I am thrilled to announce the release of my non-fiction book, Kodiak Island Wildlife. Learn about rugged, beautiful Kodiak Island and its amazing wildlife. Read about new and recent research on the animals on and near the Kodiak Archipelago, and enjoy the beautiful photographs by my husband, Mike Munsey.
Watch the trailer for more information about this book.
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.
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.
Varied Thrush
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.
Tufted Puffin
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.
Bald Eagle
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