Sitting south of the small fishing village of Kasilof, Tustumena Lake boasts an extensive 72,768-acre (294.5-km2) surface area—ranked not only as the biggest lake in the Kenai Peninsula, but also among the top 10 largest lakes in Alaska. Aside from being big, Tustumena Lake is also deep, and its lowest point at 941.6 feet (287 m) under the water’s surface is well below the bottom of the neighboring Cook Inlet. The name Tustumena is an English variation of the lake’s Dena’ina name Dusdubena, given by the Kenai people and translates to “Peninsula Island Lake”.
Tustumena Lake is accessible from only one point— the Tustumena Lake Boat Launch along the outflowing Kasilof River. From there, anglers can boat upstream and enter the lake. Because of its proximity to the coast, the lake hosts a diverse selection of migratory species, including trout, whitefish, sculpin, and four of the five North American Pacific salmon. After a long day of fishing and sightseeing, numerous cabins and campgrounds are available for rent nearby, including a rustic log cabin within the lake on Caribou Island.
Tustumena Lake Fish Species
1) Slimy sculpin (Cottus cognatus)
In a lake filled with the colossal likes of salmon and trout, slimy sculpins are a minuscule species trying their best to survive. This 3-inch (7.6-cm) fish is mottled with shades of brown and cream, camouflaging from predators by blending in with underlying gravel. They also have bulbous, upward-facing eyes that aid in detecting attackers approaching from above. If the sculpin’s camouflage fails and they are spotted by predators, their chances of escape are minimal. One may assume that all fish are impeccable underwater navigators, but slimy sculpins are actually terrible swimmers! This is because they lack a swim bladder, the gas-filled organ responsible for buoyancy in fish.
Because of their poor mobility, slimy sculpins have adopted a lifestyle as ambush predators. In the night, they lie motionless in wait for insects, crustaceans, and small fish to pass by before grabbing them with their mouths. They also sometimes eat fish eggs and aquatic vegetation.
Slimy sculpins are sensitive to the lake’s acidity and will experience poor reproductive rates and activity levels in waters that have a low pH. As such, the health of slimy sculpin populations is used by ecologists as a bioindicator of lake acidification.
2) Coastrange sculpin (Cottus aleuticus)
With over 102 species of sculpin in Alaska, distinguishing individuals is a challenging task, even for biologists! Coastrange sculpins are characterized by two to three large, saddle-shaped blotches below the posterior dorsal fin, though this method of identification can be unreliable since patterns are sometimes unclear. When viewed up close, coastrange sculpins are observed to possess one pore underneath their chins, while slimy sculpins have two.
Coastrange sculpins reach sexual maturity at 2 – 3 years old, when they move downstream towards estuaries to spawn. Females lay approximately 100 – 2,000 eggs under the surface of rocks. Male coastrange sculpins are one of the few fish species in Tustumena Lake to demonstrate parental care, guarding eggs until they hatch. After emerging, juveniles gradually move upstream as they develop, leading to the stratification of coastrange populations by age. Younger fish can be found near the coast, while older fish are more likely to reside in the lake. Coastrange sculpin can live for up to 8 years.
3) Rainbow trout (Oncorhynchus mykiss)
Rainbow trout are native to Alaska. They are often called steelheads, though the two names describe different forms of the same fish. Rainbow trout inhabit freshwater only, while steelheads are anadromous, spending most of their lives in the ocean and migrating inland to spawn. Subtle differences in appearance differentiate the two varieties, like the density of their spots, the shape of their bodies, and the brightness of their multichromatic hue.
Rainbow trout is one of the most popular sport fish in Alaska. The best time to target them is during the spring, when they congregate to catch and feast on young salmon (smolt) making their way to the ocean. Because their diet includes salmon at varying life stages, flies that imitate salmon eggs are often successful. They also feed on insects, and mosquito, black gnat, and nymph flies can also be used to catch sizeable fish.
Alaska has the healthiest rainbow trout population in the country, and maintaining their health is of utmost importance to locals. They are most vulnerable during late winter and early spring spawning, and fishing for them during this time is discouraged. In Tustumena Lake, only five rainbow trout may be collected per day, with no more than one measuring greater than 20 inches (50.8 cm) long. For rainbow trout that are 20 inches or longer, there is an annual harvest limit of 2 per angler, each of which must be recorded on the back of your fishing license or harvest record card.
4) Lake trout (Salvelinus namaycush)
Lake trout are the largest freshwater members of the Salvelinus genus, the char. They are a slow-growing species that attain lengths of 3 feet (0.9 m) and can live for over 50 years. To grow to such tremendous sizes, lake trout make use of a wide variety of prey, including plankton, insects, larvae, crustaceans, mollusks, leeches, fish, and even small mammals and birds if they wander into the water! Lake trout that feed on fish rather than invertebrate prey reach bigger sizes since they would have to expend more energy foraging repeatedly on smaller items to match the nutritional content of a single fish.
Lake trout are elusive fish targeted by experienced anglers. Not only do they prefer to occupy nearly unreachable depths, but they are also masters of disguise, despite their intimidating size. Lake trout have green-brown backs that dissolve to white underneath, providing them with 360° of camouflage. From above, their dark backs resemble the shadowy lake floor, while from below, their white bellies imitate the refracting sunshine that penetrates the water.
5) Dolly Varden trout (Salvelinus malma)
The appearance of freshwater Dolly Varden depends on the habitat that they occupy. Those that live in clear lakes and rivers are usually a shade of brown, while residents in glacial water bodies like Tutsumena Lake are more silvery. Additionally, Dolly Varden that are freshwater-bound throughout their entire lives are often smaller than ocean migrants, reaching only 3 – 6 inches (7.6 – 15.2 cm) long. Mature Dolly Varden in Tustumena Lake average between 11.8 and 17.7 inches (30 cm and 45 cm). Regardless of the variation in habitat or size, all Dolly Varden are marked with unmistakable bright cream or pink spots along their bodies.
Marine Dolly Varden return to Tutsumena Lake multiple times in their lifetime. Unlike salmon, which die after a single spawning, Dolly Varden can reproduce up to 3 times in their lives, making them iteroparous. Dolly Varden in lakes seek protection in submerged debris, while those in the ocean stay near the shore. Exceptions to this behavior exist, and one brave fish traveled for over 932 miles (1500 km) from Alaska to Russia in 1989!
6) Pink salmon (Oncorhynchus gorbuscha)
Unlike some members of other migratory fish species that have assumed a freshwater-only life cycle, all pink salmon in Alaska are strictly anadromous. Ocean-dwellers have shimmery, silver bodies with dark, iridescent blue on their backs, while freshwater individuals manifest a more eye-catching look. When pink salmon migrate to lakes and rivers for spawning, their appearance changes along the journey. Males develop dark brown or gray dorsums, white undersides, a hooked mouth known as a kype, and, most conspicuously, tall, humped backs. Because of males’ pronounced shoulders, pink salmon are nicknamed “humpies” in Alaska. Females transform as well, developing green backs and purple-pink blotches.
Pink salmon and the five other salmon species in the Oncorhynchus genus are dubbed the Pacific salmon by biologists, all but one of which exist in North America. Of these fish, the pink salmon is not only the smallest (averaging 20 – 25 inches or 50.8 – 63.5 cm), but also has the shortest lifespan, living for only 2 years. Their brief and predictable lifecycle is valuable economically in commercial fishing, as well as scientifically in examining how they respond to environmental changes.
7) Sockeye salmon (Oncorhynchus nerka)
Sockeye salmon are the most abundant salmon species in Tustumena Lake, and have been studied and evaluated for several decades. In 1974, sockeye eggs were collected from the lake by the Alaska Department of Fish and Game to research the rate of fish production. Starting in 1976, hundreds of thousands to millions of hatchery-reared sockeyes were stocked in the lake annually, though this program was discontinued in 2004.
For the past 23 years, the Cook Inlet Aquaculture Association (CIAA) has meticulously monitored sockeye numbers in Tustumena Lake. Like pink salmon, sockeyes enter the lake to procreate every summer. When smolt migrate back to the ocean, the CIAA traps them at the Kasilof River and counts the endless inflow of juveniles. In light of the many sockeye salmon monitoring programs in Tustumena Lake, fishing for them is prohibited year-round.
8) Coho salmon (Oncorhynchus kisutch)
The best way to distinguish coho (silver) salmon from its relatives is by observing the mouth— cohos have black tongues with white gums on the lower jaw and medium-sized teeth. When compared to other salmon, they have a wide tail peduncle and a few scattered dots on the upper lobe of the caudal fin. During breeding, males turn a deep red and develop a large, overhanging kype that is much more pronounced than that of the pink or sockeye salmon.
Coho salmon are territorial from a young age, with each fish defining its feeding zone and chasing away competitors that come near. The size of their territory depends on the availability of food— zones are larger if food is scarce, and smaller if sustenance is plentiful. Young coho salmon eat insects and smaller fish, deftly darting toward their prey and capturing them before they have the chance to escape. Coho salmon have well-developed olfactory systems that they use to smell food, avoid predators, and follow migratory patterns.
9) Chinook salmon (Oncorhynchus tshawytscha)
Though the Chinook salmon’s red-brown reproductive form is impossible to miss, its non-spawning morphology is equally striking. Chinook salmon are mammoth, silver-gray fish with a small dorsal fin about halfway along the anteroposterior axis. Dense black spotting covers their backs, the tops of their heads, and the entire tail fin.
Chinook salmon, also nicknamed king salmon for their size, are the biggest Pacific salmon species, regularly weighing more than 30 pounds (13.6 kg). Despite their hulking size at maturity, both young fish and adults constantly face threats of predation. Juveniles are regularly consumed by other fish because of their small size, while freshwater adults are taken by bears and eagles. Marine Chinook salmon are also a favorite meal of orcas and sea lions.
The species epithet “tshawytscha” comes from the name of the fish used by the Alaskan native people, many of which rely heavily on Chinook salmon for subsistence fishing. Economically, they are the most significant salmon species, with an average of 382,373 salmon caught each year from 2014 to 2018.
10) Threespine stickleback (Gasterosteus aculeatus)
Threespine sticklebacks are only found in the Northern Hemisphere, where they occupy an incredibly diverse range of habitats. They can be found in marine environments, brackish waters, and even freshwater systems. Some spend their entire lives in the ocean, in non-saline lakes and rivers, or migrate back and forth between the two. Populations within water bodies may be even further stratified, with some fish preferring to reside near the water’s surface, while others are demersal.
Due to their abundance across such a wide range of ecosystems, threespine stickleback show tremendous phenotypic (physical) variation between populations. There are thousands of morphological variants, known as ecotypes, within the species. Each ecotype has special adaptations suited to its home and lifestyle. Despite this variation, threespine stickleback can always be identified by the 2 – 4 (usually 3) short projecting spikes anterior of the dorsal fin. Though the profile impression of stickleback varies depending on where in the water column they reside, fish are almost always less than 3.9 inches (10 cm long).
11) Round whitefish (Prosopium cylindraceum)
Freshwater whitefish are members of the Coregoninae subfamily within the Salmonidae. These fish are defined by their silver bodies, the absence of teeth, and fleshy dorsal and adipose fins. Round whitefish are more colorful than other members of this group, with large, dark-rimmed scales, bronze backs, and yellow-orange fins that contrast their metallic flanks. As their name suggests, round whitefish have long bodies that are cylindrical in cross-section.
The round whitefish is a bottom-dwelling species, though it does not exceed depths of 150 feet (45.7 m). These fish use their overhanging mouths to scoop up zooplankton, bivalves, snails, insect larvae, crustaceans, and fish eggs from the lake floor.
Round whitefish are not highly sought after by anglers in Tustumena Lake, though they have a sweet, mild flavor that makes for great table fare. They are primarily utilized by natives in subsistence fishing, having highly nutritious meat with significant levels of omega-3 fatty acids.
