Journal of the Southeastern Association of Fish and Wildlife Agencies

Tilapia aurea were introduced into Florida by the Florida Game and Fresh Water Fish Commission in 1961. Original stocking was in managed pits at Pleasant Grove Research Station. From this beginning they have spread to numerous private ponds, four creeks, two rivers and several public lakes. Enriched bodies of water are preferred habitats and native species present have not retarded establishment of T. aurea. Most of the present study was conducted on Lake Parker, a 2291 acre eutrophic lake in Polk County. Surveys of the fish population on Parker revealed seasonal congregations of T. aurea. This gregarious behavior was correlated with temperature and habitat preference. During January and February, the species was heavily congregated at an electro-power plant. Water temperatures at the plant ranged as high as 9 degrees Fahrenheit above background lake temperatures. Concentrations were also evident in areas where the lake bottom was primarily muck.

The age composition, as determined from scale impressions, of striped bass stocks in the James, York, and Rappahannock Rivers during the period June 1967 - March 1968 indicates a relative deficiency of the 1966 year class in the James River. Similar results are shown in samples from non-selective gear (pound nets, fyke nets), selective gear (gill nets, haul seines, hook-and-line), and routine surveys using a 30-foot semi-balloon trawl. The immediate effect of this apparent deficiency on a planned winter tagging program, and the more general implications for evaluation of year-class strength, are briefly discussed.

Young-of-the-year largemouth, Micropterus salmoides (Lacepede), and spotted bass, M. punctulatus (Rafinesque), were collected period!cally from Beaver Reservoir during the growing seasons of 1964 and 1965. Scales were read to insure that all bass included in the study were young-of-the-year. Counts were made of the number of bass that had eaten a particu lar class of food rather than either how many or the volume of items eaten. Qualitative analysis of stomach contents indicated that entomostracans were eaten by a high percentage of small bass and were not eaten by the larger young-of-the-year bass. More bass of all sizes contained insects than entomostracans (excluding 10 to 19 mm largemouth bass!. More largemouth and spotted bass contained insects than fishes except more of the larger young-of-the-year largemouth bass had eaten fishes than insects.