Role of parental care and ontogenetic diets shifts in the recruitment variation of an aquatic predator

Recruitment is a highly variable process crucial for the persistence of wild fish populations and the sustainability of fisheries. Based on previous studies, nest success, ontogeny of piscivory, and winter survival are predicted to determine year class strength of largemouth bass Micropterus salmoides . In Chapter Two, family-specific DNA fingerprints were used to quantify parental effects on brood-specific contribution to fall recruitment in environments that differed in the presence of bluegill sunfish Lepomis macrochirus , an important brood predator. Overall, the majority of fall recruits originated from the broods of larger, older males that spawned earliest and had higher mating success than other males. The presence of bluegill sunfish caused size-specific variation in duration of parental care, with parental protection that extended to the free-swimming life stages of offspring needed for any brood-specific contribution to recruitment. Chapter Three examined the relative importance of zooplankton prey versus fish prey to recruitment to age 1 in wild populations of largemouth bass. Variation in ontogenetic diet shift to piscivory and availability of bluegill sunfish as prey for age 0 largemouth bass had a stronger relationship with inter-lake variation in recruitment to age 1 than variable abundance of zooplankton. In Chapter Four, the relative importance of early reproductive success, prey availability, and winter survival to recruitment to age 1 was assessed simultaneously in a multiple-lake and ---year data set. Both among and within lakes, production of age 0 largemouth bass from the parental care stage and availability of prey fish were found to be important to recruitment. Inter-system differences in recruitment strength were set prior to winter. Annual fluctuations in prey fish abundance only influenced recruitment in lakes where reproductive output of bluegill sunfish was generally low. These studies further our understanding of recruitment variation, by quantifying the influence of multiple processes operating during early life stages.