3种水产消毒剂对暗纹东方鲀稚鱼的急性毒性试验

在水温21~23℃,pH 8.20~8.50,溶解氧6.00~7.50mg/L条件下,采用半静水法研究了苯扎溴铵、戊二醛和聚维酮碘对全长(1.73±0.32)cm、体质量(0.19±0.01)g暗纹东方鲀稚鱼的急性毒性效应。试验结果表明,苯扎溴铵对暗纹东方鲀稚鱼24、48、72h和96h半致死质量浓度分别为1.04、0.95、0.72mg/L和0.53mg/L;戊二醛对暗纹东方鲀稚鱼24、48、72h和96h半致死质量浓度分别为4.27、3.55、2.94mg/L和2.40mg/L;聚维酮碘对暗纹东方鲀稚鱼24、48、72h和96h半致死质量浓度分别为269.80、200.00、158.54mg/L和151.09mg/L。苯扎溴铵、戊二醛和聚维酮碘对暗纹东方鲀安全质量浓度分别为0.24、0.74mg/L和32.97mg/L,均高于其厂家推荐使用质量浓度,可以在暗纹东方鲀生产中使用。但暗纹东方鲀对苯扎溴铵和戊二醛较为敏感,在生产过程中应严格控制使用质量浓度。     

盐度对寄主暗纹东方鲀(Takifugu obscurus)存活影响及其对车轮虫的杀灭作用

为防治河鲀车轮虫病,分别设置0、2.5、5.0、7.5、10.0、12.5、15.0、17.5、20.0、25.0、30.0、35.0和40.0共13个盐度梯度,对暗纹东方鲀进行了浸浴实验。结果显示,盐度为15以下,对暗纹东方鲀的存活没有影响;盐度为0、2.5、5.0时,4 d内车轮虫的数量没有减少反而有增加趋势;盐度7.5作用4 d,盐度10.0作用3.5 d,盐度12.5作用3 d,杀虫率可达95%以上;盐度15.0作用32 h,盐度17.5作用24 h,盐度20.0作用10 h,盐度25.0作用4 h,盐度30.0作用1.5 h,盐度35.0作用1 h,盐度40.0作用0.5 h,对车轮虫的杀虫率均可达100%。应用SPSS软件,对杀虫盐度和时间进行拟合曲线方程分析,其数学模型为对数曲线方程y=34.19-5.55lnx。另外,车轮虫在暗纹东方鲀体表的复活试验显示,用提高盐度的方法杀灭暗纹东方鲀体表车轮虫后,再恢复到正常养殖盐度5.0的情况下,暗纹东方鲀的体表车轮虫病不再复发,说明盐度7.5以上能治疗暗纹东方鲀的车轮虫病。结合提高盐度治疗暗纹东方鲀车轮虫病的生产性试验结果,建议以盐度为7.5–15.0作为治疗暗纹东方鲀体表车轮虫的适宜盐度。     

盐度对寄主暗纹东方鲀(Takifugu obscurus)存活影响及其对车轮虫的杀灭作用

为防治河鲀车轮虫病,分别设置0、2.5、5.0、7.5、10.0、12.5、15.0、17.5、20.0、25.0、30.0、35.0和40.0共13个盐度梯度,对暗纹东方鲀进行了浸浴实验。结果显示,盐度为15以下,对暗纹东方鲀的存活没有影响;盐度为0、2.5、5.0时,4 d内车轮虫的数量没有减少反而有增加趋势;盐度7.5作用4 d,盐度10.0作用3.5 d,盐度12.5作用3 d,杀虫率可达95%以上;盐度15.0作用32 h,盐度17.5作用24 h,盐度20.0作用10 h,盐度25.0作用4 h,盐度30.0作用1.5 h,盐度35.0作用1 h,盐度40.0作用0.5 h,对车轮虫的杀虫率均可达100%。应用SPSS软件,对杀虫盐度和时间进行拟合曲线方程分析,其数学模型为对数曲线方程y=34.19-5.55lnx。另外,车轮虫在暗纹东方鲀体表的复活试验显示,用提高盐度的方法杀灭暗纹东方鲀体表车轮虫后,再恢复到正常养殖盐度5.0的情况下,暗纹东方鲀的体表车轮虫病不再复发,说明盐度7.5以上能治疗暗纹东方鲀的车轮虫病。结合提高盐度治疗暗纹东方鲀车轮虫病的生产性试验结果,建议以盐度为7.5–15.0作为治疗暗纹东方鲀体表车轮虫的适宜盐度。     

盐度对暗纹东方鲀幼鱼生长及摄食的影响

为研究盐度对暗纹东方鲀幼鱼生长和摄食的影响,将暗纹东方鲀幼鱼在盐度分别为0、10、17、26、40的水体中饲养6周,比较不同盐度下幼鱼存活率、特定生长率、摄食率和饲料系数的差异。结果表明:当盐度为40时,暗纹东方鲀幼鱼的死亡率为100 %;各盐度组的特定生长率无显著差异;幼鱼的摄食率随着盐度的增高而下降。在淡水环境中,暗纹东方鲀幼鱼的摄食率最高,达5.02 %;在高盐度水体中最低,为3.75 %。暗纹东方鲀幼鱼的饲料系数随着盐度的升高逐渐升高,淡水组和26盐度组与10、17盐度组有显著差异。     

野生与养殖暗纹东方鲀肌肉中矿物元素的组成分析

对养殖暗纹东方鲀（平均体重618．5g）和野生暗纹东方鲀（平均体重685.5g）肌肉中矿物元素的组成进行了分析，结果表明：暗纹东方鲀肌肉中钙含量较高（野生鱼平均为：250mg／100g，养殖鱼平均为：141mg／100g），并含有重要生理功能的锌、锰、铁等微量元素。检测发现，投喂营养价值较高的配合饵料进行淡水养殖的人工繁殖暗纹东方鲀，其肌肉中许多矿物元素含量与野生鱼非常接近。     

非离子氨氮和亚硝酸盐氮对暗纹东方鲀稚鱼的急性毒性试验

在水温21~23℃,pH 8.2~8.5,溶解氧6.00~7.50mg/L的条件下,采用半静水法研究了非离子氨氮和亚硝酸盐氮对全长(1.6±0.2)cm、体质量为(0.11±0.05)g的暗纹东方鲀稚鱼的急性毒性效应。试验结果表明,暗纹东方鲀稚鱼受到非离子氨氮和亚硝酸盐氮胁迫后,先后出现鱼体体色变白、扭曲、侧游、失去平衡、昏迷等中毒症状。随着非离子氨氮和亚硝酸盐氮质量浓度的提高和胁迫时间的延长,暗纹东方鲀稚鱼死亡率逐渐升高,存在明显的剂量效应和时间效应关系。非离子氨氮和亚硝酸盐氮对暗纹东方鲀稚鱼96h半致死质量浓度分别为0.46mg/L(95%置信限0.34~0.64mg/L)和290.12mg/L(95%置信限255.16~329.87mg/L),安全质量浓度分别为0.046 mg/L和29.01mg/L。非离子氨氮和亚硝酸盐氮对暗纹东方鲀稚鱼具有一定毒性,且非离子氨氮毒性大于亚硝酸盐氮毒性。     

雷州马尾藻幼体培育中丛簇羽藻的生态防治

采用弱光、低盐处理雷州马尾藻(Sargassun leizhouense)幼苗及其污染生物丛簇羽藻(Bryopsis caespitosa)。结果表明:盐度0～13,培养24h丛簇羽藻死亡率达100%;盐度20,培养24h后恢复培养2d,丛簇羽藻呈负生长,成活率由66.7%降为33.3%,而雷州马尾藻在盐度20以上呈正生长,成活率100%。光照强度0～2000lx培养3d丛簇羽藻死亡率达100%,而雷州马尾藻在光照强度300Lx以下,生长出现负增长,500～2000Lx光强时呈正生长,并随着光照强度增强其相对生长率加快,成活率为100%。因此,采用海水盐度20处理24h,光照强度300Lx培养3d,可有效防治雷州马尾藻幼苗培育中丛簇羽藻危害。     

不同投饵率对暗纹东方鲀幼鱼生长的影响

比较投饵率水平分别为3%、4%、5%、6%时,对暗纹东方鲀幼鱼生长、饲料效率的影响,以确定暗纹东方鲀幼鱼阶段的适宜投饵率。在23℃下,对规格为3.45～3.56g的暗纹东方鲀幼鱼进行30d的生长实验,结果表明:不同投饵率对暗纹东方鲀幼鱼的特定生长率、质量相对增加率、饲料效率、存活率均有显著影响(p<0.05);暗纹东方鲀幼鱼的适宜投饵率为4%,在投饵率为4℅时,质量相对增加率为116.04±0.04%,饲料效率达83.70±0.02%,特定生长率为111.49±0.03%/d,存活率为84.44±0.02%。     

暗纹东方鲀越冬盐度试验

为研究不同温度条件下盐度对暗纹东方鲀幼鱼越冬成活率的影响,于2012年底进行了盐度梯度试验,测定在不同温度(8、10、12、15℃)下,(50±2.32)g的暗纹东方鲀在不同盐度(0、1.5、3.0、4.5、6.0)下的越冬成活率,并通过大棚自然越冬试验进行验证。结果表明:同一温度条件下,在试验盐度范围内,随着盐度的升高,暗纹东方鲀的越冬成活率也逐渐提高;而在同一盐度下,随着温度的升高,暗纹东方鲀的越冬成活率也逐渐提高。当盐度为0时,暗纹东方鲀无法在自然温度下安全越冬;当盐度为4.5时,水温在8℃以上,暗纹东方鲀即能安全过冬,其越冬成活率达到80%以上。暗纹东方鲀大棚自然越冬试验证明,随着温度的下降逐渐增加水体盐度的方法经济而有效,当温度为15、12、10、9℃时,将相应的水体盐度调节为1.5、3.0、4.5、4.5,经过150 d的越冬期,两种规格(50~60 g和20~40 g)暗纹东方鲀的成活率分别为93.7%和80.5%。     

施氏鲟水霉病病原的初步研究

从患水霉病的施氏鲟(Acipenser schrenckii)幼鱼肌肉中分离获得一株优势水霉菌株XJ001.大麻籽上水霉XJ001培养物的形态观察表明,菌丝透明无间隔,分枝少;新孢子囊以层出方式产生或从旧孢子囊根部长出,游动孢子按水霉属方式释放;在7℃、15℃和25℃条件下不能产生有性器官,但能够产生大量的厚垣孢子.电镜观察发现第二孢孢子表面具有大量弯曲的长毛,其在25%GY培养液中呈现出间接萌发.根据形态及生理学特征将水霉XJ001鉴定为寄生水霉(Saprolegnia parasitica).水霉XJ001的最适生长温度为25℃,对NaCl敏感,当PDA培养基中NaCl质量分数为1%和2%时,水霉生长抑制率分别为37.4%和75.6%;质量分数大于3%时,生长被完全抑制.用水霉XJ001对异育银鲫(Carassius auratus gibelio)进行人工感染,结果表明XJ001有较强的致病力,异育银鲫感染严重,体表出现棉花状白毛,感染率为83.3%,感染后的死亡率为100%,可见XJ001是施氏鲟水霉病的病原菌.[中国水产科学,2009,16(1):89-96]     

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.