The largemouth bass (Micropterus salmoides) is a species of fish in the sunfish family (Centrarchidae). Other common names include “black bass,” “green trout,” and “bigmouth bass.”

Identification

The largemouth is marked by a series of dark, sometimes black, blotches forming a jagged horizontal stripe along each flank. They are usually green with dark blotches that form a horizontal stripe along the middle of the fish on either side. The underside ranges in color from light green to almost white. They have a nearly divided dorsal fin with the anterior portion containing nine spines and the posterior portion containing 12 to 13 soft rays.The upper jaw (maxilla) of a largemouth bass extends beyond the rear margin of the orbit. The largemouth is the largest of the black basses, reaching a maximum recorded overall weight of 22 ¼ pounds. The fish can live as long as 23 years.

The northern largemouth is native to North America, while the Florida-strain largemouth is a hybrid developed by fisheries scientists. Northern and Florida largemouth are known to interbreed, an uncontrollable but undesired circumstance for fisheries resource managers. The Florida strain tends to exhibit faster growth rates and attain a larger weight than the northern, due in part to its preferred temperate climate zone.

Distribution

Largemouth bass were originally distributed throughout most of what is now the United States east of the Rockies, with limited populations in southeastern Canada and northeastern Mexico. Because of its importance as a game fish, the species has been introduced into many other areas worldwide, including nearly all of Mexico and south into Central and South America and even across the globe in Europe and Africa.

Behavior

Except for humans, adult largemouth bass are the top predators in the aquatic ecosystem. Fry feed primarily on zooplankton and insect larvae. Largemouth become active predators in the juvenile stage, usually when they reach two inches in length.

Largemouth spawn in early spring, with the timing contingent on water temperature. In the South, spawning can begin when the surface temperature reaches at least 65 degrees Fahrenheit. Males build spawning nests in two to eight feet of water and can become very aggressive. Females stay on the nest long enough to deposit eggs and then move back out to deeper water. Largemouth bass prefer to nest in quieter, more vegetated water than other black bass, but will use any substrate besides soft mud, including submerged logs.

Immature largemouth bass congregate in schools, while mature adults are usually solitary. Sometimes several bass will gather in a very small area, but they do not interact.

Diet

The juvenile largemouth bass consumes mostly small baitfish, crawfish and insects. Adults consume the same forage, plus frogs, snakes, salamander and even small water birds and mammals. In larger lakes and reservoirs, adult bass occupy deeper water than younger fish, and shift to a diet consisting almost entirely of smaller fish like shad, trout, shiners, and sunfish. Prey items can be as large as 25 to 35% of the bass's body length. Studies of prey utilization by largemouth show that in weedy waters, bass grow slower due to difficulty in acquiring prey. Less weed cover allows bass to more easily find and catch prey, but this consists of more open-water baitfish. Paradoxically, with little or no cover, bass can decimate the prey population and starve or get stunted. Under overhead cover such as overhanging banks, brush, or submerged structure such as weedbeds, points, humps, ridges, and dropoffs, the largemouth will use its senses of hearing, sight, vibration, and smell to attack and seize its prey.

Habitat

Largemouth are structure-oriented by their predatory nature. Any combination of rock, vegetation and wood that is located near a variation in bottom depth, are attractive to this game fish.