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020-Nekton

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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  1. Marine Nekton

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

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

  4. 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

  5. Euphausia superba

  6. Who eats Krill?

  7. Krill & the Antarctic Food Web Critical components of Antarctic food webs

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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

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

  15. Marine Reptiles Saltwater crocodile Marine iguana Sea snake Marine turtle

  16. Sea Snakes

  17. 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

  18. 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

  19. 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.

  20. 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

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

  22. 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.

  23. Marine Birds

  24. Marine Mammals

  25. 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

  26. Marine mammals: Order Sirenia • Sirenian characteristics: • Large body size • Sparse hair all over body • Vegetarians • Toenails (on manatees only) • Includes: • Manatees • Dugongs

  27. 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

  28. 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

  29. 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

  30. Pinnipeds Hawaiian Monk Seal Family Phocidae Walrus Sea Lion Family Otariidae Family Odobenidae

  31. 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

  32. Differences between seals and sea lions/fur seals

  33. 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)

  34. Sea Lion Family Otariidae • Eared seals • Front flippers propel animal when swimming • Rear flippers act as rudders • Fairly mobile on land

  35. Walrus Family Odobenidae • Found in Arctic region • Lack external ears • Paddle with front flippers • Rear flippers act as a rudder • Fairly mobile on land

  36. Marine mammals: Order Cetacea • Cetacean characteristics: • Blowholes on top of skull • Skull telescoped (streamlined shape) • Very few hairs • Includes: • Whales, dolphins, and porpoises

  37. Marine mammals: Order Cetacea

  38. 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

  39. Differences between dolphins and porpoises • Dolphins have: • An elongated snout (rostrum) • A sickle-shaped (falcate) dorsal fin • Conical-shaped teeth Killer whale jawbone

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

  41. Deepest Diver (3km~1.5 miles)

  42. 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

  43. Baleen

  44. 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)

  45. Whale Migration

  46. Whale Carcass Removal http://perp.com/whale/video.nc.html

  47. 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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