MarBiolNekton_IIOct_15

MarBiolNekton_IIOct_15 - Nekton II Nekton Salmon and...

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Unformatted text preview: Nekton II Nekton Salmon and Cephalopods A little more on sharks little White shark tagging shows migration from South Africa to Australia (99 days, 4.5 knots) Dives to 1000 m There are over 40 species of freshwater sharks freshwater Bull shark can also Live in freshwater Most live in rivers Australia, India, etc There are 7 species of Pacific Salmon and all spawn in the western Pacific, but only 5 spawn in North America. Two trout species also go from seawater to freshwater to spawn seawater The Atlantic has only one species of salmon of They don’t die after spawning Are grown in west coast fish farms Escapees will compete with our native salmon You can identify from lack of spots on tail and presence of spots on back & gill cover Chinook (King) are the largest salmon salmon Different species prefer different spawning areas. Chinook (King) salmon spawn in larger rivers while Coho spawn in smaller streams salmon Pink Salmon males grow a hump and a curved jaw when ready to spawn spawn Female spawns in shallow water. Hump of male usually sticks out of water making him easy prey for bears. This may protect the female who is less noticeable. There are big differences in sizes of salmon species salmon Chinook Salmon can reach an incredible 100 lbs Pink Salmon average about 5­6 lbs There are also two trout species, Steelhead (Rainbow) and Cutthroat that live in the ocean but spawn in freshwater like salmon ocean Unlike Salmon, the trout species do not die immediately after spawning Salmon use their sense of “smell” to find their birth river to As they enter freshwater on their spawning run they stop feeding and their stomachs begin to disintegrate to make more room for eggs and sperm. They can detect the unique taste of the stream or river they were born in. Small amounts of magnetite in their brain may function as tiny magnets to aid navigation navigation After the adult salmon die, they decompose and the released nutrients are utilized by terrestrial plants Up to a third of the nitrogen in trees growing near salmon streams comes from the decomposed salmon REVIEW: Salmon Osmoregulation: the salt content of a fish’s blood is about 1/3 that that of seawater and they try to keep it at that level whether they are in SW or FW are In the ocean, salmon tend to become dehydrated and they drink seawater constantly. A salt gland is used to remove the salts. In freshwater, salmon stop drinking water, they absorb salts through gills, and retains salts Salmon migrate in the ocean, then swim into freshwater to spawn swim The female digs a nest (called a redd) with her tail by laying on her side and flapping it up and down. As she lays eggs in it the male lays parallel and releases sperm to fertilize the eggs. releases Here the salmon eggs are being fertilized fertilized The salmon eggs need oxygen and will die if there is extensive silt or dirt covering the redd. Logging of forests adds silt to streams plus cuts shade so the streams heat up. Eggs can’t take the heat up. The eggs develop for many months and then hatch out as “yolk sac larvae” (alevins). They continue to get nourishment from the yolk for a few days yolk The salmon generally stay in freshwater for months to years and are called “smolts” are Salmon have several life cycle stages – alevin, fry, parr, smolt & adult adult Why are salmon populations declining? declining? Dams on rivers prevent upstream migration Young fish die in passing through turbines as they go downstream Silt from logging and road building smothers their eggs, thus preventing oxygen from reaching the eggs Over fishing of adults Global warming reduces their habitat Young are eaten by invasive species Pesticides Get fish lice from farmed salmon Streams heat up due to logging Oceanic conditions changing – less upwelling with global warming = less food for adult salmon Fish ladders help salmon get upstream – but they have to find the entrance to the ladder the Pink Salmon today are only found in Alaskan, Canadian & NW US waters. Now extinct in California California Sockeye salmon are also endangered and threatened. Gone from California threatened. Coho Salmon in California and Oregon are present but threatened Oregon In Marin and Sonoma, Coho salmon are present in only 6 of the 17 watersheds they used to inhabit. Green = OK, yellow = sometimes present, red = none and black = no data present, Chinook (King) Salmon can still be found in the blue areas of the major tributaries of the Central Valley Central There is a fall and a winter migration of Chinook Salmon in California California The Winter run has few salmon today and is protected under the Endangered Species act The Fall run typically has a lot more salmon. However something happened in 2007 The Fall Chinook run in 2008 in the Sacramento was only 66,000 fish Sacramento In 2002, it was 770,000 fish, an alarming decline Chinook Salmon spring ’08 show marked decline marked Reasons not known. May be changes in Pacific ecosystem from global warming or taking too much water for agriculture The Oregon­California commercial Fishery for spring ’08 & ‘09 is closed Populations of wild salmon are declining declining Salmon populations are composed of thousands of “stocks”. Stocks are self perpetuating populations which Stocks are adapted to a specific local environment by inherited biological attributes. biological Many stocks are threatened today Wild salmon on left, farmed on right Wild Notice how much darker and less fatty the wild salmon is. They also have fewer pollutants. Chemicals are added to farmed salmon diets to give that “pink” color color canthaxanthin and astaxanthin added If they weren’t added, the color of the salmon flesh would be gray Canthaxanthin has been associated with damage to the human retina The total marine fish harvest is ~2% of food produced by humans and ~12% of the human protein supply. In 1987 ~28% of the fish harvest was converted to fish meal and fed to poultry. Recent studies have shown that the salmon in fish farms have high populations of fish lice fish These are small crustaceans which attach to the migrating wild salmon and suck out blood & tissue, weakening them. These lice escape and infect wild salmon. Fish Lice on young salmon Fish Young wild salmon infected while passing near a salmon farm. 2006 study in Proc Nat Acad Sci Found that up to 95% of wild juvenile salmon are killed by sea lice from salmon farms Another study found that the farms generate 73 X more sea lice than natural levels with impacts extending 30 km beyond the farm. Alaska Fishery Research Bulletin found 1­3 sea lice per juvenile can be fatal. Alaska prohibits fish farms Chile and Norway produce the most farmed salmon most Chile’s salmon are being attacked by a virus “infectious salmon anemia” (ISA) Chile adds antibiotics from the quinolone family to hold down bacterial attacks. 850,000 lbs in 2007. Illegal to use in USA. Residuals are present in fish in US markets. Canthaxanthin added to salmon to make them pink can negatively affect the human retina. Pink Salmon in British Columbia Pink SCIENCE 2007 p. 1772. Louse induced mortality of juvenile wild Pink Salmon is 80%. It exceeds commercial fishing mortality. A 99% collapse of wild populations is expected in 4 generations DON’T EAT FARMED SALMON! Location of some BC Salmon Farms and migration routes of Pink Salmon Salmon Many many more farms farther north 2005 study in Journal of Nutrition 2005 Cancer risks from dioxins and PCBs in farmed salmon “farmed salmon contain levels of 13 persistent organic pollutants that are on average 10X higher than found in wild salmon” JAMA Oct 2006 found rate of cancer risk 3X higher for farmed salmon Fish Populations and Human impact. Salmon Ranches Takes ~8 lb of protein to produce a 2 lb salmon. Protein is made from fish guts, heads & trash fish. Escaped salmon from pens in Japan consume juveniles of wild salmon reducing the number of wild salmon. US West Coast grows Atlantic Salmon and many escape. Atlantic Salmon are used because the first salmon farming was done in the Atlantic and most is known about growing this species. Farmed salmon are genetically weak, and when they escape and breed with wild salmon, they weaken the wild population Bluefin Tuna are another threatened fish. threatened These tuna have declined in population by 80% since 1970 Can reach 1400 lbs! A favorite for making sushi Barbara Block (Stanford Univ., in yellow below) tags the tuna electronically and can follow its movements follow In Atlantic tuna migrate all the way from the Gulf of Mexico to the Mediterranean Thus any conservation efforts must encompass the whole Atlantic (And this goes for Pacific too) Bluefin Tuna Bluefin Pacific Bluefin tuna spawn midway between Okinawa and the Philippines and possibly in the Sea of Japan, then migrate over 6,000 nautical miles (11,112 km) to the eastern Pacific, eventually returning to their birth waters to spawn. They are severely overfished Bluefin Tuna often used to make Sushi Sushi Recent laboratory tests performed for The New York Times found so much mercury in tuna sushi that a regular diet of even two or three pieces a week at some restaurants could be a health hazard for the average adult, based on guidelines set out by the Environmental Protection Agency. Yellowfin Tuna and Dolphins often swim together swim Fishermen would encircle the dolphins with a purse seine This would often kill or weaken the dolphins The US outlawed this practice and bans the import of tuna from countries that permit this practice Purse Seine Purse After the fish are circled, the bottom is closed off is Note the dolphin in the purse seine with tuna with About 7 million dolphins were killed by setting nets on them by Yellowfin Tuna Yellowfin The Bush Administration tried to weaken the ban on purse seining dolphins To catch tuna Today, Dolphin Safe doesn’t mean the same as it once did the On December 31, 2002, Secretary of Commerce Donald Evans announced for the second time that the "dolphin­safe" label would be "weakened" to allow its application to tuna caught by encircling dolphins with tuna nets, as long as an on­board observer claims that no dolphins were killed or seriously injured during the fishing set. If the government's reports had failed to prove that the encirclement fishing method causes a "significant adverse impact" on any depleted dolphin populations, the law would have allowed the Secretary to weaken the "dolphin­safe" label in this way. In 2007 the ninth circuit court said it is illegal for the Bush Administration to weaken the Dolphin Safe label, The Eastern Pacific Dolphin populations are not recovering populations mercury in fish mercury One way to protect fish resources is to establish Marine Reserves or Sanctuaries establish Sanctuaries generally allow fishing but forbid oil & gas exploitation and other types of commercial activities Marine Reserves in addition to the above, do not permit fishing Today 90% of the large (tuna, swordfish, sailfish, etc) fish in the ocean are gone The US has a system of marine sanctuaries in which fishing may be permitted but oil & gas exploration and alteration of the seabed are not. exploration Gulf of Farallones Sanctuary is off San Francisco. South of here is the Monterey Sanctuary Monterey Farallones Sanctuary allows fishing and is home to many puffins, elephant seals, sharks and whales elephant Monterey Sanctuary Monterey Marine reserves are also sanctuaries, but no fishing of any kind is allowed kind Reserves are important for marine life life Research on reserves has shown that they enhance the commercial fishing success in adjacent areas. They act as nursery areas for fish which then migrate to other areas. Sex Change in Marine Fish Sex Many fish change their sex as they age. Some hermaphrodites can function as a male and female at the same time The tropical Cleaner Fish grooms larger fish and removes their parasites larger These fish live in groups of about 10 and there is only one dominant functional male present present This male breeds with all the females and when he dies, the dominant female changes to become a male (ca. 2 weeks). This social & breeding organization is called POLYGYNY (one male has several wives) PROTANDRY & PROTOGYNY PROTANDRY Protandry: begin life as a male (i.e. Clownfish) and change to female as they age Protogyny: begin life as a female and change to a male with age i.e. Tropical Cleaner Fish Clownfish (Anemonefish) Clownfish Each sea anemone is inhabited by a single large female that mates only with the large dominant male. All the other fish living with the anemone are small males. If the female dies, her mate turns into a female and the largest of the non­breeding males then becomes the new dominant male. For reproductive success, it is an advantage to be a large female so you can produce more eggs. more Thus it makes sense to start out as a male and become a female later in life when you are bigger Maybe Nemo changed his Sex? An amazing 77 fish species change sex from male to female. sex A recent study looked at the size at which they changed sex. Surprisingly, they all changed sex when they reached exactly 72% of their maximum size! This must be the optimum size from an evolution perspective to change Hamlet fish can be both male and female at the same time female This is a Caribbean fish In courtship, one fish “acts male” and releases sperm to fertilize the eggs. Next, the other fish acts male and the “male” acts female Seahorses do not change their sex, but the male incubates the eggs but The female transfers the eggs to the male, and he incubates the eggs in a pouch until the young develop. There are between about 30 and 120 species of seahorses in the ocean tropics Seahorse populations are declining because they get caught in fishnets accidentally Also they are used as “medicine” by some people There is one species of Sea Horses in California waters: Pacific Seahorse Seahorse Cephalopods are molluscs, and they are also important members of the nekton the Most have lost or reduced their CaCO3 shell These are fast predators and very successful Cephalopods are the largest of the invertebrates invertebrates Squids and Nautilus usually found in open water Octopus and Cuttlefish usually found near the bottom Cephalopods can squirt water by contracting their muscular mantle and squirting water out through a siphon Octopus Octopus Note mantle and siphon Cuttlefish hunting Cuttlefish Mouth has a beak The Nautilus is the Cephalopod with the biggest shell. with In other species it is reduced or absent The shell has chambers to help it with buoyancy Live in tropical Pacific Nautilus hides deep in water in day to escape predators and swims up to surface to feed at night to Have over 90 tentacles. Unchanged for 150 mil yrs Primitive eye Beak like a Parrot Swims with jet propulsion Nautilus Nautilus “Golden Spiral” Nautilus growth Similar. Draw a square, Then draw a line midway Next draw diagonal (this is radius of arc that defines next rectangle). Draw out to arc to size next rectangle Here’s another Here’s Golden Spiral Cuttlefish have 8 arms and two retractable tentacles retractable Swims with jet and fins on body Can squirt ink which affects olfaction and confuse predators Fast & intelligent Ink of Sepia used for food dyes Cuttlefish Anatomy Cuttlefish Photophores and chromatophores in skin help to change cephalopod shading to hide from predators from Chromatophores change skin color Photophores emit light of different colors Note reflector & lens & color filters of photophore Photocytes are bioluminescent bacteria Chromatophores control skin pigmentation by expanding or contracting by Great camouflage ! Great Cuttlefish hunt prey by shooting out their two sticky tentacles their Cuttlebones from Cuttlefish Put in birdcage for birds to chew on Squid are similar to Cuttlefish but can’t retract their two tentacles can’t Squid Anatomy (she won’t forget!) Squid Giant squid are mysterious. They live deep and few have been caught. Largest was 18 meters in length meters Calamari (Squid) fishery in USA is strong strong The Octopus also has 8 arms. Can release ink to confuse predator. release They are the most intelligent invertebrate invertebrate Can learn fast and are hard to keep in an aquarium because they escape easily Study Guide Study Characteristics of different salmon species How salmon find their home stream How do they osmoregulate Life cycle stages of salmon Why are salmon populations declining, what needed for successful spawning What salmon species still present in California Status of Bluefin tuna, migration & spawning pattern Why are marine reserves important Polygny, Protandry, Protogyny, Why? What fish have highest mercury content What does “Dolphin Safe Tuna” mean today? Seahorse reproduction What are cephalopods How cephalopods change color How squid different from cuttlefish ...
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This note was uploaded on 11/07/2011 for the course BIO 160 taught by Professor Dr.jonstern during the Fall '08 term at S.F. State.

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