Use of alternative protein sources for fishmeal replacement in the diet of largemouth bass (Micropterus salmoides). Part II: effects of supplementation with methionine or taurine on growth,feed utilization,and health

Fishmeal has long been a staple protein feedstuff for fish, but its global shortage and high price have prompted its replacement with alternative sustainable sources. In this experiment involving largemouth bass (a carnivorous fish), a new mixture of feedstuffs (45% poultry byproduct meal, 30% soybean meal, 15% blood meal, and 10% krill shrimp meal) was added to low (14.5%) fishmeal diets along with 0.0%, 0.5% taurine, 0.5% methionine, or 0.5% taurine plus 0.5% methionine (dry matter basis). The positive control diet [65.3% fishmeal (46% crude protein on dry matter basis)] and all low-fishmeal diets contained 40% true protein and 10% lipids. There were 3 tanks per treatment group (20 fish/tank). Fish with the mean initial body weight of 16.6 g were fed to satiety twice daily. Compared with the unsupplemented low-fishmeal group, supplementing either 0.5% methionine or 0.5% methionine plus 0.5% taurine to the low-fishmeal diet improved (P < 0.05) the growth, feed utilization, retention of dietary protein and lipids, and health of largemouth bass, reduced (P < 0.05) the occurrence of black skin syndrome from ~ 40 to ~ 10%. Histological sections of tissues from the fish with black skin syndrome showed retina degeneration, liver damage, and enteritis in the intestine. Compared with methionine supplementation, supplementing 0.5% taurine alone to the low-fishmeal diet did not affect the growth or feed efficiency of fish and had less beneficial effects (P < 0.05) on ameliorating the black skin syndrome. These results indicated that: (a) the basal low-fishmeal diet was inadequate in methionine or taurine; and (b) dietary supplementation with methionine was an effective method to improve the growth performance, feed efficiency, and health of largemouth bass. Further studies are warranted to understand the pathogenesis of the black skin syndrome in largemouth bass.

     

在低蛋白质饲料中补充必需氨基酸对大口黑鲈生长、体组成和免疫指标的影响

为了研究在低蛋白质饲料中补充晶体必需氨基酸对大口黑鲈生长、体组成和免疫指标的影响,根据鱼体的必需氨基酸组成模式设计了7种等能的试验饲料。其中4种饲料（45CP、40CP、35CP和30CP）的粗蛋白质水平分别为45%、40%、35%和30%,另3种饲料（40AA、35AA和30AA）是在低蛋白质饲料（40CP、35CP和30CP）的基础上添加必需氨基酸,使它们的必需氨基酸含量与45CP（对照组）相一致。用上述饲料对初始体重为（10.13 0.01） g的大口黑鲈进行了89d的饲养试验。饲养试验在室内循环水养殖系统中进行,每种饲料设3个重复,每重复放养30尾鱼。方差分析显示:试验鱼的生长性能、饲料效率、全鱼和肌肉的粗蛋白质含量、成活率以及免疫指标均随着饲料蛋白质含量的降低而显著降低（P0.05）。添加必需氨基酸的35AA和30AA的饲料效率和蛋白质保留率分别显著高于对应的未添加必需氨基酸的35CP和30CP组（P0.05）,但仍显著低于45CP组（P0.05）。40AA的试验鱼血清溶菌酶活性和血清补体活性与45CP组差异不显著（P0.05）。35AA和30AA组的头肾白细胞呼吸爆发活性显著高于35CP和30CP组（P0.05）。30AA组的全鱼粗蛋白质含量以及肥满度显著高于30CP（P0.05）。各组试验鱼的水分和灰分均无显著差异（P0.05）。回归分析显示:在低蛋白质饲料中补充晶体必需氨基酸对大口黑鲈幼鱼的生长、饲料效率和蛋白质保留率所产生的影响与其引起增加了的饲料蛋白质水平而不是饲料的必需氨基酸水平正相关。研究表明,在低蛋白质饲料中补充的晶体必需氨基酸对大口黑鲈的生长、体组成和免疫指标产生的有益作用不及等量的以蛋白质为来源的必需氨基酸。       

Predation of Japanese dace, Tribolodon hakonensis, by largemouth bass, Micropterus salmoides, in experimental aquaria

 To test the size range of prey fish that largemouth bass, Micropterus salmoides, can successfully consume, live Japanese dace, Tribolodon hakonensis, were given as prey fish to individual largemouth bass in aquaria. The ratio of maximum standard length (SL) of the Japanese dace consumed by largemouth bass was 46–69% of bass SL. The maximum length of Japanese dace consumed did not differ significantly between largemouth bass and smallmouth bass (M. dolomieu) previously studied, although largemouth bass have relatively larger mouth sizes than smallmouth bass. Largemouth bass occasionally injured and killed Japanese dace larger than the limit that could be consumed.     

发酵豆粕替代鱼粉对大口黑鲈幼鱼生长、脂质代谢、血清非特异性免疫及肠道菌群的影响

为探讨发酵豆粕替代鱼粉对大口黑鲈(Micropterus salmoides)幼鱼生长、脂质代谢、血清非特异性免疫及肠道菌群的影响, 试验在基础饲料中用发酵豆粕分别替代0、10%、20%、30%和40%鱼粉, 用晶体氨基酸平衡各组间蛋氨酸与赖氨酸的差异, 配制成共5种等氮等能(CP47%, GE19 MJ/kg)的试验饲料, 分别为FM、FSM10、FSM20、FSM30和FSM40。将初始体重为(22.05±0.09) g的大口黑鲈随机分成5组, 每组设3个重复, 养殖58d。生长试验结果表明: 各组之间增重率(WGR)、特定生长率(SGR)、肥满度(CF)、肝体比(HSI)和脏体比(VSI)均无显著差异(P>0.05), 但替代组饲料系数(FCR)均显著高于FM对照组(P<0.05), FSM40组的存活率(SR)和干物质表观消化率(ADDM)显著低于其余各组(P<0.05)。脂质代谢方面结果显示, FSM30和FSM40组的血清甘油三酯(TG)水平显著低于FM对照组(P<0.05), FSM40组的血清总胆固醇(T-CHO)水平显著低于FM对照组(P<0.05)。血清非特异性免疫方面结果表明, FSM40组的溶菌酶(LZM)和超氧化物歧化酶(SOD)活性有显著增加的变化(P<0.05)。对肠道菌群进行了Illumina Mi Seq高通量测序分析, 结果表明: 各组肠道菌群的Alpha多样性指数(Sobs、Shannon、Simpson、Ace和Chao)无显著差异(P>0.05), 但OTU数量发生了变化。在门水平上, 优势菌群为软壁菌门(Tenericutes)、变形菌门(Proteobacteria)和梭杆菌门(Fusobacteria); 而属水平上, 优势菌群为支原菌属(Mycoplama)、邻单胞菌属(Plesiomonas)和鲸杆菌属(Cetobacterium)。FSM20组与FM对照组相比, 软壁菌门和支原菌属的相对丰度显著提高(P<0.05), 变形菌门和邻单胞菌属的相对丰度显著降低(P<0.05)。综上所述, 在试验条件下, 大口黑鲈饲料中发酵豆粕替代20%鱼粉不会对大口黑鲈幼鱼生长、脂质代谢、血清非特异性免疫及肠道菌群多样性造成负面影响, 且能显著降低肠道中邻单胞菌属在内的有害菌的相对丰度, 因此, 发酵豆粕替代鱼粉的适宜比例为20%。     

Trophic position estimates of formalin-fixed samples with nitrogen isotopic compositions of amino acids: an application to gobiid fish (Isaza) in Lake Biwa, Japan

To evaluate the influence of formalin-fixation on the nitrogen isotopic composition of individual amino acids, we conducted a formalin-fixation experiment over 62 weeks using muscle tissues of largemouth bass (Micropterus salmoides) and freshwater minnow (Zacco platypus) collected in Lake Biwa. The results indicated that the formalin-fixation does not affect the nitrogen isotopic composition of amino acids including glutamic acid and phenylalanine from muscle protein of the fish. We applied this technique to formalin-fixed gobiid fish “Isaza” (Gymnogobius isaza, Tanaka) specimens that had been collected from Lake Biwa through the twentieth century. The pattern of the δ¹⁵N values for these amino acids remains relatively constant, even though each amino acid exhibits a gradual increase by ~3 ‰ from 1916 to 1992. With a formula proposed by Chikaraishi et al. (Limnol Oceanogr Method 7:740–750, 2009), we estimated the temporal variations in the trophic position of Isaza in Lake Biwa. The trophic position of Isaza remained quite constant (3.2–3.3) across a major eutrophication period in 1960–1980. The estimated trophic position of Isaza fish is consistent with the stomach content analysis in the previous reports. The constant trophic position suggests that the eutrophication did not apparently affect the trophic position of Isaza fish, although Isaza’s dietary preference changed from zooplankton to gammarids around 1970.     

Comparative energy metabolism in cultured heart muscle and hela cells

The yields of energy from oxidation of fatty acids, glucose, and glutamine were compared in cultures of chick embryo heart muscle (heart) and HeLa cells. Aerobic energy production, as measured by oxygen utilization, was comparable in the two cell types. In media containing dialyzed sera, the rates of incorporation of fatty acids directly into lipids were similar in both cells and accounted for > 97% of fatty acid metabolism in HeLa cells. However, in heart cells only 45% ended in lipid, 42% in protein, and 13% was released as CO₂; the latter two products probably reflect the oxidation of fatty acids to acetyl-coenzyme A (-CoA) and its subsequent metabolism in the citrate cycle. Increased serum concentration in the medium did not affect fatty acid metabolism in HeLa cultures, but resulted in greater oxidation by heart cells (> 100 times that by HeLa cells). The metabolisms of both glucose and glutamine were similar in heart and HeLa cells with ? 60% of glucose carbon ending as medium lactate and only 3–5% converted to acetyl-CoA. About 25% of glutamine carbon ended as CO₂ and increased utilizations with increasing serum concentrations was accountable in both cells by increased lactate from glucose and glutamate from glutamine. CO₂ production (and energy) from glutamine was independent of glutamine concentration within a tenfold range of physiological concentrations. The yields of energy have been calculated. In 10% dialyzed calf serum, oxidation of glutamine carbon provided about half of the total energy in heart cells, glucose about 35–45%, with most coming from glycolysis; oxidation of fatty acid carbon provided only 5–10%. That > 90% of the aerobic energy comes from glutamine in both cells can account for the comparable rates of oxygen utilization. HeLa cells derived little or no energy from fatty acids.     

Glutamate metabolism in a human intestinal epithelial cell layer model

Plasma glutamate concentrations are constant despite dynamic changes in diets. Most likely, virtually all the dietary glutamate is metabolized in the gut. The present study investigated permeability and metabolism of dietary glutamate in a Caco-2 intestinal epithelial cell layer model by tracing the fate of [U-¹³C] or [¹⁵N]glutamate added to the apical medium. For comparison, several other labelled essential and non-essential amino acids were tested as well. Almost all the labelled glutamate in the apical medium (98% and 96% at 24 h of the culture, respectively) was incorporated in the cell layer, while it barely appeared at the basolateral side, indicating an almost complete utilization of glutamate. Indeed, the ¹³C was incorporated into alanine, proline, ornithine, and glutamine, and the ¹⁵N was incorporated into alanine, glutamine, ornithine, proline, branched chain amino acids and also found as ammonia indicative of oxidation. In contrast, substantial apical-to-basolateral transport of amino acids (8–85% of uptake) other than glutamate and aspartate was evident in studies using amino acid tracers labelled with ¹³C, ¹⁵N or D. These results suggest that the intestinal epithelial cell monolayer utilizes dietary glutamate which adds to maintaining glutamate homeostasis in the body.

     

Metabolism of absorbed aspartate,asparagine, and arginine by rat small intestine in vivo

l-[U-¹⁴C]aspartate, l-[U-¹⁴C]asparagine, and l-[U-¹⁴C]arginine were administered luminally into isolated segments of rat jejunum in situ, and the radioactive products appearing in venous blood from the segment were identified and quantified, in a continuation of similar studies with l-glutamate and l-glutamine (Windmueller H.G. and Spaeth, A. E. (1975) Arch. Biochem. Biophys. 171, 662–672). Aspartate, administered alone (6 mm) or with 18 other amino acids plus glucose, was absorbed more rapidly than glutamate, but, as with glutamate, less than 1% was recovered intact in intestinal venous blood. More than 50% of aspartate carbon was recovered in CO₂, 24% in organic acids, mostly lactate, 12% in other amino acids (alanine, glutamate, proline, ornithine, and citrulline), and 10% in glucose, apparently the first demonstration of gluconeogenesis by intestine in vivo. In contrast to aspartate and glutamine, nearly all asparagine was absorbed intact, less than 1% being catabolized. About 4% of the absorbed dose was incorporated into the acid-insoluble fraction of intestine, as was the case with all the amino acids studied. In conventional or germ-free rats, only 60% of arginine was absorbed intact, while 33% was hydrolyzed to ornithine and urea. The urea and 38% of the ornithine were released into the blood; the remaining ornithine was metabolized further by intestine to citrulline, proline, glutamate, organic acids, and CO₂. Catabolism of several amino acids from the lumen plus glutamine from arterial blood may provide an important energy source in small intestine.     

Use of alternative protein sources for fishmeal replacement in the diet of largemouth bass (Micropterus salmoides). Part I: effects of poultry by-product meal and soybean meal on growth,feed utilization,and health

Five isonitrogenous and isocaloric diets [containing 54, 30, 15, 10, and 5% fishmeal crude-protein (CP), dry matter (DM) basis] were prepared by replacing fishmeal with poultry by-product meal plus soybean meal to feed juvenile largemouth bass (LMB, with an initial mean body weight of 4.9 g) for 8 weeks. All diets contained 54% CP and 13% lipids. There were four tanks of fish per treatment group (15 fish/tank). The fish were fed twice daily with the same feed intake (g/fish) in all the dietary groups. Results indicated that the inclusion of 15% fishmeal protein in the diet is sufficient for LMB growth. However, some of the fish that were fed diets containing ≤ 15% fishmeal CP had black skin syndrome (characterized by skin darkening and retinal degeneration, as well as intestinal and liver atrophies and structural abnormalities). The concentrations of taurine, methionine, threonine and histidine in serum were reduced (P < 0.05) in fish fed the diets containing 5, 10 and 15% fishmeal CP, compared with the 30 and 54% fishmeal CP diets. Interestingly, the concentrations of tyrosine and tryptophan in serum were higher in fish fed diets with ≤ 15% fishmeal CP than those in the 54% fishmeal CP group. These results indicated that 15% fishmeal CP in the diet containing poultry by-product meal and soybean meal was sufficient for the maximum growth and feed efficiency in LMB but inadequate for their intestinal, skin, eye, and liver health. A reduction in dietary methionine and taurine content and the possible presence of antinutritional factors in the fishmeal replacements diets containing high inclusion levels of soybean meal may contribute to black skin syndrome in LMB. We recommend that the diets of juvenile LMB contain 30% fishmeal CP (DM basis).

     

Preliminary description of lesions in juvenile largemouth bass injected with largemouth bass virus

Juvenile largemouth bass Micropterus salmoides were intraperitoneally injected with largemouth bass virus (LMBV), a member of the genus Ranavirus, family Iridoviridae. Moribund fish which had been injected with 10(6.2) tissue culture infectious doses, 50% endpoint (TCID50), were sampled 4 d after injection; other largemouth bass injected with this dose died between 3 and 5 d after injection. Fish injected with 10(2.8) TCID50 of LMBV were also examined after 4 d and had lesions similar to those of fish injected with the high dose. Clinical signs included darker pigmentation, inflammation and necrosis at the site of injection, distended abdomen, corkscrew swimming, and lateral recumbency. Internally, fish had focally pale livers, bright red spleens and reddened intestinal ceca. Histologically acute fibrinous peritonitis affected the surface of all organs in the peritoneal cavity, but deeper portions of organs appeared normal. There was also necrosis of the gastrointestinal mucosa. Except for the injection site, lesions were confined to the peritoneal cavity.     

Failure of low-velocity swimming to enhance recovery from exhaustive exercise in largemouth bass (Micropterus salmoides)

This study was intended to discover whether forcing largemouth bass (Micropterus salmoides) to swim at 0.5 body lengths/second following exercise would expedite recovery relative to fish recovered in static water. Exercise resulted in a suite of physiological disturbances for largemouth bass that included a depletion of anaerobic energy stores, an accumulation of lactate, and increased cardiac output. At 1 h following exercise, exhaustively exercised largemouth bass forced to swim exhibited expedited recovery relative to fish in static water, evidenced by lower concentrations of lactate in white muscle, elevated concentrations of phosphocreatine in white muscle, and reduced concentrations of glucose in plasma. By 4 h postexercise, largemouth bass forced to swim during recovery exhibited signs of physiological disturbance that were absent in fish recovered in static water. These signs of disturbance included a loss of osmotically active particles from plasma, elevated lactate in plasma, reductions of phospocreatine in white muscle, and increased cardiac output. These results are discussed in relation to the body of work with salmonid fishes showing physiological benefits to recovering fish in flowing water.     

Behavioral thermoregulation of largemouth bass,Micropterus salmoides,and bluegill,Lepomis macrochirus,in a nuclear reactor cooling reservoir

Synopsis Behavioral responses which allow largemouth bass, Micropterus salmoides, and bluegill, Lepomis macrochirus, to survive under unusually high temperature conditions were examined. Distribution of fish was ascertained by angling. Body temperatures of 4 fish were obtained using radio transmitters. Temperatures of other fish were measured after fish were captured by angling. Both species were restricted in range by lethal water temperatures and therefore inhabited a greater portion of a thermally altered reservoir in winter than in summer. Under unheated conditions (during reactor shutdown), bass occupied shallow areas with an abundance of submerged logs and stumps, a deep area with springs, and a cove where the effluent canal entered the reservoir. Commencement of reactor operation resulted in an increase in water temperature to more than 50°C in summer. Bass and bluegill retreated to three refuges and remained there until the reactor shut down and the reservoir cooled. In the refuges, bass experienced a wide variety of temperatures, but adults generally avoided temperatures above 31°C. Large adult bass (>40 cm) occupied particular positions in a refuge cove, medium size bass (15–40 cm) swam in the open water, and small bass (相似文献   

Considerations of blood parameters of largemouth bass, Micropterus salmoides

To evaluate physiological stress resulting from environmental influences, a haematological study of a natural population of largemouth bass, Micropterus salmoides , was undertaken to establish a 'normal' blood profile. Several parameters including haemoglobin concentration, haematocrit, erythrocyte count, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, plasma protein concentration and glucose levels were investigated. Haematocrit, haemoglobin, and total plasma protein were positively correlated with fish length. Haemoglobin and haematocrit were positively correlated with fish age while mean corpuscular haemoglobin, concentration was negatively correlated with fish age. Both haemoglobin and haematocrit values were related to erythrocyte counts.     

Gape Limitation, Prey Size Refuges and the Top–down Impacts of Piscivorous Largemouth Bass in Shallow Pond Ecosystems

Top–down control of phytoplankton biomass through piscivorous fish manipulation has been explored in numerous ecological and biomanipulation experiments. Piscivores are gape-limited predators and it is hypothesized that the distribution of gape sizes relative to distribution of body depths of prey fish may restrict piscivore effects cascading to plankton. We examined the top–down effects of piscivorous largemouth bass on nutrients, turbidity, phytoplankton, zooplankton and fish in ponds containing fish assemblages with species representing a range of body sizes and feeding habits (western mosquitofish, bluegill, channel catfish, gizzard shad and common carp). The experimental design consisted of three replicated treatments: fishless ponds (NF), fish community without largemouth bass (FC), and fish community with largemouth bass (FCB). Turbidity, chlorophyll a, cyclopoid copepodid and copepod nauplii densities were significantly greater in FC and FCB ponds than in NF ponds. However, these response variables were not significantly different in FC and FCB ponds. The biomass and density of shallow-bodied western mosquitofish were reduced and bluegill body depths shifted toward larger size classes in the presence of largemouth bass, but the biomass and density of all other fish species and of the total fish community were unaffected by the presence of largemouth bass. Our results show that top–down impacts of largemouth bass in ecosystems containing small- and deep-bodied fish species may be most intense at the top of the food web and alter the size distribution and species composition of the fish community. However, these top–down effects may not cascade to the level of the plankton when large-bodied benthivorous fish species are abundant.     

Experimental trophic ecology of juvenile largemouth bass,Micropterus salmoides,and blue tilapia,Oreochromis aureus

Synopsis The potential for feeding competition between largemouth bass, Micropterus salmoides, and blue tilapia, Oreochromis areus, in Lake Fairfield, Texas was evaluated experimentally. Largemouth bass and blue tilapia were grown in cages alone and in combination with each other. The fish were allowed to feed on the natural food within the lake. Largemouth bass grown in combination with blue tilapia were significantly shorter and weighed less than largemouth bass grown alone. Blue tilapia grown in combination with largemouth bass were statistically significantly longer and heavier than blue tilapia grown alone. Largemouth bass grown alone had diets (volume and number of food items) significantly different than the largemouth bass grown with the blue tilapia. Largemouth bass fed primarily on chironomid larvae and pupae, and odonates, whereas blue tilapia consumed vegetable matter, detritus, and chironomid larvae. Length and weight differences between large-mouth bass grown alone and in combination with blue tilapia, in conjunction with the largemouth bass diet shift, support the theory that these two species compete for food resources.     

Examination of the effects of largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) on the ecosystem attributes of lake Kawahara-oike,Nagasaki, Japan

The introduction of largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus) into the freshwater ecosystems of Japan has resulted in the suppression and/or replacement of native species, generating considerable concerns among resource managers. The impacts of largemouth bass and bluegill on native fauna have been examined in aquaria and isolated farm ponds, but there is limited work examining the likelihood to fundamentally modifying Japan's lakes. The objective of the present study is to examine the direct and synergistic ecological effects of largemouth bass and bluegill on the biotic communities of Lake Kawahara-oike, Nagasaki, Japan, using an ecosystem (Ecopath) modeling approach. Specifically, we examine whether the two fish species have played a critical role in shaping the trophodynamics of the lake. We attempt to shed light on the trophic interactions between largemouth bass and bluegill and subsequently evaluate to what extent these interactions facilitate their establishment at the expense of native species. We also examine how these changes propagate through the Lake Kawahara-oike food web. Our study suggests that the introduction of bluegill has induced a range of changes at multiple trophic levels. The present analysis also provides evidence that largemouth bass was unable to exert significant top-down control on the growth rates of the bluegill population. Largemouth bass and bluegill appear to prevail over the native fish species populations and can apparently coexist in large numbers in invaded lakes. Future management strategies controlling invasive species are urgently required, if the integrity of native Japanese fish communities is to be protected.     

Foraging in Non-Native Environments: Comparison of Nile Tilapia and Three Co-Occurring Native Centrarchids in Invaded Coastal Mississippi Watersheds

We examined the diet of the alien Nile tilapia and bluegill, redear sunfish, and largemouth bass over a two-year period in coastal Mississippi. Nile tilapia diet was visually separated from the three natives based on group-average linkage cluster analysis. Sequential two-way nested analysis of similarities indicted there was no season effect (Global R = 0.026, P = 24.3%), but there was a moderate size class effect (Global R = 0.457, P = 0.1%) and a strong species effect (Global R = 0.876, P = 0.1%). Pairwise tests indicated species fed on different components of and locations within the environment, with bluegill, redear sunfish and largemouth bass (all R ≤ 0.683, P = 0.1%) having the most similar dietary components and Nile tilapia (all R ≥ 0.953, P = 0.1%) having the most distinct. Multivariate dispersion indicated that largemouth bass (1.425) and bluegill (1.394) had the most diverse diets compared to redear sunfish (0.906) and Nile tilapia (0.918). Similarities of percentages indicated that diets were separated based on prey: bluegill and redear sunfish consumed chironomids and insects; largemouth bass consumed fish and insects; and Nile tilapia fed most often on sediment resources such as nematodes, rotifers, bryozoans and hydrozoans. Nile tilapia had the highest frequency of mud, sand and detritus in their stomachs, suggesting they fed directly on bottom sediments. These data and the fact that Nile tilapia has a 1.3–7.6 times longer intestine on average than its body length, support our contention that this alien species feeds at the base of the food web and is well adapted to survive and proliferate in non-native environments.     

Annual cycles of growth and reproduction in hatchery–reared Florida largemouth bass, Micropterus salmoides floridanus, raised on forage or pelleted diets

Annual cycles of growth and reproduction of hatchery–reared Florida largemouth bass, Micropterus salmoides floridanus , were investigated. Animals were raised on either forage (goldfish, Carassius auratus ) or a pelleted salmon feed. Male and female year–class 1 largemouth bass were sampled throughout one complete yearly cycle (January–December). A biphasic growth cycle was observed in both forage–fed and pellet–fed fish. No increase in body length or weight was observed until approximately midway through the spawning period (May), after which fish grew at a consistent rate for the remainder of the study. The reproductive cycle of forage–fed fish was characterized by a rapid increase in gonadosomatic index (GS1) between January and April, followed by a prolonged spawning period (April–July) during which GSI progressively declined. Fully regressed gonads were observed in September and October, and a resumption of gonadal recrudescence was observed between October and December. Visceral adipose deposits (expressed as mesenteric fat index; MFI) were resorbed during gonadal growth and the initial stages of the spawning period, and restored during the post–spawning phase. Fish raised on pelleted feed had growth and reproductive cycles that parallelled those of forage–fed fish, but several significant differences were observed between the two diet groups. During the growth phase of the cycle, pellet–fed largemouth bass grew significantly faster than forage–fed largemouth bass, and had significantly larger MFIs than forage–fed largemouth bass at all times of the year. Pellet–fed fish also had significantly larger GSIs than forage–fed fish. These data indicate that diet composition may be an important determinant of growth and reproductive function in this species.     

饲料蛋白质水平与投喂频率对大黄鱼生长、体组成及蛋白质代谢的影响

以初始体重为(13.640.18)g的大黄鱼( Pseudosciaena crocea R.) 幼鱼为实验对象, 采用32双因子实验, 研究饲料蛋白质水平(40%、45%、50%)和投喂频率(2次/d、1次/d)及其交互作用对其生长、体组成和蛋白质代谢的影响。养殖实验在海水浮式网箱中进行, 养殖周期为8周。结果表明: 饲料蛋白质水平和投喂频率对大黄鱼幼鱼的增重率(WGR)、特定生长率(SGR)和饲料转化率(FCR)均影响显著(P0.05)。在40%和45%蛋白质组, 1次/d投喂的大黄鱼幼鱼的WGR和SGR均显著低于2次/d投喂组, 而FCR则相反。在2次/d投喂时, 45%蛋白质组的大黄鱼幼鱼SGR显著高于40%蛋白质组, 但与50%蛋白质组差异不显著(P0.05)。而在1次/d投喂时, 50%蛋白质组的大黄鱼幼鱼SGR显著高于40%和45%蛋白质组。在两种投喂频率下, 随着饲料蛋白质水平提高, 鱼体水分含量均有升高趋势, 蛋白质含量显著升高而脂肪含量显著下降(P0.05)。饲料的蛋白质水平和投喂频率分别对大黄鱼幼鱼的肝脏指数(HSI)、内脏指数(VSI)和血清中的谷丙转氨酶(ALT)及谷草转氨酶(AST)均影响不显著(P0.05)。投喂频率对肝脏的ALT和AST的影响不显著(P0.05)。在同一投喂频率下, 肝脏ALT和AST均随着饲料蛋白质水平的增加而显著提高(P0.05)。饲料中的蛋白质水平和投喂频率对大黄鱼幼鱼的生长和FCR的影响存在显著的交互作用(P0.05), 而对血清和肝脏中的ALT和AST、HSI、VSI、肥满度(CF)以及体组成的影响均无交互作用。       

The influence of environmental temperature and oxygen concentration on the recovery of largemouth bass from exercise: implications for live–release angling tournaments

The impact of variation in water temperature and dissolved oxygen on recovery of largemouth bass Micropterus salmoides from exercise was examined. For this, largemouth bass were first exercised and recovered for either 1, 2 or 4 h at ambient water temperatures (25° C) in fully oxygenated water. Results showed that exercise forced fish to utilize anaerobic metabolism to meet energy demands, and resulted in reductions in anaerobic energy stores adenosine triphosphate (ATP), Phosphocreatine (PCr) and glycogen. Exercise also resulted in a seven‐fold increase in lactate within white muscle. After 2 h of recovery in oxygenated water at acclimation temperature, physiological recovery from exercise was under way, and by 4 h most variables examined had returned to control levels. Next, largemouth bass were exercised at ambient temperatures and recovered for 2 h in environments with either elevated temperature (32° C), reduced temperature (14 and 20° C), hypoxia or hyperoxia. Both elevated and reduced temperature impaired recovery of tissue lactate and tissue ATP relative to fish recovered in water at acclimation temperature, while hyperoxic water impaired recovery of tissue ATP. Moderately hypoxic waters impaired the recovery of plasma glucose, plasma lactate and tissue PCr relative to fish recovered in fully oxygenated water. Results from this study are discussed in the context of critical oxygen and temperature guidelines for largemouth bass. In addition, several recommendations are made concerning remedial treatments used in livewells (tanks) during angling tournaments when fish are recovering from exercise associated with angling.