工厂化水体LED光照沉水植物对氨氮的吸收

本文研究了沉水植物伊乐藻（Elodea nuttallii）在白色LED灯处理水产养殖中氨氮的效果。在50×33cm和45×28em鱼缸中放入体质量150±5g鲫（carassius auratus）7尾,放入伊乐藻1．2kg,应用白色LED灯为光源,用遮光纸遮光,放入28w循环泵进行交叉循环。12d饲养结果表明：伊乐藻不仅可吸收养殖排泄的氨氮、增加水体溶解氧,而且养殖鱼类代谢的二氧化碳可以促进沉水植物生长,具有生态循环利用的效能,为进一步研究循环水养殖的生态利用提供了参考。     

汉江中段伊乐藻过度生长的生态调度调控研究

汉江中游丹江口至王甫洲江段近年来伊乐藻（Elodea nuttallii）过度生长，对水生态系统平衡和水电站运行造成较大影响。基于伊乐藻生长与关键生境要素的响应关系，构建控制伊乐藻过度生长的生态调控方案。采用野外调查和受控试验观测方法，探明伊乐藻生长的环境影响因子及其阈值。结果显示，岸边伊乐藻形成单一优势群落的临界水深为3.0~3.5 m，生长极限深度的光照强度阈值为400~500 lx，生长水温在3~30℃，其中10℃可能是伊乐藻由慢速向快速生长转变的温度阈值；影响伊乐藻生长分布的临界流速约为0.14 m/s，流速越大对其生长越不利。研究表明:(1)大坝加高蓄水后，丹江口至王甫洲江段下泄流量和水温等条件变化，可能是促进伊乐藻过度生长的重要原因，通过丹江口水库联合王甫洲水电站开展生态调度控制伊乐藻过度生长具有可行性；(2)根据伊乐藻萌发和定植规律，每年春季和秋末是开展水生态调度以控制伊乐藻过度生长的最佳时机，建议丹江口水库下泄流量峰值不小于1 500 m3/s，或达到最小下泄流量的2~3倍（峰值流量不低于1 000 m3/s），每次调度持续时间不少于5 d，调度过程不少于2次。     

枸杞岛海藻场角蝾螺夏季摄食选择性及其生态学意义

于2013年夏季对枸杞岛海藻场螺类优势种角蝾螺进行了稳定同位素、摄食选择性、消化代谢物粒径等系列实验.稳定同位素结果显示,角蝾螺是牧食性生物,在藻场中的营养级为2.12,属初级消费者,底栖海藻是角蝾螺的主要食源,贡献率为94.5％;摄食选择性实验结果显示,角蝾螺具有较宽的摄食选择,能够摄食海带、铜藻、粗枝软骨藻等1 1种大型藻类,其中铜藻及蜈蚣藻是枸杞岛潮下带的重要优势种;消化代谢物实验结果显示,角蝾螺的啃食作用能为藻场碎屑提供增量,角蝾螺对海藻场碎屑的增量为(0.016 ～0.094)g/d,经过啃食及消化作用产生的碎屑主要粒级为1Φ(＞ 250 μm).稳定同位素分析—摄食选择偏好实验—螺类消化代谢物粒径分析的系列研究表明,角蝾螺在枸杞岛海藻场的群落食物网中,可以起到连接牧食食物链和碎屑食物链的重要作用.     

控制汉江丹江口-王甫洲区间伊乐藻的生态调度及其效果评估

为科学有效控制汉江丹江口至王甫洲区间伊乐藻过度生长繁殖,研究生态调度的实施效果。采用生物量调查法、分布面积统计法、数学模型模拟法分别分析评价生态调度实施前后总生物量的变化情况,分布面积的变化情况,以及对丹江口水库下泄流量的需求。结果表明,连续三年实施生态调度,伊乐藻总生物量由2019年的4.8万t减少至2022年的40.11t,分布面积由11.60 km₂^减少至0.23km2,减幅均达到了95%以上, 伊乐藻生物量占沉水植物总生物的比重从99.99%减少至17%,生态调度效果较好。春季生态调度应重点从增加流量极值比出发进行中度干扰,夏秋季生态调度重点从满足0.14m/s临界流速出发进行大流速冲刷。     

瘦肉型猪苏钟Ⅰ、Ⅱ系肥育性能与胴体性状的观测

选取十世代苏钟Ⅰ系，八世代苏钟Ⅱ系及两系生产的杂交猪120头，进行肥育性能测定结束后选取32头屠宰，观测其胴体性状，结果表明：苏钟Ⅰ系日增重（g）618.56±18.29，饲料报酬3.23，胴体瘦肉率（％）为54.12±0.88，脂肪率（％）25．77±0.73，眼肌面积（cm2）29、40±2.70，平均膘厚（cm）2.35±0.12；苏钟Ⅱ系日增重（g）634.74±21.52，饲料报酬3.21，胴体瘦肉率（％）54.47±0.40，脂肪率（％）25.58±0.35,眼肌面积（cm2）29.60±2.20，平均膘厚（cm）2.37±0.11；Ⅰ系杂交猪日增重（g）702．69±11.60，饲料报酬3.14，胴体瘦肉率（％）58.90±0.40，脂肪率（％）20.59±0.41，眼肌面积（cm2）32.10±2.80，平均膘厚（cm）2.3±0.11；Ⅱ系杂交猪日增重（g）72.722±12.30，饲料报酬3.11，胴体瘦肉率（％）58.80±0．45，脂肪率（％）20．27±0．41，眼肌面积（cm2）32．60±3．00，平均膘厚（cm）2．31±0.17，观测结果表明，苏钟Ⅰ、Ⅱ系及其杂交猪具有较强的肥育性能和良好的胭体品质，是生产商品杂交猪的优良母系猪。     

典型滨海翅碱蓬盐沼湿地土壤理化特征研究

为了解滨海潮间带盐沼湿地翅碱蓬生长的土壤环境,2013年7月～8月采集辽宁盘锦、辽宁庄河、天津、山东东营及江苏连云港5个不同纬度典型滨海翅碱蓬生长区域土壤,研究了其理化特征。结果表明,翅碱蓬可生长的我国滨海潮间带湿地土壤含盐量（2.5±0.5）g/kg～（19.0±6.1）g/kg、氯离子含量（1.16±0.04）g/kg～（11.27±0.3.43）g/kg、pH （7.05±0.01）～（8.96±0.01）、碱度（3.56±0.59）mmol/kg～（8.78±0.78）mmol/kg、全碳含量（7.70±1.84）mg/kg～（21.73±4.11）mg/kg,全氮含量（0.36±0.03）mg/kg～（0.87±0.04）mg/kg、无机氮含量（1.95±0.95）mg/kg～（16.10±1.57）mg/kg、速效磷含量（5.26±0.33）mg/kg～（39.98±0.61）mg/kg、速效钾含量（0.53±0.19）mg/kg～（1.77±0.01）mg/kg,其中铵氮含量（1.60±0.58）mg/kg～（8.76±0.16）mg/kg、亚硝酸盐氮含量（0.01±0.00）mg/kg～（0.11±0.00）mg/kg、硝酸盐氮含量（1.00±0.20）mg/kg～（2.54±1.09）mg/kg。土壤N:P比平均值为0.80±0.25、N:K比平均值为17.77±6.08、P:K比平均值为26.90±4.67;TC:TN比平均值为26.50±4.67。在符合这些土壤特征的滨海潮间带光滩可采用翅碱蓬进行生态修复。     

3种沉水植物对夏季高温强光照环境的生理响应

为了研究外来沉水植物伊乐藻（Elodea nuttallii）和埃格草（Egeria densa）对夏季自然高温强光照环境的生理响应,选择同科本地种轮叶黑藻（Hydrilla verticillata）作对比,在2014年8月夏季自然环境下进行实验处理,分别在第0、3、6、9、12、15天测定各物种的叶绿素含量、最大光能转化效率（Fv/Fm）、丙二醛含量和脯氨酸含量,以分析其变化情况。结果显示,高温与强光照对3种沉水植物的生理特征都有显著影响,特别是对其光合作用影响显著,且长期高温强光照环境的影响更大。第1-3天,温度升高至31℃左右,伊乐藻的叶绿素含量和3种植物的Fv/Fm显著低于初始值（P<0.05）;第4-6天温度持续在32℃左右,3种植物的叶绿素含量和Fv/Fm显著低于初始值（P<0.05）,且伊乐藻和埃格草的丙二醛含量显著高于初始值（P<0.05）;除了第3天埃格草的叶绿素含量外,整个实验期间伊乐藻和埃格草的叶绿素含量和Fv/Fm显著低于初始值（P<0.05）,在第12天和第15天时轮叶黑藻的叶绿素含量与初始值无明显差异（P>0.05）,第9天和第12天轮叶黑藻的Fv/Fm与初始值无明显差异（P>0.05）,并且整个实验期间轮叶黑藻的丙二醛含量和脯氨酸含量与初始值均无明显差异（P>0.05）,表明轮叶黑藻通过较快恢复光合作用并维持体内抗氧化系统的稳定,对夏季高温强光照环境展现出较好的适应能力。光合作用能力降低以及长期高温强光照条件下,丙二醛含量显著增加,使得外来种伊乐藻和埃格草不适合在高温强光照环境中生长,夏季高温与强光照环境将会抑制其入侵和扩散。外来种伊乐藻和埃格草对高温强光照的耐受力低于本地种轮叶黑藻。     

湖北梁子湖四种螺的形态与壳强度初步研究

测定了湖北梁子湖的铜锈环棱螺（Bellamya aeruginosa）、长角涵螺（Alocinma longicornis）、中华沼螺（Parafossarulus sinensis）和耳萝卜螺（Radix auricularia）的壳形态性状和壳强度。四种螺类壳形态可量性状之间以及壳形态可量性状与壳强度之间均呈显著的正相关,且存在明显的种间差异。还探讨了螺类形态和壳强度与反捕食功能的关系。     

三沙湾大黄鱼网箱养殖衍生有机物的沉降特征

为了解三沙湾大黄鱼（）网箱养殖衍生有机物（AOM）的沉降特征，采用原位实验方法，收集区域内使用颗粒饲料和冰鲜饵料两种典型饲喂方式下距离网箱200 m范围内AOM样品，分析其沉降量、营养物质[颗粒有机物（POM）、颗粒有机碳（POC）、颗粒态氮（PN）、总磷（TP）]沉降通量和扩散特点。研究结果表明，饲喂颗粒饲料状态下AOM沉降量显著高于投喂冰鲜饵料，两者均值分别为（563.66±119.18）g/（m²·d）和（266.07±139.15）g/（m²·d）。POM、POC、PN和TP沉降通量在两种饲喂方式下的差异与之相似，饲喂颗粒饲料时各参数均值分别为（27.25±2.43）g/（m²·d）、（6.03±0.58）g/（m²·d）、（0.66±0.06）g/（m²·d）和（0.39±0.04）g/（m²·d）；饲喂冰鲜饵料时各参数均值分别为（13.04±1.62）g/（m²·d），（3.57±0.45）g/（m²·d）、（0.51±0.06）g/（m²·d）和（0.22±0.04）g/（m²·d）。沿近底层海流主导流向距离养殖网箱100 m的空间范围内，AOM沉降量和营养物质沉降通量均呈现自网箱处递减的变化特征，下降程度在饲喂冰鲜饵料时尤为显著。AOM中POC、PN和TP含量在饲喂冰鲜饵料时较高，在距离养殖网箱50 m范围内呈现递减趋势。综上，在三沙湾大黄鱼网箱养殖过程中，投喂颗粒饲料引发的环境污染程度高于冰鲜饵料，两种情形下的AOM沉降影响主要限于距离养殖网箱50~100 m的空间范围。三沙湾内饲喂颗粒饲料引发较高营养物质沉降通量源于较大的AOM沉降量，此现象说明养殖过程中可能存在颗粒饲料过度投喂、饵料利用效率较低等问题，围绕此类问题的针对性研究对于减缓区域内养殖活动的环境影响具有重要意义。     

2种塔形马蹄螺肌肉营养成分分析与品质评价

为分析深圳大鹏湾和海南琼海塔形马蹄螺(Tectus pyramis)的营养成分与品质,采用国标法检测了2种塔形马蹄螺肌肉的基本营养成分、氨基酸组成、脂肪酸组成及部分矿物元素含量,氨基酸评价采用氨基酸评分、化学评分和必需氨基酸指数方法。结果显示,海南琼海捕捞的塔形马蹄螺肌肉灰分含量显著高于深圳大鹏湾海域,其他基本营养成分无显著差异(P>0.05);深圳大鹏湾和海南琼海塔形马蹄螺肌肉总氨基酸含量分别为(18.45±0.13)和(18.83±0.03) g/100g,必需氨基酸含量均高于27%,支链氨基酸含量超过13%,鲜味氨基酸含量为55%。2种塔形马蹄螺肌肉多不饱和脂肪酸含量均>48%,其中,深圳大鹏湾塔形马蹄螺亚油酸、α-亚麻酸、二十碳五烯酸(EPA)、二十二碳六烯酸(DHA)含量显著高于海南琼海海域,且DHA+EPA含量高达11.79%。检测的3种矿物元素中,含量最高的均是常量元素钙(Ca),微量元素铁(Fe)次之,最低的是微量元素锌(Zn),且海南琼海塔形马蹄螺肌肉的Ca和Zn含量显著高于深圳大鹏湾海域。研究表明,2种塔形马蹄螺蛋白含量高,多不饱和脂肪酸含量丰富,肌肉营养价值高,具有很大的开发潜力,研究数据为进一步开发利用岛礁海域新型螺类食品提供参考。     

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.