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?