • Reproduction:
  • Krates are oviparous and lay eggs on land
  • Hydrophiids are viviparous and produce young in the water
  • Not much known about breeding
  • However, olive sea snake breed in spring; seasonal courtship displays

Olive Sea Snake


Saltwater crocodiles

  • Largest living crocodilians: 6-7 m long
  • Eggs laid and incubated on land
  • Tropical and subtropical

Marine Iguanas

  • Marine lizard endemic to Galapagos islands
  • Herbivorous: graze on seaweeds
  • Salt-glands on nose to eliminate excess salt
  • Recently observed feeding on land for first time
  • They return to land to escape predators.
marine mammals
Marine mammals
  • Characteristics of marine mammals:
    • Warm-blooded
    • Breathe air
    • Have hair (or fur)
    • Bear live young
    • Females have mammary glands that produce milk for their young
marine mammals order sirenia
Marine mammals: Order Sirenia
  • Sirenian characteristics:
    • Large body size
    • Sparse hair all over body
    • Vegetarians
    • Toenails (on manatees only)
  • Includes:
    • Manatees
    • Dugongs
marine mammals order carnivora
Marine mammals: Order Carnivora
  • All members of order Carnivora have prominent canine teeth
  • Includes:
    • Sea otters
    • Polar bears
    • Pinnipeds (flipper-footed)
      • Walrus
      • Seals
      • Sea lions/fur seals

Hawaiian Monk Seal


Sea Otter

  • Enhydra lutris
    • Native to north Pacific
    • 394,000 hairs/cm2
    • No blubber
    • Female 45 lbs; Male 65lbs
    • Diet: Sea urchins, abalone, mussels, clams, crabs, snails and about 40 other marine species.
  • Uses tools
  • Dives to 330 ft
  • Rests in coastal kelp forests

Polar Bear

  • Ursa maritimus
    • United States, Canada, Russia, Greenland and on the Arctic islands of Norway
    • Male: 10 feet tall and weigh over 1400 lbs
    • Female: seven feet and weigh 650 lbs
    • wild polar bears live up to age 25.
  • Good swimmers
  • Thick blubber
  • Thick fur


Hawaiian Monk Seal

Family Phocidae


Sea Lion

Family Otariidae

Family Odobenidae


Biology and Natural History

  • Order Pinniped (seals, sea lions, & walruses)
    • Family Phocidae- true, earless seals
    • Family Otariidae- eared seals and sea lions
    • Family Odobenidae- walruses
  • 34 known species
  • Evolved 20 mya from Order Carnivora (ancestors of dogs and bears)
  • Differ in possession of external ears and mode of locomotion

Hawaiian Monk Seal

Family Phocidae

  • Lack external ears
  • Hind flippers propel them while swimming
  • Front flippers act as rudders
  • Travel on land is difficult (wiggle)

Sea Lion

Family Otariidae

  • Eared seals
  • Front flippers propel animal when swimming
  • Rear flippers act as rudders
  • Fairly mobile on land


Family Odobenidae

  • Found in Arctic region
  • Lack external ears
  • Paddle with front flippers
  • Rear flippers act as a rudder
  • Fairly mobile on land
marine mammals order cetacea
Marine mammals: Order Cetacea
  • Cetacean characteristics:
    • Blowholes on top of skull
    • Skull telescoped (streamlined shape)
    • Very few hairs
  • Includes:
    • Whales, dolphins, and porpoises
two suborders of order cetacea
Two suborders of order Cetacea

(55 mya- entered sea)

  • Suborder Odontoceti (toothed whales)
    • Echolocate (send sound through water)
    • Includes killer whale, sperm whale, dolphins, porpoises, and many others
  • Suborder Mysticeti (baleen whales)
    • Have rows of baleen plates instead of teeth
    • Includes blue whale, finback whale, humpback whale, gray whale, and many others
differences between dolphins and porpoises
Differences between dolphins and porpoises
  • Dolphins have:
    • An elongated snout (rostrum)
    • A sickle-shaped (falcate) dorsal fin
    • Conical-shaped teeth

Killer whale jawbone

differences between dolphins and porpoises41
Differences between dolphins and porpoises
  • Porpoises have:
    • A blunt snout (rostrum)
    • A triangle-shaped dorsal fin
    • Spade-shaped teeth

Deepest Diver

(3km~1.5 miles)

mysticeti the baleen whales
Mysticeti: The baleen whales
  • Mysticeti whales have baleen instead of teeth
  • Baleen plates:
    • Hang as parallel rows from the upper jaw
    • Are made of keratin
    • Are used as a strainer to capture zooplankton
    • Allows baleen whales to eat krill and small fish by the ton
types of baleen whales
Types of baleen whales
  • Baleen whales include three families:
    • Gray whale (a bottom-feeder with short baleen)
    • Rorqual whales (medium-sized baleen)
      • Balaenopterids (blue whales, finback whales, and other large whales )
      • Megapterids (humpback whales)
    • Right whales (surface skimmers with long baleen)

Whale Carcass Removal



  • Contrast the differences between nekton and plankton.
  • What characteristics distinguishes the three groups of pinnipeds?
  • Which marine reptiles bear live young (ovoviviparous)?
  • Why do whales migrate to Hawaii?
  • What is echolocation?
  • What is the difference between an odontocete and mysticete?
  • Why shouldn’t you load a dead whale with dynamite?