Population Dynamics of a Reservoir Sport Fish Community in Response to Hydrology

Sport fish from Normandy Reservoir, Tennessee, were sampled for more than 6 years with a variety of gears targeting different life stages. Normandy Reservoir experienced different hydrologic regimes over the sampling period that we roughly grouped into dry years (1992 and 1995), intermediate years (1993 and 1997), and wet years (1994 and 1996). Year‐class strength of largemouth bass Micropterus salmoides was fixed each year by late summer or early fall. Catch of age‐1 largemouth bass in spring electrofishing samples was directly related to the number of days the reservoir was at or over full pool when the fish were age 0. Largemouth bass produced in a wet year and intermediate year were more than twice as abundant at age 3 than fish produced in two dry years. Recruitment of spotted bass M. punctulatus could not be linked to reservoir hydrology. Crappies Pomoxis spp., white bass Morone chrysops , and saugeyes (walleye Stizostedion vitreum × sauger S. canadense ) produced poor year‐classes in dry years and strong year‐classes in wet years. The responses of these latter three taxa in intermediate years were variable, although they were more characteristic of dry‐year responses than wet‐year responses. Recruitment of crappies, white bass, and saugeyes was positively related to mean daily discharge of the reservoir in the prespawn period (1 January to 31 March) each year. Recruitment of largemouth bass was dependent on high water during the spring and summer when fish were age 0. Water‐level fluctuation in this Tennessee reservoir played a pivotal role in regulating year‐class strength of most sport fish species. Attempts to enhance year‐class strength of fishes in tributary storage impoundments should focus on altering the hydrology of systems.