Age-0 largemouth bass Micropterus salmoides were studied in Bay Springs Reservoir, Mississippi, to determine if the larger young had greater survival through their first winter and if this survival was influenced by levels of energy reserves. Abundance decreased from 542 young/ hectare in June, when fish averaged 37 mm total length, to 12/hectare in March, when lengths averaged 149 mm. The length-frequency distribution of this year-class was positively skewed during June-August, became bimodal during September-January', and lost most of the smaller mode by March. During September-January, fish in the smaller mode decreased in abundance from 176 to 9/hectare and their mean length remained near 60 mm; fish in the larger mode decreased in abundance from 76 to 27/hectare and increased in length from 108 to 154 mm. Whole-body lipid content increased from 3.5% of dry body weight in fall to 5.9% in December and decreased to 3.3% in March. All young had equal amounts of stored lipid by late fall, but by March the surviving small young had less lipid than large young, suggesting that during winter smaller fish spent their reserves at a faster rate. Protein content averaged 74.6% of the dry body weight and neither differed among months nor changed with fish length. Mortality of the smallest young was accelerated in late fall and winter, coinciding with decreases in lipid stores and rapid drops in water temperature.

Winter mortality of age‐0 largemouth bass Micropterus salmoides is sometimes size dependent, with smaller fish experiencing higher mortality. We conducted this study to determine if the presence of predators influenced winter mortality of young largemouth bass, if predators influenced all sizes of young equally, and if increased shelter availability moderated a possible relation between predator‐induced mortality and fish size, We stocked 0.06‐ha experimental ponds with largemouth bass (30 fish/pond) of five length groups (55–100, 101–125, 126–150, 151–175, and 176–200 mm total length), with and without predators (three largemouth bass 250–350 mm long), and four levels of shelter (0, 10, 16, and 26% brush coverage of surface area of ponds). In ponds without shelter, survival ranged from 10 to 97% in the presence of predators and from 77 to 93% in the absence of predators. Fish less than 126 mm long had gradually lower survival in the presence of predators, but near 80% survival in the absence of predators; fish 126 mm long or longer had more than 80% survival in the presence or absence of predators. In ponds with predators and shelter, survival increased with fish length and amount of shelter, but the lifesaving value of increased length and shelter relative to winter survival faded in fish 126 mm or more in length. We suggest that in lower latitudes predators may be a major source of mortality of small age‐0 largemouth bass in winter, and that the effects of predators can be tempered by shelter.

We evaluated the precision of 5–60‐min electrofishing samples for estimating relative abundance of largemouth bass Micropterus salmoides and developed guidelines for optimizing sample duration so that catch rates may be estimated precisely and with the least effort. Catch per hour in the study reservoirs ranged from 16 to 98 and was independent of sample duration. However, the variation in catch per hour among samples of equal duration increased as catch rate and sample duration decreased, resulting in the need for more samples. The total effort (i.e., time spent electrofishing, traveling between sample sites, and processing fish) needed to estimate a mean catch rate with specified precision was a function of sample duration, catch per hour, and travel time. More effort was needed as catch rate decreased and travel time increased, but the relation between sample duration and total effort was parabolic. Short‐duration samples (5 and 10 min) generally resulted in greater total effort as catch rate decreased and travel time increased. In contrast, although more samples were needed, short‐duration samples resulted in less total effort when travel time between sample sites was shorter than about 30 min. Long‐duration samples (50 and 60 min) were more efficient only when travel time was long and catch rates were low. Samples of intermediate duration were generally the least efficient.

We evaluated electrofishing catch per effort in 27 state‐operated fishing lakes in Mississippi to identify patterns of centrarchid community composition and to determine whether those patterns were related to selected environmental characteristics and to artificial nutrient enrichment. Ordination with detrended correspondence analysis recognized two major axes accounting for 77% of the variability in species ordination. Axis 1 showed a distinct separation between the body sizes of various species. A notable exception was the density of small (<30 cm) largemouth bass Micropterus salmoides, which aligned with the large individuals of other centrarchid species. This pattern suggested that through predation, high densities of small largemouth bass exerted significant control over the size structure of fish communities. Axis 2 separated species of crappies Pomoxis spp., suggesting that conditions other than strong species interactions also moderated the composition of crappies in the assemblages. However, neither lake morphometry nor watershed composition exhibited a major influence over axes 1 or 2. In small, intensively managed lakes with low habitat complexity, the regulatory importance of biotic interactions may overwhelm that of abiotic factors. Nutrient enrichment influenced community structure by changing the densities of bluegill Lepomis macrochirus and largemouth bass substantially but had a minor or no effect on other species. The management techniques used in these state‐operated lakes are usually targeted toward a particular species without adequately considering the other species within the community. Our results show that attention to community‐level interactions could provide valuable insight into factors that affect the quality of the fishery, insight that is not available through traditional population‐level assessments.

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