Are Largemouth Bass Invasive?

The largemouth bass (Micropterus salmoides) is an olive-green to greenish-gray carnivorous freshwater gamefish that belongs to the Centrarchidae family. Although these black bass species are generally native to eastern and central North America, Canada, the United States, and northern Mexico, you can also find them elsewhere. The largemouth bass is a popular sport fish; however, is it invasive?

Largemouth bass is invasive. Many countries blamed them for the declines, displacement, and extinctions of species in their new habitat. This highly-adaptable fish feeds on fish, but its diet varies from planktons to frogs as it matures — and it carries many parasites

The rest of this article will explain the largemouth bass and how its invasion can damage an ecosystem.

Largemouth Bass Characteristics

The largemouth bass is such a popular game fish that millions of anglers in the USA strive to catch it — but why? Perhaps because these anglers are attracted to the fish’s massive strength, fighter attitude, and the challenge of finding the fish itself. Let’s explore more about this fish together.

Physical Appearance

The largemouth bass is a big fish with a robust body and a big, extended head. It has a deep, wide dorsal surface and a wide lower jaw slightly longer than the upper jaw. The largemouth bass’ back and top head are olive to golden green,

The largemouth bass’ dorsal and caudal fins are opaque, green to live. The ones that live in clear, weedy water are darker, with more apparent black pigment than those living in dark water, which are pale green overall. The largemouth bass often feeds in schools, from the surface, water, or bottom.

The largemouth bass has a slightly sizable sloped mouth. This fish species has eyes that respond particularly to red and green. The fish can see red and green well and make high selective decisions using these colors.


The adults are solitary, although several basses will come together where food is abundant. The largemouth bass will fight their best for survival, hence their reputation for being aggressive. Due to their natural demeanor, the largemouth bass is usually the apex predator in its habitat.

The largemouth bass usually hides between rocks and water vegetation, and the reason being, they can easily ambush their prey from the covers. The species prefers quiet, calm, and water, although they are highly adaptable. The largemouth bass can live in rivers, ponds, lakes, reservoirs, and streams.

Although this fish species can live in colder waters, it prefers dam water because it is warmer. In winter, the largemouth bass would also swim into deeper waters. The fish also prefers clear water so they could see their prey better.

Due to their adaptability, you can find this species in Central and South America, Europe, Asia, and Africa. Largemouth bass must have a hydrological condition with dissolved oxygen to ensure it gets a healthy habitat. In the wild, the largemouth bass could live between 10 and 16 years on average.


Female largemouth basses lay many eggs, between 2,000 and 7,000 eggs paper pound of their body weight, and they will leave the eggs right after. The males will care for the eggs, and they become more aggressive and territorial in that period. The males build their nests in shallow water, where the bottoms are muddy. 


The largemouth bass feeds on a wide variety of food, like small fish, snakes, insects, frogs, and little aquatic birds — with small fish like perch, sunfish, and minnows being its favorites. Small largemouth bass, called “fry,” will not prey on big prey; instead, they feed on crustaceans, insect larvae, or little fish. Largemouth bass can grow quickly — some can weigh 7 pounds (3.2 kg) at the age of 2. 

On average, the largemouth bass measures 16 inches (40.64 cm) long. The fish can grow up to 12 inches (30.48 cm) in adulthood. The juveniles, on the other hand, can grow to between 4 and 6 inches (10.16 and 15.25 cm).

Some largemouth bass can be cannibalistic, as the northern pike. During spawning or when the water temperature is below 41°F (5°C) or above 98.6°F (37°C), largemouth basses usually do not feed and can survive 3-4 weeks without eating. The fish will only eat after spawning.

A largemouth bass never stops growing. The older the bass gets, the bigger the fish becomes. Due to light intensity, largemouth bass usually goes out to feed early in the day or in the late evening.

The juveniles feed every 3 hours. On the other hand, the adults feed every 14 to 24 hours, depending on their prey size. The largemouth bass can swallow their food whole, not surprisingly.


Many basses carry LBV, which is related to the virus commonly found in frogs and other amphibians. When the virus attacks the swim bladder, the bass will lose its ability to maintain buoyancy. Some basses with the disease might experience bloating.

Ecological and Economic Impacts

The largemouth bass is so invasive that it has caused the decline or extinction of aquatic life that share the same habitat with it. This fish-eating predator can dramatically alter the native food web. The largemouth bass is invasive in New Brunswick, Canada.

As discussed earlier, the largemouth bass is highly adaptable, so it’s no surprise they can live in colder waters, too. Their adaptability has caused them to be a danger to native fish like salmon and trout. This fish species also targets small birds and has been blamed for causing the Atitlan Grebe’s extinction, which once inhabited Lake Atitlan, Guatemala.

The largemouth bass is not native to Japan, but the species has created havoc in Japan waters — the catch for native species at Lake Biwa, Japan, had decreased tremendously, from more than 8,000 tons in 1972 to a total of 2,174 tons in 2000. This species has harmed native fish and caused them not to thrive, thus interrupting the local ecosystem. Currently, many initiatives for controlling the largemouth bass population take place globally.

Many anglers regard the largemouth bass as a trophy fish, and that popularity has led to positive economic effects in the tourism sectors, from hotels and lodging to recreation services. Anglers generate more than $48 billion in retail sales — a $115 billion impact on the economy, which has created employment for more than 800,000 people. This fish species is also an important food source all around the world.


Largemouth bass adults are primarily apex predators, but smaller largemouth basses are preyed on by great blue herons Ardea Herodias, northern pike Esox Lucius, walleye Sander vitreus, and more. Birds like kingfishers and bitterns also feed on smaller largemouth bass.

Both smaller and adult largemouth basses are targets of the bald eagle Haliaeetus leucocephalus. And, of course, the largemouth bass is targeted by humans. Overall, the largemouth bass population is not in danger.

Ecosystem Roles

Although largemouth basses are the top predators in their habitat, they play essential roles in the ecosystem. Largemouth basses are hosts to parasites such as Clavunculus bursatus, Clinostomum complanatum, and more. The most common parasite that this fish species carries is an ectoparasitic protozoan, Scyphidia tholiformis.

Final Thoughts

Anglers worldwide value the largemouth bass, and it is also an important food source in many parts of the world. However, the largemouth bass is an invasive species. This fish species has caused a lot of damage to many other aquatic species, such as preventing them from thriving in their natural habitat, moving toward extinction, or worse, extinct.

Do not simply release a largemouth bass into the waters. If you are not sure, seek advice from your local authority. If not done correctly, letting go of a largemouth bass could lead to more damage to native fish.


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