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

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Presentation on theme: "Marine Nekton. Nekton Organisms capable of swimming against a current Fishes Marine mammals Marine reptiles Cephalopods Some crustaceans Sea birds."— Presentation transcript:

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 Nektonic Cephalopods

11 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

12 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://video- 013/None/EdithWidder_2013-low- en.mp4

13 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

14 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

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

16 Sea Snakes Yellow- bellied sea snake

17 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; 33-36 o C Sea Snakes

18 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 Snakes

19 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 Snakes

20 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 Snakes Banded sea krates forming mating group

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

22 Marine Iguanas 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/cm 2 –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 Sea Lion Walrus Family Phocidae Family Otariidae Family Odobenidae Hawaiian Monk Seal Pinnipeds

31 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 Biology and Natural History

32 Differences between seals and sea lions/fur seals

33 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)

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 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)

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


42 Deepest Diver (3km~1.5 miles)

43 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

44 Baleen

45 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)

46 Whale Migration

47 Whale Carcass Removal

48 Inquiry 1.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?

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