American Falls Reservoir is situated near the town of American Falls in Idaho. This reservoir was created in 1927 by constructing a concrete gravity-type dam on the Snake River. It is large, spanning 55,291 acres in area and covering parts of Bannock, Bingham, and Power counties.
The temperature at American Falls Reservoir varies considerably throughout the year, with hot, dry summers and freezing cold winters. The lake is used for flood control, irrigation, and recreation, including water sports as well as fishing. It is home to a wide variety of fish species, from the small northern leatherside chub to the enormous white sturgeon.
List of Fish Species in American Falls Reservoir
1) Rainbow trout (Oncorhynchus mykiss)
The rainbow trout is one of the most common fish in American Falls Reservoir and is a popular game fish. It can reach lengths of up to 122 cm (4 ft), although the current record for this lake is 79 cm (31.1 in). This fish has a reddish coloration along its lateral line, a dark olive back, and a paler belly – interestingly, lake-dwelling individuals are reported to be lighter in color than river dwellers.
This species prefers clear, cold water with a rocky substrate, and requires areas of vegetative cover to escape to. It also needs gravelly streams in which to reproduce. Spawning takes place between November and May, during which time the female digs a pit using her tail, while the male defends her from conspecifics. Males leave soon after spawning is complete, while the female may remain for several hours to cover the eggs.
The diet of the rainbow trout includes fish, insects, crustaceans, and mollusks. Individuals may also consume zooplankton, particularly Daphnia.
2) Brown trout (Salmo trutta)
The brown trout, also known as the sea trout, can attain lengths of up to 140 cm (4 ft 7 in). As the name suggests, this fish is brown in color, usually slightly darker across the back and paler on the belly. Some individuals may display orange or red spots along the sides. Breeding males tend to become slightly brighter in coloration and show a lengthened lower jaw, forming a hook that points upwards.
Salmo trutta resides in cool or cold areas of lakes, often where the water is deep. As with the rainbow trout, this species requires streams with a gravel substrate in which to spawn. Where brown trout and rainbow trout overlap, the two species are known to compete for resources.
Brown trout are voracious predators, attacking prey with a burst of energy and sucking it into their buccal cavity. The diet of this species includes small fish, mollusks, and crustaceans.
3) Brook trout (Salvelinus fontinalis)
The brook trout grows to up to 86 cm (2 ft 10 in) in length, although it is more commonly found at lengths of 26 cm (10.2 in). This fish is usually dark green or brown across the back, with the color fading as it descends from the sides to the belly. There are red spots outlined with blue along the sides.
Salvelinus fontinalis is flexible in terms of habitat, although does tend to be found in cool, clear waters with a rocky substrate – silt-free areas are usually preferred. Populations do not typically occupy areas with an excess of aquatic vegetation. Brook trout have a varied diet, including insects, crustaceans, mollusks, worms, leeches, small fishes, and amphibians.
The bag limit for brook trout in American Falls Reservoir is twenty-five. This is an easy species to catch as it will readily take bait or lures – it is also highly palatable and thus makes an excellent table fish.
4) Cutthroat trout (Oncorhynchus clarkii)
The cutthroat trout is a popular gamefish, as it often puts up a bit of a fight when caught. This fish can grow to lengths of up to 99 cm (3 ft 3 in) and its coloration varies: the back may be gold, green, or gray, fading to a silvery color on the belly. There are red, pink, or orange markings on the gill plates, which have earned this species its name.
This species occupies cold waters with a fine substrate and an abundance of aquatic vegetation – it relies on having plenty of cover, such as overhanging banks and boulders. Oncorhynchus clarkii faces a number of threats, such as habitat loss, competition with other species, and hybridization.
Conservation strategies recommended for cutthroat trout include habitat restoration and reintroduction of populations. Further research into this species has also been highlighted as an area of importance, as well as genetic testing of individuals.
5) White crappie (Pomoxis annularis)
The white crappie can attain lengths of up to 53 cm (1 ft 9 in), although individuals are more commonly found at lengths of 25 cm (9.8 in). This fish has a deep body and a large mouth. Its coloration is silvery white on the sides and belly, while the back is gray-green – there are also dark vertical bands on the sides.
This species prefers waters with high turbidity and a muddy or sandy substrate, and groups of white crappie are reported to congregate around sunken debris such as trees and boulders. The diet of white crappie varies depending on their size: when small, they feed on plankton, whereas once they reach 16 – 17 cm and above, they begin to feed on fish.
White crappie spawn in nests constructed by the male, usually in areas with aquatic vegetation. A shortage of food in the weeks leading up to spawning can cause females to invest less energy in reproduction, resulting in fewer offspring.
6) Black crappie (Pomoxis nigromaculatus)
The black crappie has been reported to reach lengths of 49 cm (1 ft 7 in), however, most individuals that are caught are around 27.5 cm (10.8 in). This species is similar in appearance to the white crappie, displaying the same deep body and large mouth with a significant underbite. Its coloration is much darker, with a silvery base covered by dark blotches across the sides and back.
Pomoxis nigromaculatus resides in areas with a muddy or sandy substrate, and plenty of aquatic vegetation in which it spawns. Populations do better in clear water and have been shown to grow more quickly in areas with low turbidity. During the day this fish occupies shallower waters, entering deeper waters at night to feed on insect larvae and fish. Very small individuals consume planktonic crustaceans.
In areas where black crappie and white crappie coexist, they may hybridize. The hybrids show faster growth rates than the parent species and are often misclassified as black crappie, which presents concerns for the monitoring of populations.
7) Yellow perch (Perca flavescens)
The yellow perch has a stocky build with a torpedo-shaped body, growing up to 50 cm (1 ft 8 in) in length. The dorsal fin is clearly divided into two sections with a small space in between. This fish’s coloration is yellow, with orangish pectoral, anal, and pelvic fins, and dark bars running vertically down the sides.
This species prefers well-vegetated areas with clear water and is often associated with the shoreline in waters with low turbidity. The diet of the yellow perch varies with age: the youngest individuals feed on water fleas, transitioning to insects and medium-sized crustaceans in their second year, and then onto decapod crustaceans and fish.
Perca flavescens is susceptible to predation by piscivorous fish such as largemouth bass, as well as eagles, ospreys, and herons. Smaller individuals may also be predated by gulls or kingfishers.
8) Black bullhead (Ameiurus melas)
The black bullhead is a relatively small species of catfish that reaches lengths of around 66 cm (2 ft 2 in). Individuals have four pairs of barbels on the snout, smooth skin without scales, and a small notch in the tail fin. The coloration of this fish can be yellow, olive, or green-gold, with paler skin below and dark chin barbels and fins.
The habitat of Ameiurus melas in lacustrine environments usually includes shallow, vegetated areas, with individuals often occupying regions near the shore. The diet of this species includes crustaceans, plant material, midge larvae, and small fish, which it detects using its barbels.
When fishing for the black bullhead, locations such as shore banks, coves, sand bars, and around rocks are ideal places to try. Minnows, jigs, and cut bait are recommended for this species.
9) Channel catfish (Ictalurus punctatus)
The channel catfish is very large, growing to lengths of 132 cm (4 ft 4 in). It does not have scales, and its skin is blue-gray across the back, fading to white below. There are usually dark spots along the sides, and the tail is forked in shape – a key distinguishing feature when comparing this species with the flathead catfish.
This species occupies clear, open water over gravelly, rocky, or sandy substrate – individuals tend to avoid muddy areas with excessive aquatic vegetation. Channel catfish seek out the warmest regions of lakes and reservoirs, often seeking cover underneath banks or around sunken logs and rocks.
Ictalurus punctatus is a suction feeder; it sucks water and organisms into its mouth after it has detected them using its barbels. Common prey items of the channel catfish include fish, crustaceans such as crayfish, clams, snails, and small mammals.
10) Largemouth bass (Micropterus salmoides)
The largemouth bass can attain lengths of 97 cm (3 ft 2 in), although it is more commonly found at around 40 cm (1 ft 4 in) in length. This fish has a large gape, and a key distinguishing feature that can aid in its identification is that the mouth extends beyond the rear of the eye. Largemouth bass are green or olive in color, with a paler ventral region and a dark band running along the lateral line.
In American Falls Reservoir, there is a total bag limit of six basses, and fish under fourteen inches in length are not permitted to be taken. Live baits are good for catching this species. Micropterus salmoides occupies areas with depths between 3 – 15 m, often with an abundance of aquatic vegetation.
During breeding season, males select a site close to shore, where they construct a shallow nest by sweeping the substrate away. The male then guards the nest while waiting for a female to arrive, and after spawning has taken place, he remains to fan the eggs and guard the fry after hatching.
11) Smallmouth bass (Micropterus dolomieu)
The smallmouth bass can grow to 69 cm (2 ft 3 in) in length and can be discriminated from the largemouth bass due to its jaw not extending beyond the back of the eye. This fish is olive, gold, or brown across the back, with a paler underside. There are dark vertical bars on the sides, and dark stripes radiating from the eye.
The best time of year to fish for smallmouth bass on American Falls Reservoir is in the fall. This species prefers gravelly or rocky substrate and requires submerged cover such as sunken trees, overhanging banks, and rocks in its habitat. Juveniles consume plankton and immature aquatic insects, while adults feed on crayfish, fish, and insects.
Prior to spawning, the male constructs a nest in the substrate, and the breeding pair undergo a courtship ritual. Females have been shown to select larger males during breeding – these males have been suggested to be capable of greater investment in their offspring, thus increasing chances of survival.
12) Sockeye salmon (Oncorhynchus nerka)
The sockeye salmon is a popular sport fish that can reach lengths of 84 cm (2 ft 9 in). Ordinarily, sockeye salmon are silvery-gray in color, but during spawning their body turns bright red, with an olive-green head. During this time the male also develops an elongated jaw with ‘canine-like teeth’, and a hump appears in front of the dorsal fin.
The landlocked form of Oncorhynchus nerka, which is the type residing in American Falls Reservoir, is known as the kokanee. This species prefers open waters, usually over a gravelly substrate. Smaller individuals consume zooplankton and macroinvertebrates, whereas larger individuals are piscivorous.
During breeding season, these fish become highly aggressive towards conspecifics of the same sex. Females construct a nest in the substrate, usually attended by a dominant male and a handful of subordinate males – despite both the dominant male and the female showing aggression to the subordinates, they may still attempt to join in with the spawning. The adults die after spawning is complete.
13) Tiger muskellunge (Esox masquinongy x lucius)
The tiger muskellunge is a sterile hybrid between the northern pike and the true muskellunge. This fish can grow to lengths of 86 – 122 cm (2 ft 10 in – 4 ft) and is cylindrical in shape, with the dorsal and ventral fins sitting far back along the body, making it highly streamlined. The coloration of this fish is silvery with olive-gold vertical stripes across the back, turning into blotches as they extend down the sides.
True muskellunge typically occupy deeper waters during the spring and fall, and shallower areas through the summer – it is likely that tiger muskellunge follow the same pattern of distribution throughout the lake. Individuals may be seen taking shelter among vegetation, or around submerged logs or rocks.
Tiger muskellunge are a popular sport fish as they are strong fighters, so they make for an exciting catch. Recommended baits for targeting this fish include crankbaits, jigs, spinners, and swimbaits.
14) Northern leatherside chub (Lepidomeda copei)
The northern leatherside chub is a small fish, reaching just 15 cm (6 in) in length. Its name arises from its small scales, which lend it a leather-like appearance, and it is silver-blue in color, with black specks across the back. Breeding males develop a reddish color on the bases of their anal fins, the caudal fin, and the upper edge of the gill cover.
This species prefers habitat with small cobbles, particularly for spawning. Populations of northern leatherside chub are decreasing, and it is considered near threatened by the IUCN. Factors contributing to this decline are thought to include the construction of dams and irrigation systems, as well as the presence of invasive species.
The diet of the northern leatherside chub most likely consists of bottom-dwelling aquatic insects, as well as some crustaceans and terrestrial insects. Conservation aquaculture has been suggested as a potential strategy to help restore this species.
15) Bluehead sucker (Catostomus discobolus)
The bluehead sucker is a member of the carp family that can attain lengths of 41 cm (1 ft 4 in). The body of this fish is golden-olive in color, with a paler yellow belly, while the broad head is blue-gray. During breeding season, the males develop red along their lateral line and may show orange or yellow fins.
Although this species is typically a stream-dweller, it may be found in the American Falls Reservoir. It prefers a rocky substrate and may be found in open areas with greater depth, where it feeds on algae and aquatic insects, which it usually scrapes from the rocks along the lake bottom.
Catostomus discobolus is considered to have a conservation status of least concern, however, it may still face threats due to habitat fragmentation and degradation, and invasive species.
16) Bluegill (Lepomis macrochirus)
The bluegill is a type of sunfish with a maximum length of 41 cm (1 ft 4 in), although it is more commonly found at lengths of 19 cm (7.5 in). This fish has a deep, vertically compressed body, and is usually olive-green in color with blue or purple along the sides – breeding males may also display orange on their sides. The name ‘bluegill’ is due to the dark blue opercular flap.
This species typically resides in deep weed beds, although throughout their life history, individuals may move between the littoral and pelagic zones. Research has found that the age at which they make these transitions is dependent on the presence of predators in the lake.
In areas with a greater density of aquatic vegetation, bluegills consume more gastropods and insects, whereas in areas with less vegetation, the diet shifts towards more benthic prey. Feeding amongst vegetation is a predator-avoidance strategy, however, it does result in reduced growth.
17) White sturgeon (Acipenser transmontanus)
The white sturgeon can grow to enormous lengths, with some individuals reaching 610 cm (20 ft)! This species is also incredibly long-lived, with some individuals being reported to live until 104 years of age! There is a row of bony plates along the back in front of the dorsal fin, which is positioned towards the tail, and there are barbels on the snout.
Acipenser transmontanus is an introduced species in American Falls Reservoir and is restocked every year. This fish prefers a rocky substrate with clear water – at particular times of the year, water quality in areas of the lake may decline; the sturgeon avoid this by moving to refuge areas.
The conservation status of white sturgeon is that of least concern. It predates on a variety of animals, including fish, crustaceans, mollusks, and insects, although stops feeding altogether prior to spawning.
18) Common carp (Cyprinus carpio)
Common carp can grow to 120 cm (3 ft 11 in) in length; however, individuals tend to be found at lengths of around 31 cm (1 ft). This fish can have quite a variable appearance: it may have a stocky build, and the development of the fins and the coloration can differ between individuals. The scales tend to be large and may be gray, bronze, or yellow.
Cyprinus carpio occupies warm, well-vegetated regions of lakes, often over areas of muddy or silty substrate. Individuals may also seek cover around submerged logs or rocks, which are good locations for resting and feeding. The diet of this species includes benthic organisms and plant matter.
The common carp is classified as vulnerable by the IUCN. Management of rivers and lakes may affect the spawning habits of this species, and it may hybridize with other introduced fish species, which affects the genetic makeup of individuals.
19) Utah chub (Gila atraria)
The Utah chub can attain lengths of up to 56 cm (1 ft 10 in) and is a deep-bodied fish with a short, blunt snout. Its back is olive-brown or blue-black, while the sides are yellow or brassy in color. The head may have a golden sheen to it, and males show golden fin bases.
Gila atraria is fairly flexible in its habitat preferences, although it does require submerged vegetation for spawning. The juveniles also reside amongst the aquatic plants, which provide them with shelter from predators. The diet of this species is variable, ranging all the way from herbivorous to carnivorous – interestingly, individuals consuming more plant matter have a more distended abdomen, whereas those that consume animal matter are more streamlined.
In some areas, Utah chubs are considered to be a pest. They are not desirable game fish, but will often take bait, which can prove frustrating for fishermen! These fish also compete with trout for resources.
20) Walleye (Sander vitreus)
The walleye can attain lengths of 107 cm (3 ft 6 in), although they are more commonly found at lengths of around 54 cm (1 ft 9 in). This fish is torpedo-shaped and varies in color from olive brown to yellowish gold. Its name arises due to the tapetum lucidum – a reflective layer in the eye that aids vision in the dark.
Sander vitreus traditionally inhabits rivers, but in lacustrine environments, it may be found in the littoral and sublittoral zones. This species is not especially tolerant of anoxic conditions, and water pollution may reduce the success of spawning. Individuals predominantly feed on aquatic insects and fish, but will also consume frogs, snails, crayfish, and small mammals.
The best time to fish for walleye is first thing in the morning, or later in the evening. This fish responds well to live bait such as minnows or worms, and can often be found near submerged structures in deeper water.
