养殖刺参“化板症”病原菌的分离与鉴定

本研究对辽宁4家刺参育苗场患“化板症”的稚参进行了病原学分析,从患有“化板症”的稚参体表病灶处分离得到一株优势菌Aj2010072802A90.人工回接感染试验证实,该细菌能使稚参发生厌食、萎缩、降低附着力、溃烂、死亡等现象,具有较强的致病性,为此次“化板病”的病原菌.在此基础上,利用细菌形态观察、生理生化及16S rDNA分子生物学方法对该菌株进行了鉴定,结果显示,该菌为副溶血弧菌Vibrio parahaemol yticus.这是副溶血孤菌导致海参感染的首次报道.此外,本研究针对该病原菌进行了药敏学测试,证实所分离的副溶血弧菌菌株对氟苯尼考等药物高度敏感,相关研究结果将为刺参疾病防控和健康养殖提供了理论依据和技术支撑.     

养殖刺参溃疡病病原菌RH2的鉴定及其生物学特性分析

从患溃疡病养殖刺参(Apostichopus japonicus)病灶处分离出3株优势菌(RH1、RH2、RH3),以浸浴、体腔注射、体壁肌肉注射等方式进行感染实验,证实菌株RH2为养殖刺参溃疡病的病原菌,其对刺参的LD50(半数致死量)每尾为5.68×106CFU,并证实浸浴、体腔注射的方式无法感染刺参,该菌可能通过体表创伤侵入的方式感染刺参。经形态学观察、生理生化特性分析、16SrRNA和HSP60基因测序确定菌株RH2为溶藻弧菌(Vibrio alginolyticus)。基于16S rRNA基因构建的系统发育树显示,菌株RH2与溶藻弧菌(AF513447)亲缘关系最近,置信度为50%;HSP60基因序列分析表明RH2与溶藻弧菌(AY332570、AF230931)聚为一个分支,且置信度高达99%。菌株RH2的最适生长盐度为25~35,最适生长pH为7.2~8.0,最适生长温度为14~22℃。对18种药物的敏感实验证实菌株RH2对诺氟沙星、复方新诺明、壮观霉素等较为敏感。     

刺参养殖池塘中一株植物乳杆菌的分离及其生物学特性

2017年5月，从山东东营刺参(Apostichopus japonicus)养殖池塘底泥中分离获得49株乳酸菌。以刺参“腐皮综合征”的2株致病菌[灿烂弧菌(Vibrio splendidus)和假交替单胞菌(Pseudoalteromonas nigrifaciens)]为指示菌进行拮抗作用实验，获得1株具有显著抑菌活性的乳酸菌CLY-5，对该菌株进行了生理生化实验、16S rDNA序列分析、生长特性及其对刺参的安全性研究。结果显示，菌株CLY-5对灿烂弧菌和假交替单胞菌具有较好的抑制作用，且菌株的胞内产物与胞外产物均具有抑菌效果，抑菌圈分别为20 、23 mm和27 、38 mm，胞外产物的拮抗作用优于胞内产物。利用该菌对刺参进行高浓度浸浴测试其安全性，浓度为1×109、1×108和1×107 CFU/ml，实验期间刺参状态良好，无死亡现象。16S rDNA序列分析表明，CLY-5与植物乳杆菌(Lactobacillus plantarum NR117813.1)的相似性为100%，初步鉴定该菌株为植物乳杆菌。菌株CLY-5在30℃~44℃、pH 6~8范围内生长较快，20 h进入对数生长期，28~32 h达到生长高峰。筛选的植物乳杆菌具有良好的抑菌能力，且其生长特性适应刺参池塘的养殖环境，为刺参疾病的生态防控及乳酸菌资源的开发提供应用数据参考。     

福建海区网箱养殖刺参“腐皮综合症”病原分析与鉴定

2011年冬季,福建省宁德市霞浦县海区网箱养殖刺参发生"腐皮综合症",并伴有死亡现象出现。刺参的发病症状表现为:厌食、排脏、身体萎缩、体表局部溃烂乃至大面积溃烂。从患病刺参病灶处分离得到两种优势细菌CS1和CS2。经人工回接感染实验证明两种菌对健康刺参都具有较强的感染性,且感染病参的症状与自然发病刺参的症状相同。通过生理生化试验、16S rDNA序列分析及系统进化树分析,结果表明两株菌分别与灿烂弧菌(Vibrio splendidus)和假交替单胞菌(Pseudoalteromonas sp.)相似。菌株CS1与灿烂弧菌的亲缘关系最近,相似率达到99%,菌株CS2与假交替单胞菌的亲缘关系最近,相似率达到95%。菌株CS1可鉴定为灿烂弧菌,菌株CS2可鉴定为假交替单胞菌。另外,在患病刺参呼吸树膜和腔体内发现大量后口虫(Boveria sp.)。所以导致本次刺参"腐皮综合症"的原因可能是致病性细菌和寄生虫共同作用的结果。本文首次揭示了该地区"腐皮综合症"导致养成刺参大规模死亡的致病原因,对刺参病害防治和健康养殖具有重要的指导意义。     

刺参养殖池塘一株贝莱斯芽孢杆菌的分离及其生理特性

2014年5月,在东营的刺参(Apostichopus japonicus)养殖池塘环境中对水样和底泥样品进行了细菌分离和益生菌的筛选,共获得66株可培养细菌。以刺参"腐皮综合征"主要致病菌为指示菌进行拮抗作用实验,使用选择培养基对菌株的产淀粉酶和蛋白酶能力进行测定,筛选获得一株潜在益生菌株——DY-6,并进行了生理生化实验、16S r DNA基因序列分析、菌株生长特性及其对刺参的安全性研究。结果表明,DY-6对其指示菌假交替单胞菌(Pseudoalteromonas nigrifaciens)、灿烂弧菌(Vibrio splendidus)、副溶血弧菌(Vibrio parahaemolyticus)和溶藻弧菌(Vibrio alginolyticus)均有良好的抑制作用,抑菌圈直径分别达到24 mm、22 mm、27 mm和37 mm,对淀粉和蛋白培养基的水解直径分别为28 mm和20 mm。利用该菌对刺参进行高浓度胁迫实验测试其安全性,实验期间浸浴组和投喂组刺参状态良好,没有发病和死亡现象。利用细菌生理生化和16S r DNA基因序列分析表明,DY-6与贝莱斯芽孢杆菌(Bacillus velezensis CP015911)的相似性为99%。因此,初步鉴定该菌株为贝莱斯芽孢杆菌。同时,将该菌株与商品化微生态制剂产品中分离的4株益生菌进行了比较,DY-6在温度20~35℃、盐度0~35范围内生长较快,优于上述4株菌,4 h进入对数生长期,10 h达到生长高峰。筛选的贝莱斯芽孢杆菌具有良好的抑菌能力,生长速度快,并且具有广温广盐的优点,不仅能够降低疾病发生率,还可更好地适应黄河口地区夏季水温偏高、盐度波动大的特点,由此具有良好的益生菌商业化开发潜力。     

南移仿刺参体表溃疡症病原菌的分离鉴定及药敏分析

从福建省霞浦县网箱吊笼养殖的患病仿刺参(Apostichopus japonicus)体壁中分离得到1株优势菌。人工感染实验证实该菌株为致病菌,经形态学、生理生化指标、16S rRNA序列分析和Biolog自动微生物鉴定系统鉴定,确定该病原菌为哈维氏弧菌(Vibrio harveyi)。药敏试验表明,该病原菌对阿奇霉素、大观霉素、呋喃妥因、氯霉素、头孢吡肟、头孢呋辛、头孢噻肟、头孢他啶、头孢哌酮和复方新诺明等11种抗生素类药物敏感。     

养殖刺参溃疡病病原学研究

自2002年冬季以来,山东、辽宁等省的养殖刺参几乎每年冬天都大规模爆发溃疡病。本文研究了刺参溃疡病的特征和症状,从病参体表和体内分离出优势菌,经回归感染证实其就是引发本次刺参溃疡病的病原菌。对病原菌进行鉴定发现,该菌革兰氏染色呈阴性,电镜下观察呈短杆状,极端单鞭毛,综合研究该菌在形态、生理生化等方面的特性,确认分离到的病原菌为交替假单胞菌,交替假单胞菌作为养殖刺参的病原菌在国内外属首次报道。     

刺参腐皮综合征重要病原灿烂弧菌DNA的探针制备及应用

腐皮综合征是近年来刺参养殖最重要的疾病，导致刺参大批死亡和惨重的经济损失。以其主要致病原灿烂弧菌（Vibrio splendidus）DNA为模板，PCR扩增出16s-23s间隔区序列，将该片段克隆进pMD19-T Vector，转化大肠杆菌DH5a，获得重组质粒转化菌并进行测序。根据序列、设计引物，合成177bp的地高辛标记DNA探针。该探针对灿烂弧菌的DNA呈现特异性，而对其它细菌Vibrio fluvialis、Vibrio anguillarum、Vibrio alginolyticus、Aeromonas hydrophila、Vibrio harveyi、Vibrio parahaemolyticus、Vibrio vulnificus的核酸均呈阴性；探针对灿烂弧菌DNA的检出极限为6.25pg, 具有较高敏感度。应用该探针对人工感染以及从青岛、烟台、威海获取的腐皮综合征发病海参和养殖水体进行斑点杂交探针检测，其检出率均为100%。研究结果表明，该探针具有良好的特异性和敏感性，可成功用于快速检测养殖刺参“腐皮综合征”重要病原灿烂弧菌。该方法应用于刺参腐皮综合征的检测尚属首次，它将为刺参腐皮综合征的快速诊断、疾病防治和养殖生产提供技术支撑和参考。     

养殖刺参腐皮综合征 2 种致病菌间接荧光抗体快速检测方法

以养殖刺参(Apostichopus japonicus)腐皮综合征的2种致病菌:灿烂弧菌(Vibrio splendidus)和假交替单胞菌(Pseudoalteromonas nigrifaciens)为抗原,分别制备兔抗血清。以载玻片为介质,建立了2种病原菌的间接荧光抗体检测技术(IFAT)。交叉反应、阻断试验和吸收试验结果均表明本方法特异性强。对人工感染实验中的养殖水体及发病刺参溃烂组织检测,可以检出水体和患病刺参溃烂组织中的相应病原菌,病原菌被染成明亮的黄绿色,检测灵敏度2.4×104cell/mL。冰冻切片检测结果显示,在刺参肿胀嘴部与溃烂肌肉处有大量染成黄绿色的细菌颗粒。结果表明:采用IFAT可以对刺参腐皮综合征2种致病菌进行准确快速的检测。该方法的建立对刺参腐皮综合征的流行病学调查及快速诊断具有重要意义。     

池塘养殖刺参病原菌塔式弧菌的分离与鉴定

2013年春季,福建漳州地区池塘养殖刺参(Apostichopus japonicus)感染不明病原而患病。病参表现出排脏、身体萎缩、体表溃烂等症状,俗称为"腐皮综合征"。为确定引起该病的病原菌,从患病刺参病灶部位分离得到1株优势菌FJY001,经回接感染试验,证实所分离的细菌为刺参的病原菌。经形态、生理生化、16S rRNA序列分析和Biolog微生物自动鉴定系统等多项指标鉴定,确定该病原菌为塔式弧菌(Vibrio tubiashii)。     

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.