Lake Oahe is a large reservoir created by the Oahe Dam on the Missouri River in South Dakota. The Oahe Dam is one of the largest earth-rolled dams in existence. It has been functioning since 1962 and creates flood control and electric power in multiple Midwestern states. The river holds three additional reservoirs, where Lake Oahe is the second largest. With its 231 miles (371.76 km) and a maximum depth of 205 feet (62.5 m), Lake Oahe is the largest lake in the state. The deep clear water makes it excellent for fishing and the lake is particularly famous for its walleye population.
The area surrounding Lake Oahe is filled with recreational areas, offering anything from camping to hunting. The area is situated in a continental climate zone with four distinct seasons. It experiences warm summers and cold winters. Since Lake Oahe is a water collection reservoir, the water levels are very variable and can fall dramatically during droughts. It supports a vast fish community, and some of the more charismatic members are described in the list below.
Fish Species in Lake Oahe
1) Atlantic salmon (Salmo salar)
The Atlantic salmon is a member of the Salmonidae family (salmon). This species is normally anadromous, which means that they spend most of their adult life at sea before returning to freshwater to spawn. However, the population in Lake Oahe is landlocked. The juveniles have 8 – 12 spots of a blueish hue on their flanks and are known to be territorial. With age, the fish become silver with a blue or green dorsal side, white belly, and a few black spots. In contrast to many salmonids, the female Atlantic salmon sometimes survives spawning and returns to spawn again, with a few known cases of single females spawning four times in their lifetime!
The Atlantic salmon is a somewhat new member of the fish community in Lake Oahe. The species does not occur naturally in the lake but has been stocked there in recent years, although in lower numbers than the Chinook salmon. Since the stocking program is still new, the return of adult salmon to the Whitlock Bay Spawning Station remains to be assessed, which is necessary to evaluate the success of the introductory stocking program.
2) Bigmouth buffalo (Ictiobus cyprinellus)
The bigmouth buffalo is the largest member of the Catostomidae family (sucker). It is deep-bodied and laterally compressed with a long dorsal fin, comparable to other suckers. In contrast, it has a large oblique terminal mouth. The species have no teeth in their mouth but more than 160 pharyngeal teeth. The bigmouth buffalo prefers backwaters of small and large rivers as well as impoundments, where it feeds on copepods and insect larvae.
The bigmouth buffalo is a long-lived species with individuals documented to reach a lifespan passing 100 years, which makes them the longest-living freshwater teleost. The females do not reach sexual maturity before 10 years of age. They are known to recruit sporadically with more success in non-drought periods. They enter marshes or flooded river bottoms to spawn when the water temperature increases in April or May. Bigmouth buffalo spawn in units consisting of one female and 2 – 4 males. The female frequently breaks the surface of the water, making loud splashes while making big swirls. The spawning period is short, and after 1 – 3 days the fish leave the marshes to return to the lake.
3) Bluegill (Lepomis macrochirus)
The bluegill sunfish is a part of the Centrarchidae family (sunfishes). They have an olive-green dorsal side, which becomes a deeper blue down the sides. This blue color becomes more prominent in breeding males. They can be recognized on the dark blue opercular flap – an extension of the gill cover which is also sometimes referred to as the “ear”. Younger individuals have six to seven vertical dark bars that fade and can completely disappear in large adults. The bluegill sunfish is common in lakes, ponds, reservoirs, and slow-flowing streams, where they are an important prey item for larger predatory species. They are primarily active during dusk and dawn, where they feed opportunistically on snails, crayfish, insects, and worms.
The bluegill sunfish was assessed by the IUCN Red List of Threatened Species as recently as 2018, where it was listed as Least Concern. The decision was based on the large number of subpopulations and a relatively large adult population size. In addition, the bluegill sunfish have established populations in many non-native countries.
4) Burbot (Lota lota)
The burbot is the only freshwater member of the Lotidae family (hakes and burbots). Despite being a freshwater species, populations of this species exist circumarctic, which makes it one of the most widespread freshwater species. They can be recognized on their single barbel on the lower jaw and their long second dorsal fin. They have a gorgeous yellow to brown background color pattered with dark and brown.
The burbot is adapted to thrive under chilly conditions, and they require temperatures less than 43 °F (6 °C degrees) to spawn. They occupy a very variable range, from small streams to the depths of Lake Oahe. They are also among the few freshwater fishes known to use vocalizations to communicate. They have drumming muscles, which allow them to generate sound with their swim bladder. Both sexes have this muscular adaptation, which suggest that both engage in vocalization, and that these sounds might be important for the mating system of the burbot. Due to this, commercial fishing activities and other anthropogenic noises might disrupt the fish and interfere with mate selection and spawning success.
5) Channel catfish (Ictalurus punctatus)
The channel catfish is a member of the Ictaluridae family (North American freshwater catfishes), and the most fished catfish species in the United States. They have a blue to grey dorsal side and a cream-colored belly with dark spots sprinkled across the body. They prefer lakes and deep pools with clean, well-oxygenated water, where they hunt small fish, crayfish, clams, and snails.
The channel catfish has an incredible sense of taste, often nicknamed ‘swimming tongues’, because they have taste receptors distributed over most of their external body surface, meaning that they can taste anything their body encounters. They are so sensitive to taste, that a single amino acid is enough to trigger feeding behavior!
The adult population of channel catfish is very large and, in contrast to many other species, is increasing. Over the last 10 years, the population trend has most likely been increasing, as the species is common in most of its range, however the distribution and abundance have increased mostly through introductions of the species to new areas.
6) Chinook salmon (Oncorhynchus tshawytscha)
The Chinook salmon is a member of the Salmonidae family (salmon), which, like the Atlantic salmon it shares Lake Oahe with, is naturally anadromous. The adult fish has a dark green to blue dorsal side with silver sides and a white belly. It can be distinguished by small black spots on the back and caudal fins in addition to the black gums of the lower jaw. Naturally, they can migrate up to 3000 miles upstream (4828 km), however here they return to the Whitlock Bay Spawning Station.
The Chinook salmon is artificially maintained in Lake Oahe, where they have been stocked and tracked since the mid-1980s. Research on the species shows that the primary determining factor for explaining Chinook recruitment to the spawning stock is average surface elevation in May, and not the abundance of gizzard shad or rainbow smolt, as one might have guessed, especially as the recruitment turned out to be higher in years with lower surface elevation. This could potentially be explained by the primary productivity in the lake, which increases when water levels are low, providing more nutrients for the lower trophic levels.
7) Cisco (Coregonus artedi)
The cisco, also known as the lake herring, is a member of the Salmonidae family (salmon). They inhabit open waters of lakes and large rivers, where their silvery color with the faint iridescence on the sides makes them harder to spot. They feed on plankton and large crustaceans. The cisco’s spawning season is temperature-dependent and occurs between November and December, while the event itself typically takes place at night. While continuously swimming, the male and female release milt and eggs, respectively, resulting in the fertilized eggs being scattered far and wide.
The cisco is an important food resource for large predatory species such as northern pike, Atlantic salmon, and walleyes. The high-fat content of the cisco, as well as the rainbow smelt, promotes the fast growth of their predators, therefore a solid population of these species is necessary to sustain populations of large predatory fish. In Lake Oahe, the rainbow smelt has historically taken that role, but the Missouri River flood in 2011 dramatically reduced the rainbow smelt population, while the cisco population grew, functioning as a safety net for the sportfish populations in the reservoir.
8) Common carp (Cyprinus carpio)
The common carp is a member of the Cyprinidae family (minnows and carp). The species is also known as the European carp. The Latin species name ‘carpio’ is a Latinized version of ‘carp’. They are not native to North America and have been introduced in waves by immigrants since the mid-1800s. In Asia, they were already a cultivated food source utilized as a symbol of strength and courage for more than 4000 years. While the introduction of the species was initially seen as a success, today it is often seen as a nuisance. The flesh of the common carp is rarely considered comparable to native fish species in taste, and the species competes with native species and threatens water quality.
The common carp is listed as ‘Vulnerable’ on the IUCN Red List of Threatened Species, since it is slowly but continuously declining due to hybridization with domesticated stock and changes to the river systems. Currently, only a few populations are regarded as ‘untainted’ by domesticated individuals, however, it is not possible to identify a ‘pure carp’ by genetic analysis. They are a long-lived species capable of reaching 50 years of age with an average age of a spawning fish being 20 – 25 years old. Therefore, they adapt slower and are particularly vulnerable to changes in their natural habitat, especially the introduction of channelization and dams.
9) Gizzard shad (Dorosoma cepedianum)
The gizzard shad is a member of the Clupeidae family (herrings, shads, sardines, and menhadens) with silvery sides and a darker back. The common name of the species stems from its thick-walled stomach, which makes it resemble the hind part of the stomach in many birds, known as a ‘gizzard’. They are also known to eat sand, which most likely helps them grind up their diet of microscopic plankton and algae in their special stomach. Due to their diet, they are typically abundant in surface waters.
The gizzard shad is not a commercially valuable species, although it is sometimes used as fertilizer or cattle food. Instead, its importance stems from its role as a prey species in the food web. They often become the dominant prey item for adult walleye when populations of rainbow smelt and cisco are low. However, the species was extirpated from Lake Oahe in 2011 due to a succession of hard winters. Since then, the stocking of gizzard shad has attempted to return the population to a viable level.
10) Largemouth bass (Micropterus salmoides)
The largemouth bass is a member of the Centrarchidae family (sunfishes) with a robust, laterally compressed body. They have two – what you might call layers – of teeth. In the lower and upper jaw, they have strong pointed teeth, and also have numerous fine teeth on their lower pharyngeal arch. The body is a light green, that deepens towards the dorsal side, while the belly and lower jaw are cream-colored. They have a prominent lateral line running through the eye to the base of the tail. However, the overall color darkens to an olive brown in adults from a habitat with a muddy bottom.
The largemouth bass spawn in late spring to early summer when the temperature reaches approximately 64 °F (17.8 °C degrees). They normally spawn a little sooner than the smallmouth bass. They prefer shallow, protected sites hidden by emergent vegetation, where the male builds a nest on a bottom of mud and plant fibers. The female might decide to spawn with several different males, after which the male guards and fans the eggs for about a month. The male is known to strike almost anything that comes within their range while they protect their eggs. When the fry hatch, they are transparent, and there might be as many as 6000 in one nest!
11) Northern pike (Esox lucius)
The northern pike is a formidable predatory member of the Esocidae family (pikes), which can be found circumpolar in fresh water. It has an elongated cylindrical body and a characteristic snout loosely resembling the bill of a duck. The large mouth contains short strong teeth in the lower jaw and sharp, recurved teeth on the roof and tongue. Damaged or worn-out teeth are replaced by new ones as they are lost. The body is olive green and becomes lighter towards the belly. It has lighter markings dispersed in rows on the sides of the body. They prefer weedy lakes, ponds, and slow-flowing rivers.
The northern pike becomes an efficient and opportunistic hunter already early on in life as the young feed on terrestrial and aquatic vertebrates that fit their size. As they grow older, they feed on almost anything. Amphibians, birds, mammals, fish, and even other northern pikes are known to be on their menu! As lone wolves of the lake, they are usually solitary and very territorial.
12) Orangespotted sunfish (Lepomis humilis)
The orangespotted sunfish is a member of the Centrarchidae family (sunfish) with a prominent black operculum (ear flap) with a white margin. The orange spots that have given the species its name are only present in males. The males are olive green with a white belly, their back and sides have up to 7 broad dark bands, and the orange spots speckle the sides of the body and head. The colors become even more pronounced in the breeding males. In contrast, the female is a duller brown with brown spots on their fins. This makes the species a good example of sexual dichromatism, where the male and female have different colors.
Sound production has been recorded in at least 6 different species of sunfish, and the orangespotted sunfish is one of them. The sound is produced by the nesting male when sighting a female. The sound itself has been described as a series of grunt-like sounds. The calls are unique to each species of sunfish and probably help them avoid hybridizing with other closely related species.
13) Pallid sturgeon (Scaphirhynchus albus)
The pallid sturgeon is a Missouri native member of the Acipenseridae family (sturgeon). Like other sturgeons, it has a ‘prehistoric’ look, belonging to an ancient group that dates all the way back to the Early Jurassic Epoch 174 – 201 million years ago. The sturgeons are recognizable by their shark-like tail fin and built-in body armor of bony plates arranged in five lateral rows. These bony plates are known as ‘scutes’ and are absent from the belly. Despite the impressive size this fish can reach (a max length of 6.56 feet (2 m)), the pallid sturgeon feeds mainly on aquatic insects and small fish, that it locates using the barbels hanging in front of its mouth.
The pallid sturgeon was assessed by the IUCN Red List of Threatened Species in 2004 and declared ‘Endangered’. The entire adult population is likely less than 20,000 individuals across the whole range, with only a couple of hundred surviving in the Missouri River. Habitat modification through the damming of the Missouri River is generally viewed as the primary challenge the species faces to ensure continued existence, since the damming inhibited the pallid sturgeon from undertaking its spawning migration to its upstream spawning sites. A conservation stocking program has released around 1,000,000 juveniles and fry in the Missouri River Basin in an attempt to re-establish a viable population.
14) Rainbow smelt (Osmerus mordax)
The rainbow smelt is a member of the Osmeridae family (smelts) and is said to smell like freshly cut cucumber, which ‘osmerus’ stemming from the Greek word ‘osme’ meaning odorous, hints at. The common name of the species nods to its incredible iridescent colors, which can be green, purple, blue, and pink. They inhabit cool clear waters and prefer to feed on small invertebrates. They avoid light even during spawning, which typically happens at night. The female releases her eggs in clusters simultaneously with the males releasing their milt to fertilize them.
The rainbow smelt has been present in Lake Oahe since the early 1970s, where it has become the dominant forage species for walleye. It was initially stocked in Lake Sakakawea by North Dakota Game and Fish in 1971. The population established and sustained the walleye population and recreational fishing until 2011, when the population crashed following the Missouri River flood. A study published in 2021 investigated Lake Oahe for ‘hot spots’ of spawning behavior by the rainbow smelt, however following multiple years of intense surveying, widespread use of the reservoir as a spawning site was discovered.
15) Sauger (Sander canadensis)
The sauger is a member of the Percidae (perch) family and belongs to the top primary predators in Lake Oahe. Their eyes are adapted to rapid-moving waters and low light, where most other fish species struggle to see, which makes them effective predators. Compared to most other species on this list, the sauger is more adapted to backwaters or muddy pools and occurs less frequently in lakes and impoundments, such as Lake Oahe. However, the population here stems from before the creation of the lake, since they were once common in the Missouri River basin.
Human alterations to their natural habitat through the construction of dams have historically been associated with declines in local sauger populations. Another threat is the ecologically similar walleye, which is also a prominent species in the lake and is often blamed for a decline in sauger populations. However, there is a lack of direct evidence for this mechanism. A recent study investigating the abundance of sauger and walleye in the lake suggests that both species are currently in decline and have been over the last 30 years.
16) Smallmouth bass (Micropterus dolomieu)
The smallmouth bass is a predatory member of the Centrarchidae family (sunfishes), closely related to the larger largemouth bass. The two species can be distinguished from each other by the clearly connected dorsal fins of the smallmouth bass and its more brownish color. Despite the common name, the smallmouth bass is a top carnivore, feeding on smaller fish and crayfish. Compared to the walleye, benthic species such as crayfish make up a larger percentage of the smallmouth bass’ diet, which allows the two species to co-exist. The young feed on plankton and zooplankton, while the adults prefer a more benthic diet of crayfish.
The smallmouth bass was stocked in Missouri River reservoirs such as Lake Oahe in the 1980s, and the population was shown in a recent study to be increasing. Over the same period, the sauger has been in decline. Direct competition between the species is lacking, but there is a negative correlation between the two species, which suggests that the smallmouth bass might have a negative influence on the sauger. This could stem from a resource or diet overlap.
17) Walleye (Sander vitreus)
The walleye is a member of the Percidae family (perch), which also includes the sauger. Their common and Latin names are a reference to their large, silvery eyes. They have a white belly and olive sides. Five dark blotches mark their upper sides. They have a large mouth filled with sharp teeth and spines in their operculum and first dorsal and anal fins. Without internal investigation of the fish, it is difficult to differentiate between the sexes.
As one of America’s most popular sports fish, the substantial walleye population at Lake Oahe is a big part of making it a popular destination for anglers. This is due to the historical high population numbers and large individuals in the population. However, the population is known to fluctuate wildly, perhaps due to natural variation in recruitment and fluctuations in the primary food source for adults: the rainbow smelt. When they are abundant, about 85% of the walleye’s diet is rainbow smelt, which allows for excellent growth rates. These growth rates greatly diminish when the rainbow smelt populations are troubled.
18) White bass (Morone chrysops)
The white bass is a member of the Moronidae family (temperate basses), which contains 6 species living in fresh, brackish, and saltwater. They have a light silvery green color with several horizontal stripes and white bellies. They congregate in schools with individuals of a similar size and feed in the open water of the lake. White bass feed primarily at dusk and dawn and may be observed feeding on gizzard shad, which they force to the surface, creating a chaotic feeding frenzy.
The annual harvest of white bass by anglers decreased in Lake Oahe from 2006 to 2015, from around 60,000 fish in 2005 to just 10,000 annually the following years. The sudden drop in the population numbers stemmed from a confirmed case of columnaris disease, a bacterium disease affecting fish species and white bass in particular. Since then, the population has struggled to rebound, potentially due to predation by walleye and a higher susceptibility to columnaris disease in larger individuals compared to age-0 fish, making it challenging for individuals to reach reproductive maturity.
19) Yellow perch (Perca flavescens)
The yellow perch is an adaptable member of the Percidae family (perches) found in a broad range of habitats, although they prefer cool, clear weedy backwaters and rivers with a heavy growth of aquatic plants. The yellow perch spawn shortly after ice-out. They do not construct nests or guard their eggs; however, the females do deposit their eggs in a sheltered area in neat ribbons, which the males simultaneously fertilize by releasing milt.
The yellow perch is often found seeking refuge in cooler pools, such as the tailwaters below release dams in the summer months. The reproductive success of the species has been linked to overwinter thermal conditions, where long, cold winters result in higher quality eggs and an overall larger number of eggs laid. Therefore, the species is particularly susceptible to increasing temperatures due to climate change. The IUCN currently considers the species as ‘Least Concern’ because of the large number of subpopulations and large distribution of the species. However, due to increasing temperatures, the most southern populations might be slowly declining.
