单次投喂乳酸诺氟沙星在鳜鱼体内的代谢消除规律

水温(28±2)℃时,按20mg/kg的剂量给平均体质量(500±10)g的鳜鱼单次口服乳酸诺氟沙星,服药后0.5、1、2、3、4、6、8、12、24、48、72、96h,分别测定鳜鱼血浆、肌肉、肝脏和肾脏中的药物含量,采用非房室模型分析药物在鳜鱼体内的代谢消除规律。结果显示,乳酸诺氟沙星在鳜鱼血浆、肌肉、肝脏、肾脏中的达峰时间分别为4.333、6、3、5h,达峰质量浓度分别为3.625、2.39、33.089、19.375mg/L,各组织中肝脏吸收的药物含量最高,其次是肾脏、血浆和肌肉;乳酸诺氟沙星在鳜鱼血浆、肌肉、肝脏、肾脏中的消除半衰期分别为42.589、131.652、16.830、30.558h,药物在肝脏中消除速度最快,而在肌肉中消除最慢。以肌肉中药物残留限量为50μg/kg计,建议单次投喂乳酸诺氟沙星的休药期不低于24d。     

盐酸氯苯胍在眼斑拟石首鱼体内的药代动力学和残留消除规律研究

在水温(28±2)℃、盐度28条件下,采用30mg/kg的剂量口灌法,用HPLC-MS/MS检测研究了盐酸氯苯胍在体质量为(350.15±5.18)g的眼斑拟石首鱼体内的药代动力学和残留消除规律。结果显示,单剂量口灌给药后,眼斑拟石首鱼血浆中盐酸氯苯胍的药时数据符合一级吸收二室模型,药物在血浆中的达峰时间、血药质量浓度峰值、药时曲线下面积和消除半衰期分别为2.39h、958.78μg/L、33 247.57μg/(L·h)和19.24h;盐酸氯苯胍在肌肉、肝脏和肾脏的血药含量峰值分别为156.72、227.68μg/kg和553.44μg/kg,达峰时间分别为2.0、1.5、2.0h;药时曲线下面积分别4664.04、4897.74、17 228.19μg/(kg·h);消除半衰期分别为19.68、24.33、22.81h。按30mg/kg剂量连续5d口灌给药后,鱼血浆、肌肉、肝脏、肾脏中的药物消除半衰期(t1/2)分别为24.46、35.39、39.60、33.94h。若以10μg/kg为最高残留限量,肌肉作为食用靶组织,在本试验条件下,建议休药期不少于7d。     

诺氟沙星在日本鳗鲡体内的代谢动力学及残留消除规律

为研究诺氟沙星(NFX)在鳗鲡体内的代谢和消除规律,以超高效液相色谱-串联质谱法测定日本鳗鲡在混饲口灌后血液和组织中NFX的含量变化,并进行药动学分析。结果表明,NFX以30 mg/kg的剂量单次混饲口灌日本鳗鲡后,吸收分布迅速,达峰时间(T_(max))、吸收(T_(1/2Ka))和分布半衰期(T_(1/2α))分别为3.000、1.012和1.570 h;NFX在鳗鲡体内消除较快,消除半衰期(T_(1/2β))为15.267 h,总清除率(CL)为1.315 L/(h·kg)。此外,峰浓度(C_(max))为1.273 mg/L,药时曲线下面积(AUC_(0~∞))为22.670 mg/(L·h)。NFX以30 mg/kg的剂量连续3 d混饲口灌日本鳗鲡后,在肌肉、肝脏、肾脏和血浆中的消除速率常数分别为0.144、0.125、0.102和0.093 1/d。根据WT1.4计算的理论休药期(WDT)分别为肌肉22.97 d,肝脏21.30 d,肾脏33.40 d,血浆18.29 d。本研究结果为诺氟沙星在水产动物中的实际应用提供理论依据。     

甲砜霉素在大菱鲆体内的代谢及消除规律

为研究甲砜霉素(thiamphenicol)在大菱鲆(Scophthalmus maximus)体内的代谢动力学特征和残留消除规律,本研究采用液相色谱-串联质谱法检测甲砜霉素混饲口灌后在大菱鲆血浆、肌肉、肝脏和肾脏等样品中的时间-浓度变化。甲砜霉素以30 mg/kg的剂量单次混饲口灌,采集给药后48 h内的药时数据,并以DAS软件非房室模型进行分析,结果显示,甲砜毒素在大菱鲆血浆中达峰浓度(C_(max))和达峰时间(T_(max))分别为21.968μg/m L和9 h,药时曲线下面积[AUC_((0—∞))]为319.754 mg/(L·h),表观分布容积(Vz/F)为6.206 L/kg,平均滞留时间[MRT_((0—∞))]和消除半衰期(T1/2z)分别为33.984 h和45.841 h。甲砜霉素在大菱鲆的肌肉、肝脏和肾脏组织中达峰浓度(C_(max))分别至22.346、27.128和47.718μg/g;在肝脏中达峰时间较快(4 h),在肌肉和肾脏组织中均在9 h;在肾脏中的达峰浓度(C_(max)=47.718μg/g)和药时曲线下面积AUC(0-∞)最大,为517.768 mg/(L·h),表明肾脏对甲砜霉素的吸收能力最高;在肝脏中的平均滞留时间[MRT_((0—∞))=36.565 h]最长,消除半衰期T1/2z为42.370 h,即给药后48 h内甲砜霉素在肝脏中的消除较慢。甲砜霉素以60 mg/kg的高剂量单次给药后,采集30 d内的药时数据并以WT程序进行计算,结果显示甲砜霉素在大菱鲆血浆、肌肉、肝脏和肾脏中的理论休药期分别为8.90、10.64、18.19和23.95 d。本研究结果可为甲砜霉素在大菱鲆中的合理应用提供科学依据。     

三聚氰胺在斑点叉尾鮰体内的残留及代谢规律研究

(21±1)℃水温条件下,研究了三聚氰胺在斑点叉尾鮰(Ictalurus punctatus)体内的残留消除规律。结果显示:血浆中药时数据符合有吸收一室开放模型,动力学方程为:C=3.952660(e-0.027279t-e-0.127279t),吸收半衰期(T1/2kα)为5.4469 h,消除半衰期(T1/2ke)为25.4093 h,达峰时间(Tp)为15.4045 h,达峰浓度(Cmax)为20.3985 mg/L,表观分布容积(Vd)为2.5763(mg/kg)/(mg/L)。肌肉、肝、肾中吸收半衰期(T1/2kα)分别为3.5582、4.1884、5.4397 h,消除半衰期(T1/2ke)为50.8081、23.3504、23.7242 h,达峰时间(Tp)为14.6766、12.6524、14.9967 h,达峰浓度(Cmax)为7.6449、22.9249、40.6047 mg/L,表观分布容积(Vd)为8.5657、2.3970、1.2712(mg/kg)/(mg/L)。结果表明:药物在体内吸收迅速,药物浓度较高,分布广泛,消除较为缓慢。以80 mg/kg剂量混饲口灌3 d后,各组织中三聚氰胺含量总体呈现肾脏>肝脏>肌肉。停止灌药后第5天肌肉中及第7天肝脏和肾脏组织中三聚氰胺含量低于我国(2008)卫生部公布的乳制品及含乳食品中三聚氰胺临时管理限量值和欧盟对中国进口产品设定了三聚氰胺的最大残留限2.5 mg/kg。     

复方磺胺嘧啶口灌给药在拟穴青蟹(Scylla paramamosain)体内药动学和组织分布与消除

研究了水温为(27±1)℃、盐度为10条件下,单剂量(100 mg/kg)口灌给药复方磺胺嘧啶(磺胺嘧啶SD∶甲氧苄啶TMP=5∶1)后,SD和TMP在拟穴青蟹(Scylla paramamosain)体内的药动学以及在肌肉、肝胰腺和鳃组织中的分布和消除规律。结果显示,拟穴青蟹口灌复方磺胺嘧啶后,血淋巴中SD和TMP药物浓度-时间关系曲线均符合一级吸收二室模型,SD和TMP的峰浓度(C_(max))分别为49.56 mg/L和2.79 mg/L,药时曲线下面积(AUC)分别为1417.6 mg/L·h和82.7 mg/L·h;肝胰腺是SD和TMP峰浓度最高的组织,其C_(max)分别为59.36 mg/kg和74.82 mg/kg。由此可见,大量TMP蓄积在肝胰腺中,进入血液循环的TMP很少。在鳃组织中,SD和TMP的C_(max)分别为51.89 mg/kg和42.58 mg/kg,消除半衰期分别为23.28 h和25.29 h;鳃组织中药物浓度比较高,且消除速度较快,推测其在药物代谢中承担着消除功能。在肌肉中,SD和TMP的C_(max)分别为44.95 mg/kg和10.09 mg/kg,消除半衰期分别为25.09 h和35.08 h。以0.1 mg/kg和0.05 mg/kg分别为SD和TMP的最高残留限量(MRL),95%置信区间,推算SD和TMP在拟穴青蟹肌肉中的理论休药期分别为290.6 h和302.8 h,在肝胰腺中分别为340.4 h和377.0 h。     

复方磺胺嘧啶口灌给药在拟穴青蟹(Scylla paramamosain)体内药动学和组织分布与消除

研究了水温为(27±1)℃、盐度为10条件下,单剂量(100 mg/kg)口灌给药复方磺胺嘧啶(磺胺嘧啶SD:甲氧苄啶TMP=5:1)后,SD和TMP在拟穴青蟹(Scylla paramamosain)体内的药动学以及在肌肉、肝胰腺和鳃组织中的分布和消除规律.结果显示,拟穴青蟹口灌复方磺胺嘧啶后,血淋巴中SD和TMP药物浓度-时间关系曲线均符合一级吸收二室模型,SD和TMP的峰浓度(Cmax)分别为49.56 mg/L和2.79 mg/L,药时曲线下面积(AUC)分别为1417.6 mg/L.h和82.7 mg/L·h;肝胰腺是SD和TMP峰浓度最高的组织,其Cmax分别为59.36 mg/kg和74.82 mg/kg.由此可见,大量TMP蓄积在肝胰腺中,进入血液循环的TMP很少.在鳃组织中,SD和TMP的Cmax分别为51.89 mg/kg和42.58 mg/kg,消除半衰期分别为23.28 h和25.29 h;鳃组织中药物浓度比较高,且消除速度较快,推测其在药物代谢中承担着消除功能.在肌肉中,SD和TMP的Cmax分别为44.95 mg/kg和10.09 mg/kg,消除半衰期分别为25.09 h和35.08 h.以0.1 mg/kg和0.05 mg/kg分别为SD和TMP的最高残留限量(MRL),95％置信区间,推算SD和TMP在拟穴青蟹肌肉中的理论休药期分别为290.6 h和302.8 h,在肝胰腺中分别为340.4 h和377.0 h.     

恩诺沙星及其代谢物环丙沙星在欧洲鳗鲡体内的代谢动力学

采用高效液相色谱法,研究药饵口灌给药途径下,恩诺沙星及其代谢物环丙沙星在欧洲鳗鲡(Anguilla anguilla)体内的药代动力学。欧洲鳗鲡口灌给药恩诺沙星10 mg/kg后,其血浆、肌肉和肝脏中药物时量曲线关系符合一级吸收的二室开放动力学模型。恩诺沙星在欧洲鳗鲡不同组织中分布较广,血浆、肌肉和肝脏的Vd分别为6.362 L/kg、8.081 L/kg和15.870 L/kg;恩诺沙星在鳗鲡体内消除较慢,在血浆、肌肉和肝脏中的消除半衰期(tβ1/2)分别为161.10 h、333.21 h和611.26 h,总体清除率(CLs)分别为27.4 mL/(kg.h)、16.8 g/(kg.h)和18.0 g/(kg.h)。代谢物环丙沙星在鳗鲡血浆、肌肉和肝脏中药物水平的变化趋势与恩诺沙星基本相似,呈现出多峰现象,但3种组织中环丙沙星出现第一个药峰时间分别为给药后第24小时、24小时和12小时,3种组织中环丙沙星峰值水平肝脏中最高、肌肉中次之、血浆中最低,环丙沙星在肌肉和肝脏中的消除速率比较缓慢。鉴于恩诺沙星和其代谢物环丙沙星在欧洲鳗鲡体内消除较慢,建议养成阶段使用其他药物。     

洛美沙星在鲤鱼体内的药物动力学及残留

用高效液相色谱 (HPLC)测定方法研究洛美沙星在鲤鱼 (Cyprinuscarpio)体内的药物动力学和残留。洛美沙星以 2 0mg/kg体重单剂量口灌鲤鱼后 ,测定其血浆药物浓度 ,最低检测限为 0 0 5 μg/mL ,动力学模型符合开放性有吸收二室模型 ,药物动力学参数 :表观分布容积 (Vd/F)、吸收半衰期 (tl/ 2kα)、分布半衰期 (t1/ 2α)以及消除半衰期 (t1/ 2 β)分别为 5 2 1L/kg、 0 31h、 1 0 2h、 2 0 0 3h ,其药时曲线下面积(AUC)为 110 92 μg·h/mL。以相同剂量单次口灌鲤鱼后 ,在不同的天数测定了鲤鱼皮肤、肌肉和肝胰脏中洛美沙星的残留 ,在给药 12天后 ,洛美沙星在各组织中均能检测到且残留均低于 0 0 8μg/g ,结果表明洛美沙星在鲤鱼体内消除缓慢、残留期较长 ,休药期不低于 12天。     

诺氟沙星在大菱鲆体内药代动力学及残留消除规律

利用高效液相色谱法分别测定了单次和多次混饲口灌大菱鲆诺氟沙星(NFLX)后鱼体主要组织中的NFLX含量。通过MCP-KP药动学程序对NFLX在大菱鲆体内的药代动力学及残留消除规律进行了分析研究。结果表明,以30mg/kg的剂量单次混饲口灌大菱鲆,NFLX在大菱鲆体内的达峰时间(Tmax)为2h,血、鳃、肾脏、肝脏、肌肉的达峰浓度(Cmax)分别为:8.365、7.519、1.871、6.485和4.060μg/g;NFLX在组织中的消除半衰期(T1/2)由小到大依次为:肝脏8.18h<肌肉12.39h<鳃丝15.29h<血液23.22h<肾脏23.25h。连续5d以30mg/kg的剂量混饲口灌大菱鲆,消除半衰期(T1/2)由小到大依次为:肌肉74.88h<血液98.16h<肝脏186.43h<鳃192.12h<肾脏200.45h。以上研究表明,诺氟沙星在大菱鲆体内的吸收较为迅速,有利于疾病的预防和治疗用药。在组织中以肾脏中的残留最为显著。使用诺氟沙星进行大菱鲆疾病的预防和治疗时,至少停药30d后方可上市销售。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.     

Migratory dynamics of stream-spawning longnose gar (Lepisosteus osseus)

Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions.     

Nutritional regulation of hepatocyte fatty acid desaturation and polyunsaturated fatty acid composition in zebrafish (Danio rerio) and tilapia (Oreochromis niloticus)

The desaturation and elongation of [1-¹⁴C]18:3n-3 was investigated in hepatocytes of the tropical warm freshwater species, zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus). The hepatocyte fatty acid desaturation/elongation pathway was assayed before and after the fish were fed two experimental diets, a control diet containing fish oil (FO) and a diet containing vegetable oil (VO; a blend of olive, linseed and high oleic acid sunflower oils) for 10 weeks. The VO diet was formulated to provide 1% each of 18:2n-6 and 18:3n-3, and so satisfy the possible EFA requirements of zebrafish and tilapia. At the end of the dietary trial, the lipid and fatty acid composition was determined in whole zebrafish, and liver, white muscle and brain of tilapia. Both zebrafish and tilapia expressed a hepatocyte fatty acid desaturation/elongation pattern consistent with them being freshwater and planktonivorous fish. The data also showed that hepatic fatty acid desaturation/elongation was nutritionally regulated with the activities being higher in fish fed the VO diet compared to fish fed the FO diet. In zebrafish, the main effect of the VO diet was increased fatty acid Δ6 desaturase activity resulting in the production of significantly more 18:4n-3 compared to fish fed the FO diet. In tilapia, all activities in the pathway were greater in fish fed the VO diet resulting in increased amounts of all fatty acids in the pathway, but primarily eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). However, the fatty acid compositional data indicated that despite increased activity, desaturation of 18:3n-3 was insufficient to maintain tissue proportions of EPA and DHA in fish fed the VO diet at the same level as in fish fed the FO diet. Practically, these results indicate that manipulation of tilapia diets in commercial culture in response to the declining global fish oil market would have important consequences for fish fatty acid composition and the health of consumers. Scientifically, zebrafish and tilapia, both the subject of active genome mapping projects, could be useful models for studies of lipid and fatty acid metabolism at a molecular biological and genetic level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of diatom–bacteria biofilm isolated from Seriola lalandi cultures for aquaculture application

Controlled incorporation of selected microalgae and bacteria in aquaculture systems can be beneficial because they can act as microbiological control. That is why the characteristics of biofilm generated naturally in Seriola lalandi culture cages were analysed, their potential benefit to the growth of larvae was studied, and their controlled use for improving the larval viability and as a vector to improve incorporation of previously studied probiotic bacteria was tested. According to biodiversity results, these biofilms are composed of a diatom–bacteria mix showing a decrease in biodiversity in laboratory culture conditions being dominated by Navicula phyllepta and bacteria of the family Rhodobacteraceae. This can be produced on mesh substrates incorporated in bioreactors with rapid growth rate and adhesiveness. Preliminary results from the addition of substrates with this specific biofilm in larvae culture systems showed that it is consumed by the larvae without negative effects, while positive effects on the viability of larvae in combination with probiotics were observed. Considering preliminary results, the addition of these specific substrates with diatom–bacteria biofilms could be a good improvement for aquaculture systems and together with the use of probiotics can contribute to maintaining a stable and controlled system improving the viability of the larval fish culture in its early stages.