nekton notes.ppt
TRANSCRIPT
Marine NektonMarine Nekton
NektonNektonOrganisms capable of swimming against a current
• Fishes• Marine mammals• Marine reptiles• Cephalopods• Some crustaceans• Sea birds
Importance of NektonImportance of Nekton
• Large nekton can profoundly influence marine communities
• Important in current or historical harvests
• Fishes of critical importance to world food supply
Nektonic CrustaceaNektonic 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
Euphausia superba
Who eats Krill?
Krill & the Antarctic Food WebCritical components of Antarctic food webs
Krill Fishery• Annual consumption by natural predators =
470 million MT• 1972: Japan and Russia began harvesting
krill
Krill Fishery…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
Nektonic Cephalopods
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
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
http://video-subtitle.tedcdn.com/talk/podcast/2013/None/EdithWidder_2013-low-en.mp4
Squid FisheriesSquid 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
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
Drift-netsDrift-nets
• 1993: UN General Assembly accepted a resolution calling for a moratorium on all high-seas drift-netting
• Some illegal drift-netting continues
Marine turtle
Marine iguana
Saltwater crocodile
Marine ReptilesMarine Reptiles
Sea snake
Sea SnakesSea 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
Sea SnakesSea 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 SnakesSea 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 SnakesSea 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
Sea SnakesSea Snakes
• Largest living crocodilians: 6-7 m long• Eggs laid and incubated on land• Tropical and subtropical
Saltwater crocodiles
Marine IguanasMarine 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 BirdsMarine Birds
Marine MammalsMarine 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
Sirenian characteristics:– Large body size– Sparse hair all over body– Vegetarians– Toenails (on manatees only)
Includes:– Manatees– Dugongs
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 OtterEnhydra 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 BearUrsa 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
Sea Lion
Walrus
Family Phocidae
Family Otariidae Family Odobenidae
Hawaiian Monk Seal
Pinnipeds
Order Pinniped (seals, sea lions, & walruses)Family Phocidae- true, earless sealsFamily Otariidae- eared seals and sea lionsFamily 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
Biology and Natural History
Differences between seals and sea lions/fur seals
Family Phocidae
Hawaiian Monk Seal
• Lack external ears• Hind flippers propel them while swimming• Front flippers act as rudders• Travel on land is difficult (wiggle)
Sea LionFamily Otariidae
• Eared seals• Front flippers propel animal when swimming• Rear flippers act as rudders• Fairly mobile on land
WalrusFamily 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
• Cetacean characteristics:– Blowholes on top of skull– Skull telescoped (streamlined shape)– Very few hairs
• Includes:– Whales, dolphins, and porpoises
Marine mammals: Order Cetacea
Two suborders of order Cetacea
• 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
(55 mya- entered sea)
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 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 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
Baleen
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 Migration
Whale Carcass Removal
http://video.google.com/videoplay?docid=-4126934954744847447&hl=en
Inquiry1. Contrast the differences between nekton
and plankton.2. What characteristics distinguishes the three
groups of pinnipeds?3. Which marine reptiles bear live young
(ovoviviparous)?4. Why do whales migrate to Hawaii?5. What is echolocation?6. What is the difference between an
odontocete and mysticete? 7. Why shouldn’t you load a dead whale with
dynamite?