Tag Archives: Kodiak Wildlife

Sea Cucumbers

February 23, 2022Living in the wilderness on Kodiak Island, Marine InvertebratesEchinoderms, Harvesting Sea Cucumbers, Kodiak Wildlife, Robin Barefield, Sea Cucumbers, Sea Cucumbers in Alaskaadmin

Sea cucumbers are some of the strangest-looking organisms on the beach. They might have the shape of a cucumber, but that is where the resemblance ends. At first glance, a sea cucumber looks like a plant, but it is an animal. As I mentioned in my last post, they are echinoderms related to sea stars, sea urchins, and sand dollars.

There are more than 1,250 species of sea cucumbers, and they occupy nearly every marine habitat worldwide.They range in size from one to two inches (2.5 to 5 cm.) to 10 ft. (3 meters). Most species reach a maximum length of between four to twelve inches (10 to 30 cm). Most, but not all, sea cucumbers have a cylindrical shape with protruding tube feet covering their bodies. All sea cucumbers live in the ocean, but some live in the. shallows, while others inhabit the deep ocean floor. They are benthic animals, meaning that they are bottom dwellers at whatever depth they live.

Sea cucumbers feed on algae, tiny aquatic animals, or waste particles. They gather their food with the eight to thirty tube feet surrounding their mouth.

When threatened by a predator, some species of sea cucumbers can discharge sticky threads to ensnare their attacker. Other species violently contract their muscles and propel their toxic organs from their bodies toward their attackers. They can quickly regenerate the missing organs. Sea cucumbers can also expose skeletal hooklike structures, making it more difficult for a predator to eat them.

While sea cucumbers can reproduce asexually, sexual reproduction is more common. They are broadcast spawners and gather in groups to release their eggs and sperm into the water simultaneously. When the eggs and sperm happen to meet, fertilization occurs. Sea cucumbers have a life span of five to ten years.

A sizeable culinary market for sea cucumbers exists in Asia, where certain species are considered a delicacy. The giant red cucumber is harvested in Alaska. Red sea cucumbers are found in many nearshore areas from Baja California, north and west to the Gulf of Alaska. Alaska’s largest sea cucumber fishery occurs in Southeast Alaska, with smaller fisheries near Kodiak and Chignik. Scuba divers commercially harvest cucumbers and then deliver eviscerated but live animals to shore-based processors. The cucumbers are processed by separating the five longitudinal muscle bundles from the skin with a scraper or a knife. The processor then boils the skin and dries it into a product called trepang or beche de mer. The processor freezes the longitudinal muscles and markets the dried skin and frozen muscles locally in the U.S. and Asia.

In early October, we often see sea cucumber harvesters diving for animals near our lodge. I often think they have a tough job jumping into the frigid ocean, searching for a small sluggish animal on the ocean floor.

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Robin Barefield is the author of four Alaska wilderness mystery novels: Big Game, Murder Over Kodiak, The Fisherman’s Daughter, and Karluk Bones. She recently released the non-fiction book Kodiak Island Wildlife. Sign up below to subscribe to her free, monthly newsletter on true crime and mystery in Alaska, and listen to her podcast, Murder and Mystery in the Last Frontier.

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Echinoderms in Alaska

October 24, 2021Kodiak Wildlife, Marine InvertebratesBrittle Stars, Echinoderms, Echinoderms in Alaska, Kodiak Wildlife, Robin Barefield, Sand Dollars, Sea Cucumbers, Sea Stars, Sea Urchins, Starfishadmin

Echinoderms are my favorite intertidal animals. They belong to the phylum Echinodermata and live only in marine environments. You won’t find an echinoderm in a river or stream. Their name originates from the Greek word for spiny skin, and all echinoderms have either a hard spiny covering or spiny skin.

What is an echinoderm? While there are around 7,000 species of echinoderms, they fall into seven major classes. These are the sea lilies, sea urchins, sand dollars, sea cucumbers, brittle stars and basket stars, sea daisies, and sea stars – or starfish. Echinoderms live in every marine habitat from the intertidal zone to the deep ocean. They are often brightly colored, and their reds, greens, purples, and oranges make them stand out against the monochromatic background of clam and cockle shells.

Some species of echinoderms do not look as if they should belong to this phylum. A sea urchin does not resemble a sea star, and sea cucumbers look nothing like other echinoderms. Body types range from flowerlike sea lilies to slug-shaped sea cucumbers. However, in addition to the spines, all echinoderms have pentamerous (five-part) radial symmetry, an internal skeleton, and a water-vascular system derived from a central cavity. Look at a sand dollar the next time you pick up one and note the star in the center of the disk and the five-part symmetry. Examine a dead sea urchin once its spines have dropped, and you will see the five plates. If you dissect a sea cucumber, the pentamerous symmetry reveals itself. Some sea stars have many legs, but look closely, and you will see the five-part divisions.

An echinoderm has a simple digestive system with a mouth, stomach, intestines, and anus. In many species, the mouth is on the underneath side of the animal, and the anus is on the top. A sea stars can push its stomach through its mouth, allowing it to digest its prey externally. For example, it can insert its stomach into a clam shell once its powerful legs have pried open the shell. The ability to extrude its stomach allows a sea star to eat animals larger than its mouth.

While echinoderms do not have brains, they do have nervous systems. They have tiny eyespots that can detect only light and dark, and some of their tube feet are sensitive to chemicals, allowing them to find food. They do not have a heart, but they have a network of fluid-filled canals. To breathe, they use simple gills, and their tube feet take in oxygen and pass out carbon dioxide.

Echinoderms are either male or female, and they reach sexual maturity when they are two to three years old. Most species broadcast spawn by releasing their eggs and sperm into the water at the same time. A sperm meets up with an egg by chance and fertilizes it. This type of reproduction is hit or miss, but a female releases as many as one hundred million eggs at one time, improving the chances of some being fertilized. Larvae float free for a period and eventually settle to the bottom and develop into their adult form.

Lifestyles of the different groups of echinoderms vary greatly, and over the next few posts, I will take a closer look at some of the species found in Alaska.

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Kodiak Island Wildlife by Robin Barefield with Photos by Mike Munsey

Robin Barefield is the author of four Alaska wilderness mystery novels: Big Game, Murder Over Kodiak, The Fisherman’s Daughter, and Karluk Bones. Sign up below to subscribe to her free, monthly newsletter on true crime and mystery in Alaska, and listen to her podcast, Murder and Mystery in the Last Frontier.

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Killer Whale or Orca?

August 22, 2021killer whale, Kodiak Wildlife, Orca, Uncategorizedkiller whale, Killer Whale Predation, Killer whales near Kodiak Island, Kodiak Wildlife, Minke Whale, Robin Barefield, whales in Alaska, What do killer whales eat?admin

Do you refer to the sleek black and white animal pictured above as a killer whale or an orca? Of course, a killer whale is not a whale but is the largest member of the dolphin family, but let’s set aside that fact. What you call these marine mammals may depend on your experience with them. If you’ve watched them perform at a marine park, then the name “orca” fits their apparent playful, intelligent demeanor. If you’ve observed them in the wild, then “killer whale” might be a more apt moniker.

We are in the middle of our summer wildlife-viewing and sportfishing trips at our lodge here on Kodiak, and over the last few weeks, we’ve had several encounters with killer whales. One day, they breached, spy hopped, and slapped the water while we watched with delight. They were orcas that day.

Another morning, we had a very different experience. Soon after we left our mooring, we encountered a bull and a cow orca, and we watched and photographed the killer whales for a while, trying to get the perfect shot of the male with his large, majesti

c dorsal fin. Then, we realized the horrific scene playing out in front of us.

The killer whales slowly maimed, tortured, and ate a minke whale while we watched. They first ate the whale’s tail, probably so it couldn’t escape. The poor minke continued to attempt to swim while the orcas followed it, ripping pieces out of it as the whale slowly died. While we watched the killer whales toy with the dying minke, we did not doubt we were watching “killer whales,” not “orcas. They behaved as the apex predators they are, but to us, their actions seemed cruel. Later, when I thought about the incident, I wondered if the killer whales left the minke alive, so it wouldn’t sink, and they could more easily consume it at the surface. Perhaps their actions were practical and not cruel. To those of us watching the saga, it seemed that the whales enjoyed taunting their prey and reveled in watching it suffer.

Male killer whale following maimed minke whale

Our recent encounters with these beautiful, large dolphins have again made me question what we should call them. Where they sit at the top of the food chain, I think they would prefer the name “killer whales.” The title makes them sound majestic and fierce.

Killer whales have strong jaws and up to 52 interlocking teeth. Their powerful tail fluke can stun or kill prey by slapping the water at speeds as high as (52 km per hour). They often feed in groups and can communicate with each other with sonar and by other means. Observers recently reported 50 orcas stalking a blue whale, the largest of all whales.

In the 1970s, marine parks such as Sea World began capturing orcas and training them to do tricks for public shows. People watched these shows and thought the whales were cute and lovable. Many believed they did not deserve the name “killer whale” and began calling the animals “orcas.”

I tend to use both names, just as I have in this post, but it does this majestic animal a disservice to consider it docile and cute. Killer whales are very intelligent, and they are also the top predators in the ocean. They eat sharks, whales, dolphins, fish, seals, sea otters, octopuses, squid, and anything else they want to eat. They deserve our respect, and to watch them in the wild is a rare treat. I know the image of the large bull chewing on the live minke whale will stay with me for the rest of my life. I might never again call a killer whale an orca.

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Weathervane Scallop (Patinopecten caurinus)

July 31, 2021Kodiak Wildlife, Marine InvertebratesAlaska Bivalves, Kodiak Wildlife, Scallops, Scallops in Alaskaadmin

Kodiak is synonymous with giant bears, king crabs, and weathervane scallops. The weathervane, also known as the giant Pacific scallop, is the largest scallop in the world. Its beautiful orange shell makes it a treasure for beachcombers, and gourmet chefs prize its large adductor muscle for its taste and texture.

Weathervanes range from California to the Bering Sea and west to the Aleutian Islands. They prefer a mud, sand, or gravel substrate and live anywhere from the intertidal zone to depths of 984 ft. (300 m). They are more common in the deeper parts of their range. Adult scallops form dense, oblong beds that parallel the current.

The round valves of a weathervane can grow to 11.8 inches (30 cm) in diameter, and they differ slightly in color, ribbing, and shape. The upper valve appears reddish-pink and has approximately ten primary ribs alternating with smaller ribs. The bottom valve is lighter in color and has about twenty primary ribs separated by several smaller ribs. The top valve of a weathervane is relatively flat, and the organism rests on the rounder bottom valve.

Unlike most other bivalves, such as clams and mussels, scallops cannot burrow into the substrate to escape predation. Instead, they detect predators with their primitive “eyes” located on the front of their bodies, just inside the shell opening. These eyespots can detect movement, even in the dark depths where the scallops live. When a scallop detects a predator, it swims away from danger by rapidly opening and closing its shell. This movement requires a large adductor, or hinge, muscle. Processors remove this hinge muscle from the shell and market it as a “scallop.” They then dispose of the rest of the animal.

Scallops are either male or female, but gonad color is the only way to distinguish the sexes. Female gonads range in color from orange to red, while a male has creamy white gonads. Weathervanes become sexually mature when they are three to four years old and have a shell height of three inches. Scallops are broadcast spawners and reproduce by gathering in a large group and releasing clouds of eggs and sperm. When a sperm encounters an egg, it fertilizes it in the water column. Biologists think the increasing water temperature in May and June induces the scallops to spawn.

Fertilized scallop eggs sink to the bottom, where they remain for a few days until they develop into tiny larvae. The larvae swim and feed in the water column for a few weeks before sinking to the bottom and transforming into a benthic, filter-feeding scallop. Weathervane scallops can live for 28 years. Primary threats to weathervanes include predation by crabs, sea stars, and octopuses, diseases, habitat damage, and ocean acidification.

Consumers consider scallops a delicacy, and the commercial demand is high. Fishers use dredges to harvest scallops, though, and dredges can severely impact benthic organisms and their habitat. Concerns regarding the effects of dredging have prompted the Alaska Board of Fisheries to enact extensive closures of the scallop fishery and tightly regulate the scallop harvest. The commercial fleet of weathervane harvesters in Alaska is small, with a handful of vessels located in Kodiak. These boats dredge from beds located fifty to one-hundred meters deep, but their bounty does not meet commercial needs.

In the late 1980s, my husband and I volunteered to join an experimental mariculture venture for weathervane scallops sponsored by the Japanese government and several U.S. agencies, including the Alaska Department of Fish and Game. We suspended cages covered with fine mesh in the ocean and collected scallop larvae, as well as the larvae of several other invertebrate species. We then began growing the scallops to a marketable size. We didn’t gather many weathervanes, but we learned where to place the cages to collect the most scallop larvae. Unfortunately, the scallop project ended abruptly in 1989 when the Exxon Valdez oil spill occurred, and state and federal agencies focused their attention on cleaning up the oil and assessing the damage caused by the spill.

More than thirty years later, scientists still have not given up on raising scallops in a mariculture setting, but first, they realize they need to fill the gaps in their knowledge about weathervane biology. Researchers do not know how to determine the age of a weathervane properly, how fast they grow, or how abundant they are in Alaska’s waters. Biologists are also not sure about when weathervanes spawn or if they spawn several times a year. Once researchers can answer some of these questions, they hope to successfully induce weathervanes to grow and reproduce in captivity and make them a viable species to raise in a mariculture operation. Biologists think that farm-raised scallops and wild-caught weathervanes will someday complement each other in the worldwide marketplace.

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Skates in Alaska

March 14, 2021Fish, Kodiak WildlifeAlaska Skate, Kodiak Wildlife, Robin Barefield, Skates and Rays, Skates in Alaskaadmin

Skates are mysterious creatures, and scientists still know little about them. We often catch skates when we sportfish for halibut. The angler usually thinks he has a halibut when the heavy fish hits the lure, but we soon know it’s a skate when the animal exerts long, steady pulls instead of the head-jerking motions of a halibut.

“What is it?” The angler asks when he reels the strange creature up to the side of the boat.

“It’s a skate,” I say.

“What’s a skate? Is it like a stingray?” He asks.

“It’s related,” I reply, “but skates and rays belong to different families.”

Skates in the family Rajidae differ from rays in the family Myliobatidae mainly because skates lay eggs, while rays give birth to live young. Both skates and rays are cartilaginous fish (they have no bones) and are related to sharks.

Biologists have identified 14 species of skates in Alaska, and eight of these species are considered common in the Gulf of Alaska and the Bering Sea. Two of the most abundant species in Kodiak Island’s waters are the Alaska Skate and the Big Skate.

The Alaska Skate ranges from the Gulf of Alaska to the Bering Sea and the Aleutian Islands and west to Japan. They live at depths from 56 to 1286 ft. (17-392 m) and prefer soft bottoms of sand, silt, or mud. They grow to 53 inches (135 cm) in length.

Alaska skates are long-lived and do not reach sexual maturity until they are ten years old. A female lays 20 to 40 eggs per year, and each egg is enclosed in a tough case to protect the embryo as it grows. Since a female skate has dual uteri and shell glands, she can form two single encased embryos at a time. The embryo grows for an average of 3.7 years before it emerges from its case as a fully developed young skate. In certain areas, skate egg cases litter the ocean floor, and beachcombers who find them on the shore call them mermaids’ purses or devils’ purses. Biologists have identified several skate nursery areas in Alaska’s waters. Some of these nursery areas have egg densities of over 100,000 eggs per square kilometer.

A skate’s exceptionally long gestation period and its prolonged maturation until it can reproduce concern biologists. Skate populations are potentially fragile, and if targeted by commercial or sport fisheries, they could easily be overfished. Once considered a trash fish, skate wing is now presented as gourmet food in some regions. The Monterey Bay Aquarium lists skate as seafood to avoid because several North Atlantic species are now in decline from overfishing.

Juvenile Alaska skates eat mainly crustaceans such as amphipods and hermit crabs. As they grow, they begin to eat fish. While enclosed in their tough egg casing, skates remain protected from most predators, but hairy triton snails can prey upon a developing embryo by drilling through the case. Once they hatch, young skates are vulnerable to predation by any larger fish. Steller sea lions and other sea mammals sometimes feed on adult skates.

In my next post, I will profile the big skate, the largest species of skate in the waters off of North America.

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Pacific Sleeper Shark (Somniosus pacificus)

January 31, 2021Fish, Kodiak WildlifeKodiak Wildlife, Pacific Sleeper Shark, Robin Barefield, Sharks, Sharks in Alaska, Somniosus pacificus, Steller Sea Lionsadmin

The reclusive, deep-dwelling Pacific sleeper shark (Somniosus pacificus) remains an enigma to biologists. Once believed to be sluggish bottom-dwellers that scavenged or fed on small fish and slow-moving prey, researchers now think Pacific sleeper sharks play a pivotal role in the North Pacific’s food web. Biologist Lee Hubert with the Alaska Department of Fish and Game studies Pacific sleepers, and he has learned the sharks spend little time on the bottom but instead move continually through all depths and are stealth predators of fast-moving prey.

I can understand how Pacific sleepers earned their reputation as sluggish sharks. We occasionally catch immature Pacific sleeper sharks when we halibut fish, and when reeled up to the boat, they look dead and move very little. I was surprised to hear these sharks are voracious predators. This shark’s ability to remain still, though, is one of the reasons it is such a successful predator. When it glides through the water, barely moving its body, it minimizes hydrodynamic noise, allowing it to elude acoustic detection by its prey.

Pacific sleeper sharks dive to depths exceeding 6500 ft. (1981 m). They typically remain deep during the day and then move to the surface at night, where they feed under cover of darkness. These sharks probably have poor eyesight, but they are extremely sensitive to electromagnetic fields. They can detect even minute electrical signals, such as the beating of an animal’s heart or its diaphragm’s movement. The shark does not need vision to detect these signals and attack its prey. Its dark grey body and stealth movements make it an efficient predator under the cloak of darkness.

The mouth of a Pacific sleeper shark is large and acts as a vacuum to inhale prey. Fish, such as salmon and cod, can be swallowed whole, but the shark uses its teeth to aid in eating larger prey items. Its upper jaw has small, sharp conical teeth used to hold the prey, while the teeth in the lower jaw interlock, forming a serrated blade used for slicing. A Pacific sleeper shark’s bite resembles the shape of a three-quarter moon.

Because they make little noise when traveling, a sleeper shark attacks with little warning. It might slowly swim up underneath a seal resting on the surface and attack the seal’s midsection, inflicting a fatal wound. Researchers know Pacific sleeper sharks eat fish, squid, octopuses, and marine mammals, but they are still trying to discern how much impact these sharks have on the their ecosystem. The number of Pacific sleeper sharks has increased dramatically in the North Pacific since the 1980s. Because they live very deep much of the time, it is difficult for biologists to estimate their population size. Still, in many areas where commercial fishermen caught few sleeper sharks in the 1970s, they now catch many.

Investigators are particularly interested to learn how many marine mammals Pacific sleeper sharks kill and eat. Pacific sleepers can grow to twenty feet (6.1 m) in length and weigh more than 8000 lbs. (3600 kg). They grow nearly as large as an adult orca, and recent evidence suggests these sharks might eat endangered Steller sea lions, especially sea lion pups.

In a 2014 study, biologists inserted “life-history transmitters” into the abdomens of 36 juvenile Steller sea lions.These transmitters record temperature, light, and other properties during the sea lions’ lives. When a sea lion dies, the tags either float to the surface or fall out onshore and transmit the data by satellite to researchers. After 17 of the original 36 tagged sea lions died, researchers noted that 15 of the transmitters indicated that predators killed the sea lions. Usually, when a predator kills a sea lion, the tag is ripped from the body and floats to the surface, recording a rapid temperature change and exposure to light. Three of the transmitters relayed data that suggested a very different type of predator, though. They recorded an abrupt drop in temperature, but they did not float to the surface and sense light, indicating that tissue surrounded them. The apparent explanation is that a cold-blooded animal, such as a shark, had eaten them. Other than sleeper sharks, great white and salmon sharks are the only other candidates living in the area near where the sea lions died. But both great white sharks and salmon sharks have counter-current heat exchangers in their bodies, giving them higher body temperatures than those recorded. Biologists think a Pacific sleeper shark is the only predator in the area that is large enough to eat a sea lion and has a body temperature as low as those recorded.

Pacific sleeper sharks live in polar and sub-polar regions year-round. They range from Baja California north to the Bering, Chukchi, and Beaufort Seas and the Okhotsk Sea off Japan. Biologists know little about Pacific sleeper shark reproduction and only recently learned they give birth to live young. Their social structure is also unknown, but researchers have photographed them feeding together in large numbers on whale carcasses.

Pacific sleeper sharks probably have a lifespan of more than forty years. Their tissue is toxic to humans and believed to be toxic to many other animals, so they have few natural predators except perhaps for other sharks.

Robin Barefield is the author of four Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter, and Karluk Bones. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska, and listen to her podcast, Murder and Mystery in the Last Frontier.

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Osmoregulation in Salmon

July 5, 2020Fish, Kodiak WildlifeKodiak Wildlife, osmoregulation in salmon, Osmoreulation, Pacific Salmon, Robin Barefieldadmin

Osmoregulation is the process of maintaining salt and water balance across the body’s membranes. Any fish faces a challenge to maintain this balance. A freshwater fish struggles to retain salt and not take on too much water, while a saltwater fish tends to lose too much water to the environment and keeps a surplus of salt. Fish have developed behaviors and physiological adaptations to survive in their environments, whether fresh or marine water, but how do fish manage to thrive in both fresh and saltwater?

A catadromous fish spends most of its life in freshwater and then migrates to the ocean to breed. Eels of the genus Anguilla represent catadromous organisms. Anadromous fish begin life in freshwater, spend most of their lives in saltwater, and then return to freshwater to spawn. Pacific salmon and some species of sturgeon are anadromous fish.

How does a salmon maintain the composition of its body fluids within homeostatic limits? How does it reverse its osmoregulation physiology when it swims from a freshwater environment into the ocean or from the ocean to freshwater?

In the ocean, a salmon swims in a fluid nearly three times more concentrated than the composition inside its cells. In such an environment, the fish tends to take on salt from the water and lose water to the denser ocean. This exchange would result in severe dehydration and quickly kill the salmon if the fish did not adequately deal with the issue.

A Salmon faces the opposite problem in freshwater, where it lives in a solution nearly devoid of salts. In this case, the fish has more salt in its body than in its environment, presenting the problem of losing salt to the environment while flooding its body with water.

How does a salmon deal with these two warring issues of osmoregulation? The salmon has evolved behavioral and physiological adaptations to allow it to live in both fresh and saltwater habitats.

In the ocean, a salmon drinks several liters of water a day to maintain its water volume, but in freshwater, it does not drink at all, except for what it takes on during feeding. In freshwater, a salmon’s kidneys produce a large volume of very dilute urine to offset the excess water diffusing into its body fluids. In the ocean environment, though, a salmon’s urine is highly concentrated, consisting mostly of salt ions, and it excretes very little water.

A salmon also has a remarkable adaptation that allows osmoregulation by the fish in both marine and freshwater environments. A salmon uses energy to actively pump Na and Cl ions across the gill epithelial cells against their concentration gradients. In saltwater, the fish pumps NaCl out of its blood and into the surrounding ocean. In freshwater, the pump works in reverse, moving NaCl out of the water, over the gills, and into the blood.

These amazing behavioral and physiological adaptations allow a salmon to move from fresh to saltwater when the fish leaves its nursery area to travel to its ocean feeding grounds and then back from its marine habitat to freshwater when the salmon returns to spawn. The critical changes in osmoregulation are not immediate, though. When a salmon smolt first leaves its home stream, it must rest in brackish water for several days or weeks while it adjusts, and then it will slowly move into water with higher salt concentrations. As the smolt adjusts, its kidneys begin producing more-concentrated urine while the NaCl pumps in its gills reverse direction and start pumping NaCl out of the blood. When the salmon returns to its natal stream to spawn, it must again remain in brackish water for a period while its kidneys adjust, and the NaCl pump changes direction to pump NaCl out of the water and into the blood.

I am always amazed by how animals and plants adjust to the demands of their environment. Anadromous and catadromous fish, however, must adapt to two environments with opposite physiological requirements, and to do this, they flip the switch on osmoregulation from one extreme to the other.

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Incredible Spot Shrimp

June 14, 2020Kodiak Wildlife, ShrimpKodiak Wildlife, Robin Barefield, Shrimp, Shrimp in Alaska, Spot Shrimpadmin

Spot shrimp are the largest wild species of shrimp found in Alaska, with females reaching more than 12 inches (30 cm) in length. Because of their large size, marketers often refer to them as “spot prawns,” but they are not prawns.

What is the difference between a prawn and a shrimp? They might look similar, but shrimp differ from prawns in many ways. Prawns and shrimp are both decapod crustaceans, but they belong to separate sub-orders. Shrimp have plate-like gills and a set of claws on their front two pairs of legs, while prawns have branching gills and claws on three sets of their legs. Shrimp have three body segments, with the middle segment overlapping the front and rear sections, causing their bodies to curve. Prawns, however, lack the body segmentation and have straighter bodies than shrimp. Shrimp and prawns vary in many other ways too, including their reproductive habits. Prawns release their progeny into the water to survive on their own, while a female shrimp carries her eggs on her abdomen for five months.

Spot shrimp range from Southern California to the Aleutian Islands to the Sea of Japan and the Korea Strait. They occupy a variety of habitats and water depths from very shallow to 1510 ft. (460 m), but they most commonly live at approximately 300 ft (90m.). They usually remain close to the bottom and stay near rock piles, crevices, under boulders, or in other areas where they can seek protection from predators. Juvenile spot shrimp remain in shallow, inshore areas and migrate offshore when they mature.

Spot shrimp appear reddish-brown to tan and have horizontal bars on the carapace. The distinctive white spots, from which they derive their common name, are located on the first and fifth abdominal segments. The slender body of a spot shrimp has five pairs of swimmerets on the underside of its abdomen. A spot shrimp repeatedly molts throughout its life and grows larger with each molt.

The most amazing fact about spot shrimp is, like some other shrimp species, spot shrimp are protandric hermaphrodites. They mature as males and later transform into females. They reach sexual maturity at age three when they can produce sperm and spawn as males. As they grow, they pass through a transitional stage and become females capable of producing eggs. Research indicates not all spot shrimp follow this pattern, though. Some skip the male-phase of the life cycle and develop directly into females.

Before mating, a female molts into a shell specialized for carrying eggs. Each egg attaches to her abdomen by a hair-sized structure called a seta, and she carries the eggs from October to March. Biologists believe each spot shrimp spawns once as a male and one or more times as a female. They spawn at depths of 500-700 ft. (152.4 m to 213.4 m).

Spot shrimp are bottom feeders, and they feed at night. They eat a wide variety of bottom organisms, including worms, diatoms, dead organic material, algae, mollusks, and even other shrimp. Fish such as halibut Pacific cod, pollock, flounders, and salmon pursue and eat spot shrimp. Spot shrimp can live seven to eleven years.

Due to destructive fishing methods used to catch shrimp in many areas of the world, biologists consider the commercial harvest of shrimp to be one of the most unsustainable of all global fisheries. Bottom trawls destroy everything in their path. In Alaska, the shrimp harvest is mainly restricted to pot fisheries in certain areas.

In Southeastern Alaska, the Alaska Department of Fish and Game closed the spot shrimp fishery to commercial and sport fishermen in 2013, but the spot shrimp population in the area has continued to decline. Biologists wonder if recent warmer, more-acidic ocean waters could be the cause for dwindling spot shrimp numbers, and they are beginning to research the issue. Shrimp remain most vulnerable to acidification during early life stages when they rely on calcification to build their exoskeletons.

Robin Barefield is the author of four Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter, and Karluk Bones. You are invited to watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska, and listen to her podcast, Murder and Mystery in the Last Frontier.

Alaska Wilderness Mystery Novels by Author Robin Barefield: Big Game, Murder Over Kodiak, The Fisherman's Daughter, and Karluk Bones.

Mystery Newsletter

What Do Sea Otters Eat?

November 4, 2018Kodiak Wildlife, Sea OtterAlaskan Sea Otters, Do sea otters eat fish, Kodiak Wildlife, Robin Barefield, Sea Mammals of Alaska, sea otter, What Do Sea Otters Eatadmin

As I told you last week, a sea otter burns calories at a rapid rate to help maintain its body temperature in its home in the cold North Pacific. It consumes between 23 and 33 percent of its body weight per day, so a fifty-pound otter eats 11 to 16 lbs. (5 to 7.3 kg) of food every day. Where does a sea otter find this much food, and what do they eat?

Sea otters are known to consume more than 150 different prey species, mostly slow-moving benthic invertebrates such as mollusks, crustaceans, and echinoderms, but if they are hungry enough, they also sometimes eat fish and even seabirds. Sea otters are the only marine animals capable of lifting and turning over rocks in search of prey and the only marine mammal that catches fish with its forepaws rather than with its teeth.

Studies done in southeast Alaska, Prince William Sound, and near Kodiak Island indicate that clams are the primary and preferred prey of sea otters in these regions. Clams constituted anywhere from 34% to 100% of the diet of sea otters near Kodiak. In areas where clams are less plentiful, and in areas where otters have depleted the clam populations, mussels and sea urchins comprise a larger percentage of otters’ diets. Crabs are also important prey species where they are available. On the west side of Kodiak Island, we see otters eating clams, scallops, crab, and octopus. Sea otters’ diets vary not only from one location to another and in response to available prey species, but also because individual otters have different food preferences, and a mother often passes on her fondness for certain foods to her pup.

A sea otter has a loose pouch of skin under each foreleg where it can store food collected on a dive. When the otter returns to the surface, it can rest on its back and leisurely retrieve one piece of food after another from its pouch. In addition to food, the sea otter also stores a rock in one of its pouches. The otter can use the rock underwater to pry loose mussels or other attached bivalves or to dislodge sea urchins wedged in crevices. When floating on the surface, the otter places the rock on its chest and pounds crabs, snails, clams, and other prey against the rock to break through the tough shells. Sea otters are one of the few animals other than humans known to use tools.

Sea otters are very efficient at finding and eating shellfish, and where large groups of sea otters reside, they reduce populations of abalones, clams, and sea urchins to the point where a commercial fishery for these species in the area is not viable. This competition between sea otters and fishermen creates a conflict which cannot be easily resolved by fish and wildlife managers.

Sea otters are considered a “Keystone” species, meaning they affect the ecosystem to a much greater degree than their numbers would suggest. Sea otters protect kelp forests off Northern California by eating herbivores such as sea urchins that graze on the kelp. In turn, the kelp forests provide food and cover for many other species of animals, and kelp forests play an important role in capturing carbon and reducing atmospheric carbon dioxide levels. Without sea otters, urchins over-graze the kelp, throwing the ecosystem out of balance.

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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. If you like audiobooks, check out her audiobook version of Murder Over Kodiak. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.

Mystery Newsletter

Kodiak Birds

November 27, 2016Bald Eagle, Birds, Kodiak WildlifeAlaska Birds, Alaska wildlife, Birds of Alaska, Birds on Kodiak Island, Eagles, Kodiak Birds, Kodiak Wildlife, puffinsadmin

More than 240 species of birds have been identified in the Kodiak Island Archipelago. Kodiak is not on a major flyway, but many species migrate to Kodiak in either the summer or winter, and many other species are year-round residents. Common species include golden-crowned sparrows, Wilson’s warblers, fox sparrows, black-capped chickadees, hermit thrushes, and winter wrens.

Due to its mild maritime climate in the winter, wide variety of habitats, and plentiful food supply, the Kodiak Archipelago is a winter home to more species and numbers of birds than anywhere else in Alaska. Over a million sea ducks and other aquatic migratory birds flock to Kodiak in the winter. Sea ducks commonly seen in the archipelago in the fall and winter include harlequins, surf scoters, buffleheads, Barrow’s Goldeneye, oldsquaws, and mergansers.

In the spring, Arctic terns arrive from as far away as Antarctica, and bank swallows return from South America. Horned and tufted puffins fly from their winter home on the deep North Pacific Ocean to the rocky cliffs of the archipelago where they nest.

Without question, the bald eagle is Kodiak’s most noticeable bird, and with 600 nesting pairs on the archipelago, biologists believe the nesting real estate is saturated, and many adult eagles here may never mate. In the winter, hundreds of eagles congregate near the town of Kodiak where they feed on cannery effluent and scraps of fish from boats when the fishermen offload their catch. Many of these eagles seen near town in the winter are seasonal migrants from the mainland.

Over the next few weeks, I will cover a few of these bird species in more detail, including bald eagles, tufted and horned puffins, Arctic terns, and oystercatchers.

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