Relationship between largemouth bass recruitment and water level dynamics in a puerto rico reservoir

Recruitment of largemouth bass at age-1 in a Puerto Rico reservoir can be predicted from water level variables of the previous year. Age-1 largemouth bass electrofishing catch-per-unit-effort (CPUE) as an index of year-class strength varied five fold between 1994 and 2001 in Lucchetti Reservoir, Puerto Rico. The CPUE of age-1 largemouth bass was higher in years when the water level of the previous years (1993–2000) remained high during the spawning period (January-June). The greatest water level drop (11.2 m) during the spawning period was observed in 1999, resulting in a water volume decrease of 66.5%, which corresponded to the lowest recruitment (CPUE 24.2 fish·h?1). With only 2.6 m of water level drop and 18.3% water volume decrease during the spawning period, the 1995 largemouth bass cohort was the strongest (CPUE 128.3 fish·h?1). The effect of these hydrological variables on largemouth bass recruitment appeared to be exponential rather than linear. Age-1 largemouth bass comprise the majority of the fishable stock in Lucchetti Reservoir, and the stock is typically below carrying capacity. Thus, the potential exists to adopt a water level management plan during the spawning period of largemouth bass to ensure successful largemouth bass recruitment into the next year's fishable stock. © 2005 Taylor & Francis Group, LLC.