Smallmouth Bass Acrochelius alutaceus
> Smallmouth Bass were first detected in Oregon in 1905.
> Smallmouth Bass are renowned for their strong fight and acrobatic jumps when hooked.
> They belong to the sunfish family, Centrarchidae, and are closely related to largemouth bass and bluegill.
> They are often considered indicators of good water quality due to their preference for clear, oxygen-rich waters.
> Smallmouth Bass are considered to be a significant predator of juvenile salmon and steelhead in the Columbia River basin.
Identification Tips
> Smallmouth Bass have a robust, elongated body with a bronze to greenish-brown coloration and dark vertical bars along their sides.
> This species can be identified by their red or orange eyes (although that trait is not present in all individuals.)
> Unlike Largemouth Bass, the upper jaw of the Smallmouth Bass does not extend past the rear margin of the eye.
> Smallmouth Bass have two dorsal fins: the first is spiny, and the second is soft-rayed. Their pelvic fins are connected by a membrane, and their anal fin has three spines along the leading edge.
Natural History
> Smallmouth Bass prefer cool waters with rooted vegetation, they can use as cover to ambush prey.
> Smallmouth Bass are carnivorous, feeding on fish, crayfish, and insects, but they also consume other small aquatic animals.
> Male Smallmouth Bass mature sexually at 3 to 5 years of age, females at 4 to 6.
> In late spring to early summer Smallmouth Bass move to shallow waters (2 to 20 ft) to spawn when water temperatures reach 60-70°F (15-21°C). Males build large circular nests out of gravel and sand, near rocks or boulders.
> Pairs spawn in batches over several hours. Female Smallmouth Bass may spawn with several males.
> Eggs sink and adhere to the substrate. Incubation is generally 4 – 10 days. Males fan the nest to improve water circulation and guard it from intruders.
> After hatching, the male continues to guard the fry until they are capable of swimming and foraging independently.
Distribution
> Native to the eastern and central United States and southeastern Canada, particularly the Great Lakes region and the Mississippi River basin.
> Introduced to many regions across North America, including the western United States and parts of Canada, for recreational fishing.
> In Oregon, they can be found in almost every major river system, including the mainstem Willamette River and some of its tributaries.
Size
> Adult Smallmouth Bass typically range from 10 to 20 inches (25 to 50 cm) in length, although some can grow up to 27 inches (69 cm).
> They generally weigh between 1 to 5.5 lbs (0.5 to 2.5 kg), with larger specimens reaching weights of 10 lbs (4.5 kg).
Habitat
> Compared to other members of their family, Smallmouth Bass prefer cooler water habitats (10 to 30 °C). Therefore, they tend to prefer lakes and reservoirs with deep cool waters, and in rivers they select areas of cold-water input.
> Optimal habitats provide gravel or rocky substrates with cover structures such as rocks, submerged logs and vegetation, which are crucial for ambushing prey and for spawning.
Diet
> Smallmouth Bass are opportunistic feeders, consuming a variety of prey based on availability.
> The diet of Smallmouth Bass includes fish, crayfish, insects, amphibians, and occasionally small mammals. They are known to consume salmonids, such as juvenile salmon and steelhead.
> Juvenile Smallmouth Bass primarily feed on zooplankton and small invertebrates.
Management Considerations
> No current conservation actions in place to manage Smallmouth Bass
> In the past, there have been management efforts to reduce Smallmouth Bass numbers to improve Chinook salmon smolt survival, particularly in the Coquille River.
> Monitoring programs help assess population health, angler success, and guide management practices.
Similar Species
> Largemouth Bass have upper jaws that extend past the rear margin of the eye, unlike Smallmouth Bass.
> Many Smallmouth Bass have a red eye, while Largemouth Bass do not.
> Also, Smallmouth Bass tend to be smaller than Largemouth Bass.
References
For more information, see references.