The Spinney Mountain Reservoir is an impoundment of the Platte River located in Park County, Colorado. This 2,500 surface-acre reservoir sits right by Spinney Mountain State Park, which is full of history dating back 12,000 years ago. The area surrounding the reservoir was once inhabited by Ute Native Americans who were able to hold on to the land for hundreds of years.
Today the Spinney Mountain State Park is operated by Colorado Parks and Wildlife, and it serves as a recreational site for many in Colorado. When visiting the park, one can camp, canoe, kayak, picnic, hike, and hunt. The area is also great for birdwatching since many migratory and native bird species rely on the park for survival, including rare bird species like bald eagles, American peregrine falcons, and white pelicans.
Visitors can also use the Spinney Mountain Reservoir to boat, whether it be motorboating, sailing, or paddling throughout the water. There are also opportunities to fish out on the water and along the shore after the ice melts in the spring up until late fall. In fact, the Spinney Mountain Reservoir is considered a Gold Medal water and is one of the best stillwater fisheries in the western United States. Below are the most common species of fish that can be caught or seen swimming in the Spinney Mountain Reservoir.
Spinney Mountain Reservoir Fish Species
1) Brown trout (Salmo trutta)
Brown trout are a regularly stocked species in the Spinney Mountain reservoir, and the reservoir is known for some extra-large brown trout that anglers love to catch. These fish prefer to live in slow-moving, deep streams, but they are also known to inhabit lakes, reservoirs, and marine environments. Brown trout have a brown or olive green body with dark colored spots, and their undersides are tannish. Also, female brown trout tend to have a larger abdomen and a smaller head compared to males. Adult brown trout range from about 7 – 22 inches in length and weigh anywhere from 1 – 52 pounds, and the brown trout at Spinney Mountain Reservoir usually weigh in on the heavier end of that range.
Brown trout are very active and sociable fish. Social hierarchies are formed within populations, and the males that exhibit the most assertive behaviors, such as quivering, charging, and biting, are at the top of the hierarchy. Brown trout primarily feed on invertebrates and crustaceans, but larger individuals will prey on other fish. These fish have been introduced to waters all over the world, and they are considered invasive in many areas. While they are a popular sport fish, brown trout seem to be having many negative impacts on ecosystems, including the decline of other fish species, as well as the alteration of algal biomass in certain waters where the number of brown trout is not controlled.
2) Rainbow trout (Oncorhynchus mykiss)
Rainbow trout are one of the most popular fish species in the Spinney Mountain Reservoir. This species comes in two forms: freshwater resident and anadromous. Rainbow trout that reside in freshwater, like those in the Spinney Mountain Reservoir, are typically a lighter silver color with intense dark markings along the body, and they have a light pink line running laterally from head to tail. Rainbow trout generally grow between 12 – 20 inches and weigh 1 – 4 pounds, although Spinney Mountain Reservoir is known for its massive rainbow trout that get even larger. This species is also closely related to the cutthroat trout, but unlike cutthroat trout, rainbow trout do not have basibranchial teeth.
Rainbow trout are extremely hostile towards each other as soon as they hatch because only the strongest and largest will be able to outcompete for space and food. Juvenile and adult rainbow trout primarily feed on larvae that float through the water. Relying on this food source saves a lot of energy since they are not actively foraging, but adults will also eat other fish, crustaceans, and worms. Rainbow trout are an incredibly popular sport fish, and this species has been introduced to every continent except for Antarctica. While this species is thriving in certain areas, some populations of steelheads, or anadromous rainbow trout, are actually endangered or threatened mainly due to the creation of dams that block access to spawning streams.
3) Cutthroat trout (Oncorhynchus clarkii)
Cutthroat trout have more than 10 subspecies in varying geographic locations, but the subspecies that are found in Colorado include the Snake River, Greenback, Rio Grande, and the Colorado River subspecies. Each subspecies looks slightly different from the others; however, there are characteristics that all of these subspecies share. While coloration varies among different subspecies, all cutthroat trout have red marks on their lower jaws. Cutthroat trout also have teeth on the base of their tongue called basibranchial teeth. These fish range from about 7 – 16 inches in length and weigh around 4 – 9 pounds, although the Lahontan cutthroat trout is the largest subspecies, which can weigh up to 40 pounds. There are both anadromous and freshwater cutthroat trout.
Cutthroat trout are largely solitary animals and will only interact with other trout during spawning season. This species of trout is also relatively sedentary, and will only be active to migrate or to hunt. Cutthroat trout feed on algae, small crustaceans, and insects when they are young, and adults will feed on just about anything including other fish. These fish are not threatened or endangered as a whole species; however, their populations are being threatened by habitat loss as well as the stocking of other trout species like the rainbow trout.
4) Cutbow trout (Oncorhynchus clarkii x mykiss)
Cutbow trout are a hybrid species created by breeding a rainbow trout with a cutthroat trout. These fish are often bred in fisheries and stocked in waters of the western United States, but they are a fertile breed, so cutbows can also be born outside of fisheries where there are populations of both rainbow and cutthroat trout in the same waters. In the Spinney Mountain Reservoir, cutbows are stocked every year, and they make up almost half of the fish species composition in the reservoir.
Cutbow trout look very similar to both rainbow trout and cutthroat trout, but the best way to determine if a fish is a cutbow trout is by looking to see if prominent features of rainbows and cutthroats are occurring concurrently. Cutbows will have white-tipped fins much like the rainbow trout, but they will also have red or orange gill plates and a red slash under the jaw, which they inherit from the cutthroat trout.
This species generally grows to around 12 – 24 inches in length, and they can weigh anywhere from 1 – 8 pounds. When young, cutbow trout will feed primarily on insects, but as adults, these fish will eat forage fish. In the Spinney Mountain Reservoir, the daily bag limit for all trout species is one fish, and the trout must be 20 inches or longer.
5) Northern pike (Esox lucius)
Northern pike are the second most abundant fish in the Spinney Mountain Reservoir, and these fish are able to survive very well because they are able to tolerate many water conditions. This species is characterized by torpedo-shaped bodies that are dark green or brown and covered in gold spots. They also have pointed mouths that contain many sharp teeth. Northern pike grow to about 18 – 25 inches long and weigh around 2 – 5 pounds, although it is possible to catch pike that are 40 inches long and 20 pounds in the Spinney Mountain Reservoir.
Due to the structure of their body, northern pike prove to be vicious predators and will lunge to eat other fish, frogs, crayfish, small mammals, and ducklings. In fact, northern pike can eat prey at least one-half of their body length, so fisheries only stock trout that are greater than 10 inches in length, giving the trout a better chance of survival when put into water with northern pike. Because pike can eat many larger fish, Colorado Parks and Wildlife encourages anglers to catch as many northern pike as they can in order to keep a healthy balance of all fish species in the reservoir.
6) Yellow perch (Perca flavescens)
Yellow perch are not incredibly abundant in the Spinney Mountain Reservoir, but they can still be caught by anglers where the water is cool and clear. This species is known for its golden yellow to greenish body covered in 6 – 8 dark vertical bars. These fish have yellow or green eyes and orangey-red tinted fins.
Yellow perch generally grow to about 7 – 10 inches long and weigh around a pound, although this species is prone to having stunted growth in areas where food is limited. When food is abundant, adults will feed on the bottom of the lake with their subterminal mouth, and they will search for items such as benthic macroinvertebrates as well as smaller fishes. These fish also have a unique way of spawning, where females lay eggs in long, gelatinous ribbons that hang onto vegetation and other structures. There are currently no bag or size limits on yellow perch in the Spinney Mountain Reservoir.
7) White sucker (Catostomus commersonii)
White suckers are not sportfish in the Spinney Mountain Reservoir, but they make up about 10% of the fish species composition in the reservoir. These fish are found in clearer waters; however, they are very tolerant of many water conditions including high turbidity and polluted waters. This species is characterized by long slender bodies that are olive-brown on the back, silver on the sides, and white on the belly. During breeding season, males will develop gold coloration on their backs and red stripes across their sides.
As adults, white suckers will reach about 10 – 16 inches long and will weigh less than two pounds. White suckers also have toothless terminal mouths with thick lips, which they use to suck zooplankton, larvae, fish eggs, and benthic invertebrates off of the reservoir floor.
