Marine 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 gt 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-researc
hers-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 coastal estuaries, 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
(3km1.5 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 shouldnt you load a dead whale with
  dynamite?