Notes: Largemouth Bass Size Distributions under Varying Annual Hydrological Regimes in the Illinois River

Abstract

Little is known about the population dynamics of largemouth bass Micropterus salmoides in temperate large river–floodplain ecosystems. However, the hydrological regimes in these systems are often similar to those of large reservoirs where fluctuating water levels during spawning have been shown to affect largemouth bass population dynamics. Most backwater lakes of the Illinois River have soft, silty substrates. These substrates are not conducive to nest building, so spawning centrarchids may use annual spring floods to access inundated terrestrial vegetation and previously dry, compacted substrates on the floodplain. We used electrofishing catch data from La Grange Reach of the Illinois River (1990–1995) to assess how spring and early‐summer river levels influence the cohort strength of largemouth bass. Strong cohorts were produced during years with high spring floods (1990, 1993, and 1995) when largemouth bass could access the floodplain for spawning and nursery habitat. In both 1990 and 1993, fish had access to the floodplain for extended periods during spring and summer, which resulted in exceptionally strong cohorts. These cohorts probably benefitted from abundant forage and cover on the floodplain, which bolstered survival rates. Weak cohorts were produced in 1992 and 1994 when river levels were low and fluctuating during spawning and in 1991 when river levels declined dramatically during spawning. Length distributions of other centrarchids mirrored those of largemouth bass, indicating that river levels probably affected other nest‐building species in La Grange Reach.

Patterns in the Use of a Restored California Floodplain by Native and Alien Fishes

“…While they do not require floodplain conditions for spawning, greatest success of spawning seems to coincide with extensive flooding (King et al 2003). Many of the fishes of the MississippiMissouri river system historically were opportunistic floodplain spawners, taking advantage of long-term floods when temperatures were high enough for spawning (15-25°C, April-June) resulting in higher abundance and diversity in the rivers (Raibley et al 1997, Galat et al 1998). These species include fishes now present in California, such as largemouth bass and bluegill.…”

“…North American examples include golden shiner, largemouth bass (Micropterus salmoides), bluegill (Lepomis macrochirus), and redear sunfish (L. microlophus). Such species may have substantially faster growth rates on floodplains than in non-floodplain habitats (Gutreuter et al 1999), as well as higher survival rates (Raibley et al 1997). In years when there is extensive prolonged flooding, adults of these species may move onto the floodplains to spawn, along with floodplain pond fishes.…”

Relations between hydrological variables and year-class strength of sportfish in eight Florida waterbodies

“…Increased water level may increase the amount of spawning habitat and food resources available to sportfish by inundating shoreline vegetation (Jenkins, 1970;Aggus & Elliot, 1975;Keith, 1975;Timmons et al, 1980;Miranda et al, 1984;Meals & Miranda, 1991). Alternately, above average flow rates in lotic systems have both positively and negatively influenced recruitment of fish, depending on the system and species (Filipek et al, 1991;Mason et al, 1991;Sallee et al, 1991;Kriksunov & Mamina, 1995;Raibley et al, 1997). Thus, variations in flows and water levels may influence fish recruitment.…”

Relationship Between Largemouth Bass Recruitment and Water Level Dynamics in a Puerto Rico Reservoir

“…2). Several studies have demonstrated that higher largemouth bass recruitment occurs when water levels remain relatively higher during the spawning periods (Aggus and Elliot 1975;Morgensen 1981;Miranda et al 1984;Reinert et al 1995;Raibley et al 1997;Sammons and Bettoli 2000). Neal et al (1999), in a telemetry study of largemouth bass in Lucchetti Reservoir, found that adults quickly left spawning grounds when water levels declined.…”