Spawning Season and Nest Fidelity of Largemouth Bass in a Tropical Reservoir

Abstract

Largemouth bass Micropterus salmoides, an intensively studied sport fish of temperate North America, have been introduced into tropical regions, but with little evaluation. Studies in Puerto Rico suggest that reproduction occurs over many months and that life spans are short and annual mortality rates high. We tracked 44 adult largemouth bass with ultrasonic telemetry over an 18-month period (two spawning seasons) to determine the temporal and spatial utilization of spawning grounds. During the 1998 spawning season, both males and females demonstrated high site fidelity to specific areas characteristic of spawning grounds over the first half of the calendar year. Within this period, two distinct spawning events were evident from fish movements and were subsequently verified by hatch frequencies of young. The two spawning events, from mid-January through March and from late May through June, coincided with highly fluctuating water levels. When levels were high, shallow, vegetated areas were available and used for spawning. The reoccupation of nest areas corroborates previous gonad analyses that suggested multiple partial spawns by individual fish. During the 1999 spawning season, water levels were high in January and spawning occurred for 3 weeks, but levels rapidly declined thereafter, minimizing reproduction. Both male and female largemouth bass exhibited strong homing and nest site fidelity by returning to previous nesting areas. Individual fish were observed nesting in the same spawning grounds, and several males repeatedly utilized the same nest site during each of the separate spawning events and during both years. Because in tropical reservoirs recruitment to the fishable largemouth bass stock is directly related to the abundance of age-0 fish, maintaining high, stable water levels during the spawning season should enhance the largemouth bass population.