Robert S. Hayward

Use of Compensatory Growth to Double Hybrid Sunfish Growth Rates

Abstract We studied the use of compensatory growth (CG) to grow fish larger than control fish that were fed every day without restriction. Five treatment groups of 10 juvenile hybrid sunfish (F1 hybrid of female green sunfish Lepomis cyanellus × male bluegill L. niacrochirus) received repeating cycles of no feeding and refeeding; fixed no-feed periods of either 2, 4, 6, 10, or 14 d distinguished the treatment groups. No-feed periods elicited the CG state and were immediately followed by days of ad libitum refeeding. Refeeding periods within each treatment group (D2, D4, D6, D 10, or D14) were continued until mean daily food consumption by fish no longer exceeded that of controls fed ad libitum every day (i.e., ad libitum refeeding was continued for as long as hyperphagia persisted, then another no-feed period began). Fish in two groups, D2 and D 14, consumed more food and significantly outgrew controls by 2 and 1.4 times, respectively, in 105-d experiments. Gross growth efficiency (GGE, fish weight gained...

Effect of feeding frequency on food consumption, growth, size variation, and feeding pattern of age-0 hybrid sunfish.

Four treatment groups of age-0 hybrid sunfish (female green sunfish Lepomis cyanellus×male bluegill L. macrochirus) were fed to satiation at one of four frequencies (one, two, three or four meals per day) for 30 days. Fish fed three and four times daily showed the greatest consumption and growth rates; food conversion ratios did not differ among the four treatments (P>0.05). Because growth and food conversion were not enhanced when feeding was increased from three to four times daily, the optimal feeding frequency for growth was considered to be three times per day. However, the extent of inter-individual size variation (% change in CV) declined with increasing number of daily feedings (P<0.05), suggesting that more frequent feeding may produce fish of more uniform sizes. Daily feeding patterns also changed in response to feeding frequency, indicating that when fish are fed at a particular frequency, knowledge of feeding pattern is necessary so that appropriate food amounts can be supplied at each provisioning. Our results suggest that an optimal feeding frequency should be determined not only on the basis of growth and food conversion efficiency, but also according to influences of daily feeding pattern and the desire to achieve size uniformity.

Group holding impedes compensatory growth of hybrid sunfish.

An earlier study with a repeating no-feed/refeed schedule (D2 schedule) elicited compensatory growth (CG) in age-0 hybrid sunfish (F1: female green sunfish, Lepomis cyanellus×male bluegill L. macrochirus) held individually and fed ad libitum on feeding days. Weight gain under these conditions exceeded that of daily-fed controls. The present study sought to determine whether similar growth improvement would result when hybrid sunfish were held in groups and fed to satiation on the D2 schedule. In Experiment 1, age-0 hybrid sunfish were held in groups of 10 fish per 25-l chamber at 24°C and fed four times daily to apparent satiation on feeding days. Under this regime, fish fed according to the D2 schedule gained less weight than the controls (P<0.10). Experiment 2 was run in an effort to duplicate the results of the previous study. When age-0 fish were held individually at 24°C and fed ad libitum on feeding days, those fed on the D2 schedule gained significantly more weight (P<0.10) than the controls. These results indicate that group holding in combination with satiation feeding impedes the full expression of the CG capacity of hybrid sunfish. The major impediment under group holding may be the negative effects of social interactions on food consumption and growth efficiency.

Variation in food consumption, growth, and growth efficiency among juvenile hybrid sunfish held individually

Abstract Daily food consumption, growth, and gross growth efficiency (GGE) were studied in juvenile hybrid sunfish (female green sunfish, Lepomis cyanellus×male bluegill, Lepomis macrochirus) fed ad libitum and held individually for 112 days. There were substantial inter-individual differences in food consumption; mean specific daily ration differed significantly (P

Laboratory Evaluation of a Bioenergetics Model for Largemouth Bass at Two Temperatures and Feeding Levels

Abstract We evaluated a bioenergetics model for adult largemouth bass Micropterus salmoides at two temperatures (22°C and 27°C) and two feeding levels (ad libitum and 2% wet body mass) in the laboratory. Three statistical methods were used to assess agreement between predicted and observed growth and consumption during a 9-week period. Multivariate profile analysis indicated no significant deviations between predicted and observed mean body masses at the end of each week of the experiment; partitioning mean square error revealed that 87% of the variance was attributed to random variation rather than to systematic variation; and a reliablility index indicated agreement between predicted and observed masses within a factor of 1.03. Predicted cumulative food consumption during the 9-week period was 9.4% less than that observed. Model predictions of mean daily consumption rates closely tracked observed values when fish were not fed to excess, but the model did not perform as well under ad libitum feeding cond...

Temperature Dependence of Maximum Daily Consumption in White Crappie: Implications for Fisheries Management

Abstract Maximum daily consumption (C max) by adult white crappies Pomoxis annularis (164–532 g live weight) provided ad libitum rations of prey fish was determined at 18, 21, 24 and 27°C. Observed increases in C max between 18 and 24°C followed by a sharp (two-thirds) decline at 27°C indicated that a low to negative physiological “scope for growth” exists for white crappies at 27°C and above. Examination of temperature and dissolved oxygen (DO) profiles from numerous Missouri impoundments for May–August 1991 suggested that white crappies were forced to occupy water of 27–32°C (warm water) in 40% of these impoundments by early June and 85% by early August. White crappies were forced into warm water in only a slightly lower percentage of the deep (>5 m) impoundments we examined than in shallow (≤5 m) ones. Evaluation of year-to-year differences (1988–1991) in time periods when white crappies were forced to occupy warm water in Lake Pomme de Terre, Missouri, showed that range (15–64 d) and time of occurrenc...

Testing Bioenergetics Models under Feeding Regimes That Elicit Compensatory Growth

Abstract We tested bioenergetics model predictions of fish growth and food consumption under feeding regimes that elicited compensatory growth (CG) responses and for control fish fed ad libitum daily. Three treatment groups of seven juvenile hybrid sunfish (F1 hybrid of female green sunfish Lepomis cyanellus × male bluegill L. macrochirus) received repeating cycles of no feeding and refeeding; fixed no-feed periods of either 2, 4, or 14 d distinguished the treatment groups. The no-feed periods induced CG and were immediately followed by days of ad libitum refeeding. The refeeding periods for each treatment group were continued until the groups mean daily consumption no longer exceeded that of the controls, after which another no-feed period began. Bioenergetics model predictions of cumulative consumption and fish weight in 105-d experiments were not significantly different from observed values in the control group (2–3% model error). However, the model underestimated cumulative consumption (18–25%) and o...

Effects of Social Interaction on Growth of Juvenile Hybrid Sunfish Held at Two Densities

Abstract The effects of competitive social interaction on cumulative food consumption (CC), absolute growth rate (AGR), gross growth efficiency (GGE), and development of interindividual weight variation were quantified for juvenile hybrid sunfish (F1: Female green sunfish Lepomis cyanellus × male bluegill L. macrochirus) held in low-density (5 fish in 25 L) and high-density (20 fish in 25 L) groups for 50 d. Individually held hybrid sunfish without social interaction were used as controls. All groups were fed a commercial diet to apparent satiation three times daily. Mean CC, AGR, and GGE declined 7% and 24%, 21% and 34%, and 14% and 15%, in the low- and high-density groups, respectively, relative to controls. Patterns of declining CC and GGE with increasing fish density indicated that elevated activity and stress from social interaction caused much of the growth decline at the low density, while reduced food consumption caused the additional growth loss at the high density. Coefficients of weight variati...

Bioenergetics Insight into Black Bass Distribution Shifts in Ozark Border Region Streams

Abstract Population densities of smallmouth bass Micropterus dolomieu (SMB) have declined in streams of the Missouri Ozark border region since the 1940s while replacement by largemouth bass M. salmoides (LMB) has occurred in some cases. A recent field study found that two habitat variables, known to have been influenced by human activities, largely explained present densities of SMB and LMB throughout streams in this region. Densities of SMB declined with increasing maximum summer temperature (range, 23–33°C) and percent pool area while LMB densities increased with these variables. To explore these correlations from a bioenergetics perspective, we determined maximum consumption rates of SMB and LMB at 18, 22, 26, and 30°C. Consistent with the field studys findings about temperature, maximum consumption results indicated that SMB scope for growth becomes progressively restricted at temperatures higher than 22°C, whereas this does not occur until 26°C for LMB. Maximum consumption rates of SMB also averaged...

Inherent Growth Capacity and Social Costs of Bluegill and Hybrids of Bluegill and Green Sunfish: Which Fish Really Grows Faster?

Abstract There is interest in knowing whether the bluegill Lepomis macrochirus or a hybrid of bluegill and green sunfish L. cyanellus (F1: male bluegill × female green sunfish; hereafter called B × G hybrids) can be grown faster to food market size (225–340 g). The predominant view is that the hybrid grows faster. In this study, the inherent growth capacities (IGCs) of age-1 bluegills and B × G hybrids were determined over four successive 25-d periods (May–August 2000) by holding them individually at 22°C and feeding them to apparent satiation three times daily. The hybrids IGC was greater during period 1 but fell to only 33% of the bluegills over the three subsequent periods; the consumption and gross growth efficiency (GGE) of the hybrid showed similar declining patterns. The growth-in-weight trajectory of bluegills crossed above that of the hybrids at about 30 g. Gonadosomatic index values suggested that hybrid growth rates declined below those of the bluegill because the former invested more energy ...