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Smallmouth Bass Facts


The smallmouth bass (Micropterus dolomieu) is a species of freshwater fish found within the sunfish family.  Smallmouth bass were first introduced to Nova Scotia in 1942 by the government for a source of sport fishing. It is known as an invasive species in most of Nova Scotia’s watersheds due to its habit of outcompeting native species. To this day, illegal introduction still occurs to induce sport fishing.  This fish can be known as a smallmouth, bronzeback, brown bass, brownie, smallie or bronze bass. The smallmouth bass is normally dark brown ranging to a shade of sandy yellow, depending on its habitat. Their eyes are red and there body has dark brown vertical bands, rather than a horizontal band going along its side. There are 13–15 soft rays in the dorsal fin. To distinctly distinguish a smallmouth bass from a largemouth, notice the upper jaw of a smallmouth bass extends to the middle of the eye rather than past it. The males are smaller than the females, obtaining a weight of about 2 pounds while the females can grow up to 6 pounds, averaging a length of 15-30 cm. The size, color and weight of the bass all depends on its habitat. It’s surrounding habitat influences whether it’s got the proper amount of food supply and the appropriate climate to grow.


Smallmouths are found in both rivers and larger still waters. They are visual predators, which mean they require clear water to survive and thrive. Smallmouth bass prefer cooler water temperatures and can be found in both still and moving water. Smallmouth bass prefer rivers and lakes with a rocky or sandy substrate to provide the best habitat. They can also be found in many other habitats such as rock outcroppings, logs, and weed beds. Unlike largemouth bass, smallmouths can often be found in fairly fast currents. Due to its intolerance to pollution, the smallmouth bass is a good natural indicator of a healthy environment.


The diet of the smallmouth bass varies depending on its surrounding habitat and the amount of foraging available. They are opportunistic eaters meaning they will essentially eat anything it can swallow at any time. As juveniles their diet consists of mainly zooplankton then shifts to aquatic insects and invertebrates as the fish increase in size. Once the fish is large enough, typically at the age of 1 they begin feeding on small fish, insects and crayfish which composes their main diet.


Smallmouth bass spawning times and spawning success rates vary annually and geographically. Spawning time correlates to the water temperature and its rate of increase or decrease.  Being very sensitive to water temperature, a drop in temperature of as little as 2°C can result in abandonment of the nest. Bass spawning becomes altered especially when the water temperature drops below 15°C. Smallmouth bass spawning occurs typically in May and June, sometimes leading into the beginning of July when the water temperature reaches 18-20°C. Spawning can last from 6 to 60 days. The male smallmouth bass begins nest-building when the water temperature is around 15°C and mating begins when water warms to 18°C. The male will lure the female to the nest to spawn .Several females may spawn in the nest of one male, and individual females may spawn in the nests of several males Females lay approximately 2,000 eggs at each spawning, and a female can produce from 2,000 to 21,000 eggs. Females have been found to lay a maximum of approximately 7,000 eggs per pound of fish. The male is responsible of taking care of the eggs, which lasts about 6 days then protects the fry for about two weeks before they scatter into the wild.

Impacts on Ecosystem

Smallmouth bass are a major threat to the Atlantic Whitefish population due to the fact that they are voracious eaters and out-compete this population of food supply and habitat. Bass also play a major role in decreasing the Atlantic Whitefish population by feeding on juveniles which leads to the population not being able to establish themselves. The Atlantic Whitefish population is decreasing every year and is becoming more and more vulnerable to threats such as invasive.  Without protection, under the pressure of invasives, the Atlantic Whitefish population could be decreased to the point where they can no longer sustain a steady population. Smallmouth bass populations can establish themselves and reproduce very quickly. Once bass have entered a watershed they basically take over the habitat, it is important to prevent the introduction of these invasives while also playing your role by protecting the watershed in any way to ensure a future Atlantic Whitefish population.