largemouth bass

Largemouth Bass: Beloved Gamefish or Problematic Predator?

By Ben Team

If you are reading this, I probably don’t have to sell you on largemouth bass.  However, while largemouth bass provide economic and recreational benefits (as well as the occasional bout of frustration, but that’s a different story) to those living alongside them, they can also cause environmental problems.  

In fact, many places in the world consider largemouth bass an invasive species.

Native Range of Largemouth Bass

Historically, largemouths were native to portions of central and eastern North America.  Some of the areas in which they occurred included the St. Lawrence River, the Great Lakes and the Mississippi River system.  They were found in both Gulf Coast drainages as well as those on the eastern side of the Appalachian Mountains, from roughly North Carolina to Florida.

Current Range

Because they are such amazing gamefish, anglers throughout the ages have desired to introduce them to their local waters, and accidental introductions have introduced the fish to even more locations.  Ultimately, these factors have resulted in a drastic range expansion for the species.

Currently, largemouth bass are found throughout the contiguous 48 states, as well as Puerto Rico.  They have also been introduced throughout much of southern largemouth bassEurope, South Africa, Japan, Lebanon, Guam and the Philippines.  Additionally, largemouths have been introduced to numerous private ponds and other small waters around the world.

The species has been exterminated from a few areas where they were previously introduced, such as southern Great Britain, but that doesn’t happen often.  Ecologists and fisheries managers have been largely unable (and sometimes unwilling) to eradicate the fish from most places they have colonized.

Traits that Spell Trouble

Fish and other aquatic organisms invade novel waters all the time.  Some make their way into new waters by clinging to the waders of anglers, while others lurk in the cracks and crevices of boats.  Some are deliberately planted in new waters by humans, while others arrive through purely accidental means.  However, most of these vagabonds perish, and fail to establish viable populations.  Meanwhile, largemouths have a unique suite of physical and behavioral characteristics that allow them to colonize many new waters.  Some of those traits include:

  • Largemouth bass produce an abundance of young each year.
  • They protect their eggs and fry for the first few days of their lives, which helps to lower the mortality rate.
  • They’re highly opportunistic predators, capable of feeding on a wide variety of species.
  • They grow quickly, which not only increases the number of species that represent suitable prey, but also reduces the number of predators they must avoid.
  • They’re able to thrive in waters with varying clarities, temperatures and current speeds.

The Invasive Species’ Impact

In some places, largemouth bass feed on prey found in their native east coast habitat.  In some parts of Japan, for example, they feed on bluegill, which were introduced as a food source for the bass (as well as native species).  But elsewhere bass have proven highly flexible predators, able to feed on whatever local fish they encounter. For example, juvenile bass living in streams of the Iberian Peninsula often shift their dietary preferences. Rather than feeding on fish that spend their time high in the water column, as they do in their native range, scientists have learned that these European bass often consume bottom-dwelling fish and insects.

Biologists have also discovered that largemouth bass living in the Kowie River, Eastern Cape Province, South Africa, feed on three native estuarine species.  Apparently, the bass in this river system – who also prey heavily on the river’s native freshwater crabs – are able to catch these estuarine species as they migrate up stream. (For the record, the largemouth bass’ most famous cousin, the smallmouth bass, represents a similar threat in non-native waters.)

As you can imagine, largemouth bass are causing problems in some of the places in which they have been introduced.  While the ideal solution may be to remove the bass from these waters, this isn’t always possible.  Accordingly, largemouth bass may elicit a joyous reaction in some places and scorn in others.

Weigh in: joy or scorn?  Let us know in the comments.


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