Effect of body colour of Oreochromis mossambicus (Peters) on predation by dragonfly nymphs

Abstract. Gold and black Oreochromis mossambicus (Peters) fry were stocked in 0.043-m³ hapas along with early instar dragonfly nymphs to determine the effect of body colour of the tilapia on vuinerability to predation by the insect. Hapas were stocked with either: 10 gold fry, 10 black fry and no dragonfly nymphs (10-10-0); 5 gold fry, 5 black fry and 2 dragonfly nymphs (5-5-2); 10 gold fry, 10 black fry and 2 dragonfly nymphs (10-10-2); or 10 gold fry, 10 black fry and 3 dragonfly nymphs (10-10-3). Four levels of predation were assessed: no predation, 1 dragonfly nymph per 5 fish, 1 per 6.7 fish, and 1 per 10 fish. Hapas were censused daily for 14 days. Fish that had been eaten were replaced with similar-sized fish to restore stocking densities. Average daily predation rate ranged from 0.24 to 3.0 and averaged 1.94 fry/dragonfly nymph/day. Average daily predation rates for all treatments were significantly (P = 0.05) different and were a function of both dragonfly and fish stocking rates. Dragonfly nymphs ate significantly more black fish than gold fish in the 10-10-2 and 10-10-3 treatments: overall (10-10-2, 10-10-3 and 5-5-2 treatments combined), dragonfly nymphs ate significantly more black (324) than gold (245) tilapia. Results from this study indicate that the bright body colour of the gold tilapia does not increase rate of predation by dragonfly nymphs.     

Diet of the largemouth bass, Micropterus salmoides (Lacepède), in Lake Naivasha, Kenya

Abstract The major food items of adult largemouth bass, Micropterus salmoides (Lacepède), in Lake Naivasha, Kenya are not markedly different from those in its native range. Although insects and their larvae are major components of the diet for both temperate and equatorial populations of juvenile bass, the equatorial population also eats Procambarus clarkii (Girard), juvenile fish and aquatic weeds. In temperate populations they also eat crustaceans, rotifers and oligochaetes. The frequency of occurrence of the major prey organisms in the stomachs of M. salmoides varies seasonally with population peaks in these organisms. Similar to North American populations, the Naivasha population feeds during the day between dawn and dusk. In contrast to temperate populations, the population of M. salmoides in this equatorial lake feeds throughout the year, with feeding intensity correlated with water temperature.     

Study on the pathogenicity of Nocardia asteroides to the Formosa snakehead, Channa maculata (Lacepède), and largemouth bass, Micropterus salmoides (Lacepède)

Abstract. The Formosa snakehead, Channa maculata (Lacepède), and the largemouth bass, Micropterus salmoides (Lacepède), were given an intraperitoneal (i.p.) and/or intramuscular (i.m.) inoculation of Nocardia asteroides isolated from cultured Formosa snakehead, Typical granulomatous lesions induced by the experimental fish were similar to the naturally infected cases. The Formosa snakehead showed 100% and 93% mortality at 14 and 35 days after i.m. inoculation with 8 mg and 0·8 mg of bacterial suspension, respectively. The largemouth bass was slightly resistant to N. asteroides but still had 95% mortality at 35 days after inoculation (i.m.) with 8 mg bacterial suspension. The bacteria were easily reisolated from spleen and kidney of the experimental fish. Many typical multifocal granulomata were found at the sites of injection and the internal organs such as liver, spleen, kidneys, pancreas, intestine, gills, eyes and brain. The result indicated that the N. asteroides isolated from the field ease was pathogenic to Formosa snakehead and largemouth bass.     

Effects of oestradiol-17β or 17α-methyltestosterone administration on gonadal differentiation of largemouth bass Micropterus salmoides (Lacepède)

Monosex populations can be a valuable management tool in culture of larger size largemouth bass (>400 g). In this study, we investigated the effective mode and duration of oestrogen and androgen administrations to produce monosex largemouth bass populations. The experiment consisted of nine treatments. In oral administration groups, we fed 40-day-old fry either 200 mg of an oestradiol-17β (E₂) kg⁻¹ diet or 60 mg of a 17α-methyltestosterone (MT) kg⁻¹ diet for 30, 45 or 60 days. In bath treatments, we immersed fry in a 1 mg MT L⁻¹ solution for 5 h a day on three or six occasions. For control treatment, we fed fry an ethanol-treated diet for 45 days. The frequency of females in the control group was 53.1%. Oral administration of E₂ at all durations resulted in slight increases in the frequency of females (59.8–70.5%). Both modes of androgen administration at all durations were ineffective in altering phenotypic sex. The experimental results of our study indicated that male differentiation passed the point of being completely and functionally influenced by exogenous oestrogens, while female differentiation had already taken place and was no longer responsive to exogenous androgens in 40-day-old (33.5 mm) largemouth bass fry.     

Effect of catch-and-release angling on growth of largemouth bass, Micropterus salmoides

Catch‐and‐release angling is popular in many parts of the world and plays an increasingly important role in management of recreational fisheries. Although the magnitude of catch‐and‐release mortality is well documented for many species, potential sublethal effects have been little studied. An experiment was conducted to assess directly the effects of catch‐and‐release angling on growth of largemouth bass, Micropterus salmoides Lacépède. Angling mortality was 0.00 ± 0.092% for largemouth bass caught on plastic grubs. There was no difference (P = 0.57) in weight gain between caught and uncaught fish over a 40‐day angling and recovery period. Although catch‐and‐release angling appears to have no effect on largemouth bass growth, previous studies documented sublethal effects on growth and reproduction in other species, suggesting that the occurrence and magnitude of sublethal effects vary among species.     

Diet composition of largemouth black bass, Micropterus salmoides (Lacepède), in southern Portuguese reservoirs: its relation to habitat characteristics

Abstract  During the summer of 1990 the diet of Micropterus salmoides (Lacepède) was studied in four southern Portuguese reservoirs. The dominant food items were insects (especially Odonata and Ephemeroptera naiads, and Odonata and Hemiptera adults), the crayfish, Procambarus clarkii (Girard), and pumpkinseed sunfish, Lepomis gibbosus (L.). There was an increase in the consumption of L. gibbosus as bass changed from 100–200 mm total length to over 200 mm, and a corresponding decline in the insect and crayfish components. Carp, Cyprinus carpio L., and other benthic cyprinids were absent from the stomach contents. The association between the different prey consumed and the habitat characteristics are discussed in relation to the feeding ecology of largemouth bass, an exotic species in Portugal.     

加州鲈商品鱼网箱养殖技术

<正> 加州鲈又名大口黑鲈,是一种名贵淡水鱼类,具有适应性广、生长快、病害少、肉味美、营养丰富、商品价值高、养殖效益好等特点。据对沅江市部分加州鲈商品鱼网箱养殖者调查,平均产量为20～28kg/m~2,产值为700～850元/m~2、利润300～360元/m~2,投入产出比1:(1.7～1.8)。现将其主要技术介绍如下。     

Persistence of Florida largemouth bass alleles in a northern Arkansas population of largemouth bass, Micropterus salmoides Lacèpéde

Abstract– Lake Ashbaugh, located in northeast Arkansas, was constructed in 1981, and initially stocked with Florida largemouth bass followed by supplemental stockings of northern largemouth bass. Allele frequencies of three discriminant allozyme loci (sAAT-B, sIDH-B, sMDH-B) between Florida and northern largemouth bass were determined for 414 largemouth bass collected between 1994 and 1996. F_x bass dominated our sample, with 62.3% possessing Florida largemouth bass alleles. A high incidence of Hardy-Weinberg disequilibrium was observed, indicative of genetic change within the population. No significant differences were identified for frequency of age classes, relative weight, and length at age between the northern, F₁ and F_x phenotypes. Despite being located north of what is generally considered suitable for stocking Florida largemouth bass, it was demonstrated that temperature is not selective at present against bass possessing Florida largemouth bass alleles. However, caution should prevail when introducing non-native stock into native gene complexes, as introduced genes persist through many generations.     

Digestibility of plant protein-based diets by largemouth bass Micropterus salmoides

Commercial farming of carnivorous fish demands the reduction of environmental impact of feeds; that requires minimal use of dietary animal protein. This study investigated the digestibility of diets formulated exclusively out of plant protein, added feed attractants, by the carnivore largemouth bass, Micropterus salmoides . Juvenile largemouth bass (14.0 ± 1.0 cm) conditioned to accept artificial, dry feed were confined in polypropylene cages and fed ad libitum in three daily meals, seven experimental diets containing varying levels of vegetable and animal protein sources, added of different feed stimulants. After last daily meal, cages were transferred to cylindrical–conical-bottomed, 200-L aquaria, where faeces were collected by sedimentation into refrigerated containers, preserved and later analysed for chemical composition. Soybean meal can be used as partial substitute of animal protein in diets for largemouth bass; the poultry by-product meal shows as a good option as animal protein source in these rations. Control treatment – 50PP : 50AP – yielded best performances; the need for the use of fish meal in the formulation for carnivorous diets is, at least, questionable. Results of the digestibility trials demonstrated the importance of determining the diet digestibility, if precision in the formulation of least-cost feeds for carnivorous fish is the ultimate goal.     

Temporal genetic structure of an intergrade largemouth bass (Micropterus salmoides) population

Since 1972, numerous impoundments throughout Texas have been stocked with Florida largemouth bass Micropterus salmoides floridanus. In order to examine some of the long-term effects of such efforts, the present study summarizes past studies and complements those with more current observations on the intergrade largemouth bass population in Aquilla Lake, Hill Country, Texas. The reservoir received 4 annual stockings during the month of May from 1982 to 1985. Collections occurred periodically from February 1984 to June 1987, February to August 1988, and monthly from August 1991 to November 1992. Horizontal starch-gel electrophoresis was conducted to determine allele frequencies at loci sAAT-B*, SOD*1. Mean heterozygosity and percent introgression were highest for age-0 fish of the 1986 year class. Assortative mating was not apparent in 1991 or 1992 year classes. Collections of specific year classes over time consistently indicated decreases in the relative abundance of the northern phenotype. Relative to the northern phenotype, the abundance of Florida year classes remained relatively constant over time. Relative abundances of F₁ hybrids and F_x, intergrades (i. e., F₁) from specific year glasses were observed to generally increase with age.     

大口黑鲈生长性状相关标记的聚合效果分析

选择已经获得的8个与大口黑鲈(Micropterus salmoides)生长性状相关的分子标记, 其中4个单核苷酸多态性标记分别位于IGF-I、POU1F1、PSSIII和MSTN基因上, 4个微卫星位点分别是JZL60、JZL67、MisaTpw76和MisaTpw117。从养殖群体中筛选出具有4个以上优势基因型数量的大口黑鲈亲鱼20尾进行群体繁殖, 其中雌鱼9尾, 雄鱼11尾。所产子代进行同塘饲养, 9月龄时随机挑选288尾进行体质量测量与STR基因分型。结果显示:子代体质量为103~401 g, 含有生长优势基因型的数量在1~6之间, 含有1~6个生长优势基因型的个体其平均体质量依次为227.83、239.56、258.81、273.02、302.50和305.60 g, 生长优势基因型的数量与大口黑鲈生长速度呈正相关。进一步分析表明子代中优势基因型的平均数量为2.99, 相比亲本群体的优势基因型平均数量(2.36)得到提高。研究结果说明, 利用有限的与生长相关的优势基因型进行聚合可以获得具有优良生长性状的大口黑鲈, 也为下一步大口黑鲈分子标记辅助育种提供理论依据。

     

大口黑鲈对饲料中蛋氨酸需求量的评定

为了评定大口黑鲈对饲料中蛋氨酸的最适需求量,配制了蛋氨酸含量分别为0.61%,0.82%,0.98%,1.21%,1.42%和1.59%的6水平等氮等能饲料(44.39%粗蛋白质,0.30%胱氨酸,19.81 kJ/g总能),以初始体重为(37.88±0.40)g的大口黑鲈为试验对象,进行了66 d的饲养试验。饲养试验在室内循环水养殖系统中进行,每饲料处理设3个重复,每重复放养试验鱼25尾。饲养试验采取表观饱食投喂,每天投喂两次(8:30和15:30)。试验期间水温(27±1)℃,溶解氧6 mg/L以上。结果表明,试验鱼的特定生长率、饲料效率、蛋白质效率、蛋白沉积率随着饲料中蛋氨酸水平从0.61%到1.21%的升高而显著提高(P<0.05),此后则呈降低的趋势。饲料中蛋氨酸水平对全鱼和肌肉中粗蛋白含量有显著影响(P<0.05);但各组间水分、粗脂肪和粗灰分含量差异不显著(P>0.05)。0.61%蛋氨酸的饲料组的肝体比和脏体比显著大于其他组(P<0.05),其他组间无显著差异(P>0.05)。饲料中蛋氨酸水平显著影响血清溶菌酶活力,头肾白细胞吞噬活性及其呼吸爆发活性(P<0.05)。以特定生长率为评价指标经二次回归分析得出,当饲料中的胱氨酸占饲料蛋白质的0.68%时,大口黑鲈对饲料中蛋氨酸的最适需求量为1.22%,占饲料蛋白质的2.75%。     

An evaluation of total body electrical conductivity to estimate body composition of largemouth bass,Micropterus salmoides

Measurement of total body electrical conductivity (TOBEC) recently has been used to estimate the body composition of several fish species in a noninvasive manner. The present study was conducted to evaluate the use of TOBEC in estimating body composition of largemouth bass (Micropterus salmoides). A total of 85 largemouth bass weighing 154 to 3 245 g were measured for electrical conductivity after which their proximate composition was determined by chemical means. Significant linear relationships existed between the natural logarithm of whole-body ash, lean body mass, lipid, protein, and water content and the natural logarithm of length and/or weight with r² values ranging from 0.860 to 0.999. Inclusion of the TOBEC value did not significantly improve the prediction accuracy of these models. Equations were developed to allow the prediction of body composition of largemouth bass based on length and weight measurements. Prediction models including only length and weight as variables provided estimates of body components of an independent set of fish that were not significantly different from chemically derived measurements of these components. These models should allow the rapid, nondestructive estimation of body composition of largemouth bass varying in size and condition without the added cost and processing time associated with measurement of TOBEC, although large prediction errors might prevent the detection of ecologically significant differences in body composition. However, with additional data involving narrower fish-size ranges and constant temperatures for the development of prediction equations, TOBEC may improve the prediction accuracy of body composition estimates for largemouth bass.     

加州鲈的人工繁殖及苗种培育技术

<正> 1 人工繁殖 加州鲈一般养二周年可达性成熟,也有一周年成熟的,繁殖适宜水温为18～25℃。1.1 亲鱼培育 加州鲈亲鱼平时可与家鱼混养,池塘里需有一定数量的小鱼、小虾作为它的食物,也可投喂人工饲料。至繁殖季节之前,再行强化培育,强化培育在池塘或水泥池均可。     

加州鲈肌肉生长抑制素(MSTN)cDNA的克隆和序列分析

肌肉生长抑制素是抑制肌肉生长和发育的生长调控因子。对运用RT-PCR和RACE技术从加州鲈成鱼肌肉总RNA中扩增得到的MSTN cDNA全序列进行了序列分析。结果表明,加州鲈MSTN cDNA全长为1626bp,其开放阅读框为1 134bp,共编码377个氨基酸,前面的22个氨基酸为信号肽,中间有四个氨基酸(RARR)为蛋白水解加工位点;该基因总共有13个半胱氨酸残基,后面9个在蛋白水解加工位点之后的C端生物活性区,与其它脊椎动物比较,它们的位置完全一致,对该基因的结构和功能非常重要。与GenBank中已知的条纹狼鲈、金鲷、斑马鱼、虹鳟、斑点叉尾鮰、人、猪、鸡、鸽MSTN的ORF相比较,核苷酸序列同源性为63%~94.4%,氨基酸同源性为61.4%~96%,特别是在C端生物活性区氨基酸同源性为88.1%~100%,高度的保守性反映了该基因受到了高度的进化限制以及功能的重要性。加州鲈MSTN基因的克隆为研究该基因打靶和鱼类肌肉发育调控机理奠定了基础。     

大口黑鲈饲料中适宜的淀粉源及添加水平

以4种淀粉,蜡质玉米淀粉(L)、高直链玉米淀粉(Z)、小麦淀粉(X)和木薯淀粉(M),分别以5%和10%的添加量配制了8种等氮和等能(CP 48%,GE 18.5 MJ/kg)的饲料(L5、L10、Z5、Z10、X5、X10、M5和M10)。用上述饲料饲养初始体重为(23.46±0.19)g的大口黑鲈45 d,以评定大口黑鲈饲料的适宜淀粉源及添加水平。结果显示,饲料中淀粉的添加水平和淀粉源对大口黑鲈的生长、饲料利用、体组成和非特异性免疫指标均有显著影响。随着同一种淀粉的添加量从5%升至10%,L10、X10和M10组实验鱼的特定生长率和摄食率显著降低,但饲料效率和蛋白质效率显著升高,而Z5和Z10组间的上述指标的差异不显著;L10、X10和M10组的肝体比、脏体比和肝糖原含量均显著升高,但Z5和Z10组间的脏体比差异不显著;全鱼和肝的脂肪含量及肝的蛋白质含量均显著降低;L10组的红细胞数和红细胞压积、Z10组的血清甘油三酯及X10组的红细胞压积和血清甘油三酯水平显著降低;Z10组的血清补体活性显著降低;L5、Z5、X5和M5组的餐后3~12 h的血糖水平各自低于L10、Z10、X10和M10组。不同的淀粉源在相同的添加量的情况下,Z5组的淀粉表观消化率和肝体比显著地低于L5、X5和M5组,而脂肪沉积率显著高于L5、X5和M5组;M5组的蛋白质表观消化率显著低于L5、Z5和X5组;Z10组的淀粉表观消化率、肝体比、脏体比和肝糖原含量显著低于L10、X10和M10组,而脂肪沉积率显著高于L10、X10和M10组;M10组的蛋白质表观消化率显著低于L10、Z10和X10组。饲料中淀粉的添加水平和淀粉源对大口黑鲈的摄食率、特定生长率、蛋白质消化率、脂肪沉积率、肝体比、肝糖原含量、红细胞数、血清甘油三酯含量和血清补体活性均有显著的交互作用。本研究表明,饲料的淀粉源和水平对大口黑鲈的生长、体组成、血液学指标、餐后血糖和非特异性免疫指标均有不同程度的影响,饲料中添加5%的蜡质玉米淀粉、高直链玉米淀粉、小麦淀粉和木薯淀粉均无妨碍,但添加10%的淀粉水平唯有高直链玉米淀粉较为合适。     

Freshwater mussels increase survival of largemouth bass (Micropterus salmoides) in drying pools

Between global climate change and anthropogenic water needs, freshwater systems are becoming more intermittent, stressing organisms adapted to perennial waters. Drought-induced intermittency concentrates aquatic organisms into drying pools. These pools represent refugia from desiccation but apply other stressors, such as extreme temperatures and increased competition for dwindling resources. In the Southern United States, fishes and freshwater mussels are often concentrated together in drying pools during seasonal, summer droughts. This can result in increased competition for food among invertivorous fish, but also increased food abundance for these fish because mussels increase macroinvertebrate abundance. Further, since mussels require fish as hosts for their ectoparasitic larval phase, glochidia, competition with their host during this biologically active time is detrimental to mussels. We conducted an experiment to examine the effects of freshwater mussels on trophic resources and fish survival in drying pools. We stocked mesocosms with juvenile largemouth bass that were infected or uninfected with glochidia and tracked abiotic conditions, trophic resources and fish survival for 10 days. We found that fish survived longer in the presence of adult mussels, regardless of their infection status. We suspect that prey items supplemented by adult freshwater mussels increased the survival of fish. Thus, the presence of adult mussels and the resources that increase in their presence potentially mitigate stress to fish in “ecological crunch times.” By conserving mussels, fish populations might withstand droughts more easily.     

大口黑鲈对四种蛋白质饲料原料的表观消化率研究

为大口黑鲈的营养研究和配合饲料研制提供理论依据,试验以Cr2O3为消化指示物,测定了大口黑鲈（Micropterus salmoides）对进口白鱼粉、国产鱼粉、普通豆粕和发酵豆粕的干物质、蛋白质和脂肪的表观消化率。试验饲料由基础饲料和试验原料以70：30的质量比混合挤压成软颗粒饲料。试验结果表明,大口黑鲈对动物性蛋白白鱼粉和红鱼粉的干物质表观消化率分别为78．56％和9．12％,高于植物性蛋白普通豆粕的68．28％和发酵豆粕的72．19％,而发酵豆粕的干物质表观消化率比普通豆粕要高一些。大口黑鲈对4种饲料原料的蛋白质表观消化率在80．21％～85．55％,对4种饲料原料的脂肪表观消化率为81．18％～91．06％。大口黑鲈可以很好地利用4种饲料原料中的蛋白质和脂肪。     

大口黑鲈肝脾肿大病病原研究

为了查明2009年10月广东省佛山地区养殖大口黑鲈(Micropterus salmoides)中暴发的传染性疾病的病原,对病鱼的肝脏、脾脏和腹隔膜进行切片电镜观察,发现细胞质中有大量病毒颗粒,切面为六角形,直径约145～150 nm,病毒为二十面体对称结构、无囊膜、似虹彩病毒的病毒粒子.用除菌的病鱼组织滤液感染健康大口黑鲈,被感染鱼死亡率达90%以上.根据已知虹彩病毒主要衣壳蛋白(MCP)基因序列设计特异引物,提取人工感染发病鱼的肝脏、脾脏、肾脏组织的DNA进行PCR扩增,将扩增片段进行序列测定与分析,结果表明该序列与已报道的鳜(Siniperca chuatsi)传染性脾肾坏死病毒(Infectious Spleen and Kidney Necrosis Virus,ISKNV)MCP基因同源性为98%.电镜观察和MCP基因测序分析结果显示,该病毒的分类地位为虹彩病毒科(Iridoviridae)细胞肿大病毒属(Megalocytivirus).     

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 ( R ²) 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.