Comparison of dietary essential amino acid requirements determined from group‐housed versus individually‐housed juvenile bluegill,Lepomis macrochirus

Two 60‐day experiments were conducted sequentially to determine (i) lysine requirement of juvenile bluegill, Lepomis macrochirus based on the dose–response method, (ii) requirements for other essential amino acids (EAAs) using whole‐body amino acid profile and (iii) whether differences in growth rates of group‐housed versus individually‐housed bluegills lead to different lysine requirement levels because of the presence and absence, respectively, of social hierarchies. Seven, semi‐purified, experimental diets (isonitrogenous, isocaloric) were prepared to contain graded levels of digestible lysine (10–31 g kg⁻¹). Experiment‐1 involved group‐housed bluegills (approximately 27 g, n = 10 fish/chamber, 4 chambers/diet) whereas experiment‐2 involved individually‐housed bluegills (approximately 30 g, n = 1 fish/chamber, 14 chambers/diet). Fish were fed twice daily to apparent satiation. Bluegill growth responses in both experiments generally improved (P < 0.05, anova ) with increasing dietary lysine levels from 10 to 16 g kg⁻¹, and then levelled off with further increase in lysine level (P > 0.05). Optimal dietary lysine level (digestible basis) was estimated to be 15 g kg⁻¹ based on broken‐line regression analyses of relative growth rate and feed conversion ratio with no differences being observed between the two rearing methods. Determined dietary requirement levels for other EAAs ranged from 2.4 g kg⁻¹ (tryptophan) to 15.3 g kg⁻¹ (leucine).     

高寒地区蓝鳃太阳鱼养殖技术研究

本探讨了蓝鳃太阳鱼（Lepomis macrochirus)在高寒地区的生长成活状况。实验结果表明，在东北地区蓝鳃太阳鱼夏季养殖成活率可以达到85%（单养）和65%（混养），6-8月生长速度较好，混养比单养生长速度快，冰下可以安全越冬。     

美国蓝鳃太阳鱼养殖技术

报道了蓝鳃太阳鱼(Lipomis macroehius)的外部形态、生活、生长、繁殖习性、食性等生物学特征，以及鱼苗培育、成鱼养殖、鱼病防治技术。分析了该鱼发展中存在的问题，并提出建议。     

蓝鳃太阳鱼诺卡氏菌的分离鉴定及药敏分析

为探明患结节病蓝鳃太阳鱼的病因,从蓝鳃太阳鱼(Lepomis macrochirus)脾脏结节处分离获得一病原菌SD1810。通过菌落形态、细菌生理生化鉴定和16S rRNA基因序列分析,确定所得菌株为鰤鱼诺卡氏菌(Nocardia seriolae)。人工回归感染试验结果显示,注射浓度为2.8×107 CFU/mL的菌液能使蓝鳃太阳鱼患病致死,发病症状与原感染鱼相似。从死亡太阳鱼体内可重新分离到与SD1810形态特征、生理生化指标相一致的病菌。对分离获得的鰤鱼诺卡氏菌进行药敏试验分析,结果表明,鰤鱼诺卡氏菌SD1810对红霉素、利福平、庆大霉素、氯霉素、阿米卡星、氟苯尼考等10种抗生素极其敏感,对头孢唑啉,诺氟沙星,青霉素、氨苄青霉素和阿莫西林等6种抗生素具有耐药性。     

Habitat characteristics at bluegill spawning colonies in a South Dakota glacial lake

Abstract –  Bluegill ( Lepomis macrochirus ) primarily reproduce in spawning colonies. We assessed habitat characteristics at 15 bluegill spawning colonies in a South Dakota glacial lake. Nesting sites were visually identified and angling was used to verify the species of nesting fish. Habitat characteristics were measured at each nesting site and compared with those measured at 75 randomly selected sites. In Lake Cochrane, mean water depth of spawning colonies was 1.0 m. Of the 13 habitat characteristics measured, four (substrate type, substrate firmness, vegetation density and dissolved oxygen levels) were significantly different ( P  ≤ 0.05) between nesting and random sites. Every bluegill nest site contained gravel substrate, despite the availability of muck, sand and rock. Substrate firmness was indexed at 0-cm penetration and vegetation density was low at all nesting sites. Additionally, bluegills selected nesting locations with relatively moderate dissolved oxygen levels. Lake Cochrane bluegill nest sites consisted of shallow, gravel areas with short, low-density, live submergent Chara vegetation.     

Prey fish selection by Far Eastern catfish <Emphasis Type="Italic">Silurus asotus</Emphasis> and largemouth bass <Emphasis Type="Italic">Micropterus salmoides</Emphasis>

ABSTRACT:   Prey fish selection by Far Eastern catfish and largemouth bass were examined using bluegill, Japanese dace and crucian carp as food fish. In both aquaria (1.2 m × 0.45 m) and ponds (2.8 m × 1.2 m), bluegill was not preyed on by catfish and bass more than dace and crucian carp. In aquaria, there was no significant difference in the consumption of dace and crucian carp between catfish and bass, but in ponds, catfish preyed on dace and crucian carp more and less than bass, respectively. In the case that only bluegill and catfish were introduced in ponds, catfish consumed 4–15 g of bluegill per day. The introduction of catfish into ponds and lakes for the purpose of eradicating bluegill is considered appropriate for areas with few native fish species.     

Cholinesterase (ChE) inhibition in pumpkinseed (Lepomis gibbosus) as environmental biomarker: ChE characterization and potential neurotoxic effects of xenobiotics

Inhibition of cholinesterases (ChEs) has been widely used as an environmental biomarker of exposure to organophosphates (OP) and carbamate (CB) pesticides. More recently, this biomarker has been suggested as a putative biomarker for exposure to detergents. The use of cholinesterase inhibition as effect criterion in Ecotoxicology requires the previous characterization of the specific enzymatic forms that may be present in different tissues or organs. Different ChEs isoforms may be present in the same tissue and may exhibit distinct sensitivities towards environmental contaminants. This work intended to characterize the soluble ChEs present in pumpkinseed sunfish (Lepomis gibbosus) total head and dorsal muscle homogenates, through the use of different substrates and selective inhibitors of cholinesterasic activity. Also, the in vitro effects of sodium dodecylsulphate (SDS - anionic detergent) and chlorfenvinphos (organophosphate pesticide) on the enzymatic activity of the mentioned species were investigated. In general terms, the predominant cholinesterasic form present in both tissues was acetylcholinesterase. Chlorfenvinphos was responsible for inhibitory effects on AChE activity, while SDS did not cause any significant effect. These results suggest that in environmental monitoring programs, L. gibbosus head and dorsal muscle AChE can be an adequate diagnostic tool for exposure to OP pesticides; this conclusion however is not applicable to detergent residues. We also discuss the usefulness of L. gibbosus as an alternative model system and valuable option for freshwater ecotoxicological monitoring programs.     

大口黑鲈和蓝鳃太阳鱼鳃结构的扫描电镜观察

应用扫描电镜对大口黑鲈Micropterus salmoides和蓝鳃太阳鱼Lepomis macrochirus鳃的表面微细结构进行了观察。结果表明：大口黑鲈和蓝鳃太阳鱼鳃的表面结构和微细结构与其它硬骨鱼类基本相似,鳃弓和鳃耙表面被具环形微嵴的上皮细胞所覆盖,表面观凹凸不平;大口黑鲈鳃耙的尖齿直径和长度分别为蓝鳃太阳鱼鳃耙的3.4-3.8倍和2.1-3.8倍;两种鱼的鳃丝末端略为膨大呈勺状,鳃丝表面都具有规则或不规则分布的环形微嵴、沟、坑、孔等结构;大口黑鲈鳃丝之间的距离相对较大,蓝鳃太阳鱼的鳃丝间距离仅为大口黑鲈的83%-88%;大口黑鲈鳃小片的高度、厚度和片间距都大于蓝鳃太阳鱼。文中还比较探讨了大口黑鲈和蓝鳃太阳鱼的形态结构与其生理功能之间的关系。     

Apparent digestibilities of common feedstuffs for bluegill Lepomis macrochirus and largemouth bass Micropterus salmoides using individual test ingredients

Apparent digestibility of dry matter and energy, and availability of amino acids from blood meal (BM), fish meal (FM), meat and bone meal (MBM), poultry by-product meal (PBM), soybean meal (SBM), corn, wheat and yellow grease (YG) were determined for bluegill Lepomis macrochirus (mean weight, 57 g), and likewise, but not for BM or wheat, for largemouth bass Micropterus salmoides (mean weight, 30 g). To avoid nutrient interaction from a reference diet, diets containing 98.5% (985 g kg⁻¹) of test ingredients were used, except for semi-solid, YG which was mixed with corn to permit pelletization. Faeces were collected by a siphoning method. Apparent dry matter digestibility values ranged from 50% (corn) to 87% (BM) for bluegill and from 53% (MBM) to 76% (PBM) for largemouth bass. Apparent energy digestibility values ranged from 53% (corn) to 92% (BM) for bluegill and from 63% (MBM) to 93% (YG) for largemouth bass. Apparent digestibility of most amino acids exceeded 90% for evaluated protein sources, except for MBM which showed slightly lower values (80–90%) for both fishes. Isoleucine digestibility from BM was relatively low (82%) for bluegill. High digestibility values for SBM, PBM and BM, indicate good potential for replacing FM in diets for both fishes.