1. Marine Nekton Marine Nekton
Plankton are animals that cannot swim against a horizontal current. In the next series of classes, we’ll examine larger, stronger swimming animals that are able to move against currents. While plankton occupy lower trophic levels in marine food webs, nekton are predators that occupy higher levels ranging up to the top of oceanic food webs.

2. Nekton Organisms capable of swimming against a current Fishes
Marine mammals
Marine reptiles
Cephalopods
Some crustaceans
Sea birds
Nekton
When we think of nektonic organisms, fishes are the most likely group to come to mind. Fish are certainly important and prominent groups of nekton, however, there are other nekton including marine mammals, marine reptiles, cephalopods, some crustaceans and sea birds. In the series of lectures, we’ll take a look at nektonic organisms. We’ll begin with the less common groups and finish with fishes.

3. Importance of Nekton
Large nekton can profoundly influence marine communities
Importance of Nekton
Nekton are the most visible components of marine food webs. Further, their energy requirements are such that they can profoundly influence the marine communities that they inhabit. Recall the influence of just a few orcas on the sea otter populations off Alaska.
Some are of current commercial importance, others such as whales were of historical commercial importance.
A large component of the protein supply of the world comes from the fishes of the oceans. Indirectly, many fishes are captured to manufacture high-protein animal feeds. Thus even when we consume chickens or hogs, we are often deriving energy from the oceans.
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
Nektonic Crustacea
Nektonic crustacea consist of pelagic swimming crabs, shrimp and larger euphausiids. The most famous of the euphausiids is the antarctic krill (Euphausia superba).
Krill are large animals that may be 5-6 cm in length. They occur in massive swarms that may be kilometers in length. These swarms are a rich food supply for baleen whales.
A commercial fishery for krill has also developed. Krill decompose rapidly and after dying they release powerful enzymes that rapidly break their tissues down. For this reason, it has been difficult to provide a fresh enough product for human consumption. The majority of krill are harvested as animal feeds. They are used in fish farming to provide farmed fish such as salmon with the desirable pink flesh color.

5. Euphausia superba Euphausia superba
Note the large swimming legs on the euphausiid that give them their mobility and classification as nekton.

6. Who eats Krill?

7. Krill & the Antarctic Food Web
Critical components of Antarctic food webs
Krill & the Antarctic Food Web
Krill are essential components of antarctic food webs. They are consumed by baleen whales, seals, squid, penguins and winged birds, carnivorous zooplankton and pelagic fishes. How many trophic levels are their above krill?

8. Krill Fishery Annual consumption by natural predators = 470 million MT
1972: Japan and Russia began harvesting krill
Krill Fishery
This graph illustrates the development of the krill fishery in antarctic. Exploratory fishing took place in 1972 and since ‘73, catches have been recorded. The landings are in thousands of tonnes. Note how the fishery increased through the late 70’s. The dip in the early 80Õs was due to a drop in demand for krill rather than a change in their abundance. The fishery remained high through the rest of the 80’s. In the early 1990’s the Russian component of the fishery diminished leaving the Japanese and Chileans.

9. Krill Fishery… Potential harvest = 25-30 million MT/yr
Economic cost of fishery high
Patchy distribution complicates location
Depths may be m
Single net haul may collect 10 MT
Ecological consequences of removal poorly understood
Krill Fishery…
Why are we so interested in harvesting krill? This is potentially one of the largest single species fisheries in the world. The potential krill harvest is estimated at million metric tons per year.
Economically, it can be a difficult species to catch. The location of the fishery is remote and conditions in Antarctic waters can be difficult. The patchy distribution of krill means that swarms can be hard to locate. The depths of the swarms may also complicate collection. Once located, a single net tow through a large patch may yield 10 MT.
We still don’t know what the consequences of the removal of krill are to the Antarctic ecosystem. Clearly this is an important species in that food web. We must ensure that sufficient krill are left to sustain the other users of the resource. The fishery has had a very positive impact on research in the Antarctic. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has conducted the most extensive research on the Antarctic ecosystem. Funding for CCAMLR came from interest in managing the krill fishery. Without a fishery for krill, it is unlikely that we would have learned nearly as much as we have about that ecosystem.

10. Nektonic Cephalopods Nektonic Cephalopods
Nektonic cephalopods consist of squids, cuttlefish and octopods. Squid make up the largest proportion of commercially-fished cephalopods and the potential world catch is estimated at 10 million tons annually. (Compare that to the potential million tons of krill that could be harvested each year).
We will concentrate on squids. Cuttlefish and octopods are less common and more often are associated with demersal habitats.

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
Squids
Squids come in a wide of sizes. Small species may only be a few centimeters in length while the giant squid (Architeuthis) is the largest invertebrate on the planet with a length of over 20 m.
All utilize waterjet propulsion. Water is taken in via the mantle and expelled through a nozzle called a siphon. This nozzle can be rotated and provides the squid with remarkable agility and speed. Squid can move at up to 10 m/s.
They are voracious predators that may consume % of their body mass per day.
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
Giant Squid
These enormous animals are poorly understood. The problem is that their habitat is the deep-sea and no live specimen has ever been collected. All we know of them comes from dead specimens and the stomach contents of their predators (sperm whales).
What do they eat? As one scientist who studies them put it Òanything they want to!Ó Their diet includes deep-sea fishes and other squids.
Most cephalopods grow very rapidly. For example, an octopus can reach full size in less than a year and may only live one year. Giant squids are similar. Their large size doesnÕt imply longevity and slow growth. They can reach full size in 3-5 years and probably only live for up to 7 years.
When young, they are prey for a variety of fishes including the species that they later consume as adults. When they mature, their only natural predators are sperm whales.
Predators: fishes when squid are young, then sperm whales

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
Squid Fisheries
As mentioned earlier, squids make up 70% of the world cephalopod catch and they are a major source of food for humans. Large number of squid inhabit the pelagic waters of the North Pacific.
In 1981, a driftnet fishery for squid began in that region. Driftnets are vertical panels much like gillnets. They may be 8-10 m tall and hang vertically in the water-column. What makes them different is their length. A single net may be as much as 50 km in length. The nets are set at night and allowed to drift while entangling squid that swim into them.

14. Driftnets Harvested 300,000 T squid annually
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 Nets
The problem with driftnets is that they are indiscriminate in their catch and many organisms other than squid are captured. The capture of non-target organisms is called by-catch. Bycatch in the N. Pacific driftnet fishery became a serious problem.
By 1989, three countries: Japan, Korea and Taiwan were deploying 800 drift-net vessels in the region. This fleet harvested 300,000 tons of squid annually. The bycatch from this fishery was enormous. Salmon and tuna were intercepted and landings from the driftnet fishery constituted a large source of mortality for species that were already fished heavily.
Diving birds also encountered the nets and 750,000-1 million birds of a variety of species were thought to have died each year.
Marine mammals had difficulty detecting the thin nets and 20,000-40,000 cetaceans died each year.
The nets probably resulted in the destruction of salp chains and other gelatinous zooplankton and that impact wasn’t 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
Drift Nets…
In 1993 the United Nations passed a moratorium on high seas drift netting and the fishery ended. Illegal drift-netting operations continue in the Pacific and drift-nets are still used in the Mediterranean by countries such as Italy.

16. Sea Snakes Yellow- bellied sea snake Sea Snakes
Snakes are cold-blooded (poikilotherms). Consequently, their distributions are restricted to warm waters and sea snakes are only found in the Indo-Pacific region. There is concern that if a sea-level canal were constructed across Panama, they could become introduced to the Caribbean.
Sea snakes inhabit estuaries, coral reef areas and the open sea and they are often found in large schooling groups.
Normally, sea snakes are quite docile and donÕt pose a threat to humans. They have powerful venom which they use to incapacitate fishes or squid. Human fatalities have occurred and these are most common when the snakes wash up on beaches and humans handle the reptiles.
They have few natural predators other than sharks, saltwater crocodiles and eagles.
Yellow- bellied sea snake

17. Sea Snakes Diversity: Location: Habitat:
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

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.
Developing salt excreting glands under the tongue.
2.Developing a flattened paddle-shaped tail and a laterally compressed body making it an efficient swimmer.
3.Reducing its metabolic rate. Sea snakes are capable of remaining submerged for up to 2 hours by decreasing its metabolic rate and developing an increased tolerance for low oxygen levels. After one breath at the surface, it can dive again. A sea snake also has valve-like flaps over its nostrils to stop water flowing into the lungs.
4.The lungs of sea snakes are greatly enlarged, extending to the base of the tail enabling a large volume of oxygen to be stored in the lungs.
5.Parts of the lung are believed to function as a hydrostatic organ regulating the snake's buoyancy.
6.Gaseous exchange occurs through both the lungs and the skin. Up to 22% of the oxygen is supplied from the sea water through the skin and all excess carbon dioxide is lost into the sea.

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
Banded sea krates forming mating group
Olive Sea Snake

21. Saltwater crocodiles Largest living crocodilians: 6-7 m long
Eggs laid and incubated on land
Tropical and subtropical
Saltwater Crocodiles
Saltwater crocodiles are the largest of living crocodilians and adults can reach 6-7 m in length. These seagoing animals may travel thousands of miles in the ocean. They are wide-ranging and may move into freshwater areas as well. They havenÕt entirely left land and must return to lay their eggs which are incubated in a terrestrial nest. Their poikilothermic nature means that their distributions are limited to warm areas. Diets include fishes, invertebrates and vertebrates.

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.
Marine Iguanas
These are the only marine lizards and they are endemic to the Galapagos Islands off Ecuador. Marine iguanas have flattened tails that assist them in swimming and they have adapted to an aquatic life. Their primary diet are algae that encrust the rocks around the islands. Iguanas dive to feed on the algae and in the process, their bodies undergo substantial cooling. After diving and feeding bouts, they must warm themselves on land to raise their body temperature. During feeding they accumulate a lot of salt that is excreted via specialized salt-glands on their noses. Recently, iguanas have been observed feeding on terrestrial vegetation. The stresses of El Ni–os may have driven them to forage ashore.

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
STATUS: California, or southern, sea otters are listed as "threatened" under the federal Endangered Species Act (ESA) and "fully protected" under California state law. No other U.S. otter population is currently listed under the ESA. In 2003, there is a push to list a stock of the Alaskan sea otters, or northern sea otters, as "endangered" under the ESA. In Canada , the otter population in British Columbia is classified as "threatened" by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). All of the otters in the U.S. are protected under the U.S. Marine Mammal Protection Act (MMPA). DESCRIPTION: The sea otter has the thickest fur in the animal kingdom. Unlike other marine mammals, the sea otter does not have a layer of blubber (fat) to help keep it warm. If an otter's fur gets coated with oil or any other substance, it can easily die from cold and exposure.
SIZE: The sea otter is the largest member of the weasel family. Southern sea otters typically reach about four feet in length. Females average 45 pounds, while males average 65 pounds. Northern sea otters can reach up to 100 pounds.
POPULATION: Today there are about 2,500 southern sea otters off the coast of California. There are between 27,500 and 52,500 northern sea otters residing in Alaska, Canada and Washington. There are approximately 15,000 in Russia. Two hundred years ago, demand for the otter's pelt nearly led to its extinction.
LIFESPAN: Male sea otters live an average of ten to 15 years, while female sea otters live an average of 15 to 20 years.
RANGE: The sea otter?s historic range stretched from Japan, along the coast of Siberia and the Aleutian Chain and down the Alaska, British Columbia, Washington, Oregon and California coast to Baja California.
HABITAT:Shallow coastal waters of the northern Pacific.
FOOD:Sea urchins, abalone, mussels, clams, crabs, snails and about 40 other marine species.
BEHAVIOR: Sea otters are the only mammals other than primates known to use tools. Otters use small rocks or other objects to pry prey from rocks and to hammer or pry open their food. They can dive up to 330 feet when foraging for food. Otters rest in coastal kelp forests, often draping the kelp over their bodies to keep from drifting away.
OFFSPRING: Sea otters breed throughout the year. Females give birth to one pup after a gestation period of six to eight months.
THREATS: Oil spills, habitat loss, disease, gill net entanglement and conflict with shellfish fisheries.
PROTECTION: *CITES, Appendix I, Marine Mammal Protection Act, Endangered Species Act
*Convention on International
The Sea Otter (Enhydra lutris) is a large otter native to the North Pacific, from northern Japan and Kamchatka east across the Aleutian Islands south to California. The heaviest of the otters, Sea Otters are the only species within the genus Enhydra.
Hunted extensively for their luxurious fur—the densest of all mammals with up to 394,000 hairs per square centimeter— from 1741 onwards, sea otter populations were greatly reduced to the point of extermination in many parts of their historic range. By 1911 the world population was estimated to be just 1,000-2,000 individuals in 13 colonies. Its estimated that a half million to a million otters were killed over time and over hunted and the population is thought to have been 150,000 to 300,000 historically before the years of the great hunt. Although several subspecies are still endangered, the otters have since been legally protected, and reintroduction efforts have shown positive results in some areas.

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.
Not federally listed as endangered or threatened. The International Union for Conservation of Nature (IUCN), Polar Bear Specialist Group lists most populations as "stable." DESCRIPTION: The polar bear rivals the Kodiak bear as the largest four-footed carnivore on Earth and can live up to 25 years. Although the polar bear?s coat appears white, each individual hair is actually a clear hollow tube that channels the sun?s energy directly to the bear?s skin and helps it stay warm. The polar bear?s entire body is furred, even the bottom of its paws. That helps prevent bears from slipping on the ice. The polar bear is classified as a marine mammal. Its feet are partially webbed for swimming, and its fur is water-repellent. A formidable predator, it has extremely sharp claws.
SIZE: Males are 8 to 11 feet long and weigh 500 to 1,100 pounds but can reach as much as 1,500 pounds. Females are smaller, measuring 6 to 8 feet long, and weigh from 350 to 600 pounds, occasionally reaching 700 pounds.
POPULATION: Worldwide there are thought to be 22,000-27,000 polar bears in 19 separate populations. They can be found in the United States, Canada, Russia, Greenland and on the Arctic islands of Norway. There are estimated to be about 3,000 to 5,000 polar bears in Alaska.
RANGE:Polar bears are found throughout the Arctic and are the most nomadic of all bear species. They travel an average of 5,500 miles a year or 15 miles a day. In the United States, polar bears are located in two Alaskan populations: the Chukchi/Bering Seas of western Alaska and the Beaufort Sea off northern Alaska.
HABITAT: The entire circumpolar Arctic region is polar bear habitat. They are equally comfortable in the water and on land. Polar bears can be found on pack ice, coastal islands, coastlines and even out in Arctic waters. They are exceptional swimmers and have been observed in the sea more than 100 miles from the nearest land or pack ice.
FOOD: Polar bears are strictly carnivores and feed or scavenge only meat. Their primary prey is the ringed seal though they also take bearded, harp and hooded seals and the occasional walrus youngster. They will also scavenge walrus and whale carcasses. That sometimes results in temporary aggregations of polar bears at such sites. Other species, such as the Arctic fox, rely entirely upon "polar bear left-overs" after the bears have eaten their fill of seal skin and blubber, leaving the remaining meat for such scavengers.
BEHAVIOR: The two main focuses of this solitary creature's life are to conserve energy and to hunt. Only pregnant females dig dens and hibernate in the traditional sense for extended periods. The other bears may enter into what is referred to as "walking hibernation" where they remain active and continue to hunt and feed, even though some of their metabolic processes may slow (decreased heart rates, respiration, lowered temperatures, etc.). Polar bears depend mostly on their sense of smell to determine the location of prey. Their white coats make great camouflage for hunting seals, and they will wait patiently for hours next to a seal?s air hole waiting for the seal to take a breath. Once the seal arrives, the polar bear will use its immense strength and sharp claws to clutch the seal and drag it through the small blowhole.
OFFSPRING: Females are able to breed at the age of five years. They dig dens either on the coastal mainland or out on the drifting pack ice in late October or early November, and then remain denned until the next spring. An average of two cubs are born, each weighing about 1 pound at birth and growing to about 15 pounds by the time they emerge in the spring. The cubs have much to learn and usually remain with their mothers for more than two years.
THREATS:
The primary threat facing polar bears today may be global warming. Scientists have already documented measurable effects in the body sizes and reproductive success of bears at Hudson?s Bay. This southern-most population of polar bears has adapted to an ice-free summer by moving onshore at Churchill, Manitoba, and fasting through the short summer season until freeze-up occurs, and the bears can return to the ice. Global warming has resulted in prolonged ice-free periods, and the polar bears are left stranded onshore for longer and longer periods. Break-up in the spring occurs an average of days earlier than 20 years ago and was four weeks earlier in Scientists estimate that for every week of delay in freeze-up, polar bears lose at least 22 pounds of critical fat reserves. Pregnant females are losing so much weight that they fail to produce enough milk for their cubs, which then suffer increased mortality. Once females fail to attain a minimum weight they won?t give birth at all, and scientists can already document a 15 percent drop in birth rates.
Another globally produced impact to polar bears are chemical pollutants that find their way into the cold Arctic ecosystems and then never disappear. Such chemicals as PCB?s (polychlorinated biphenyls), banned from the U.S. plastics industry since the 1970s, concentrate in the blubber of prey species that are then eaten by the bears. Such concentrations of these and other toxins are linked to immune deficiencies and generally reduced fitness in some polar bears.
The third threat of note is the proposed oil and gas development on the Arctic National Wildlife Refuge in northeastern Alaska. This is the most important onshore denning habitat for polar bears in the United States. About half of the bears from the Beaufort Sea population den onshore, and half of these select the refuge?s coastal plain. This is the very place proposed for oil exploration. Both the seismic exploration phase and an eventual oil extraction phase could introduce serious disturbances that may result in den abandonment and death of the offspring.
PROTECTION: CITES* Appendix II, U.S. Marine Mammal Protection Act, Agreement on the Conservation of Polar Bears.
Good swimmers
Thick blubber
Thick fur

30. Pinnipeds Hawaiian Monk Seal Family Phocidae Sea Lion Walrus
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. Hind flippers propel them while swimming Front flippers act as rudders
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. Front flippers propel animal when swimming
Sea Lion
Family Otariidae
Eared seals
Front flippers propel animal when swimming
Rear flippers act as rudders
Fairly mobile on land

35. Paddle with front flippers Rear flippers act as a rudder
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. Echolcation - the location of objects by their echos - is a highly specialized faculty that enables dolphins to explore their environment and search out their prey in a watery world where sight is often of little use. As sound travels four and a half times faster in water than in air, the dolphin's brain must be extremely well adapted in order to make a rapid analysis of the complicated information provided by the echoes. Although the ability to echolcate has only been proven experimentally for a few odontocete species, the anatomical evidence - the presence of the melon, nasal sacs and specialized skull structures - suggests that all dolphins have this ability.
The dolphin is able to generate sound in the form of clicks, within its nasal sacs, situated behind the melon. The frequency of this click is higher than that of the sounds used for communication and differs between species. The melon acts as a lens whi ch focuses the sound into a narrow beam that is projected in front of the animal.
When the sound strikes an object, some of the energy of the soundwave is reflected back towards the dolphin. It would appear that the panbone in the dolphin's lower jaw receives the echo, and the fatty tissue behind it transmits the sound to the middle e ar and thence to the brain. It has recently been suggested that the teeth of the dolphin, and the mandibular nerve that runs through the jawbone may transmit additional information to the dolphin's brain.
As soon as an echo is received, the dolphin generates another click. The time lapse between click and echo enables the dolphin to evaluate the distance between it and the object; the varying strength of the signal as it is received on the two sides of th e dolphin's head enable it to evaluate direction. By continuously emitting clicks and receiving echoes in theis way, the dolphin can track objects and home in on them.
The echolocation system of the dolphin is extremely sensitive and complex. Using only its acoustic senses, a bottlenose dolphin can discriminate between practically identical objects which differ by ten per cent or less in volume or surface area. It can do this in a noisy environment, can whistle and echolocate at the same time, and echolocate on near and distant targets simultaneously - feats which leave human sonar experts gasping

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
I am absolutely not making this incident up; in fact I have it all on videotape. The tape is from a local TV news show in Oregon, which sent a reporter out to cover the removal of 45-foot, eight-ton dead whale that washed up on the beach. The responsibility for getting rid of the carcass was placed with the Oregon State Highway Division, apparently on the theory that highways and whales are very similar in the sense that both are large objects. So anyway, the highway engineers hit upon a plan (remember, I am not making this up) to blow up the whale with dynamite. The thinking was that the whale would be blown into small pieces, which would then be eaten by seagulls and fish. That would be that--a textbook whale removal. So they moved the spectators back up the beach, put a half-ton of dynamite next to the whale and set it off. What follows, on the videotape, is one of the most priceless events in the history of the universe. First you see the whale carcass disappear in a huge blast of smoke and flame. Then you hear the happy spectators shouting "Yayy!" and "Whee!" Then, suddenly, the crowd's tone changes. You hear a new sound like "splud, splap," and you hear a woman's voice shouting "Here come pieces of...OH MY GOD!" Something smears the camera lens. Later, the reporter explains: "The humor of the entire situation suddenly gave way to a run for survival as huge chunks of whale blubber rained down everywhere.“ One piece caved in the roof of a car parked more than a quarter of a mile away!! Remaining on the beach were several large rotting whale sections the size of condominiums...
Posted on: Saturday, June 15, 2002 Removal of carcass a whale of a task
By Mike Gordon Advertiser Staff Writer State and city officials are used to removing things that wash up on island beaches, but two tons of smelly, decomposing whale carcass was a challenge yesterday. The dead sperm whale — what's left of it, anyway — floated in on Thursday night's high tide, coming to rest at Kualoa on a sliver of beach within sniffing distance of Kamehameha Highway, just north of the ruins of the sugar mill smoke stack at Kualoa Ranch.
Normally, the city takes care of removing things that wash ashore but this was too much.
"This thing is big," Jeff Walters of the Department of Land and Natural Resources' division of aquatic resources, said yesterday morning as the state weighed its options. "We need something big. We either have to have a crane to lift it up whole or something to cut it up into smaller pieces.“ At one point, he thought a backhoe could be used to chop it up, but anyone getting close to the carcass would have to wear protective clothing. "It is putrid," he said. So yesterday afternoon they hired a crane from Bob's Equipment. By 4 p.m. the biggest chunk had been removed and taken across the highway to Kualoa Ranch. DLNR spokesman Mike Markrich said four large chunks still remaining on on the beach will be taken away today by backhoe. The dead whale was first spotted Wednesday on a reef about 100 yards offshore, and signs were posted warning beachgoers to stay out of the water because of the possibility of sharks.
The signs remained up today, but Walters said the carcass is so decomposed that even sharks probably don't want it.

48. 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?