Growth Of Largemouth Bass Research Articles

Evaluation of Four Commercial Grower Diets for Production of Largemouth Bass

We compared performance (growth, survival, condition, and health indices) of largemouth bass, Micropterus salmoides, fingerlings (10.3 g [SE ± 0.5 g] and 92 mm [SE ± 1 mm] total length) fed one of four commercial grower feeds: Purina Aquamax Grower 400 (PAG; PMI Nutrition International LLC), Bio-Oregon BioDiet Grower (BDG; Bio-Oregon), Silver Cup Steelhead (SCS; Silver Cup), and Richloam Bass Fry Diet 12 (RBF; Silver Cup). Sixteen 833-L circular tanks, connected in parallel to a recirculation system, were initially stocked with 2.25 kg of fish (219 fish each, 0.32 fish/L) with four replicates per feed treatment. Water temperature was 25°C, and photoperiod was 15 h light:9 h dark. Feed sizes (2.4–3.0 mm) were comparable, and protein compositions ranged from 49% to 61%. Fish were fed to satiation multiple times per day (trial duration = 100 days). Overall, performance was best for fish fed RBF, followed by PAG and BDG, and then SCS. The SCS feed resulted in significantly lower growth and survival (P ≤ 0.05). The PAG and BDG feeds resulted in significantly lower growth than the RBF feed (P ≤ 0.05); however, survival did not differ (P > 0.05). Performance measures were positively correlated with protein, and protein to energy ratio and negatively correlated with fat and carbohydrate compositions. The four commercial grower feeds resulted in highly varied growth, survival, and health indices, and this research should facilitate feed choice for various largemouth bass production strategies as well as increase contribution of stocked fish.

Effect of dietary vitamin E and selenium supplementation on growth, body composition, and antioxidant defense mechanism in juvenile largemouth bass (Micropterus salmoide) fed oxidized fish oil

Six oxidized fish oil contained diets were formulated to investigate the effect of graded levels of vitamin E (V(E)) (α-tocopherol acetate: 160, 280, and 400 mg kg(-1)) associated with either 1.2 or 1.8 mg kg(-1) selenium (Se) on growth, body composition, and antioxidant defense mechanism of juvenile largemouth bass. Another control diet containing fresh fish oil with 160 mg kg(-1) V(E) and 1.2 mg kg(-1) Se was also prepared. Over a 12-week feeding trial, about 5 % of Micropterus salmoide fed diet OxSe1.2/V(E)160 showed inflammation and hemorrhage symptoms at the base of dorsal, pectoral, and tail fin. Fish in all treatments survived well (above 90 %). Feed intakes (88.42-89.58 g fish(-1)) of all treatments were comparable. Growth performances (weight gain and specific growth rate) and feed utilization (feed and protein efficiency ratio) were significantly impaired by dietary oil oxidation, and they did not benefit from neither V(E) nor Se supplementation. Regardless of dietary V(E) and Se supplementation, oxidized oil ingestion resulted in markedly decreased hepatosomatic index and intraperitoneal fat ratio. Oxidized oil ingestion also induced markedly lower liver and muscle lipid contents, and these effects could be alleviated by dietary Se supplementation. Dietary oil oxidation stimulated hepatic catalase activities relative to the control, and supplementation of V(E) abrogated this effect. Hepatic reduced glutathione content in the control was markedly higher than that of treatment OxSe1.2/V(E)160, without any significant differences comparing with the other oxidized oil receiving groups. Hepatic glutathione peroxidase activity and liver Se concentration reflected dietary Se profile, whereas liver V(E) level reflected dietary V(E) profile. Compared with the control, fish fed diet OxSe1.2/V(E)160 obtained markedly higher serum, liver and muscle malondialdehyde contents, which droppe significantly with increasing either V(E) or Se supplementation. In conclusion, the overall results in this study suggested that both V(E) and Se inclusion could protect largemouth bass from the oxidative damage challenged by dietary oil oxidation.

Effects of lipid sources and lipid peroxidation on feed intake, growth, and tissue fatty acid compositions of largemouth bass (Micropterus salmoides)

A 12-week growth trial was conducted to study the effects of replacement of fish oil (FO) with four alternative lipid sources (soybean oil, SO; beef tallow, BT; poultry fat, PF and; palm oil, PO, respectively) on the growth performance, feed intake (FI), and fatty acid (FA) composition in muscle and liver of largemouth bass (Micropterus salmoides) with initial body weight of 6.6 ± 0.01 g. Five isonitrogenous and isoenergetic diets were formulated and added with 5.5 % of each lipid sources, and FO was used as a control group. Until week 8 of the experiment, fish were fed on diets that were conserved at −20 °C, and fish were fed diets that oxidized at 28–30 °C with natural illumination for 4 weeks during 8–12 week. After 8 weeks of growth trial, specific growth rate and feed conversion of largemouth bass fed BT diet were significantly lower and higher, respectively, than that other dietary treatment (P 0.05). However, growth performance precisely reversed during 8–12 week, and finally, no significant difference was found on growth during 1–12 week. The FA compositions of fish muscle and liver of each treatment reflected the corresponding dietary FA compositions. These results suggested that largemouth bass was sensitive to both of lipid sources and lipid oxidation. Fresh FO, SO, and PF could be optimal lipid sources. Likewise, slightly oxidation of these oils would negatively affected fish growth performance.

The ability of zoning and land acquisition to increase property values and maintain largemouth bass growth rates in an amenity rich region

Land use change is a leading cause of environmental degradation in amenity rich rural areas. Numerous policies have been used to combat these negative effects, including zoning and land acquisition. The empirical effects of these policies on the environment and land markets are still debated. Using a coupled economic–ecological model in conjunction with landscape simulations we investigate the effect of zoning and land acquisition on property prices and largemouth bass (Micropterus salmoides) growth in Vilas County, WI, an amenity rich region with growing rural development. Using econometric models of land use change and property prices, we simulate four alternative land use scenarios: a baseline simulation, a zoning change simulation, a land acquisition program simulation, and a land acquisition program+zoning simulation. Each scenario is simulated over 82 separate lakes. For each scenario we calculate the length of a 20-year old largemouth bass, property prices, and number of new residences at simulation years 20, 40 and 60. The policies have small effects on largemouth bass size and property prices on most lakes, although the effects are more pronounced on some. We also test if the increased property values due to land acquisitions are greater than the cost of the land acquisition program and find that in our case, land acquisition does not “pay for itself”. Our methodology provides a means to untangle the complex interactions between policy, land markets, and the environment. Empirically, our results indicate zoning and land acquisition are likely most effective when targeted to particular lakes.

Growth and morphological characteristics comparison of northern large-mouth bass, Florida largemouth bass and their reciprocal hybrids

Based on northern largemouth bass and florida largemouth bass, four populations including selfing of N(Micropterus salmoides salmoides ♀×M. s. salmoides♂) and F(M. s. floridanus ♀×M. s. flori-danus♂), direct cross NF(M. s. salmoides♀×M. s. floridanus♂) and FN(M. s. floridanus♀×M. s. sal-moides♂) were established. Further comparative analysis of growth and morphological characteristics were carried out between parents and their reciprocal hybrids. The results were as follows. The growth rates had no difference between N, NF and FN on 152nd day. After 152 days the northern largemouth bass grew more rapidly than two hybrids. As meristic characters, the numbers of soft ray of pelvic, spine of anal fin, gill raker and vertebra were consistent in these four populations, and the chi-square analysis of meristic characters showed highly significant differences between parents and hybrids in soft ray of dorsal, soft ray of pectoral, soft ray of anal fin, soft ray of tail fin, scales above lateral line and scales below lateral line. The results of cluster analysis have revealed that the morph metric characters of N and F were much closer, the same to the reciprocal hybrids groups. Three principal components with accumulative variance per-centage 71.44% were summarized in principal component analysis. The principal components 1, 2 and 3 reflected the morphological variations of frame, head and caudal peduncle, with the variance percentage being 54.90%, 11.20% and 5.33%. In discriminant analysis, 11 parameters were selected from 35 measured parameters to establish discriminant functioned of the populations. Discriminant accuracy was 83.90%—100.00%. This study would be beneficial to the identification, breeding and aquaculture of largemouth bass.

Invasive carp and prey community composition disrupt trophic cascades in eutrophic ponds

The role of trophic cascades in structuring freshwater communities has been extensively studied. Most of this work, however, has been conducted in oligotrophic northern lakes that contain highly vulnerable cyprinid prey: aquatic communities where trophic interactions are likely to be stronger than in many other systems. Fewer studies have been conducted in eutrophic systems or have examined the bottom-up effects of benthivorous fishes, and none have directly compared these effects to those of piscivores on ecosystem structure and function. We conducted enclosure experiments in eutrophic ponds to examine trophic effects of invasive benthivores (common carp—Cyprinus carpio L.), native piscivores (largemouth bass—Micropterus salmoides [Lacepede]), and their interactions with common centrarchid prey with well-developed anti-predatory behaviors (age-1 bluegill—Lepomis macrochirus Rafinesque and young-of-year largemouth bass). At the end of the 60-day experiment, common carp had strong bottom-up effects that increased total phosphorus and turbidity while decreasing chlorophyll a biomass and macrophyte cover that resulted in decreased macroinvertebrate biomass and also decreased growth in both juvenile largemouth bass and bluegill. Piscivorous largemouth bass, however, did not affect the survival of either planktivorous juvenile largemouth bass or bluegill. Growth of juvenile largemouth bass was also not affected, but juvenile bluegill growth was significantly diminished, possibly due to nonconsumptive effects of predation. Our results suggest that, in a centrarchid-dominated eutrophic system, top-down effects of predators are overwhelmed by common carp-mediated bottom-up effects. These bottom-up effects strongly affected multiple trophic levels, thus altering aquatic community structure and function.

Lakeshore residential development and growth of largemouth bass (Micropterus salmoides): a cross‐lakes comparison

Gaeta JW, Guarascio MJ, Sass GG, Carpenter SR. Lakeshore residential development and growth of largemouth bass (Micropterus salmoides): a cross‐lakes comparison. Ecology of Freshwater Fish 2011: 20: 92–101. © 2010 John Wiley & Sons A/SAbstract – Lakeshore residential development is associated with changes in littoral habitat, riparian habitat, and ecosystem function with potential impacts ramifying through aquatic food webs. Effects of these changes on economically important game fishes may vary with fish size. We investigated largemouth bass (Micropterus salmoides) size‐specific growth rates across 16 lakes spanning the range of lakeshore residential development in Wisconsin’s Northern Highland Lake District using a longitudinal multilevel model. Growth rates of small fish had a strong positive relationship with lakeshore residential development. The strength of the relationship decreased with length and became increasingly negative for fish longer than 210 mm. This pattern may be driven by a release from density‐dependent growth, shifts in available prey sources, reduced macrophyte cover, or angling‐induced selection pressures. Regardless of the mechanism, our results indicate, relative to undeveloped lakes, largemouth bass in highly developed lakes take 1.5 growing seasons longer to enter the fishery (356 mm).

Investigating Interactions between Channel Catfish and other Sport Fishes in Small Impoundments

AbstractThe channel catfish Ictalurus punctatus is a popular sport fish commonly maintained by annual stocking in small impoundments. We sought to determine whether channel catfish negatively affect two other sport fishes (bluegill Lepomis macrochirus and largemouth bass Micropterus salmoides) in Alabama's state public fishing lakes (ASPF lakes) through competition or predation. Using a variety of gears, we sampled channel catfish, largemouth bass, and bluegills in 12 ASPF lakes with variable channel catfish stocking and harvest rates. Four of these lakes were sampled more intensively to quantify the diets of these three species. Bioenergetics simulations were used to predict the annual consumption of channel catfish and largemouth bass populations of average density, size structure, and growth from these impoundments. Metrics of growth, condition, abundance, and population structure were not related between species. Latitude was negatively related to channel catfish growth. The diets of channel catfish and bluegills were moderately similar across all seasons in all lakes, while those of channel catfish and largemouth bass were highly dissimilar. Within species, diet similarity was high among lakes. Bioenergetics simulations suggest that the channel catfish populations in these lakes consume relatively little fish, particularly when compared with a typical largemouth bass population. We found little evidence of negative effects of channel catfish on the bluegill and largemouth bass populations in ASPF lakes, although largemouth bass growth and condition were poorest in the lake with the highest channel catfish stocking rate. However, current stocking and exploitation rates in most lakes appear to maintain channel catfish abundance below the level at which negative effects may occur.

Mandatory Catch and Release and Maximum Length Limits for Largemouth Bass in Minnesota: Is Exploitation Still a Relevant Concern?

AbstractWe evaluated the response of Minnesota populations of largemouth bass Micropterus salmoides to implementation of 305‐mm maximum total length (TL) limits (three lakes) and mandatory catch‐and‐release regulations (six lakes). Responses were compared with population trends observed in nine reference populations where largemouth bass harvest was regulated by prevailing statewide regulations. Increased harvest regulation generally improved largemouth bass size structure, but statistically significant improvements in size structure indices were detected in only a few individual lakes. Increased regulation of harvest did not appear to influence electrofishing catch per unit effort (CPUE; fish/h) of largemouth bass less than 381 mm TL. Electrofishing CPUE of fish greater than or equal to 381 mm TL (CPUE‐381) generally improved after more stringent harvest regulations were in place, but improvements were only significant for two of the three lakes where a 305‐mm maximum length limit was implemented. With the exception of one lake, increased harvest regulation did not appear to reduce largemouth bass growth rates. Improvements in size structure and CPUE‐381 were rarely observed in reference lakes. Our results suggest that despite increases in voluntary catch and release of largemouth bass, angler exploitation is still an important factor regulating size structure in some Minnesota lakes, and more intensive harvest regulations can improve size structure in some populations.

Climate–growth relationships for largemouth bass (Micropterus salmoides) across three southeastern USA states

Abstract – The role of climate variability in the ecology of freshwater fishes is of increasing interest. However, there are relatively few tools available for examining how freshwater fish populations respond to climate variations. Here, I apply tree‐ring techniques to incremental growth patterns in largemouth bass (Micropterus salmoides Lacepède) otoliths to explore relationships between annual bass growth and various climate metrics in the southeastern USA. Among six rivers and seven reservoirs in Georgia, Alabama, and Mississippi, strong correlations between annual bass growth indices and climate were detected (73 of 96 possible correlations were significant at α < 0.05). All but two ecosystems exhibited the following pattern: annual bass growth was significantly negatively correlated with annual precipitation metrics, and significantly positively correlated with annual temperature metrics. Based on multiple regressions, climate, on average, accounted for ∼50% of variability (R2) in bass growth, although these values ranged from 28% to 65% depending on the ecosystem. Furthermore, every population showed significant correlations with at least one of the following global climate factors: El Niño‐Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), and the Arctic Oscillation (AO). Largemouth bass growth in the southeast is apparently influenced by climate in major ways. Fish ecologists and managers in the region should be aware of the strong links between annual climate conditions and annual fish growth.

Effects of Common Carp on Reproduction, Growth, and Survival of Largemouth Bass and Bluegills

AbstractThe common carp Cyprinus carpio was introduced to North America more than a century ago, but little research has focused on interactions between this invasive species and native fishes. We used large mesocosms (600 m2) within drainable 0.4‐ha ponds to examine the effects of adult common carp on (1) reproduction of largemouth bass Micropterus salmoides and bluegills Lepomis macrochirus and (2) growth and survival of the larvae and juveniles of these centrarchid species. In separate enclosures, adult bluegills or largemouth bass were stocked with or without common carp. In enclosures with common carp, turbidity was substantially higher, but both centrarchid species spawned and the densities and sizes of larval largemouth bass and bluegills were similar to those of larvae in enclosures without common carp. As juveniles grew, largemouth bass survived at a higher rate but were smaller in enclosures containing common carp compared with largemouth bass in enclosures without common carp. In a second experiment, we stocked known numbers of older juvenile centrarchids into enclosures and found decreased growth for both largemouth bass and bluegills. However, survival of largemouth bass was again higher in enclosures with common carp. Although centrarchid spawning was successful and larval growth and survival did not decrease in the presence of common carp, centrarchid growth slowed at the juvenile stage, probably due to food resource limitation resulting from direct competition with common carp for invertebrate forage, high turbidity caused by common carp, or both of these factors.

The Effect of Water Temperature on Growth and Survival of Largemouth Bass during Feed Training

AbstractWater temperature could be an important factor during the feed training phase of largemouth bass Micropterus salmoides production, as it could affect appetite and starvation time. We evaluated three water temperatures during largemouth bass feed training. Pond‐reared largemouth bass fingerlings (weight = 2.1 ± 0.6 g [mean ± SE]) were randomly stocked into twelve 0.5‐m3 polyethylene cages to achieve a stocking density of 350 fish per cage. The cages were suspended in six 3,800‐L polyethylene tanks with a common water source housed in a greenhouse with four replicate cages per water temperature treatment (20, 24, and 28°C). Each tank contained two cages, and there were two tanks per treatment temperature. In each cage, fingerlings were initially fed freeze‐dried krill, then gradually weaned onto a commercial pellet (floating trout feed; 1.5 mm) over a 24‐d period according to an established training protocol. At harvest, the average weight and the percentage of fish successfully trained to commercial feed were significantly different among temperatures (P ≤ 0.05), increasing as water temperature increased (weights averaged 5.4, 6.8, and 7.8 g and percent trained averaged 70, 82, and 90% for fish feed‐trained at 20, 24, and 28°C, respectively). The results from this experiment indicate that water temperature has a significant effect on feed training success and the average weight of feed trained largemouth bass.

The influence of littoral zone coarse woody habitat on home range size, spatial distribution, and feeding ecology of largemouth bass (Micropterus salmoides)

Coarse woody habitat (CWH) may be a critical feature of lakes that influences fish distributions, movement patterns, and feeding habits. We used radio telemetry to examine the role of CWH in determining the movements of largemouth bass (Micropterus salmoides Lacepede) in the context of two whole-lake experiments that provided a gradient of four lake basins varying in natural and manipulated CWH. We also conducted diet studies on largemouth bass in these lakes to test for correlates among consumption rate and prey selectivity with bass behavior. Our results indicated that largemouth bass in basins with lower CWH abundances had larger home ranges, spent more time in deep water, were more selective predators, and showed lower consumption rates. Largemouth bass in basins with higher CWH abundances showed the opposite patterns. Low CWH abundances were correlated with a shift in largemouth bass foraging behavior from sit-and-wait to actively searching. This increased activity, coupled with the potential decline of prey fish species in the absence of CWH, may decrease largemouth bass growth potential regardless of the prey type consumed. Our results suggest that lakeshore residential development and associated removals of CWH from lakes may influence fish behavior, while CWH augmentation may reverse some of those changes.

Latitudinal Influence on First‐Year Growth and Survival of Largemouth Bass

AbstractWe examined the effects of latitude of origin on the first‐year growth and survival of largemouth bass Micropterus salmoides. We brought largemouth bass from three latitudinally disparate populations (northern largemouth bass M. s. salmoides from south‐central Wisconsin; Florida largemouth bass M. s. floridanus, originally from central Florida but currently stocked throughout Alabama; and native northern largemouth bass from southern Alabama) to a common rearing environment to compare their age‐0 growth over two replicate growing seasons. During 1999, the northern subspecies from Wisconsin grew faster than the northern or Florida subspecies from Alabama. However, in 2000 the Florida subspecies grew faster than the age‐0 fish from either northern subspecies population. Our results indicate that the effects of prey availability and age‐0 density can overwhelm any predisposition for growth based on latitudinal or genetic origin. Given concerns about the genetic consequences of largemouth bass stockings, the lack of any consistent growth advantage in the first year represents an important piece of information to be taken into account when deciding about stocking nonnative subspecies of largemouth bass.

Comparison of Diploid and Triploid Largemouth Bass Growth and Maturation through Age 1 in Puerto Rico

AbstractTriploid largemouth bass Micropterus salmoides could be valuable both in sport fish management and in food fish production. This study compared the growth and reproductive development of diploid and triploid largemouth bass through age 1 in Lucchetti Reservoir, Puerto Rico. We produced and stocked 487 diploids and 477 triploids tagged with binary coded wire tags and recaptured these fish over 2 years. Growth rates, condition (relative weight (Wr)), and reproductive investment (gonadosomatic index (GSI)) were compared for diploid and triploid fish. Rates of mean daily growth did not differ between diploids (0.81 mm/d; SE = 0.07) and triploids (0.91 mm/d; SE = 0.09) as juveniles or overall through age 1. Diploid largemouth bass exhibited advanced reproductive development during age 1, while triploids did not. Mean GSI was higher for diploid females (mean = 1.98; SE = 0.81) than for triploid females (mean = 0.29; SE = 0.05), but male mean GSI did not significantly differ between the two groups. No difference in Wr was observed. Experimental fish in this study reached maturity in the middle of the spawning season at age 1 and therefore may not have reproduced. Additional research on triploid largemouth bass beyond age 1 is necessary to determine whether sterile triploids have growth advantages over reproductive adult diploids.

Effects of Graded Levels of Carbohydrate on Growth and Survival of Largemouth Bass, Micropterus salmoides

Abstract Excessive carbohydrates (CHO) in diets for largemouth bass (LMB), Micropterus salmoides, are suspected of accumulating glycogen in hepatocytes, which may result in liver dysfunction. This study evaluated the effect of graded levels of dietary CHO on growth, survival, and liver histology of LMB. One hundred feed‐trained advanced fingerling LMB (128.5 ± 21.5 g) were stocked into each of nine 3400‐L polyethylene tanks. Tanks were randomly assigned one of three experimental diets containing different CHO levels (13, 19, or 25% of diet). The extruded diets were approximately isonitrogenous (42% crude protein) and isocaloric (3 kcal/g energy). There were three replicate tanks per dietary treatment. Bass were fed to apparent satiation twice daily for 148 d. Survival was significantly higher (P ≤ 0.05) for fish fed the 13 and 19% CHO diets (89 and 90%, respectively) compared to those fed the 25% CHO diets (82%). Average harvest weight of fish fed the 13% CHO diet (380 g) was significantly greater (P ≤ 0.05) than for fish fed other diets. Average harvest weight of fish fed the 19% CHO diet (347 g) was significantly greater (P ≤ 0.05) than for fish fed the 25% CHO diet (310 g). Specific growth rates (%/d) were significantly higher (P ≤ 0.05) in fish fed the 13 and 19% CHO diets than in fish fed 25% CHO diet. Feed conversion ratios for fish fed the 13 and 19% CHO diets (2.3 and 2.4, respectively) were both significantly lower (P ≤ 0.05) than in fish fed the 25% CHO diet (3.6). There were no significant differences (P > 0.05) in condition factor, protein efficiency ratio, hepatosomatic index, or liver glycogen concentration among fish fed the different experimental diets. Overall, mean blood glucose levels in fish fed the 13 and 19% CHO diets (61.0 and 71.2 mg/dL, respectively) were significantly lower (P ≤ 0.05) than in fish fed the 25% CHO diet (87 mg/dL). Histopathological examination of livers from fish fed the three diets was used to score the degree of vacuolization of hepatic tissues (0 = normal, 1 = slight, 2 = mild, 3 = moderate, and 4 = severe). Regression of vacuolization scores on dietary CHO levels was statistically significant (P ≤ 0.05) and indicated a direct positive relationship between liver vacuolization and dietary CHO level (R2 = 0.57). These data indicate that LMB grow faster and use feeds more efficiently when CHO are maintained at <20% of diet. CHO levels >20% negatively impacted liver histology, but a liver tissue analyses did not document glycogen accumulation.

Effects of Different Types of Dietary Lipids on Growth and Fatty Acid Composition of Largemouth Bass

AbstractThe effects of feeding diets supplemented with oils of varying sources and fatty acid compositions on growth, survival, and biochemical composition of juvenile largemouth bass Micropterus salmoides were evaluated under controlled conditions in aquaria for 12 weeks. Feed‐trained juvenile largemouth bass (15.7 ± 0.6 g) were stocked into eighteen 114‐L glass aquaria at 25 fish/tank and were fed one of five experimental diets (3 replicate aquaria/diet). All diets were formulated to be approximately isocaloric (4,200 kcal gross energy per kilogram) and isonitrogenous (40% crude protein), containing protein primarily from solvent‐extracted fish meal and soybean meal. Each diet was supplemented with 5% oil (by weight) using lipids from various sources and with different fatty acid compositions. These included fish oil, corn oil, sunflower oil (high oleic), linseed oil, and a fungal oil (high arachidonic acid). Fish were fed twice daily to apparent satiation. At the end of the study period, there were no significant differences (P > 0.05) between treatment groups in terms of survival (98%), weight gain (595%), specific growth rate (2.2% per day), feed conversion ratio (1.5), percent protein deposited (28%), or hepatosomatic index (2.3). Whole‐body proximate composition was not significantly affected (P > 0.05) by source of added lipid, but whole‐body fatty acid composition showed large differences and primarily reflected the fatty acid compositions of added oils. Largemouth bass may be able to use diets containing vegetable‐ and animal‐source lipids, which are less expensive than the previously recommended fish oil.

Size‐specific growth of bluegill, largemouth bass and channel catfish in relation to prey availability and limnological variables

Growth of sympatric populations of three important sport fish species: bluegill Lepomis macrochirus, largemouth bass Micropterus salmoides and channel catfish Ictalurus punctatus, in 14 Illinois reservoirs was assessed in an attempt to relate size‐specific growth to environmental conditions. Multiple regression relationships for most species and size classes explained a large percentage of the variation in growth. Growth of small bluegill (50 mm total length, LT) showed a strong negative relationship with bluegill catch per unit effort (cpue), per cent littoral area and pH. Large bluegill (150 mm LT) growth was negatively related to Daphnia spp. and benthic macroinvertebrate abundance and lake volume, and positively related to bluegill cpue. Growth of small (100 mm LT) and large (250 mm LT) largemouth bass was not well explained by any of the measured variables. Growth of both small (300 mm LT) and large (450 mm LT) channel catfish was strongly positively related to forage fishes and ichthyoplankton abundance, and per cent littoral area while negatively related to benthic macroinvertebrates. By identifying environmental conditions associated with increased growth rates, these models provide direction for managing fish populations and suggest testable hypotheses for future study of the complex interactions between environmental conditions and growth.

A Bioenergetics‐Based Approach to Explain Largemouth Bass Size in Tropical Reservoirs

AbstractIn tropical systems where largemouth bass Micropterus salmoides have been introduced, maximum age is reduced to the point where few fish live beyond 3 years and adult growth rates are very slow. Concurrently, tropical largemouth bass have an extended spawning period (up to 8 months) and individual fish spawn multiple times each year. In this study, we examined the relationship between latitude and maximum size (record angler‐caught fish) of largemouth bass from temperate to tropical environments and tested the hypothesis that the slow growth of adult largemouth bass is the result of excessive energy reallocation to reproduction. State and national record‐sized largemouth bass were plotted against latitude for the USA, Cuba, Dominican Republic, Japan, Portugal (European record), Mexico, and Puerto Rico. Largemouth bass maximum weight increased as latitude decreased from 46.8°N; peak maximum weight occurred at 27.9°N. Below 27.9°N, largemouth bass size records decreased as latitude decreased (R2 = 0.67, P < 0.0001). Bioenergetics models were used to model observed growth (in Puerto Rico) and predicted growth based on a 2% mean daily ration (MDR), and reproduction scenarios were used to explain the difference between observed and predicted growth. The predicted weight in Puerto Rico was 2.7 times higher than observed weight during a simulated 6‐month spawning season. This discrepancy could be accounted for by a range of spawning frequencies (events per season) and levels (percent body weight per spawn) for females (e.g., 10 spawns at 6% body weight per spawn). Similarly, a 15% decrease in MDR of nest‐guarding males due to reduced ability to feed accounted for the difference between predicted and observed growth.

First-year growth and recruitment of coastal largemouth bass (Micropterus salmoides): spatial patterns unresolved by critical periods along a salinity gradient

Although critical periods often explain first-year growth and recruitment patterns of young fishes, isolated subpopulations in spatially heterogeneous environments can be influenced by distinct factors, preventing critical periods from explaining growth and recruitment for the overall population. When we explored first-year growth and recruitment variability of largemouth bass (Micropterus salmoides) along an upstream–downstream gradient in the Mobile–Tensaw Delta, Alabama, USA, growth was consistently faster at sites closest to or within brackish habitats in 2002 and 2003, despite different abiotic conditions between years. Energetic content of food consumed by faster-growing fish, particularly those furthest downstream, was greater than that for slower-growing fish. Although the timing of the switch to piscivory did not explain growth differences, the degree of piscivory was important. Hatch date had no influence on growth differences and consequently did not affect fall condition, overwinter survival, or age-1 recruitment. Contrary to several studies in freshwater systems at this latitude, first-winter mortality was neither size-selective nor excessive, and largemouth bass continued to grow through the winter. These results demonstrate that early growth can vary substantially among subpopulations in spatially heterogeneous environments and that these differences are not necessarily explained by the same factors thought to be important for freshwater largemouth bass populations.