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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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020-Nekton

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Marine Nekton


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Nekton

  • Organisms capable of swimming against a current

    • Fishes

    • Marine mammals

    • Marine reptiles

    • Cephalopods

    • Some crustaceans

    • Sea birds


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Importance of Nekton

  • Large nekton can profoundly influence marine communities

  • Important in current or historical harvests

  • Fishes of critical importance to world food supply


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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


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Euphausia superba


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Who eats Krill?


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Krill & the Antarctic Food Web

Critical components of Antarctic food webs


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  • Krill Fishery

  • Annual consumption by natural predators = 470 million MT

  • 1972: Japan and Russia began harvesting krill


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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


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  • Squids

  • 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


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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

http://evomech7.blogspot.com/2006/12/japan-researchers-film-live-giant.html


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  • 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


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Driftnets

  • 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


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  • Drift-nets

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

  • Some illegal drift-netting continues


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Marine Reptiles

Saltwater crocodile

Marine iguana

Sea snake

Marine turtle


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Sea Snakes


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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


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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


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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.


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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


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Saltwater crocodiles

  • Largest living crocodilians: 6-7 m long

  • Eggs laid and incubated on land

  • Tropical and subtropical


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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.


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Marine Birds


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Marine Mammals


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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


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Marine mammals: Order Sirenia

  • Sirenian characteristics:

    • Large body size

    • Sparse hair all over body

    • Vegetarians

    • Toenails (on manatees only)

  • Includes:

    • Manatees

    • Dugongs


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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


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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


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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


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Pinnipeds

Hawaiian Monk Seal

Family Phocidae

Walrus

Sea Lion

Family Otariidae

Family Odobenidae


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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


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Differences between seals and sea lions/fur seals


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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)


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Sea Lion

Family Otariidae

  • Eared seals

  • Front flippers propel animal when swimming

  • Rear flippers act as rudders

  • Fairly mobile on land


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Walrus

Family Odobenidae

  • Found in Arctic region

  • Lack external ears

  • Paddle with front flippers

  • Rear flippers act as a rudder

  • Fairly mobile on land


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Marine mammals: Order Cetacea

  • Cetacean characteristics:

    • Blowholes on top of skull

    • Skull telescoped (streamlined shape)

    • Very few hairs

  • Includes:

    • Whales, dolphins, and porpoises


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Marine mammals: Order Cetacea


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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


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Differences between dolphins and porpoises

  • Dolphins have:

    • An elongated snout (rostrum)

    • A sickle-shaped (falcate) dorsal fin

    • Conical-shaped teeth

Killer whale jawbone


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Differences between dolphins and porpoises

  • Porpoises have:

    • A blunt snout (rostrum)

    • A triangle-shaped dorsal fin

    • Spade-shaped teeth


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Deepest Diver

(3km~1.5 miles)


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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


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Baleen


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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)


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Whale Migration


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Whale Carcass Removal

http://perp.com/whale/video.nc.html


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Inquiry

  • 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?


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