A Predator In The Weeds

Smallmouth bass

The dictionary definition of a game fish is one that is fished for by recreational anglers. Any species of fish can qualify, but they usually have sporting qualities such as speed, strength, acrobatics or tenacity and are often good to eat. However, these attributes may not be enough to ensure that the species is welcomed. Smallmouth bass (Micropterus dolomieu) are a scrappy and tasty game fish, native to eastern North America, but widely introduced across the continent because of their “gamey” qualities. This is a warm-water fish and for much of BC, the water is simply too cold for them. However, across southern BC, from the Rockies to Vancouver Island, many introductions found suitable water conditions and smallmouth bass have thrived, often, unfortunately, to the detriment of native fish species. Thanks to accidental and illegal introductions, as well as natural colonization, the range of smallmouth bass has continued to expand in many BC watersheds.


Smallmouth Bass. Photo by Zweizug/Dreamstime.com.
Photo by Zweizug/Dreamstime.com.

Smallmouth bass are a robust fish with a large, elongated head and a narrow, deep body, brownish or greenish in colour. Large dark bars radiate back from the eyes and the body has a dozen or so dark vertical bars. The belly is creamy white. Their eyes are often red. There are two joined dorsal fins, the front fin is smaller with around 10 sharp fin rays. The back fin is larger and more rounded. In productive waters of their native range, these fish can grow to five kilograms. However, adult smallmouth in BC are typically 30 to 40 centimetres long and weigh one to two kilograms.

The menu for smallmouth bass includes pretty much any species of fish that will fit in their mouth, as well as invertebrates such as insects and crayfish. In spite of their name, they don’t have particularly small mouths; their mouth is only small in comparison with the closely related largemouth bass (Micropterus salmoides). Smallmouth bass are a top predator and can significantly alter the ecology of a body of water that they are introduced to, dining on both fish and the smaller invertebrates that are a key part of the food chain. If there are no predators, such as northern pike, smallmouth bass can dominate the ecosystem.


Spring is smallmouth bass spawning season. When the water gets to about 16 degrees Celsius, the males move into shallow water, less than a metre deep, and select a nest site near cover, such as a boulder or a sunken log. The preferred substrate is sand or gravel. By fanning their tails, the male bass create a depression in the gravel about 60 centimetres in diameter. Female bass soon follow from deep water and when they arrive, each is coaxed by a male to his nest. When the female is ready, the pair line up side-by-side and simultaneously release eggs and sperm into the nest. The female then returns to deep water and the male aggressively guards the nest from fish and other predators until the eggs hatch. An active male is a bit of a rake and can lure more than one gravid female to spawn in his nest. Depending on water temperature, incubation takes one to two weeks. Smallmouth bass fry feed on small invertebrates, but the fry eat progressively larger prey as they grow. These fish are sexually mature by four years old and live about 12 years.

Smallmouth bass are popular with anglers because they will strike at a variety of natural and artificial baits, then put up a spirited fight when hooked and can be a challenge to land. However, in recent years provincial fisheries management has focused on native species, and alien species, such as smallmouth bass, are no longer welcome. There are now fishing regulations in BC designed to limit the further spread of invasive fish species, and Regions 1, 2, 3, 4, 5 and 8 have regulations specific to smallmouth bass. In some regions, fishing for bass is banned outright. In other regions, bass fishing is still open in designated waters where further impacts to native ecosystems or the likelihood of further spread are low. Limits (both daily and possession) for these fish are often generous. So, bass anglers can enjoy their sport, but have to check the BC Fishing Regulations Synopsis to determine where fishing is permitted for smallmouth bass, this sporty but invasive game fish.