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Fish & Water

Fish & Water

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Download Episode: ADF&G Divers (MP3 file 1,403 kB)

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Download Episode: Aging Crabs (MP3 file 1,407 kB)

Aging Crabs

A storm rocks the North Pacific Ocean off the coast of Alaska. Beneath the waves, it's peaceful. Down through the cold, green water at the bottom, a snow crab scuttles across the sandy seafloor. Snow crab support the largest crab fishery in Alaska. This one is an old crab - but how old, and why does it matter?

Determining the age of commercial species is an important part of sustainable fisheries management. For many fish species, accurate ages are determined by looking at scales; or ear bones, called otoliths; which contain banding patterns associated with seasonal fast and slow growth, like growth rings in trees.

Crabs do not have otoliths or scales, and researchers are working on other methods to help determine the age of crab. Crabs molt their shells as they grow, and snow crab go through a terminal or final molt which, from that point on, leaves them in the same shell for the rest of their lives. This "retirement home" shell shows wear, and degrades in color and texture over time, allowing researchers to clearly distinguish actively growing or recently molted newshell crab from oldshell crab that have not molted in some time. Researchers have discovered that hard structures in the crab's stomach called ossicles display age-related banding patterns, and they are developing methods to best extract these ossicles, prepare them for microscopic examination, and use them to determine the crab's age.

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Download Episode: Alaska's Sponges (MP3 file 3,517 kB)

Alaska Sponges

On the seafloor beneath Alaska's cold ocean waters dwell some of the world's most diverse and abundant sponge communities. Sponges may evoke visions of tropical waters, but they are abundant in Alaska's marine ecosystems. Deep-sea sponges can thrive in waters that are cold, acidic, and low in oxygen - conditions common in waters off Alaska.

Deep-water sponges are slow-growing and long-lived, and some can be hundreds of years old. These living structures create habitats for other animals, including commercially important species like rockfish, spot prawns, and golden king crabs. Sponge communities provide protection from predators, feeding opportunities, and nursery grounds for commercial species. Some fish lay their eggs in particular species of sponges.

Sponges are vulnerable to disturbances from commercial fishing, construction, and oil exploration. They are also affected by climate change and ocean acidification.

Scientists have identified 52 species of sponges in the Gulf of Alaska and more than 125 in the Aleutian Islands – in fact, the Aleutians have some of the densest and most diverse coral and sponge communities in the world. There are likely hundreds of species yet to be described. Researchers are learning about sponge and coral distribution in Alaska waters and are creating a reference library of Alaska sponges. For SW…

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Download Episode: Arctic Char (MP3 file 3,522 kB)

Arctic Char

Early summer in Western Alaska and young salmon sockeye smolts are headed from freshwater lakes out to sea. But on the way they face a gauntlet of hungry predators, including other fish. One eager predator of the young salmon is their trout-like cousin, the Arctic Char.

Wild Arctic char range across the northern polar regions. Arctic char are found in lakes in the Brooks Range, the Kuskokwim Mountains, on the Alaska Peninsula, the Kenai Peninsula, Kodiak Island, and in a small area of Interior Alaska near Denali Park. The Arctic char is also widely stocked throughout Alaska in roadside put-and-take fisheries.

The Arctic char is the northernmost freshwater fish in the world. These trout are circumpolar in distribution, and their life history patterns vary between different populations. Fish over 10 pounds are found in some Alaska lakes, while other lakes may not produce fish over 2 pounds even though fish may reach great age. In Russia, Arctic char can reach 30 pounds or more.

Arctic Char exhibit both anadromous life history and non-anadromous life history patterns. Some go to sea for much of their lives and return to freshwater to spawn, and others spend their entire lives as residents of freshwater. Unlike Pacific salmon, which return to freshwater to spawn but die shortly thereafter, the anadromous forms of Arctic char and the closely-related Dolly Varden can move between fresh and saltwater easily and live to spawn several times.

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Download Episode: Basket Star (MP3 file 1,409 kB)

Basket star

I'm halibut fishing in Icy Strait near Glacier Bay when my friend hooks up in 120 feet of water. He's got something on the bottom, but it's not a halibut. He manages to pull in a big tree branch, and an odd-looking creature is attached to it. It's a foot across, a weird sea star with dozens of tentacle-like arms branching from five main arms. It's a basket star.

The smaller arms are waving and curling and I carefully peel the orangish-tan basket star from the branch... it's moving, far more active and agile than a typical sea star.

Basket stars are a group of sea stars known as brittle stars. Many of them have these characteristic many-branched arms, and they are the most mobile of all sea stars. They favor deep sea habitats - they're rarely in water less than 50 feet deep, and can be found in water thousands of feet deep. They may live up to 35 years and weigh as much as 11 pounds, although the one I'm holding is closer to three pounds. They use their tentacle-like arms to grab and hold prey, knotting the branchlets around the prey and pulling it into the central mouth.

Sea stars used to be called star fish, but they're not fish, they're echinoderms, a group of marine animals that includes sea urchins and sand dollars, named for their rough skin. Echinoderms have no blood and instead use water in their vascular system.

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Download Episode: Bering Cisco (MP3 file 1,411 kB)

Bering Cisco

An unusual whitefish is swimming up the Yukon River. It's a Bering Cisco, a type of whitefish that's anadromous, like salmon. A Bering Cisco spends part of its life in freshwater and part in saltwater. They are an important subsistence fish for people in coastal and river communities along the lower Yukon and Kuskokwim Rivers. Bering Cisco are found as far south as the Susitna River, and ranges north along the west coast of Alaska in drainages that flow into the Bering Sea.

Adult Bering cisco, about 18 inches long and ranging from 4 to 12 years old, spawn in the fall. Some undertake extreme spawning migrations, traveling more than 500 miles up the Kuskokwim River and more than 1,200 miles up the Yukon River. A big female Bering cisco may release up to 34,000 eggs, broadcasting her eggs over gravel beds in turbid and fast flowing water. The eggs hatch in the spring and the young move downstream to feed and grow in brackish estuaries and near shore coastal waters. They're tolerant of salt water but Bering cisco cannot survive cold sea water under ice and retreat to estuaries and river mouths in winter where water is not as cold. Like salmon, adult Bering cisco don't feed during spawning migrations, but unlike salmon, Bering cisco do not always die after spawning.

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Download Episode: Black Cod Reward (MP3 file 1,407 kB)

Black Cod Reward

A couple friends are fishing for halibut in Chatham Strait of Southeast Alaska and they catch a nice black cod. Black cod, also known as sablefish, are prized for their rich, oily meat and are a delicacy when smoked. This fish makes these anglers doubly happy, because it's also been tagged with a small orange plastic tag in its dorsal fin.

Almost 10,000 sablefish were caught, tagged and released in Southeast waters by biologists in the spring of 2018. Commercial and sport fishermen who catch a tagged sablefish and return the tag to a Fish and Game office are rewarded with a tee-shirt and a possible cash prize - incentives for the public to contribute to sablefish monitoring and research.

The sablefish are caught using pots, strung on a longline. Tagged fish are measured and released, and then mix with the general population of sablefish in the area. Comparing the numbers of recaptured fish to the original number of marked fish allows biologists to determine a population estimate (a method known as mark/recapture). Looking at the locations helps biologists understand sablefish movements, and comparing the measurements provides growth data.

In past years surveyors have tagged between 6,000 and 8,000 fish. The program is getting good results - In 2017, 782 tags were returned.

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Download Episode: Blackfish (MP3 file 1,414 kB)

Beringian Blackfish

On a winter day in interior Alaska, a hike along a frozen slough reveals a patch of open water. Just below the surface, a school of small fish mills about. They're blackfish, a hardy, 7-inch-long fish found only in Alaska and Siberia. They have gills, but they also have a modified esophagus and can absorb oxygen by gulping mouthfuls of air. That's what these blackfish in this oxygen depleted slough water are doing - in fact, their activity is keeping this patch of water ice free.

In summer, blackfish can be found in tundra pools and seasonal ponds in interior and western Alaska, ponds that may go dry. When seasonal tundra pools dry up, the blackfish survive by wiggling down into the smelly bottom sludge and mud, keeping moist and breathing air until the next rain.

Blackfish are a Beringian holdover from the ice age. Beringia was a great expanse of open land that included Interior Alaska, Siberia, and land that is now under the Bering Sea. Sea levels were about 300 feet lower, and the shallow Bering Sea was dry land. Giant short-faced bears, woolly mammoths and mastodons roamed this landscape, and Alaska blackfish shared the freshwater with northern pike and Arctic grayling. The range of blackfish is entirely Beringian, in fact, these little freshwater fish are found on three islands in the Bering Sea, Saint Lawrence, Saint Matthew and Nunivak, islands that were once low hills rising above the dry, windswept plain of the Bering land bridge.

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Download Episode: Chinook (MP3 file 1,403 kB)

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Download Episode: Counting Salmon (MP3 file 3,523 kB)

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Download Episode: Crawdads (MP3 file 1,409 kB)

Crawdads

A biologist in hip waders stands knee deep in the Buskin River on Kodiak Island. She's pulling a wire mesh cage from the water - a crawdad trap, and she's caught some of the fresh water crustaceans, which look like small lobsters. She's not happy about her success.

Crawdads, also known as crayfish and crawfish, are an invasive species in Kodiak's Buskin River and Buskin Lake. Crawdads are not native to Alaska, and they are potential harmful. Invasive species can damage native habitat. Burrowing crawdads can affect vegetation in lakes. Biologists are also concerned crawdads could eat salmon eggs in rivers.

The species of this crustacean found in Kodiak, the signal crayfish, are originally from the Pacific Northwest. It's not clear how they got to Kodiak. They could have been shipped live to Kodiak for eating, school projects, as pets, or as bait. The small crustaceans were spotted occasionally in Kodiak waters since the early 2000s, but in the past, only about one per year was found. In the summer of 2015, a couple dozen were caught. That changed in 2016 - as of August 2016, 228 crawdads have been caught in Buskin River and Buskin Lake - including newly hatched young. Signal crayfish are successfully breeding in both in Buskin River and Buskin Lake.

Biologists are concerned that if the crayfish population continues to flourish, it could spread from the Buskin River into other systems. They're trying to solve this issue before it expands into something that is more difficult to control.

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Download Episode: Delta Clearwater Coho (MP3 file 1,406 kB)

Delta Clearwater Coho

On a beautiful fall day in Interior Alaska, an angler is casting for coho salmon on the Delta Clearwater River. She's had pretty good luck. The Delta Clearwater

The Delta Clearwater River is a tributary of the Tanana River, near the community of Delta Junction. It's aptly named, for unlike many of the silty, glacially fed Interior Alaska rivers, the Delta Clearwater River is spring fed and runs clear. It sports the largest known coho run in the Yukon Drainage. These fish have travelled more than 1,000 miles from the mouth of the Yukon to their native spawning stream. Delta Clearwater River coho are in full spawning coloration, maroon red with dark colored heads and hook jaws with sharp teeth. Because they are in freshwater and spawning, they do not feed, but they will still strike at a lure now and then. Most anglers practice catch and release on the Delta Clearwater River because the flesh of these coho is a bit on the soft side.

Biologists with Fish and Game have conducted fall surveys of coho in the river, and in 2005, more than 100,000 coho were counted in a 17-mile stretch of river. Because the river is spring fed, it flows into the winter and the coho salmon can spawn well into December. The young salmon will stay in the river for up to three years before migrating to the ocean and then returning.

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Download Episode: Dolly Varden (MP3 file 1,411 kB)

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Download Episode: Epic Chum (MP3 file 1,407 kB)

Epic Chum

Nine hundred miles from the Bering Sea, a battle-scarred chum salmon swims through downtown Fairbanks. She left the ocean a month ago and she's covered about 30 miles a day, swimming up the Yukon River to the Tanana, and following the Tanana upriver to the Chena. The Chena River flows through the heart of Alaska's second largest city, and this is the second time this salmon has passed through Fairbanks. The first time, four years earlier, she was an inch long smolt headed downstream to the sea.

She was born in the clear, cold headwaters of the Chena's north fork, about 70 miles upstream from Fairbanks. Unlike coho or Chinook salmon, which spend a year or two in freshwater before heading to the ocean, chum salmon head downriver immediately after hatching.

This year on her upriver journey, this big female is loaded with eggs. Soon she'll do her part to create the next generation of Chena River Chums. But she's bringing more than eggs to the upper Chena. She's bringing nutrients from the Bering Sea to Interior Alaska. Like all Pacific salmon, she'll die after spawning. Her body will provide important food for birds, mammals, insects and fish, including the young salmon of the next generation. As she decays, carbon, nitrogen phosphorus and other essential elements will be released, benefitting all the life around the Chena River.

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Download Episode: Every Halibut Counts (MP3 file 1,405 kB)

Halibut release

A couple of friends are anchored up in Icy Strait on a summer day, fishing for halibut. They've caught several they've kept, and released a few as well.

Anglers in Alaska release about half the halibut they catch. Anglers release halibut that are too small or too large to keep under regulations. Some folks don't like to eat big halibut, and others release big halibut to promote conservation of the resource. Most halibut weighing more than 80 pounds are females, and big females produce a lot of eggs - and a lot of baby halibut.

In 2013, two charter fishing operators contacted the Alaska Marine Conservation Council and proposed a set of voluntary best practices for releasing sport-caught halibut. They worked the Alaska Sea Grant Marine Advisory Program to develop the project, which became known as Every Halibut Counts.

The principle is simple: treat every fish gently to maximize its chance of survival. To do this:

Decide to keep or release a fish while it's still in the water.

Keep an unhooking device or gaff ready, and release the hook with a quick push and twist motion.

If the fish is too big or gut hooked, cut the leader as close to the hook as possible. Hooks will corrode and eventually fall out.

If you must bring a fish into the boat to measure it or to roll the hook out by hand, cradle it with both hands. Never lift a fish only by the tail or the gills.

And lastly, slip the fish gently back into the water head-first. Never throw a fish back.

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Download Episode: Fast Whales, Faster Fish (MP3 file 1,407 kB)

Fast whales, faster fish

The protected Inside Waters of Southeast Alaska are a network of islands, fjords and waterways offering outstanding wildlife watching. North Pass, in Lynn Canal north of Juneau, is well-known as an excellent area for watching humpback whales. But one group of whale watchers was surprised one rainy August afternoon to see not humpbacks, but a pod of killer whales speeding through the waters of North Pass. The killer whales were chasing a Dall's porpoise.

These two animals are considered to be the fastest marine mammals on Earth. Both the Dall's porpoise and the killer whale have been clocked swimming more than 30 miles per hour. They are able to increase their speed by porpoising, a combination of swimming at the surface and leaping from the water. On this day, the animals were highly motivated: the killer whales were racing for their dinner, and the porpoise was swimming for his life. But killer whales have more going for them than speed, they are cunning strategists. The whales teamed up on the porpoise, herding the animal and swimming in relays until they were able to outmaneuver the exhausted porpoise.

Killer whales typically swim about six to eight miles and hour when they travel. These marine mammals are fast, but they're not the fastest swimmers in the sea. That honor goes to tuna, marlin and sailfish. It's difficult to accurately measure the speed of a fish, and a short burst of speed that includes multiple leaps from the water may exaggerate swimming speed. But observations by anglers and researchers indicate that powerful bluefin and yellowfin tuna can swim up to 43 miles an hour. Marlin have hit burst of speed around 50 miles an hour, and swordfish and sailfish hooked by fishermen have topped 60 miles an hour in leaping, line-stripping bursts of speed.

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Download Episode: Fish Care (MP3 file 1,407 kB)

Fish care

A couple of anglers are taking their last casts of the afternoon. It's been a successful day, and they have five nice salmon on a stringer. One will be eaten fresh, and the rest will be frozen. With a little care, those salmon that come out of the freezer in six months will still be quality fish.

The first 20 minutes after the catch is the most important time for quality. You can only keep a fish in good condition. You can't make bad fish good. For starters, there's no need to beat a fish to death with a club. Bludgeoning a flopping fish bruises the meat. Stun the fish with a single bonk on the top of the head, then break a gill with your finger or cut it so it starts bleeding, and put the fish in water. Bleeding the fish makes for better meat. By only stunning the fish, its heart will continue to beat and push out more blood. Bleeding in water can remove twice as much as bleeding the fish in air. Put the fish in a bucket of water, or use a stringer

Fish should then be cooled as rapidly as possible - preferably with ice. A slushy mix of ice and water is ideal. Bleed the fish in water for a few minutes before putting it on ice to keep your ice clean.

It's best to dress fish at a cleaning station where you have access to a clean platform and a hose with clean water. Dressing a fish on the beach or riverbank - or even a boat without a table - and keeping it clean can be difficult. Just bleed it, rinse it, and put it into the cooler of ice. Dress the fish later when you can get to a more sanitary environment.

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Download Episode: Fish Passage (MP3 file 1,404 kB)

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Download Episode: Geoducks (MP3 file 1,407 kB)

Geoducks

A light surf rolls in on a sandy beach in Southeast Alaska. Just offshore, under the blue green water - and under the sandy ocean floor, is a clam bed. These aren't ordinary clams; these are geoducks - pronounced gooeyducks. Gooeyduck clams are the world's largest burrowing clam. They live deep in the sand, up to 3 feet deep, and use a large siphon to filter food out of the water. That siphon, like a long hose, is much bigger than the body of the clam itself, which might be the size of a softball. Geoducks can potentially live a long time. One animal aged by Fish and Game was 146 years old.

There is an important commercial fishery for geoducks in Alaska. A geoduck is harvested by a diver using a water pump. Water pressure liquefies the sand, and then the diver reaches into the slurry of loose sand and pulls out the clam. The harvested clams are brought to the dock alive and immediately boxed for shipment to market, often to Asia. By the time these animals get to the consumer they may cost up to $100 each. They may be served as sushi in high end restaurants or put into an aquarium where a patron can point out the geoduck they want.

Getting top dollar for this clam depends on the animal getting it to market alive. In 2015, divers received around $4.50 a pound, but at times the price has reached 20 dollars a pound. A geoduck averages around 2.5 pounds so it ends up being worth 10 to 15 dollars an animal, and in peak years as much as $50 apiece.

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Download Episode: Giant Octopus (MP3 file 2,811 kB)

The giant north Pacific octopus

Beneath the surface of Alaska waters lurks the largest species of octopus in the world, the giant north pacific octopus. The animals can weigh more than 100 pounds, and stretch more than 20 feet from arm tip to arm tip. In Alaska waters they are more commonly 40 to 80 pounds. But what's remarkable is how quickly octopus grow. These are not long-lived animals - the giant octopus lives just three to five years, and dies after mating.

The giant pacific octopus mates just once in its relatively short life. Females lay 20,000 to 100,000 eggs and she tends them throughout the five to seven month incubation period. She doesn't feed while tending the eggs and dies shortly after they hatch.

While octopus are able to change their color and skin texture to blend into their background, their dens sometimes reveal their presence to divers. Dens are important to octopus as a refuge from predators and as a brooding chamber once the eggs are laid. Divers know that piles of shells and bones littering the sea floor outside a crevice or space under rocks is a good sign of an octopus' home. The crevice may not be very big - a 50 pound octopus can squeeze through a 2-inch hole - if its beak fits, it can go through.

Biologists don't use the term tentacles to describe the appendages of an octopus - they're called arms. And an octopus can regrow an arm if it's lost.

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Download Episode: Grayling research (MP3 file 1,405 kB)

Grayling research

A biologist in a small plane is flying over the Goodpaster River in Interior Alaska. He's tracking a grayling, a fish that has been tagged with a radio transmitter to help biologists learn about grayling migrations. The radio tag is a small, internally implanted transmitter about half the size of a triple A battery.

The tag sends a signal that can be detected up to 10 miles away. Over a one to three year period each tagged Arctic grayling is located by periodic aerial surveys. Tagged fish are also detected and documented when they pass riverside radio tracking stations, set up at the confluence of tributary streams.

During summer, Arctic grayling are spread throughout the upper Chena, Salcha, and Goodpaster rivers and their tributaries where food is plentiful. As water cools in late August, fish leave the upper portions of drainages and move downstream to overwintering areas throughout the main stem of the rivers.

After overwintering, grayling typically migrate to their spawning areas in early May just before breakup. Spawning is over within two weeks of breakup, and then the grayling migrate to their summer feeding grounds. Some move less than 10 miles total throughout the entire year, but some move long distances. After spawning in May, one grayling traveled 105 miles to the Upper North Fork Goodpaster River in 15 days. Another grayling spent a summer in the Upper Goodpaster, overwintered in the main stem of the river, and then spent the next summer 114 miles away in the Delta Clearwater River.

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Download Episode: Hagfish (MP3 file 1,406 kB)

Hagfish

In the fall of 2017, a fishing boat is working the waters of southern Southeast Alaska, deploying a string of baited five-gallon buckets. The buckets are fish traps, lowered on a long line and soaked on the bottom. This is a test fishery for black hagfish, blind, eel-like sea-floor scavengers that also eat worms and crustaceans. It's a success. But the issue is not catching hagfish, but understanding how to manage the fishery sustainably.

Some species of hagfish are hermaphroditic, meaning one animal has both genders; and some are protandric, meaning they start out male and switch to female. 90 percent of the hagfish caught in the test fishery are female, and Fish and Game biologists are learning if that's the actual sex ratio or if the fishing method favors females.

Hagfish are a popular food in Korea. Their tough, dark skin is also popular tanned as leather, and sold as eelskin. Hagfish also produce a clear, thick slime. Applications for the slime are being explored - using the slime to treat burns, to make bandages, and to make special fabric.

When hagfish scavenge something on the seafloor, they basically chew their way into the carcass, using the slime to lubricate their tunnel. They also produce slime when they are attacked by a predator, encasing themselves in a goopy ball of gelatin that impairs and distracts the predator.

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Download Episode: Hatchery Fish (MP3 file 1,408 kB)

Ruth Barnett Hatchery

In a spacious open room at the Ruth Burnett Sport Fish Hatchery in Fairbanks, water four or five feet deep circulates in big round tanks ten-feet in diameter. A window in the side of one tank shows thousands of small trout swimming inside.

The Division of Sport Fish operates two state-of-the-art sport fish hatcheries, one in Fairbanks and one in Anchorage, producing rainbow trout, Arctic char, Chinook salmon and coho salmon. The Fairbanks hatchery produces more 340,000 fish each year, which are stocked in about 125 lakes and ponds in Interior Alaska.

Eggs are taken from wild and captive brood sources, fertilized and carefully monitored in special trays until they hatch into alevin - tiny baby fish with an egg sack attached. After a few weeks they develop into fry, and they are moved from the trays to the big tanks. A start up tank may have as many as 80,000 fry. Growth is related to water temperature and the amount they are fed. As they grow and become more crowded they are either stocked in the wild as fry or moved to larger tanks to grow bigger.

Water for the Fairbanks hatchery comes from wells onsite, and up to 95 percent of the water is re-used. The hatchery uses just 10 percent of the water traditionally used by a fish hatchery. The oxygen level, temperature, Ph. and water quality is continually monitored.

Fish are stocked throughout the summer. Road-accessible waters are stocked by truck, and remote waters are stocked using a plane or helicopter. Stocking hatchery fish reduces the pressure on wild stocks, increases sport-fishing opportunity, and provides diversity in sport fisheries throughout interior Alaska.

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Download Episode: Invasive Pike (MP3 file 1,412 kB)

Invasive Pike

An angler in a canoe fishing a creek on the Kenai Peninsula has just caught a small northern pike. He kills it - not because he plans to eat it, but because pike are an introduced and unwanted fish in this part of the state. Alaskans are working to eradicate these invasive pike on the Kenai.

Pike in their native range coexist with salmon and trout in many of the big Interior Alaska river drainages. So what is the problem with pike on the Kenai? Pike are ambush predators, darting from weed beds to catch unsuspecting prey. In habitat without weedy, slow-moving water, pike are less efficient predators. Deep or fast-flowing water serves as a refuge for prey.

Southcentral Alaska has a lot of shallow vegetated lakes and streams that for thousands of years have served as nurseries for juvenile trout and salmon - fish that evolved without a large, top of the food chain predator like pike. On the Kenai, invasive northern pike have completely eliminated native rainbow trout, Dolly Varden, and juvenile coho salmon from many lakes in the Soldotna Creek drainage. Pike wiped out Arctic char and rainbow trout in Stormy Lake near Nikiski. Smaller pike feed heavily on juvenile salmon and trout when available, and when that runs out, shift to stickleback, sculpins, frogs and mice - and even cannibalize each other. Once the richest resources are depleted, pike growth stunts, and lots of small and hungry pike are the rule.

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Download Episode: Kelp (MP3 file 1,409 kB)

Kelp

Cruising up the Wrangell Narrows south of Petersburg, the amount of bull kelp is remarkable. Long ropy strands hang from channel markers and pilings, and great wads are hung up on buoys and floats. Some structures are encased in massive tangles of the brown, tubular algae. My friend says the kelp growth was phenomenal during the warm sunny spring, and recent extreme tides have torn loose tremendous amounts from the anchoring rocks.

Although kelp is washing up on beaches, there is still plenty of kelp in kelp beds, dense patches of kelp that can span acres. These large patches are known as kelp forests and are important to aquatic life, providing food and shelter for fish, invertebrates and shellfish. Some fish, like herring, spawn in kelp beds. Kelp is a particularly important food for sea urchins. As we approach my friend's cabin in the narrows, seven harbor seals watch us from the fringes of a large kelp forest nearby. The reference to a forest is more apparent when the kelp is seen underwater. Anchored to the bottom, the long ropelike stipe rises 10 or 20 feet, held upright by a bulbous, air-filled bladder. Numerous kelp blades sprout from the bladder, ribbons three to six inches wide and more than a dozen feet long. The blades are like the leaves and that's where photosynthesis takes place. A kelp plant can be more than 100 feet long and can grow as much as three feet a day - one of the most remarkable growth rates in the plant kingdom.

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Download Episode: Lake Turnover (MP3 file 1,405 kB)

Lake turnover

On a sunny day in late May in Interior Alaska, a lake is turning over. Covered with ice for the winter, over the past month the ice has been melting and the lake has been warming. The ducks and geese that have stopped on their spring migration north don't care about lake turnover, but the fish do. Lake turnover mixes the lake water, distributing nutrients from the bottom upward and oxygen from the surface down, and that's benefits the lake's aquatic inhabitants.

Most liquids become denser as they cool and are most dense when they freeze or solidify, but not water. Ice floats because it's less dense than water. If water acted like most liquids, during winter, ice would form on the surface of a lake and sink until the lake was frozen solid. But because ice floats it caps the lake and insulates the water from the frigid air.

Water is most dense at 39 degrees. Water that is warmer or colder than 39 degrees is lighter and this causes "turnover" in our lakes every spring and every fall.

In the fall, cold air chills the surface water, and at 39 degrees, it sinks below the relatively warmer water until the entire lake has "turned over." Once the lake has turned over and is at a relatively equal density, ice will form on the surface. In the spring the same thing happens in reverse - as the ice melts surface water warms to 39 degrees and sinks until the entire lake has turned over once again.

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Download Episode: Lampreys (MP3 file 1,413 kB)

Lampreys

It's a spring day in Interior Alaska and the ice is melting off a stream. In the water, a pair of eel-like fish is spawning. They're arctic lampreys, and they've come more than 2,000 miles up the Yukon River to this tributary where they were born almost a decade earlier to spawn and die. Lampreys are anadromous fish, like salmon, but that's where the similarity ends. Arctic lampreys begin their lives as mud-dwelling filter feeders and end as parasites.

Adult lampreys lack jaws and instead have a disk-like mouth filled with small sharp teeth and a sharp rasping tongue. They attach to other fish and rasp through the scales and skin of the host and feed on its blood and fluids. Some fish die from lamprey attacks, but in many cases, fish survive the experience. The lamprey releases and drops off after the meal.

Juvenile lampreys hatch in freshwater and look very different than adults. The worm-like juveniles, called ammocoetes, are eyeless, blind filter feeders that burrow into the silt and mud of shallow pools and backwaters of rivers and sloughs and filter microorganisms and organic matter from the sediment. Ammocoetes live as filter feeders in fresh water for three to seven years before metamorphosing into adults. They migrate to the sea and spend one or two years in the ocean as parasites before returning to freshwater to spawn and die.

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Download Episode: Mermaid's Purse (MP3 file 2,437 kB)

Mermaid's Purse

A beach comber has found an odd leather pouch at the high tide line on an Alaska beach. It fits nicely in her palm, like a fat coin purse made of tough dried seaweed. It rattles - something is inside. It's a mermaid's purse, and although it's not really from a mermaid, it did come from the bottom of the ocean. It's an egg case, containing dried skate eggs, from a skate - a manta ray-like fish related to sharks.

Sometimes called flat sharks, skates have cartilaginous skeletons and wing-like fins. They are bottom-dwellers and eat crabs, clams, worms, and fish. They are slow-growing, long-lived animals, found in oceans throughout the world. There are 16 species in Alaska waters, including two found only in Alaska, the leopard skate and the Aleutian skate. Skates are similar to rays like mantas but differ from rays because they lay eggs instead of bearing live young - and they don't sting.

Skates congregate by the thousands in June and July to lay their eggs in ocean bottom nurseries. These nursery sites are usually located at the heads of undersea canyons, in water 500 to 1,200 feet deep, where temperatures are constant throughout the year. By identifying the genetic makeup of the embryos found in nurseries in the Bering Sea, biologists learned that skates return to the same nurseries. A skate may lay just 25 eggs, every other year, and eggs can take as long as four years to gestate on the sea floor before hatching. Sometimes currents carry those egg cases off the sea floor and away to distant beaches.

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Download Episode: Octopus (MP3 file 2,008 kB)

Octopus

Beneath the surface of Alaska's coastal waters lurks the largest species of octopus in the world, the giant north pacific octopus. The animals can be more than 100 pounds, and stretch more than 20 feet from arm tip to arm tip. In Alaska waters they are more commonly 40 to 80 pounds. But what's remarkable is how quickly these animals grow - the giant octopus lives just three to five years and dies after mating.

Sherry Tamoney, a marine biologist with the University of Alaska Southeast, worked with a team of researchers to study the giant octopus in Kachemak Bay. (12 sec Quote: We caught octopuses and one gained 12 pounds in five weeks)

The giant pacific octopus mates just once in its relatively short life. Females lay 20,000 to 100,000 eggs and tends them throughout the five to seven month incubation period.

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Download Episode: Octopus Vision (MP3 file 1,980 kB)

Octopus vision

The giant north pacific octopus can weigh more than 100 pounds, but in Alaska waters they are more commonly 40 to 80 pounds. These fast-growing animals are able to fatten up on crabs and mollusks using a combination of skills, including keen vision and intelligence.

Sherry Tamone, a marine biologist with the University of Alaska Southeast, worked with a team of researchers to study the giant octopus in Kachemak Bay. She said the giant mollusks have excellent eyesight.

(20 sec quote about eyes structure)

The octopus has more than just good eyes, it also has the brainpower to process the information.

(Second quote about size of brain and learning. 10 sec.)

That can pay off - because octopus can learn by watching other octopus.

(34 sec quote about learning by watching.)

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Download Episode: Octopus color change (MP3 file 3,522 kB)

Octopus color change

Beneath the surface of Alaska's coastal waters lurks the largest species of octopus in the world, the giant north pacific octopus. Like other octopus, these animals are masters of camouflage and change color to match the environment.

Sherry Tamoney, a marine biologist with the University of Alaska Southeast, worked with a team of researchers to study the giant pacific octopus in Kachemak Bay. She explained that the big mollusks have pigment-containing cells that allow them to blend in.

QUOTE: Chromatophores 23 sec

"The octopus doesn't simply see the environment and respond.

QUOTE: Octo color nerves work 12 sec

"The color change is not just for camouflage. Octopus also express emotions...

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Download Episode: Old Sharks (MP3 file 1,407 kB)

Greenland Shark - the oldest animal

A giant grey fish swims slowly in the dark, cold Arctic waters. It's a Greenland shark, 20 feet long and weighing close to a ton. Greenland sharks are closely related to sleeper sharks, found in Alaska waters. A recent study of 28 female Greenland sharks found that Greenland sharks are the oldest animals on Earth - some were at least 272 years old. The largest shark in the study, a 16-foot long female, was likely close to 400 years old.

The scientists used material from the lens of the sharks' eyes to age the animals. Tis kind of Radiocarbon dating also provides an added bonus - nuclear testing in the early 1960s created a signature pulse of carbon 14 that is incorporated into the eye during development, and that enables scientists to identify that specific time period. Scientists who age fish like halibut and rockfish by looking at their otoliths, or ear bones, also use the radiocarbon bomb pulse as a time marker.

Greenland sharks are large and slow-growing. They live in waters that are just above freezing. Their tissues are cold, and so are the chemical reactions that occur in their bodies - including all the metabolic processes that turn food into fuel and run their large bodies. Big animals have slower metabolisms than small creatures; and if the metabolic rate is slowed, everything in the body is slowed - including the process of aging. Researchers found that the age of sexual maturity is also remarkable. Greenland sharks become sexually mature when they are about 150 years old.

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Download Episode: Operation Northern Creep (MP3 file 1,407 kB)

Operation Northern Creep

Traffic was brisk on the Alaska Highway in May of 2016, with cars, trucks, and recreational vehicles with canoes, kayaks, and trailered pleasure boats streaming through the border crossing east of Tok, known as the Port of Alcan. For ten days in mid-May, Fish and Wildlife Service staff inspected about 100 boats entering Alaska and met with hundreds of visitors, providing outreach materials on invasive species. This was part of "Operation Northern Creep," an effort addressing the threat of invasive species entering Alaska.

A major concern are two species of invasive mollusk, zebra mussels and quagga mussels. These mollusks were first introduced to U.S. waters in the late 1980s, and their presence has cost the Great Lakes region upwards of $200 million a year. The invasive mussels limit the ability of natural ecosystems to support commercial and sport fisheries, water uses, and wildlife watching. Twenty years later, these mollusks have made their way across the country to Colorado, Utah, Arizona, Nevada and California.

The overland movement of watercraft - boats on trailers, canoes and kayaks on cars - from invasive species infested waters carried both adult and larval stages of invasive mussels and other aquatic invasive species to western freshwater systems on their hulls, in ballast tanks and in compartments. The larval mussels can survive on a boat out of water for as long as 27 days. Aside from allowing a watercraft to completely dry for 30 or more days, hot pressurized water is the silver bullet for eliminating invasive mussels on watercraft. A few of the boats inspected at the border in May had previously been inspected in Wyoming, Idaho, or in British Columbia, and fortunately, no mussels were detected on any of the watercraft entering Alaska.

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Download Episode: Pacific Cod (MP3 file 1,405 kB)

Pacific cod

A commercial fishing boat bobs on the green water of the Gulf of Alaska, miles from shore. These fishermen are after pacific cod, a bottom dwelling fish found in huge schools in the north pacific. However, in 2018, those schools aren't as huge as they used to be.

In 1979 fishermen in the gulf caught less than a thousand tons of cod, but fishing efforts ramped up, and in five years that grew to 90,000 tons. A decade later, in 1995, fishermen caught 430,000 tons of cod in the North Pacific. Catches have since declined. For 2018, fishery managers have set the catch limit for cod at 18,000 tons.

The stocks of cod have declined, but there is more going on under the waters of the north pacific than fishing. Biologists think cod were adversely affected by an unusually warm mass of water that persisted in the Gulf of Alaska from 2014 to 2016. This warm water increased the metabolism of cod while reducing available food, resulting in poor body condition and increased mortality. It also affected egg production and larval survival, greatly reducing recruitment during these years. Fishery managers are focused on maintaining the spawning stock and helping the fishery remain viable in years to come.

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Download Episode: Pacific Herring (MP3 file 1,403 kB)

Pacific herring

On a spring day in Juneau, I take a shortcut to work and walk the docks of Aurora Harbor. There's an enormous school of fish swimming beside the dock, the harbor is filled with these small fish. I come back a few hours later with my camera and shoot some pictures and video. Thousands of silver fish about three inches long are milling about. A Fish and Game biologist later identifies them as juvenile Pacific herring.

Herring spawn in the spring, in shallow, intertidal and subtidal vegetated areas along the coast. Pacific herring are sexually mature at three or four years of age, and the fish I saw won't be spawning this year, they're juveniles.

Adult herring spawn in massive schools and an entire school can spawn in the course of a few hours. The precise staging of spawning is not understood, but biologists suspect the male initiates the process by release of milt, which has a pheromone that stimulates the female. A single female may lay as many as 20,000 eggs in one spawn, depositing the eggs on seaweed or some other substrate. The behavior seems to be collective, producing an egg density of up to 6,000,000 eggs per square meter.[6] The tiny fertilized eggs, incubate for about 10 days in near shore waters that are about 10 degrees Celsius.

After spawning Pacific herring migrate back to offshore waters to feed. They exhibit a daily vertical migration pattern, remaining near the bottom during the daylight hours and moving to shallow waters to feed at night.

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Download Episode: Pink Fry (MP3 file 3,531 kB)

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Download Episode: Pond Smelt (MP3 file 1,406 kB)

Pond smelt

The vast, open, treeless plain north of the Brooks Range is home to a number of rivers that flow into the Arctic Ocean. On a summer day, there's a shimmer beneath the surface of one of these Arctic rivers. It's a school of fish, thin, silvery fish 7 or 8 inches long, that look a little like herring. They're smelt, related to herring, and this school of smelt is in fresh water. They're pond smelt, and like salmon, they're anadromous. They're born in fresh water, move downstream to the ocean as juveniles, and live in salt water for two or three years before returning to fresh water to spawn and die. Unlike salmon, which return to the natal stream where they were spawned, pond smelt don't home in on a specific river. They use rivers, streams and ponds in the general area where they were spawned that have the best habitat conditions.

Pond smelt spawn in river backwaters with little or no current, and near the shoreline of lakes and ponds. Eggs are broadcast and one female can lay up to 4,000 eggs. The fertilized eggs are sticky; they sink and adhere to whatever they touch. The eggs hatch in 11 to 24 days, depending on the water temperature, and the juveniles migrate to the ocean, seeking out river currents to carry them downstream. They grow to maturity in the sea, where they feed mainly on plankton. After two to three years at sea, they return as adults to spawn. Since stream water temperature affects the timing of the spawning migration, the number of spawning pond smelt returning to a particular stream varies from year to year. Some streams can have two separate but overlapping migrations.

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Download Episode: Sablefish (MP3 file 1,407 kB)

Sablefish - Old and on the Move

At the western end of the Aleutian Island chain, a commercial fisherman in October of 2009 hauled in a long line with a nice catch of sablefish - also known as black cod. He noticed an orange tag sticking out of the dorsal fin of one fish. He returned the tag to a fish and Game office and learned that fish was tagged by biologists two and a half years earlier and almost 2,000 miles away in Southeast Alaska.

Fish and Game biologists tag sablefish in late spring at locations along Chatham Strait in Southeast Alaska. The sablefish are caught using pots strung on a longline, and because they are not caught with hooks, the survival rate of released fish is excellent. Tagged fish mix with the general population of sablefish in the area. Comparing the release locations to the subsequent capture locations helps biologists understand sablefish movements.

Sablefish are long-lived, and can reproduce for decades once mature. Sablefish are known to live into their 90s, and Fish and Game aged a 97-year old sablefish caught in Prince William Sound. They also inhabit some incredibly deep waters, from 300 to almost 3,000 meters deep, waters about 1,000 to 9,000 feet deep.

In past years surveyors have tagged between 6,000 and 8,000 fish each year, and in 2017 almost 800 tags were returned. One sablefish was caught five years after it was tagged. Some remarkable travels have been documented: a sablefish tagged in upper Chatham Sound in May 2012 was caught four years later in April of 2016 off the coast of Eureka, California, more than 2,000 km (1,300 miles) away.

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Download Episode: Salmon Hatchery (MP3 file 1,409 kB)

Alaska's Private Non-profit Hatcheries

A group of first graders is excited to see a million fingerling salmon on a field trip to the DIPAC fish hatchery in Juneau. DIPAC, also called the Macaulay Salmon Hatchery, is one of 30 private non-profit hatcheries in Alaska. The hatcheries in Southeast Alaska mostly raise chum and coho salmon, and also some Chinook; the hatcheries in Prince William Sound mostly raise sockeye and pink salmon, Cook Inlet hatcheries focus on sockeye, and Kodiak hatcheries focus on pinks.

Alaska's private nonprofit salmon hatcheries do not replace, but supplement, natural stock production. Egg to juvenile survival is low in nature, less than 20 percent, but close to 90 percent in hatcheries. Once juveniles are released to the ocean, they are subject to the same elements for survival as their naturally-spawned counterparts.

The hatchery program began in the mid-1970s, in response to dismal salmon returns, when a low of just 22 million fish were harvested. In 2015, more than 250 million salmon were harvested in Alaska - a mix of wild stocks and hatchery stocks. About 92 million of the 250 million salmon harvested were from hatchery stocks, the rest were wild. The highest salmon catch in Alaska history took place in 2013, when 283 million salmon were harvested.

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Download Episode: Salmon Senses (MP3 file 1,406 kB)

Salmon senses

I approach a coastal stream and a school of salmon darts away, quickly regrouping on the other side of the stream. Salmon are equipped with a range of senses, including good eyesight. Fish eyes function like our eyes, with a pupil, lens, and a retina filled with sensory cells: rod-shaped cells that work best in low light, and cone-shaped cells that detect colors. Their eyes are adapted for life in water. A fish's lens is spherical and retains that shape whereas the lens in our eye is oval and flexible and changes shape with the visual range.

Fish also have taste buds, located in the mouths and throats of most fish, but some fish also have taste buds on their gills and even their fins. Catfish have taste buds on "whiskers" near their mouths, and some catfish have taste buds all over their bodies.

The nasal organs of fish function only to detect odors. This sensory system is particularly important to salmon. Salmon remember the specific smell of the water in their birth or natal streams, and remember how it changes as they migrate to the sea as smolts. They use the memory of the smell to help them hone in on their natal stream when they return to spawn.

Sharks, tuna and salmon can detect the Earth's electromagnetic field, which allows them to maintain a compass heading at sea. Salmon spend one to five years in the ocean and migrate thousands of miles at sea before returning to their natal streams to spawn. Their ability to navigate at sea helps them to return to the coastal areas where they first entered saltwater; then their sense of smell helps lead them directly to their natal stream.

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Download Episode: Salmon Sharks (MP3 file 1,407 kB)

Salmon Sharks

Beneath the waters of Prince William Sound a remarkable fish is hunting. It's a 450 pound salmon shark, more than six feet long, cruising just under the surface, its dorsal fin knifing through the water. Salmon sharks are fast moving apex predators in the north pacific, and they are aptly named for their favorite prey. Salmon sharks are fast - they're muscular and streamlined, with large efficient gills. There's another reason salmon sharks are fast swimmers - they are warm-blooded, or homeothermic - one of the few fish that regulates its body temperature regardless of the water temperature.

Most fish lose whatever body heat they generate metabolically through their gills and skin. Salmon sharks maintain a body temperature considerably warmer than the surrounding water thanks to a specialized circulatory system. Countercurrent heat exchangers in the sharks' circulatory system prevent heat from being dissipated, especially from the gills. In one study sharks in Prince William Sound maintained a body temperature of about 77 degrees, although the water temperature varied between 40 and 60 degrees. This allows these active predators of fast-moving fish to move quickly in the cold waters of the north Pacific.

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Download Episode: Sea Cucumber (MP3 file 1,403 kB)

Sea cucumbers

A family is tide-pooling on a minus tide in Southeast Alaska, and they've discovered an odd looking creature. It's a sea cucumber, an aptly named marine animal related to sea stars. About twelve inches long, this orange cucumber-shaped animal has leathery skin and seems like a bag full of water. Although it doesn't look very appetizing, there is an important commercial market for sea cucumbers. There are many species of sea cucumber, but the giant red sea cucumber is the only species commercially harvested in Alaska.

Sea cucumbers crawl slowly across the sea floor, picking up algae and detritus on their tube feet and then transferring the nutrients to their mouths. They really are mostly water - they have no brain and few organs beyond gonads and a digestive tract.

Red sea cucumbers are harvested by divers, who hand pick them off the sea floor in a carefully managed fall fishery. An average red sea cucumber was worth about two dollars in the 2015 commercial season. About 230 divers have permits to harvest sea cucumbers in Alaska, and they harvest about one and a half million pounds a year.

The harvested sea cucumbers are sliced lengthwise and five strips of white meat are scraped off of the inside of the sea cucumber's skin. Each animal yields just a few tablespoons of meat. The skin is boiled and salted, then ground up, and often used as seasoning in Asian soups. Sometimes, the entire animal is boiled and salted. Sea cucumber is popular in Korea as trepang, and is also called sea ginseng. In Japan it's known as namako.

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Download Episode: Sea Urchin (MP3 file 1,411 kB)

Urchins

It's a minus tide on a beautiful summer morning, and some kids are tide pooling. They've found a green sea urchin, covered with spines. They handle it carefully for a moment and gently return it to the pool. Urchins are familiar to beachcombers as hollow, round white shells. Living urchins are covered with bony spines that fall off shortly after they die. Alaska is home to both green and red sea urchins.

Urchins are echinoderms, and are related to sand dollars and sea stars. The name urchin is an old word for hedgehog, and sea urchins are spiny like hedgehogs. Urchins feed on algae like kelp, and are in turn eaten by sea otters, star fish, and fish like triggerfish and wolf eels that can deal with the spines and open their shells. Alaska's red and green sea urchins have short spines, but some tropical sea urchins have venomous spines.

Urchin roe is also popular in Asia, and is known as uni (oooni). Red sea urchins are harvested by hand by divers in southern Southeast Alaska, and green sea urchins are harvested around Kodiak Island. Urchins are monitored by Fish and Game in several dozen areas in Southeast to insure that the harvest is sustainable

Although urchins in Alaska only measure a few inches across, they are surprisingly long lived. Growth rings laid down annually allow researchers to determine the age of the urchins, and the oldest green sea urchin harvested was 16 years old. A red sea urchin, also from southern southeast Alaska, was 32 years old.

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Download Episode: Shark Travels (MP3 file 2,564 kB)

Shark Travels

A shark fin cuts the cold water of the Bering sea as a four-foot-long salmon shark cruises near Saint Lawrence Island. There's something unusual about that tall dorsal fin, and a closer look reveals a cigar-size device fastened to the side of the fin, with a short antennae pointing skyward. It's a tracking device. Fish and Game researchers studying juvenile salmon in the Bering Sea have equipped several male salmon sharks, caught incidentally in salmon trawl nets, with tracking devices to learn more about how their movement patterns relate to season and prey availability.

Sleeper sharks are northern sharks that cope with near-freezing water by having a slow metabolism. Salmon sharks take a more mammalian approach - they are warm-blooded fish and can maintain their internal body temperature as much as 21°C above the ambient water temperature. This ability to hunt and thrive in cold water means salmon sharks may be one of the most northern dwelling sharks in the world. They have even been caught above the Arctic Circle.

Like most sharks, Salmon sharks segregate by sex. Biologists are learning that Female salmon sharks dominate the eastern North Pacific and Prince William Sound, while males dominate the western North Pacific and the Bering Sea. Tagged male sharks like this one are providing a unique opportunity to learn about their movements and behavior.

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Download Episode: Shells as Money (MP3 file 1,404 kB)

Shells as money

A lone beachcomber stoops to pick up a shell on a rainy Southeast Alaska morning. Alaska waters are home to a variety of shelled animals. Some, like gastropods, have a single shell; others, like scallops, are bivalves and have two shells that are hinged. Whelks are predatory gastropods that prey on other snails. The leafy thornmouth is an Alaska gastropod with a showy, fringed shell. The fringes are functional, aerodynamic in a sense, they allow the snail to land right-side-up when it's knocked off its rocky underwater perch. A calcareous thorn on the underside discourages predators from breaking into it.

Tusk shells are small, cylindical snails that live in sand. True to their name, these smooth, white shells do look like small tusks. They're also known by their scientific name, Dentalium. Dentalium shells were used as money by many Native Americans in the Pacific Northwest and Canada, from the Pacific Coast to the Dakotas. Dentalium shells were harvested by the Nootka tribe in two areas off the coast of Vancouver Island in British Columbia. They were used as ornaments and traded, and as they were traded further from their source they began to acquire a precise monetary value. The standard measure was the fathom long string, which held about 40 shells. In the 1860s in the Dakota Territory, just two or three dentalium shells would buy a buffalo robe.

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Download Episode: Shrimp Sex Change (MP3 file 1,407 kB)

Hermaphroditic shrimp

A boat idles in a cove on a summer afternoon, pulling up a set of shrimp pots. The first one comes in with a nice catch of spot shrimp. Spot shrimp are the biggest shrimp in the North Pacific and are highly valued by commercial pot fishers and subsistence users alike.

Spot shrimp, along with pink, coonstripe and humpy shrimp, are one of five species of pandalid shrimp found in the cool waters off the coast of Alaska. Pandalid shrimp are one of the rare hermaphroditic animals. They change their sex. Specifically, they are protandrous hermaphrodites - the shrimp spends the early part of its adult life as a male and then changes into a female for the rest of its lifetime. A pink shrimp will typically mature sexually as a male, spawn one or more times, pass through a short transitional phase and subsequently mature and spawn as a female.

Shrimp spawn in the fall and the eggs incubate over the winter. In the spring the eggs hatch into planktonic, free-swimming larvae. By mid-summer, the larvae have undergone several molts, rapidly increasing in size after each molt. After the last larval molt the juvenile shrimp settles to the bottom. After a year or so, the juvenile molts and develops into a mature male and may spawn as a male for one or two seasons. Some juveniles, however, never mature into males; instead, they develop directly into females.

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Download Episode: Signal Crawfish (MP3 file 1,407 kB)

Signal Crawfish

On an overcast summer day, a biologist is wading in Buskin Lake on Kodiak Island. She heard that an invasive species has been introduced to Buskin Lake, the signal crawfish, and she's flipping over rocks in the shallows. She finds one immediately, and then another, and another. After a few hours, it's clear that there are a lot of crawfish at the south end of Buskin Lake.

More than 300 different species of crawfish, also called crayfish or crawdads, are found across North America, but they are not native to Alaska. The Signal crayfish is native to the Pacific Northwest, and as an invasive species, it's particularly aggressive. Introduced to California, it outcompeted and essentially replaced every native California crawfish. The story was similar in Europe - the introduced signal crawfish also carried a crawfish disease that reduced native European crawfish species. Their commercial value is less than half of what native European crayfish would be worth. In addition, signal crayfish can dig extensive burrows in river banks and, in England, have been identified as a cause of river bank collapse and increased flooding risk. Biologists with Fish and game, and with the Sun'aq Tribe of Kodiak, are monitoring the invasive crawfish in Buskin Lake and working to remove them from Kodiak Island.

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Download Episode: Skate (MP3 file 1,407 kB)

Skates

A beach comber has found a weird looking, triangular shaped skull washed up on a beach near Pelican in Southeast Alaska. It's about the size of her hand and it's not bone, it's cartilage, and it looks like shiny white plastic. It belongs to a skate - a manta ray-like fish related to sharks. Like manta rays and sting-rays, skates have cartilaginous skeletons, flat bodies and wing-like fins. They are bottom-dwellers and eat crabs, clams, worms, and fish. They are slow-growing, long-lived animals, and take about 11 years to become sexually mature.

Skates are found in oceans throughout the world. Skates differ from rays because they lay eggs instead of bearing live young - and they don't sting. There are 14 species of skates in Alaska waters.

Skates congregate by the thousands to lay their eggs in ocean bottom nurseries; generally in June and July. Some nurseries are 500 feet to 1,200 feet deep and may contain millions of egg cases in various stages of development. These nursery sites are usually located at the heads of undersea canyons, where water temperatures are constant throughout the year. A skate may lay just 25 eggs, every other year, and eggs can take from one to four years to gestate on the sea floor before they finally hatch.

Unlike some fish, which lay thousands of eggs every year, with only a small fraction of the young surviving to adulthood; skates have a low reproduction rate but the young tend to have high survival rates.

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Download Episode: Sleeper Sharks (MP3 file 3,877 kB)

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Download Episode: Steelhead (MP3 file 3,521 kB)

Steelhead

In a deep, clear pool in a coastal Alaska stream, a large school of Dolly Varden rest almost motionless near the bottom. A giant, bright silver fish fins lazily at the tail of the pool, dwarfing the smaller char. It's a 15-pound summer steelhead, fresh from the sea. The steelhead trout is actually a rainbow trout that has adopted a different life history and has spent most of its adult life in the open ocean.

Steelhead are often classified as to the time of year they return to their natal stream, either spring, summer or fall. Regardless of when they return to freshwater, all steelhead spawn during the spring months, usually about mid-April through May to early June.

Steelhead may spawn more than once, while Pacific salmon spawn only once and then die. Many steelhead do die after spawning once, but about 30 percent return to sea and live to spawn again. Males do not survive spawning as well as females, and generally the larger and older females survive better than the smaller and younger ones. After spawning, the ragged and spent steelhead, sometimes called kelts, move slowly downstream to saltwater, and the vibrant spawning colors return to a bright silvery hue as their depleted stores of fats are restored. Most steelhead that repeat spawn come back annually but some may skip a year before returning to spawn.

After hatching out in the gravel of freshwater streams, juvenile steelhead may grow to be 2- or 3-inches by their first fall. Juvenile steelhead typically spend two to five years in freshwater before moving to the ocean in the springtime. Once in the food-rich marine environment steelhead can grow an inch per month. Most steelhead spend two or three years in the ocean and will travel hundreds of miles before returning to their natal stream to spawn.

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Download Episode: Tadpoles (MP3 file 1,407 kB)

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Download Episode: Test Fishery (MP3 file 2,337 kB)

On a sunny day in July, a purse seiner draws its net around a thousand pink and chum salmon in the Inside Waters of Southeast Alaska. This looks like a typical commercial seine operation, but these seiners are especially attentive to the catch. This is a test fishery and they are working with Fish and Game to assess the abundance of pinks and chums returning to the area. Every year here, one day a week for five weeks in June and July, contract fishermen like this note the number of salmon caught per set, their weight, and the ratio of males to females. Comparing this information to past years provides insights into abundance, run strength, run timing, and harvest rates.

males tend to be more numerous early in the run and females are more numerous later in the run. Comparing the sex ratio to the historical average indicates whether the run is earlier, later or similar to the run timing in previous years.

On this early July day, the ratio was 70 percent male, implying the run is later than normal. About twelve-hundred pinks were caught per set, well above the ten-year average. The average weight of the pinks was two and a half pounds, and the average weight of chums was about six pounds.

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Download Episode: The Intertidal (MP3 file 1,409 kB)

Intertidal

The tide is high and a scuba diver investigates a vertical rock wall about 20 feet high, covered with barnacles, mussels and marine life. Kelp reaches from the seafloor below to the surface. Just six hours later, the following low tide exposes this entire wall, and beach combers on the formerly submerged, rocky beach view the same array of marine life - now exposed to the elements.

Tides in parts of Alaska can be 20 feet or more between extreme high and low tides. Life in the intertidal means enduring wind, ice, pounding surf, hungry predators and extreme changes in temperature, moisture and salinity. The upper intertidal is more dry than wet, and creatures here, like barnacles, must endure long periods out of the water. Cemented to the rocks with one of natures' strongest glues, barnacles close up tight to wait out the low tide.

In the middle intertidal section, blue mussels anchor themselves to the rocks with strong, byssal threads. The middle intertidal can accommodate more life because it is submerged more.

The lower intertidal is almost always wet, and teems with life, home to sea stars, snails, chitons, urchins and anemones. Kelp is anchored to the seafloor with a root-like structure called a holdfast, and stretches from the lower intertidal to the upper intertidal, forming a breakwater shelter for intertidal animals and a blanket of moisture at low tide.

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Download Episode: Thermogenic Skunk Cabbage (MP3 file 1,411 kB)

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Download Episode: Trees Need Salmon (MP3 file 3,527 kB)

Trees need salmon

It's late fall on a salmon stream in Alaska, and the salmon run is over. There are no fish to be seen in the water, but the salmon are here - they're in the trees and the soil.

Bears often drag their catch onto stream banks or into the forest edges to eat, and once they consume the oily roe, belly, brain and skin, the rest of the carcass is available to other animals and insects. As leaching by rain and microbial activity breaks down carcasses, nitrogen, phosphorus and other nutrients become available to streamside vegetation.

One study found that trees on the banks of salmon streams grow more than three times faster than their counterparts on salmon-free rivers. Growing side by side with salmon, Sitka spruce take 86 years, rather the usual 300 years, to become 20-inches thick. In many areas, up to 70% of the nitrogen found in riparian zone foliage comes from the sea, way of salmon.

And just as trees need salmon, salmon need trees. Vegetation shades spawning streams and keeps developing eggs cool. Streamside plants house terrestrial invertebrates that fall into the water and feed growing young salmon. Leaves and needles in the water - and the organic matter trapped by woody debris - provide food and shelter for aquatic insects, which also feed young salmon. Tree roots stabilize stream banks to slow erosion and protect the clean water salmon need. Fallen trees create pools that and provide shelter for fish.

So next time you enjoy a salmon dinner, thank a tree.

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Download Episode: Undersea Echolocation (MP3 file 3,643 kB)

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Download Episode: Undersea Noise (MP3 file 1,233 kB)

Undersea noise

The ocean can be a noisy place. The feeding calls of humpback whales resonate in the waters off Point Adolphus in Southeast Alaska...but it isn't long before a tour boat adds engine noise to the undersea soundscape.

The ocean could be noisy even before motor boats arrived on the scene. Near the Marjerie glacier in Glacier Bay, waterfalls, creeks and melting ice create a background of white noise. In Johns Hopkins Inlet, the restless motion of icebergs adds sound, as does a distant calving off the face of the glacier.

Chris Gabriele, a biologist in Glacier Bay National Park, is studying and documenting undersea sounds. She's particularly interested in learning how marine mammals, especially humpback whales, might be affected by the sounds made by ships and boats. Whales experience the world mostly by the way it sounds, rather than by how it looks, since underwater visibility is so limited in plankton-rich Alaska waters.

Whales may move away from preferred feeding areas when disturbed by vessel sounds. Vessel noise can also interfere with whale communication, increase the chance of collision between vessels and whales, or cause short-term hearing loss. Researchers need to learn how much noise is too much, what role the frequency of the sound plays and what effects vessel type, speed, and proximity might have.

While larger vessels like cruise ships are loud at greater distances than smaller vessels, smaller boats can produce equivalent underwater noise levels at close range. But while a skiff with a 100-plus horsepower engine can potentially be as loud as a cruise ship, the volume peaks at different frequencies. Large, low RPM vessels tend to generate and radiate more noise at lower frequencies while noise from small, high RPM craft typically peaks at higher frequencies. It's not known exactly what frequencies baleen whales hear best at, but it is believed they may be more sensitive to lower frequencies, so large vessel may affect their underwater ambient noise habitat from a greater distance.

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