Category Archives: Fish

Big Skate

April 4, 2021Fish, Kodiak WildlifeBig Skate, Kodiak Island wildlife, Robin Barefield, Skates in Alaskaadmin

The aptly named big skate (Raja binoculata) is the largest skate in the waters off North America. Big skates range along the Pacific coast from Alaska to Baja California. They inhabit a variety of habitats, from bays and estuaries to the continental shelf. They prefer sandy or muddy bottoms and seem to prefer depths shallower than 390 ft. (120 m). They inhabit shallower water in the northern part of their range.

The largest big skate ever captured measured 7.9 ft. (2.4 m) in length, but they typically reach a maximum of 5.9 ft. (1.8 m) in length and weigh as much as 201 lbs. (91 kg). An average big skate weighs less than 110 lbs. (50 kg).

A big skate has a diamond-shaped, flattened pectoral fin disk. It has a pointed snout, and the eyes are small and sit just ahead of the spiracles. The tail has two small dorsal fins but no anal fin, and the caudal fin is only a simple fold. A juvenile has smooth skin, but an adult’s skin has small prickles on the dorsal surface, the underside of the snout, between the gill slits, and on the abdominal region. An irregular row of approximately 33 middorsal thorns runs down the back and tail to the first dorsal fin. A single thorn protrudes from behind each eye. The back of a big skate ranges in color from mottled reddish-brown to olive-brown to grey, and it is covered with small, pale white spots or dark blotches. The ventral surface ranges from white to gray.

A large dark spot with pale borders appears on each wing of a big skate, and biologists suspect these “eyespots” appear to predators as the eyes of a much larger animal, making a shark or another predator much less likely to attack the skate.

A big skate camouflages itself by partially burying its body in the sand and silt on the seafloor. Between its submerged position and its mottled coloration, a skate appears nearly invisible to predators and prey. When partially buried, it breathes with the aid of the spiracles on the top of its body. It takes water in through these spiracles and pushes it out through the gills on its dorsal surface.

Big skates differ from Alaska skates in that their egg cases may contain as many as seven eggs each. The big skate produces the largest egg case of any skate species, measuring 9 to 12 inches (23-31 cm) long and 4 to 7 inches (11-19 cm) wide. Big skates have a maximum lifespan of 26 years, but most big skates in Alaska don’t live past 15.

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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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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Salmon Shark (Lamna ditropis)

January 12, 2021Fish, Kodiak Wildlife, UncategorizedAlaska wildlife, Lamna ditropis, Lamnid Sharks, Robin Barefield, Salmon Shark, Sharks in Alaskaadmin

I am always thrilled when I see the dorsal fin of a salmon shark protruding from the water as it swims near the surface. I love seeing any apex predator, but sharks conjure an air of mystery and fear. I wonder if the shark is chasing prey or if it is just watching and waiting for a fish to make the fatal mistake of swimming into its strike range.

Salmon sharks (Lamna ditropis) are some of the fastest fish in the ocean, and their high metabolism makes them voracious eaters. Salmon sharks are closely related to great white sharks, makos, and porbeagle sharks. Because their body shape so closely resembles a great white shark’s shape, people sometimes mistake salmon sharks as juvenile great whites.

Like other species of lamnids, salmon sharks have a conical snout, dark, round eyes, and a keeled, lunate tail. The salmon shark and porbeagle shark can be distinguished from great whites and makos by their smaller secondary caudal keel below the primary keel at the base of the tail. While the porbeagle shark inhabits the Atlantic and Southern Pacific, the salmon shark lives in the North Pacific.

A salmon shark has a bluish-black to dusky gray back, fading to white on the stomach. It has long gill slits and large teeth. Salmon sharks can grow to over 10 ft. (3 m) in length, but they average 6.5 to 8 ft. (1.9 – 2.4 m). They can weigh more than 660 lbs. (300 kg). Females grow larger than males.

Like other lamnid sharks, salmon sharks manage to sustain elevated body temperatures, even in the cold North Pacific. Their core body temperature measures approximately 80°F (26.7°C). They maintain this warm body temperature because they have a counter-current heat exchanger of blood vessels, directing heated blood through their core and dark musculature. This elevated body temperature permits the shark to live and hunt in a wide range of depths and water temperatures. The warm blood flow allows their brain, eyes, and muscles to function at peak performance.

A salmon shark is a big marine animal with no fur or blubber to keep it warm. To maintain its body heat, it must consume a large amount of food each day. Like a great white shark or a mako, a salmon shark aggressively chases its prey and sometimes even explosively breaches out of the water while in pursuit. Salmon sharks feed on fish, squid, other sharks, seals, sea otters, and marine birds. A study done in 1998 determined that salmon sharks consumed twelve to twenty-five percent of the total annual run of Pacific salmon in Prince William Sound.

While salmon sharks are most abundant in the North Pacific Ocean near Alaska, they travel as far south as northern Mexico and the Hawaiian Islands. Researchers have recorded salmon sharks dives as deep as 2192 ft. (668 m). Although biologists do not entirely understand salmon shark migrations, they believe the sharks spend the summer in the northern part of their range, and then they migrate south to breed. In the western North Pacific, salmon sharks migrate to Japanese waters to breed, and in the eastern North Pacific, they migrate south to the Oregon and California coasts. Their migrations are complicated, though, and they segregate by size and sex. Their migrations also depend upon available prey species in various areas. Scientists have determined that although many salmon sharks migrate south in the winter, some remain in the Gulf of Alaska and Prince William Sound year-round.

Male salmon sharks mature at five years of age, while females do not reach sexual maturity until they are eight to ten years old. They breed in the late summer or early autumn. Embryos develop inside their mother for nine months until she gives birth to between two to five pups. The developing embryos consume any unfertilized eggs in the womb. The mother provides no parental care to her young after birth, and they must fend for themselves. Females usually produce a litter every two years.

Male salmon sharks have a maximum lifespan of 25 years, while females can live 17 years. Other sharks sometimes eat salmon sharks, but humans pose the biggest threat. In Alaska, no commercial fishery exists for salmon sharks, but some sport fishing companies specialize in shark charters. Salmon sharks are big, strong, aggressive fish, and they pose a challenge and thrill for sport anglers. Each angler is limited to two salmon sharks per year. Salmon shark meat reportedly tastes similar to swordfish.

In my next post, I’ll describe another species of shark common in Alaska. Pacific sleeper sharks were long ignored as large, sluggish fish, but research over the past few years suggests Pacific sleeper sharks might play an essential role in the North Pacific’s food chain.

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Pacific Spiny Dogfish Shark (Squalus suckleyi)

December 20, 2020Fish, Kodiak WildlifeDogfish Shark, Pacific Spiny Dogfish, Pacific Spiny Dogfish biology, Robin Barefield, Sharks in Alaska, Sharks near Kodiak Island, Spiny Dogfish, Squalus suckleyi, Wildlife of Kodiak Islandadmin

One of the most abundant sharks globally, Pacific spiny dogfish belongs to the family Squalidae (the dogfish family). Pacific spiny dogfish range from the Bering Sea to Baja California to Japan and the Korean Peninsula. They are most common off the west coast of the U.S. and British Columbia. Dogfish are typically bottom dwellers and inhabit depths from shallow coastal waters to 4,055 ft. (1,236 m). They prefer water temperatures ranging from 44.6° F to 59° F (7-15° C).

Pacific spiny dogfish are small, streamlined sharks. Males can grow to 3.3 ft. (1 m), while females measure a maximum length of 4 ft. (1.2 m). A dogfish has a distinctive snout, large eyes, and a flattened head. The body has a cylindrical shape. The top half is dark gray with scattered white spots, and this color fades to light gray or white on the underneath side of the fish. The teeth of a dogfish have sharp edges, but they are specialized for grinding instead of tearing. Dermal denticles comprise the scales of a dogfish. These denticles are the same rigid material found in their teeth, and they make the skin very tough.

A dogfish does not have an anal fin, but it has two dorsal fins, with a spine in front of each fin. These spines are venomous, and the shark uses them as protection against potential predators, such as other sharks or humans. The dogfish employs its two dorsal fins in different ways. The first dorsal fin helps it maintain stability while swimming, and the second dorsal fin provides thrust. The large caudal fin (or tail) allows the shark to maneuver quickly and efficiently through the water.

A dogfish has five gills on either side of its body, but unlike bony fish, a dogfish does not have gill covers. To breathe through these gills, the shark must remain in constant motion, so it either must continually swim or rest in a current where water rushes past its gills. A dogfish has an adaptation called spiracles, aiding it to breathe in calm water. These specialized gills, located behind the eyes, allow the shark to breathe when resting or eating.

Dogfish earned their common name from fishermen who observed them hunting in packs like dogs. Schools of hundreds of dogfish swim close together during the day, hunting herring, capelin, other small fish, squid, octopus, and even jellyfish. The dogfish uses its teeth and not its spines when feeding. It uses its spines for protection. Scientists think dogfish eat less in the winter when they migrate to great depths. They are preyed upon by larger sharks, seals, orcas, and some larger fish.

Spiny dogfish can live 100 years, and females do not reach sexual maturity until they are approximately 35 years old. Males can reproduce at an average age of 19. Males internally fertilize females in October or November. Dogfish are ovoviviparous, meaning females give birth to live young, and they have a gestation of nearly 24 months, the longest of any vertebrate. They give birth to up to 22 pups, and the newborns range in length from 8 ½ to 12 inches (21.6 – 30.5 cm).

Pacific spiny dogfish stocks remain stable and are carefully managed. In some areas of the world, a commercial market exists for dogfish, and they are considered a good food fish, but they are not yet in demand as a food source in the United States.

We usually catch a few dogfish each year during our sportfishing trips, but this past summer, we landed as many as 20 per day while halibut fishing. Dogfish are tricky to release because while you try to get the hook out of its mouth, the shark attempts to whip its body into a position to stab you with one of its venomous spines. I was not pleased to encounter so many dogfish this past summer, but more importantly, I wondered why we were catching so many dogfish. I speculate that the dramatic decrease in the Pacific cod population led to an increase in small fish species typically eaten by cod. Dogfish probably are exploiting an opening in the food chain. Will their presence affect the abundance of other fish species in this region of the North Pacific? Only time will tell.

Happy holidays, and I wish us all a nicer, brighter 2021!

Mystery Newsletter

Sharks in Alaska

November 30, 2020Fish, Kodiak WildlifeDogfish Shark, Pacific Sleeper Shark, Robin Barefield, Salmon Sharks, Sharks in Alaskaadmin

Our guests are often surprised to learn sharks feed and swim in the frigid North Pacific. We catch spiny dogfish sharks when halibut fishing, and large salmon sharks terrorize commercial salmon gillnetters by ripping enormous holes in their nets when stealing fish from the mesh. Pacific sleeper sharks also live in Alaska’s waters, but sleeper sharks remain elusive, and biologists do not know much about their biology, diet, and habits. These three species fascinate me, and I think you will enjoy learning about their longevity, reproductive biology, and the mechanisms each species employs to stay warm in the frigid waters surrounding Alaska. I will cover each shark in detail in future posts, but for now, let me give you an overview of sharks in Alaska.

The three shark species I listed above are the most common but not the only sharks trolling the North Pacific. Over the past several years, ocean waters in the region have warmed, encouraging other shark species to venture into these nutrient-rich areas. Great white sharks began exploring Alaska in the 1970s, but recent, more frequent sightings suggest an increasing number of great whites have discovered the North Pacific’s fertile feeding grounds. Most of these visiting sharks only stay during the warm summer months, but researchers believe a small percentage find enough to eat to keep them in Alaska year-round.

Great whites are related to salmon sharks. Like salmon sharks, great whites have a highly developed countercurrent heat exchange mechanism that allows them to maintain a body temperature several degrees warmer than the ambient temperature. Sharks in this family represent some of the few species of endothermic fish in the ocean. Unlike their cold-blooded cousins, great whites and salmon sharks can produce bursts of speed to chase down prey, even in frigid ocean temperatures.

In recent years, Alaskans living and working in the far north regions of the Bering Strait and the Chukchi and Beaufort Seas have reported sightings of marine mammals with unusual wounds. Researchers noted that several ice-associated seals and Steller sea lions in the area suffered injuries from an uncommon predator.

Reports of seals with amputated flippers alerted biologists because killer whales have pegged teeth and don’t cause a slicing-type laceration. In some instances, scientists noted penetrating stab wounds and circular bite marks. Flesh torn by sharp, triangular teeth convinced researchers they were looking at the bite marks of a very large shark. Are the warming water temperatures and melting sea ice inducing great white sharks to travel further north where they can find a bounty of sea mammals to eat?

When great white sharks reach adulthood and grow very large, they seem to prefer eating marine mammals over fish, probably because marine mammals have a high energy-rich fat content. Observers have watched great whiles kill beluga whales in Cook Inlet, and biologists suspect they may even take walruses in the Bering Sea and the Arctic Ocean. Are great whites, at least in part, responsible for the diminishing numbers of Beluga whales? If the number of great whites increases in Alaska, will they affect other marine mammals’ population densities? Much more research is needed to answer these questions.

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I’ll take a closer look at my nemesis, the spiny dogfish shark, in my next post. We used to catch one or two of these nasty little critters a year during our summer fishing trips, but we caught as many as twenty per day this past summer. Is this increase in spiny dogfish a trend, or was this past year only an anomaly?

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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Commercial Herring Fishery in Alaska

May 26, 2019Fish, Kodiak WildlifeCommercial Herring Fishing, Herring, Herring Fishing in Alaska, Pacific Herring, Sac Roe Herring Fishery, Spawn-on-Kelp Herring Harvestadmin

Herring are valuable fish to commercial fishermen, and in Alaska, herring are mainly harvested for their eggs which are shipped to Japan.

In last week’s post, I wrote about the biology and life history of the Pacific herring, and I explained how important herring are to the diets of many birds, fish, and marine mammals, but herring is also a valuable commodity to humans. For hundreds of years, Alaska native populations have conducted subsistence fisheries for herring. In the spring, villagers from coastal communities harvested herring eggs on kelp or hemlock boughs, and traditional dried herring is still an important resource in Bering Sea villages near Nelson Island where salmon is not readily available.

The commercial herring fishery in Alaska began in 1878 when 30,000 lbs. were caught for human consumption. Early Alaskan settlers preserved herring by salting the fish and storing it in large, wooden barrels. Salted and pickled herring production peaked after WWI when 28 million pounds (12,700 mt) were produced annually.

Reduction fisheries, which are the production of fish oil and fish meal from ground-up fish, began in Southeast Alaska in Chatham Straight in 1882. Reduced herring became more popular in the 1920s, and reduction plants sprang up from Craig to Kodiak in areas with large herring stocks. Harvests during the 1920s and 1930s reached 250 million pounds (113,400 mt) per year, and herring stocks declined in response to this unsustainable harvest. During the 1950s, the low cost of reduced Peruvian anchovies caused the reduction market in Alaska to collapse, and the last herring reduction plant in Alaska closed in 1966.

The Alaska sac roe fishery for herring began in the 1970s when the demand for imported herring eggs in Japan increased after Japan’s herring fishery declined. The sac roe fishery targets female herring just before they spawn. Pre-spawn egg sacs are removed from the female herring and shipped to Asia where they are a highly prized delicacy called kazunoko. Most herring for this fishery are caught by purse seining with a smaller percentage caught by gill netting. Unlike any other fishery in Alaska, managers carefully monitor the quality of the herring during the fishery to obtain the highest-value product possible. Technicians periodically test the condition of the female herring as their eggs ripen, and fishery managers use this information to carefully time the opening of the fishery to within days or even hours before the females are ready to release their eggs. This scrutiny ensures the eggs are ripe and prime for the Japanese market.

Most herring fisheries in Alaska are regulated as management units or regulatory stocks, and these stocks are very specific, often to small geographical areas. While managers might open herring fishing in one bay, the fishery could be closed in an adjacent bay because the herring return to spawn in the second bay the previous year did not meet sustainable levels. The herring sac roe fishery is competitive and intense. Fishery managers often open fishing at noon and close it a few hours later when fishermen have reached the quota for the area. Herring purse seiners work together in groups called combines and hire spotter planes to search for large schools of herring. The purse seine boats stand by near a school of herring until managers declare the fishery open, and then they quickly deploy their nets to scoop up the fish.

Since fishermen are only after the eggs in a sac roe fishery, the carcasses of the females and males caught in the nets are either processed for fishmeal or are sold for bait to commercial and sport anglers. There also is still a smaller food and bait fishery for herring.

In addition to the sac roe fishery, there is another type of commercial harvest for herring eggs called a spawn-on-kelp harvest using floating pens. Herring are caught with purse seines and then confined in floating pens containing kelp. When the herring spawn, the eggs attach to the kelp and are harvested. The eggs from this type of fishery sell for a very high value.

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. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.

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Pacific Herring (Clupea pallasii)

May 19, 2019Fish, Kodiak WildlifeAlaska Herring, Clupea pallasii, Herring biology, Herring on Kodiak Island, Kodiak Alaska, Pacific Herringadmin

Last week, I mentioned how the Pacific herring (Clupea pallasii) had returned to Uyak Bay on Kodiak Island this spring in such large numbers, even bears recently out of hibernation noticed and were feeding on them in the shallow estuaries where they spawn. Pacific herring are an essential food source for many animals living in or near the North Pacific, including birds such as cormorants, murres, auklets, puffins, and bald eagles; fish, such as salmon, halibut, cod, and pollock, and marine mammals, including harbor seals, Steller Sea Lions, fin whales, humpback whales, and orcas. When a pursuing predator forces a school of herring to the surface, seagulls take advantage of the situation and can often be spotted noisily diving and feeding on the fish. Herring are loaded with nutritious oil and nutrients and are an important forage fish for many species.

A herring has a blue-green upper body, silvery sides, and large eyes. Its body is laterally compressed with large scales, protruding in a serrated fashion. It has no scales on its head or gills. A herring has a deeply forked tail, a single dorsal fin located mid-body, and no adipose fin. Pacific herring can grow to 18 inches (45.7 cm) in length, but they are usually smaller than 9 inches (22.9 cm).

Pacific herring live throughout the coastal waters of the Pacific Ocean. In the eastern North Pacific, they range from Baja California north to the Beaufort Sea, and in the western North Pacific, they can be found in the western Bering Sea to Kamchatka, in the Okhotsk Sea and around Hokkaido, Japan southeast to the Yellow Sea.

^[Pacific herring reach sexual maturity when they are three to four years old, and they spawn each year after reaching sexual maturity. Spawning occurs in the spring in shallow nearshore areas in intertidal and subtidal zones. Females release eggs at the same time males release sperm into the water, and the eggs and sperm mix, fertilizing the eggs. A single female can lay 20,000 eggs.

Spawning is precise, and while the trigger is not well understood, researchers suggest the male initiates the process by releasing milt containing a pheromone which stimulates females to release eggs. The process seems to be synchronized, and an entire school spawns in a period of a few hours, producing an egg density of up to 6,000,000 eggs per square yard (square meter).The fertilized eggs then attach to vegetation such as eelgrass or kelp or to the bottom. Eggs hatch two weeks after they are fertilized, and the larvae drift in the ocean currents. As they grow, juvenile herring stay in sheltered bays until autumn and then move into deeper water where they spend the next two to three years. Juveniles remain separate from the adult population. Biologists estimate only one herring per ten thousand eggs reaches adulthood.

Juvenile herring feed on phytoplankton and zooplankton, and adults also eat bigger crustaceans and small fish. Pacific herring travel in large schools. They migrate inshore to the heads of shallow coves and bays to spawn and then offshore to feed. They also migrate vertically in response to their prey, remaining near the bottom during the day and rising toward the top of the water column at night.

Herring are susceptible to environmental changes. Since they depend on shallow, inshore habitats to reproduce, they are affected by storms, pollution, and warming water temperatures. The Pacific herring population in Prince William Sound collapsed in 1993, four years after the Exxon Valdez oil spill, and it has still not recovered.^[

The biggest threat to Pacific herring is a loss of their spawning grounds. Spawning habitat can be degraded or destroyed by construction, dredging, log storage, oil spills or other pollution, and by global warming.^[ If Pacific herring populations crash, their loss will affect the many species of fish, birds, and marine mammals which depend on them for food.

Mystery Newsletter

Spring on Kodiak Island

May 12, 2019Fish, Kodiak Bear, Kodiak WildlifeKodiak Bear, Kodiak Island, Pacific Herring, Robin Barefield, What Do Bears atadmin

I love spring. It is my favorite season. As winter loosens its grip and the vegetation begins to grow again, the world seems to return to life. Foxes scream in the middle of the night in search of new mates; does arrive in our yard with their wobbly, newborn fawns; eagles soar in mating spirals and begin remodeling their nests for the arrival of their chicks; and bears leave their dens in search of food after a long winter of fasting.

Spring always brings unexpected joys, and no two springs are alike. This year, we have watched an abundance of herring enter Uyak Bay to spawn. Often when large schools of herring return, we see increased whale, seal, and sea lion activity in the bay, but this year we’ve observed something different and exciting. Bears are feeding on the herring in the tidal flats at the head of Uyak Bay where the herring spawn. While in the summer months, bears typically catch and eat salmon in this same area, they don’t usually congregate to feed on herring. Herring are rich, oily fish loaded with nutritional value, and they provide a great supplement to a bear’s diet.

Bears’ stomachs contract during hibernation, and when they first leave their dens, their appetites are suppressed, and they eat little, concentrating on emerging plants and their roots. As spring progresses, bears can be seen feeding in grassy meadows and look much like grazing cattle with their heads bent to the earth. We don’t usually see bears feeding on fish until summer when they chase and catch salmon, but bears are opportunistic feeders, and since the herring are here now, bears are taking advantage of their abundance.

Herring are smaller than salmon, making them more difficult for a bear to catch. The herring swim into the eelgrass in the tidal areas at the head of Uyak Bay where they lay their eggs. When the tide ebbs, the fish temporarily become stranded in the shallow tidal pools, and bears can chase down and pounce on the fish.

As with salmon fishing, older bears are better than younger bears at landing herring. Fishing is a skill bears learn with much practice over time, so young bears are often clumsy fishermen. A sub-adult bear might gallop back and forth for thirty minutes without successfully landing a fish, while an older bear walks deliberately through the water and pounces with little effort on a passing herring. Each bear develops his own, unique fishing technique.

In the long run, this early appetizer of herring probably will make little difference to the overall health of the bears, but if Kodiak has a poor berry crop and a poor salmon run, this early addition of herring could sustain the bears until the salmon arrive.

Spring is only beginning here on Kodiak Island, and I can’t wait to see what other surprises the season has in store for us.