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1.
Incomplete eye migration is one of the major problems in intensive production of juvenile Atlantic halibut. More than 60% of an average juvenile population reared according to best practice suffers from this abnormality. In commercial production, these fish are discharged and represent a substantial economic loss and a large welfare problem. In the present investigation it is demonstrated that by controlling diurnal light and darkness periods together with a meal based feeding regime, incomplete eye migration can be dramatically reduced in production systems for Atlantic halibut.Control groups were reared under continuous light conditions, whereas the experimental groups were given 7 h of darkness and 17 h of light during a 24 hour cycle, in a period lasting from 12 to 35 days post first-feeding. Otherwise both groups were reared under continuous light conditions. All larvae were fed short time enriched Artemia supplied two times daily.The experimental conditions did not affect the overall growth or survival up to day 85 after first feeding. However, 27 ± 3% of the fry reared under continuous light conditions had complete eye migration, whereas in juveniles reared under shifting light and darkness conditions, complete eye migration was 85 ± 7%. These results represent a major improvement in production systems for Atlantic halibut juveniles.  相似文献   

2.
Abstract— Hydrogen peroxide is being evaluated for its potential as a therapeutic compound for a variety of external disease organisms of fish. The value of hydrogen peroxide as a therapeutic compound for use in walleye Stizustedion vitreum culture has been questioned due to the high sensitivity (i.e., high mortality) of walleyes to this compound. We conducted bioassays and histopathological studies to determine if exposure of walleye to hydrogen peroxide bath treatments would result in increased tolerance to subsequent exposure. Test fish exhibited increased tolerance to hydrogen peroxide after initial exposures. This phenomenon of increased tolerance of walleyes to hydrogen peroxide may be of value in the development of management strategies for the successful treatment of fish diseases.  相似文献   

3.
Three cases of pyogranulomatous cephalic osteochrondritis of intensively reared rainbow trout, Oncorhynchus mykiss (Walbaum), and Atlantic salmon, Salmo salar L., in Canada and Chile, respectively, were examined for histopathological and bacteriological changes, and by using immunohistochemistry. Bilateral exophthalmia and intraocular haemorrhage were the most common gross lesions seen in the Ontario fish. Histologically, the major pathological changes seen in all cases involved the developing bone and cartilage of the head region, including the eye. Necrosis and pyogranulomatous inflammation of the scleral cartilage (necrotic scleritis) were the major ocular changes. Similarly, lysis of cephalic cartilage and immature bone, accompanied by pyogranulomatous inflammation, usually progressing to fibrosis, were the most common lesions associated with the cranial changes in both the rainbow trout and Atlantic salmon. Routine histological staining, including special stains, failed to reveal the presence of pathogens associated with these lesions. However, immunohistochemical staining of representative sections from all cases with rabbit anti- Flexibacter psychrophilus serum (ATCC 49510) demonstrated significant numbers of antigenically related bacteria within the leading edge of some of the scleral and cephalic osteochondritic lesions. Axenic cultures of Flexibacter psychrophilus were recovered from the eye lesions of the rainbow trout, but it was not possible to reproduce ocular lesions experimentally. However, mortality was produced following intramuscular injection of rainbow trout with bacteria.  相似文献   

4.
Tilapia has a significant potential for culture in saline environments. There is an increasing demand among tilapia producers to develop a tilapia hybrid that can survive well in marine water conditions. This study compared mean weight (MWT), daily growth rate (DGR), specific growth rate (SGR), survival, feed conversion ratio (FCR), condition factor (K), production rate (PR) and rate of skin lesions, and tail and fin rot as well as eye cataract in the Genetically Improved Farmed Tilapia strain (GIFT) of the Nile tilapia, Oreochromis niloticus (NN) and the salt‐tolerant Oreochromis spilurus (SS), and their F1 reciprocal hybrids; O. niloticus ♀ x O. spilurus ♂ (NS) and O. spilurus ♀ x GIFT O. niloticus ♂ (SN) in freshwater (0 g L?1) and seawater (40 g L?1). Fish (3.5 g) were stocked at 150‐fish m?3 and fed with sea bream pellets (47% protein) for 180 days. Results showed that in seawater, the SN hybrid had the highest values for MWT (165.9 g), DGR (0.9 g fish?1 day?1), SGR (2.14% day?1), survival (96.3%), PR (23.9 kg m?3) and best FCR (1.53) followed by the NS hybrid and the NN parent. Both hybrids had significantly lower rates of skin lesions and fin and tail rot than the NN genotype. In freshwater, the NN had the highest values for MWT (255.1 g), DGR (1.40 g fish?1 day?1), SGR (2.38% day?1), K (2.13%) and PR (34.9 kg m?3) followed by the NS and SN hybrids. High estimate of heterosis for MWT (41.3%), DGR (42.5%), SGR (10.7%) and survival (22.1%) was obtained in the hybrids reared in seawater, indicating that a hybrid vigor was produced and the fast growth trait from the GIFT parent was successfully combined with the salinity tolerance trait from the O. spilurus parent. The better growth performance and survival of the SN hybrid in seawater indicate that this hybrid is more suitable for culture in seawater than its reciprocal hybrid.  相似文献   

5.
The marine leech, Zeylanicobdella arugamensis, is a major threat to aquaculture in grouper-producing countries including Indonesia. This study aimed at investigating prevalence, intensity and histopathology of the ectoparasite in humpback and hybrid groupers cultured in different rearing systems. A total of 260 groupers (60 humpback groupers and 200 hybrid groupers) were used for samples. The marine leech was observed on skin, fins, gills and mouth, followed by histopathological assay on the skin tissue. The results showed that prevalence of the leech in both groupers was higher when they were cultured in the floating net cages compared with the hatchery, p < .05. Furthermore, humpback grouper had a higher prevalence than hybrid grouper when they were cultured in a similar system, p < .05. Meanwhile, there was no significant difference in intensity between the two groupers, p > .05. Within the hybrid groupers, the highest prevalence was obtained from hybrid groupers reared in the earthen ponds. Histopathological studies showed that the infected groupers exhibited inflammation, congestion and erosion of the epidermis layer. Hybrid grouper had more severe histopathological lesions in the skin tissues. These results suggested that species and type of aquaculture system had significantly determined the prevalence, intensity and severity of lesion in Z. arugamensis infestation.  相似文献   

6.
Abstract Ocular pathologic findings in eyes of ascorbic acid-deficient juvenile red drum, Sciaenops ocellatus (L.), are described. Abnormalities in the most severely affected eyes included: reduced globe size and lack of normal globe rigidity; vascular congestion and intraocular haemorrhage; lenticular lesions which included disorganization of posterior cortex, vacuolation of posterior subcapsular cortex and posterior migration of lens epithelium; and severe central retinal degeneration. The authors suspect that retinal degeneration was related to phototoxic injury, to which these fish had increased susceptibility as a result of ascorbic acid deficiency. The cause for lenticular lesions was undetermined, but may have been related directly to ascorbic acid deficiency, indirectly to retinal degeneration, or both.  相似文献   

7.
林位琅 《齐鲁渔业》2006,23(8):14-15
从北方引进皱纹盘鲍子一代杂交种苗,在罗源湾岗屿周边海域养殖,经过2年的试养取得可喜结果,解决了现有盘鲍种质严重退化的棘手问题,改善了鲍的种质。  相似文献   

8.
Abstract.— Young-of-the-year (Age 0+) walleyes Stizostedion vitreum were exposed to hydrogen peroxide at 10 mg/L for 1 h in an effort to increase their tolerance to subsequent exposures to hydrogen peroxide at therapeutic concentrations that are considered to be toxic. The effects of age of fish and water hardness on the effectiveness of this pre-treatment protocol were examined. Trials were performed in fish at four ages (50-d, 60-d, 86-d, and 95-d post-hatch) and under three different water quality conditions (soft water: hardness = 64.4 mg/L, alkalinity = 56.5 mg/L; medium hard water: hardness = 103.3 mg/L, alkalinity = 51.5 mg/ L; hard water: hardness = 130.3 mg/L, alkalinity = 92 mg/L). A benefit of pre-treatment was only observed when it was performed under hard water conditions and only with walleyes at 60- and 86-d post hatch. The pre-treatment protocol appeared to be detrimental to fish in the youngest age group (50-d post-hatch) under all three water quality conditions.  相似文献   

9.
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10.
Many studies have documented that hatchery‐reared salmonids generally have inferior survival after being stocked compared with wild conspecifics, hatchery and wild salmonids have been observed to differ in their antipredator responses. The response of brown trout (Salmo trutta) juveniles (0+) of differing backgrounds to a live predator was compared in two experiments. First, the antipredator behaviour of predator‐naïve hatchery‐reared brown trout and wild‐exposed brown trout were assessed in behavioural trials which lasted for eight days. Second, predator‐naïve and predator‐conditioned hatchery‐reared brown trout were assessed in identical behavioural trials. Brown trout were ‘predator‐conditioned’ by being held in a stream‐water aquarium with adult Atlantic salmon (Salmo salar) and adult brown trout for two days prior to behavioural trials. Predator‐conditioned hatchery‐reared brown trout spent more time in shelters in the trial aquaria than predator‐naïve hatchery‐reared fish, but did not differ in time spent in the predator‐free area. Predator conditioning may account for the increased time spent in the shelter, but does not appear to have affected time spent in the predator‐free area. However, even if significant alteration in behaviour can be noted in the laboratory, the response might not be appropriate in the wild.  相似文献   

11.
Cobia Rachycentron canadum juveniles (119.7 mm TL, weight 8.5 g) were reared for 10 wk at three salinity levels: 5 ppt, 15 ppt. and 30 ppt. Growth and survival were determined through biweekly sampling. Blood samples obtained at termination of the study were analyzed to determine hematocrit, blood osmolality, and total protein. Results indicated that the overall growth of fish was significantly affected by salinity. Mean (± SE) total length (TL) and weight of fish reared at a salinity of 30 ppt were 201.7 ± 2.6 mm and 47.6 ± 1.9 g, respectively, followed by fish reared at 15 ppt (182.2 ± 1.7 mm, 34.1 ± 1.6 g). and 5 ppt (168.3 ± 5.8 mm TL, 28.3 ± 2.3 g). Differences in specific growth rates among treatments for the 10-wk period were also significant. No differences were detected in mean survival among fish reared at salinities of 5, 15, and 30 ppt (84, 94, and 94%, respectively). However, fish reared at salinity 5 ppt appeared to be in poor health as skin lesions, fin erosion, and discoloration were evident. Analysis of blood revealed that, while no differences existed among treatments with respect to plasma total protein, fish reared at a salinity of 5 ppt exhibited significantly reduced hematocrit (25% vs. > 30%) and plasma osmolality values (318 vs. > 353 mmolkg) relative to fish reared at higher salinities. Cobia can tolerate exposure to low salinity environments for short periods of time without mortality; however, moderate to high salinities are required for sustained growth and health of this species.  相似文献   

12.
There is a trend toward the increased incidence and prevalence of Edwardsiella piscicida septicemia in US catfish aquaculture, particularly in channel ♀, Ictalurus punctatus, × blue ♂, I. furcatus, hybrid catfish. From 2013 to 2017, a total of 3242 disease case submissions were made to the Aquatic Research and Diagnostic Laboratory (ARDL) at the Thad Cochran National Warmwater Aquaculture Center in Stoneville, MS. Of these, 1400 (43.2%) were hybrids. E. piscicida was suspected in 138 (4.3%) of cases, the majority of which (89.1%) were from hybrid catfish. A molecular survey of these isolates confirmed the majority (92.0%) to be E. piscicida. Furthermore, cases of E. piscicida from hybrids submitted to the ARDL and the Aquatic Diagnostic Laboratory of the Mississippi State University College of Veterinary Medicine in Starkville, MS, were documented for gross lesions and histological analysis. Grossly, E. piscicida presents with small dermal ulcerations, a raised fluid‐filled cranial midline lesion that is frequently ulcerated, hemorrhage in the gills, exophthalmia, and abdominal distension. Internally, lesions include splenomegaly, straw‐colored ascites, renomegaly, and occasionally hemorrhagic intestines. Histopathological examination is in agreement with gross observations, and infected fish repeatedly demonstrate a mononuclear meningoencephalitis, hemorrhagic branchitis, splenitis, ulcerative dermatitis, granulomatous interstitial nephritis, and hepatitis coupled with a hemorrhagic enteritis.  相似文献   

13.
Limb‐loss in crustaceans can reduce moult increment and delay or advance the timing of moulting, both aspects that are likely to impact upon soft‐shell crab production. Pond‐reared blue swimmer crabs Portunus pelagicus were harvested and maintained in a crab shedding system. The wet weight, carapace width (CW) and the occurrence of limb‐loss were assessed before stocking in the shedding system and after each of the next three moults. Many of the crabs were initially missing one or two limbs and these did not grow as much as the crabs that were intact at the start of the trial. Despite its strong correlation with wet weight, CW changes proved to be misleading. Limb‐loss reduced the %CW increment but not the per cent weight increment (where the later is calculated from the actual pre‐moult weight). Pre‐moult weight explained much of the variation in post‐moult weight, with crabs moulting to approximately double their weight. Limb‐loss reduced ‘growth’ and production from the pond because it reduced pre‐moult weight but limb‐loss did not alter the weight change on shedding a given weight of crabs, although some of that change now included regeneration of limbs. One can hypothesize that much of the size variation seen in pond‐reared crabs may be due to accumulated effects of repeated limb‐loss, rather than genetic variation.  相似文献   

14.
Severe clinical mycobacteriosis with consistent ocular lesion localization was diagnosed in a population of 800 juvenile tank‐reared Cobia (Rachycentron canadum) which experienced a sudden increase in mortality approximately 5 months after arriving into Trinidad and Tobago from Florida, USA. Moderate daily mortality (15–20 animals per day) persisted for just over 1 month. Moribund fish displayed circling behaviour and had an open‐mouth gape upon death. Fish consistently presented with bilateral exophthalmia, corneal cloudiness and hyphema. Non‐branching acid‐fast rods were detected in aqueous humour touch preparations. Histological analysis revealed severe bilateral intra‐ocular granulomatous responses in all specimens. Mycobacterium sp. was identified using a real‐time PCR assay detecting the RNA polymerase β‐subunit (rpoB) gene in different tissue samples. Specimens did not present with characteristic granulomatous responses usually seen in viscera. To the best of our knowledge, this represents only the third documentation of piscine mycobacterial infection presenting with only localized ocular lesions, and the second documented case of mycobacteriosis in cobia. It is, however, the first documentation of an ocular presentation of mycobacteriosis in a marine species and is the first documentation of such a presentation in cobia.  相似文献   

15.
太♂洋牡蛎与近♀牡蛎、褶♀蛎人工杂交的初步研究   总被引：17，自引：5，他引：17  
周茂德  高允田  吴融 《水产学报》1982,6(3):235-242
本文介绍了以太平洋牡蛎、近江牡蛎、褶牡蛎为亲本的多种组合杂交试验。试验共分为:近?×太?,太?×近?,褶?×太?,太?×褶?四个试验组进行;另外还有三种牡蛎的三个自交组作为对照。试验结果表明,在适宜的环境条件下几种牡蛎的正反交均可受精。其中褶?×长?的受精率较高,而长×近的正反交的受精率均较低。杂交子:代的D型幼虫的大小性状一般表现为母本特征,而且其大小变异范围比亲本自交大。此外,文中对各组合的幼体发育作了比较,并对环境因子的影响进行了探讨。  相似文献   

16.
Abstract A skin disease of intensively reared salmonids in Ontario hatcheries, known to the farmers as'no-mucus skin disease', is reported for the first time. It was characterized by erosive and ulcerative lesions found mainly on the flanks of fingerlings, which resulted in exposure of the tips of the scales. Associated with these lesions were colonies of bacteria seen in the SEM to be clustered round the mucous cell pores and under-running the margins of epithelial cells. The cause of this condition is unknown, although the response of fish to formalin treatment, and the presence of bacilli seen in skin scrapings and in the SEM, suggest that bacteria are responsible.  相似文献   

17.
Abstract The histopathology of red disease was studied in samples of Penaeus monodon from a commercial prawn farm in the Philippines and in a single pond–reared adult P. stylirostris from Hawaii. The principal lesion type observed in prawns from both locations was a marked atrophy and necrosis of the hepatopancreas that was accompanied by an intense cellular inflammatory response. Less commonly, melanized cellular inflammatory lesions were observed in the antennal gland, mandibular organ, gonads, midgut and gills. The aetiology of red disease is unknown, but because of the similarity of hepatopancreatic lesions in red disease to those observed in aflatoxicosis, mycotoxins (or other microbial toxins) present in rancid or spoiled feeds or in the detritus of organically rich ponds are suggested as its cause.  相似文献   

18.
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19.
养殖密度对杂交鳢仔鱼生长与存活的影响   总被引：3，自引：2，他引：3  
在温棚水族箱中养殖杂交鳢仔鱼,养殖密度分别为0.5、1、2、4、8尾/L,共养殖15 d,试验结果表明:养殖密度在0.5～4尾/L之间,杂交鳢仔鱼的最终体重、特定生长率、日增重都随着养殖密度的增大而升高,当养殖密度为4尾/L时,三者达到最大值;进一步增加养殖密度,仔鱼的生长反而下降。高密度组(4、8尾/L)杂交鳢仔鱼个体生长速度离散度明显加大,仔鱼的成活率随养殖密度增加而下降。  相似文献   

20.
日本沼虾体表寄生物对胚胎附着的影响   总被引：3，自引：0，他引：3  
用扫描电镜技术研究了体表寄生物对日本沼虾（Macrobrachium nipponense)受精卵（胚胎）附着的影响，发现在流产个体1－4对腹肢原肢与内肢的表面密布钟虫类原生动物，这些寄生原生动物影响粘液腺的分泌活动，使其不能正常分泌粘液，受精卵的被膜、卵柄及卵索均不能正常形成，卵与卵之间的摩擦力加大，胚胎供氧困难，最终导致死胎和流产，体表寄生物是造成养殖日本沼虾胚胎提早脱落的重要原因之一。  相似文献   

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