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1.
Abstract. An infectious pancreatic necrosis virus (IPNV) carrier stock of Atlantic salmon parr (100 g) was divided between two tanks and inoculated experimentally with tissue homogenate containing the aetiologic agent of infectious salmon anaemia (ISA) and non-ISA tissue homogenate (control), respectively. Plasma and kidney samples from ISA-infected and control fish were taken twice weekly for 25 days. In the kidney samples, IPNV was quantified by a plaque assay. In plasma, anti-IPNV antibodies were measured using an indirect ELISA. The ISA-infection did not seem to activate the IPNV-infection. Neither the proportion of fish with IPNV or anti-IPNV antibodies, nor the IPNV titre or level of anti-IPNV antibodies showed any specific trend during the study. Independently of ISA, IPNV was detected in 54 out of 132 fish (41%), while 71 out of 195 fish (36%) had plasma antibodies against IPNV. No association was found between detection of IPNV, and presence or level of anti-IPNV antibodies in individual fish.  相似文献   

2.
Abstract. An enzyme-linked immunosorbent assay (ELISA) for the demonstration of the virus of spring viraemia of carp (SVCV) in liver, kidney and spleen homogenates, and in infected cell cultures is described. The sensitivity of the method is 102·8–103·5 TCID50 0·lml−1 of the examined fluid. The specificity has been confirmed by the ELISA inhibition test and by results of virological examinations. Contamination with bacteria or fungi of samples taken from dead fish had no effect on the results of ELISA. Specific anti-SVCV sera were used successfully for the production of conjugates for the direct immunoperoxidase and immunofluorescence detection of SVCV in infected cell cultures.  相似文献   

3.
The field use of a staphylococcal coagglutination (COA) test for the detection of infectious pancreatic necrosis virus (IPNV) in tissue samples from Atlantic salmon, Salmo salar L., was evaluated. The COA test was compared with an immunohistochemical (IHC) method for the detection of clinical outbreaks of infectious pancreatic necrosis (IPN). The present paper describes the evaluation of 320 COA test results performed at local fish health laboratories in Norway from 1994 to 1996, and COA test results from two infection trials with IPNV. The agreement between the COA test and the IHC was very good. The agreement beyond chance, measured as kappa values, was 0.74 in individuals and 0.90 in pooled samples. Thus, the COA test was suited for the detection of outbreaks of IPN. Covert infections with IPNV remained undetected by the COA test. The minimum IPNV titre needed to obtain a positive COA test was ≈ 105 TCID50 mL–1.  相似文献   

4.
Rainbow trout, Oncorhynchus mykiss (Walbaum), were exposed continuously to infectious pancreatic necrosis virus (IPNV) at 0, 101, 103 or 105 plaque forming units (pfu) L−1 of water to estimate the effects of chronic IPNV exposure on early life stages. Fish density averaged 35 fish L−1 (low density) or 140 fish L−1 (high density), and the tank flow rate was 250 mL−1 min. Virus exposure began at 6 days before hatch and continued until fish were 44 days old. Cumulative per cent mortality, analysis of survival and hazard functions, and discrete-time event analysis were used to explore the patterns of survival and mortality. In eggs and fish exposed to IPNV, mortality significantly greater than in the 0 pfu L−1 exposure did not occur until IPNV concentration was 105 pfu L−1 at low fish density and 103 pfu IPNV L−1 at high fish density. These results suggest that in the natural aquatic environment, where rainbow trout densities are likely to be considerably lower than in this study, mortality resulting from infection with IPNV will very likely not occur when ambient concentrations of virus are ≤103 pfu IPNV L−1. In aquaculture rearing units, trout density is likely to be as high or higher than the densities used in this study. Therefore, continuous inputs of virus at concentrations greater than 101 pfu L−1 may result in IPN epidemics in aquaculture facilities.  相似文献   

5.
Abstract. Protein and energy maintenance and optimum feed requirements are reported in the catfish, Clarias batrachus (L.), fed a purified diet (40% CP; 1487·1kJ/100g) at 0 to 8% (BW/day) ration levels. Linear (r = 0·985) increase was observed in daily average growth increment up to a ration level of 4% (BW/day), corresponding to 6·03g protein/(kg0·8BW/day) and 224·26 kJ energy/(kg0·8 BW/day). Maintenance requirements, obtained by regressing daily average growth increment to zero, were 0·942 g/(kg0·8 BW/day) for protein and 36·02 kJ/(kg0·8BW/day) for energy. Net gains in muscle protein and energy also depicted linear increase (r = 0·975) with feeding levels up to 6·03g protein/(kg0·8 BW/day) and 224·26kJ energy/(kg0·8 BW/day). On fitting the above data to regression equations, giving the amount of dietary protein and energy required to maintain a constant amount of body protein and energy, values of 1·005g/(kg0·8 BW/day) and 42·11 kJ/(kg0·8BW/day) were obtained for protein and energy respectively. The optimum feeding rate for this species, as evident from specific growth rate and conversion efficiencies, appears to be 3% (BW/day) at 30 ± 2°C. Moisture and lipid contents in muscle were found to be significantly ( P < 0·05) affected by the ration levels.  相似文献   

6.
Abstract. The effect on the growth of freshwater angelfish, Pterophyllum scalare (Lichtenstein) (Pisces; Cichlidae), of different densities of population and diet compositions was studied. The results show that increasing the population density from 50 fish/m2 to 200/m2 significantly decreased the rate of growth of fingerlings, and that this effect is correlated to the size of fish. No significant differences were observed in growth between diets containing 37%, 41% or 47% protein. However, the addition of live food (artemia) to the diet significantly raised the growth rate, especially in the higher protein diets.
Body composition shows no changes during the growth periods, with a mean of 64·68% body protein, 35·47% dry weight fat and no significant differences in the percentage of residual ash through the growth period.
The food conversion rate was very low, ranging from 1·15 to 1·31. Total production increased with density, from 4·0g/m2/day (50 fish) to 13·7g/m2/day (200 fish) over a period of 60 days.  相似文献   

7.
Abstract. The pathogenicity of Renibacterium salmoninarum to carp, Cyprinus carpio L., and rainbow trout, Salmo gairdneri Richardson, was investigated. All carp injected with 4·8 × 108 cells/fish, or 4·8 × 107 cells/fish survived for 38 days. R. salmoninarum was isolated from all moribund fish, but not from the kidney of surviving fish, although R. salmoninarum antigen was detected in several of these fish by the dot blot assay. On the other hand, mortality in rainbow trout was 95% in the fish injected with 4·8 × 108 cells/fish, and 15% in those which received 4·8 × 107 cells/fish. R. salmoninarum antigen was detected by the dot blot assay in all surviving rainbow trout. The number of R. salmoninarum cells was immediately decreased by carp or rainbow trout serum, and the serum bactericidal activity of carp was higher than that of rainbow trout. Carp blood leucocytes had higher phagocytic activity than those of rainbow trout.  相似文献   

8.
Abstract – Larvae and juveniles of perch Perca fluviatilis and bream Abramis brama of Lake Speldrop, a highly eutrophicated gravel-pit lake in the floodplain of the Lower Rhine, were used in laboratory experiments to study predation of perch on bream. In the first series of experiments (control), 0+ perch of 30 mm total length (TL) did not prey on 0+ roach of about 24 mm TL. The perch fed only on zooplankton, resulting in low growth rates of 0.17 mm  ·  day−1. In the second series of experiments, perch (30 mm TL) were combined with 0+ bream with an average TL of 14 and 19 mm at different ratios. As in the first series, even a nine-fold higher amount of zooplankton food had no significant influence on the growth rate of perch, regardless of the perch:bream ratio. At a perch: bream ratio of 7:1 and 4:4 all bream were eaten by the perch and restocked twice daily. At the end of the experiment, the TL of perch at a perch:bream ratio of 7:1 was significantly lower compared to a perch:bream ratio of 4:4 (mean growth rates at 7:1 of 0.16 mm  ·  day−1 and at 4:4 of 0.35 mm  ·  day−1). At the perch:bream ratio of 1:7, perch fed on bream in varying amounts, averaging between 3 and 12 bream per day and per individual. After 20 days, the final length of these fish was always significantly higher than the TL of perch at other perch:bream ratios and increased in correlation to number of bream eaten per day (mean growth rate 1.13 mm  ·  day−1). The results are discussed with respect to the piscivore-dominated fish community of the eutrophied Lake Speldrop. Note  相似文献   

9.
Abstract – Age and growth of juvenile tilapia, Oreochromis niloticus , from Lakes Zwai, Langeno and Chamo (Ethiopia) were studied from microincrements in otoliths. Growth in length was best described by the Gompertz model. Average growth rate of the fish was most rapid in Lake Chamo (0.39 mm  ·  day−1, 1.14%  ·  day−1), intermediate in Lake Zwai (0.20 mm  ·  day−1, 0.72%  ·  day−1) and slowest in Lake Langeno (0.16 mm  ·  day−1, 0.62%  ·  day−1). Similarly, back-calculation from otolith increment widths gave growth rates of 0.28 to 0.43 mm  ·  day−1, 0.15 to 0.32 mm  ·  day−1 and 0.11 to 0.28 mm  ·  day−1 for Chamo, Zwai and Langeno fish, respectively. In addition, Fulton's condition factor was largest for Chamo tilapia and smallest for Langeno tilapia; the difference between fish from Langeno and Zwai was small. Rapid growth of juvenile O. niloticus in Lake Chamo was attributed to warm temperature and better food quality. Note  相似文献   

10.
Abstract – Production of cannibalistic Arctic char ( Salvelinus alpinus (L.)) and their prey conspecifics were estimated in an allopatric population, situated in an alpine ultraoligotrophic lake in central Norway. Estimates of population abundance were obtained by mark recapture and successive removal experiments. Assuming stable age distribution, we estimated mean yearly biomass (±95% CL) of char in sampled size groups vulnerable to predation (60 to 150 mm) to 7.93 (5.11–14.30) kg · ha−1. Similarly, mean yearly biomass (±95% CL) of cannibalistic char (> 250 mm) was estimated to 0.62 (0.50–1.06) kg · ha−1. Annual production (±95% CL) of char in length groups 60 to 150 mm was estimated to be 4.31 (2.74–8.03) kg · ha−1 · year−1, and production (±95% CL) of cannibalistic char to 0.19 (0.15–0.33) kg · ha−1 · year−1. Depending on the food conversion factor (set to vary from 0.1 to 0.4), the cannibalistic char removed from 10% to 40% of the production of char in sampled size-classes vulnerable to predation yearly. The overall ecological efficiency in energy transfer between the prey and predator population was 4.4%.  相似文献   

11.
Intraperitoneal (IP) injection, cohabitation and immersion routes of infection were used to determine if Atlantic cod, Gadus morhua (L.), of 1 and 3 g are susceptible to infectious pancreatic necrosis (IPN). Mortalities of cod injected IP were significantly higher when challenged with infectious pancreatic necrosis virus (IPNV) than with phosphate buffered saline. This is the first report of Atlantic cod mortalities caused by IPNV. Fish challenged by cohabitation had significantly higher mortalities than the controls, but mortalities of Atlantic cod challenged with IPNV by immersion were not significantly different from controls. Titres of IPNV in the tissues of infected fish were sometimes very high (range 102–1010 infectious units per gram of tissue) suggesting virus replication and titres of fish that died were generally higher than those of fish which survived. However, the relatively low mortality rates when challenged by cohabitation and immersion (20% and 17%, respectively), compared to the IP injection challenge (100%) suggest that 1 and 3 g cod have low susceptibility to IPN when challenged by more natural routes. These data strongly suggest that the cause of death of experimentally challenged cod was IPNV and further histological evidence for this came from 1 g cod challenged IP with IPNV in which the pancreas showed severe necrosis and heavy immunostaining for IPNV coincidentally with the peak of mortalities.  相似文献   

12.
Abstract. The autccology of chub, Leudscus cephalus (L.), in the Renlina Stream, Greece, was carried out in an effort to obtain information on the age, growth, mortality and reproduction of this species. Fork length increment during the first year of life was 8·9cm, after which it decreased. Life span was short (maximum age 8 years) and the instantaneous mortality rates were higher for the older age-groups. Chub reached sexual maturity at the second year of life for both sexes and spawning occurred from the second fortnight of April into May, at a mean water temperature of 18°C. The relationship between fecundity ( F ) and fork length (1) was F = 0·0797 L3·63 The average density and biomass were 1·06 fish.m−2 and 11·38g.m−2 respectively. The relationship between L and the pharyngeal bone size [gape ( G ), tip ( T ) and shank ( S )] in mm and caudal fin length ( C ) (cm) can be described by the equations: L = 0·8605 + 1·550 G , L = -0·0703 + 1·332 S, L = 1·092 + 1·615 T and L = 1·032 + 2·934 C .  相似文献   

13.
Abstract. Tiger shrimp, Penaeus monodon Fabricius, post-larvae (32·0±3mg, 1·43±0·03 cm) were exposed to control, 0·12, 0·60, 1·20 and 2·40mg/l ammonia-N (un-ionized plus ionized ammonia as nitrogen) which is equivalent to control, 6,32,63 and 126μg/1 NH3-N (un-ionized ammonia as nitrogen) for 8 weeks in 25 ppt, as pH of 7·85–8·18 and 26–28°C by static renewal method. Growth in weight and length of the shrimps exposed to 1·20 and 2·40 mg/l ammonia-N were significantly lower (P < 0·05) than those exposed to control. The EC50 (concentration that reduced growth by 50% of that of the controls) was 1·33 mg/l ammonia-N, 70 μg/l NH3-N for weight gain, and 2·35 mg/1 ammonia-N, 123μg/l NH3-N for length gain of P. monodon post-larvae. The'maximum acceptable toxicant concentration'(MATC) of ammonia-N and NH3-N for P. monodon post-larvae was 0·60mg/l and 32μg/l, respectively after 6 weeks of exposure.  相似文献   

14.
Abstract. A 156-day cage feeding trial was conducted with fingerling seabass, Lates calcarifer (Bloch), and grouper, Epinephelus tauvina (Forskal), so as to test six different dietary feeding regimes, namely no exogenous feeding (NF), frozen fish (FF), commercial shrimp finisher pellet (SP), in-house prepared dry pellet RDI (RDI) and RD2 (RD2), and an in-house prepared moist pellet (frozen fish: diet Rd1, 40:60 mixture w/w — code MP). Seabass fed FF and MP displayed the best growth response, with fish (30/m3) growing from an initial weight of 8·9g and 8·5g to a final weight of 285·5g and 257·5 g in 156 days, with a food conversion ratio of 3·77–5·10 (dry matter basis 1·15 – 1·95), and with a survival of 93·3 and 93·3% respectively. Similarly, grouper fed FF and MP also displayed the best growth response, with fish (30/m3) growing from an initial weight of 23·8 g and 25·8g to a final weight of 471·7g and 388·7g in 156 days, with a food conversion ratio of 3·53–4·16 (dry matter basis 0·89–1·06) and 1·73–2·96 (dry matter basis 1·06–1·80), and with a survival of 90 and 98·3% respectively. The results are analysed from an economical viewpoint and discussed on the basis of other published studies.  相似文献   

15.
Abstract. Fifty each of F2-generation gold ( gg ), bronze ( Gg ), and black ( GG ) Oreochromis mossambicus (Peters) and either zero, four or eight largemouth bass, Micropterus salmoides , (Lacepède) were stocked in 20-m2 concrete tanks. After 7 days, water in all tanks was drained, and fish in each tank were censused. Largemouth bass ate 18% of the tilapia in the four-bass treatment (1 tilapia/bass/day) and 60% of the tilapia in the eight-bass treatment (1·6 tilapia/bass/day); the difference was significant (P=0–05). In the four-bass treatment there was a greater observed mean predation rate on gold than that on black or on bronze tilapia, but the difference was not significant: largemouth bass ate 25% of the gold tilapia, 16% of the bronze tilapia, and 13% of the black tilapia. In the eight-bass treatment, predation on the gold tilapia was significantly greater than that on both bronze (P=0·05) and on black (P=0·06) tilapia; predation on bronze and black tilapia was similar: largemouth bass ate 80% of the gold tilapia, 48% of the bronze tilapia, and 51% of the black tilapia. Overall average total predation (both treatments combined) on gold tilapia was significantly (P=0·06) greater than that on both bronze and on black tilapia, which did not differ: largemouth bass ate 52% of the gold tilapia, 32% of the bronze tilapia, and 32% of the black tilapia. The increased vulnerability of gold tilapia to predation was a negative pleiotropic effect of the gg genotype.  相似文献   

16.
Abstract. Viral haemorrhagic septicaemia (VHS) is reported for the first time in sea-water cultured rainbow trout. Heavy mortalities with typical signs and lesions A VHS virus (serotype 1) was isolated from the diseased fish. The mortalities were caused only by the VHS virus and 80 days post transfer of trout to sea-water the mortalities reached 85%, of the initial population.
The disease was experimentally transmitted to rainbow trout, both in sea-water 3·104 pfu/ml of virus or by intramuscular injection of various doses of VHS1 (7·101 7·104 or 7·104 pfu per fish). Death occurred in all infected groups and started earlier in sea-water. Typical signs of VHS were observed in moribund fish. Viral multiplication was demonstrated to have occurred in fish organs.  相似文献   

17.
Abstract. The effect of four environmental conditions was investigated upon sperm output in turbot, Scophthalmus maximus (L.), submitted to three different rhythms of stripping. Males kept under a natural light cycle and under a 6-month contracted light programme released a similar sperm output in terms of total volume of semen produced per fish during the experimental period (4·9 ± 0·9ml), mean sperm concentration (29·4 ± 2·8 × 109 spermatozoa/ml) and total sperm number (163·2 ± 40·5 × 109 spermatozoa). Attempts to stimulate spermiation for a second time just after the end of the natural reproduction period resulted in the release of low sperm output (total volume of semen: 1·6 ± 0·4 ml; mean sperm motility: 2 min 36s ± 0 min 47s; mean sperm concentration: 47·6 ± 10·2 × 109 spermatozoa/ml; total sperm number: 84·5 ± 25·3 × 109 spermatozoa). Stripping frequency had no effect on total volume of semen, mean sperm motility and total sperm number. Monthly collection did not modify sperm samples in relation to stripping rank. However, decreasing volume, motility and sperm concentration were observed when males were stripped fortnightly and weekly. During the natural spawning period, the presence of females in the tank enhanced mean sperm motility (from 3 min 27s + 0 min 52s to 6 min 38s ± 1 min 38s).  相似文献   

18.
Abstract. Growth and survival response of Penaeus stylirostris (Stimpson) to fertilization, pelleted feeding and stocking density were analysed for the conditions prevailing on the Baja California peninsula (Mexico). Three 0·25-ha earthen ponds were longitudinally divided in half with mesh structures. One half received inorganic fertilization (trial F) and the other supplementary feeding using a pelletized ration (trial PF). The initial stocking rates were approximately 5, 10 and 15 PL5/m2 in both trials. After 210 days, final mean weights ranged from 15·0 to 5·3g and survival from 48·6 to 17·8%. Growth and survival were analysed by means of a reparameterization of the von Bertalanffy's growth model and the exponential mortality equation. Results indicated that: (1) final mean weight was dependent on density in both trials ( P < 0·01) although growth rate was only affected in trial PF ( P < 0·01); (2) pelleted feeding produced both greater final mean weight and increased growth rate at densities higher than 5 PL/m2 ( P < 0·005); (3) the ratio tail weight/total weight was influenced by density in trial F ( P < 0·015); (4) the mortality equation served to explain differences in survival to a limited extent. An increase in growth rate after 170 days occurring at the intermediate density in trial PF was attributed to an increase in mortality, which allowed the remaining individuals to attain larger sizes. Further research to increase biomass yields should focus on the optimization of pond depth, the supply of vigorous post-larvae and on the possible influences of seasonal variations of planktonic communities of the lagoons on the productivity of ponds.  相似文献   

19.
The use of wrasse as cleaner fish in farming of Atlantic salmon, Salmo salar L., is now widespread in Scotland, Ireland and Norway, but little is known about the susceptibility of these fish to the common pathogens of cage-cultured salmon. The susceptibility of goldsinny wrasse, Ctenolabrus rupestris L., to infectious pancreatic necrosis virus (IPNV) was investigated. Captive-bred C. rupestris were infected with IPNV-Sp (Shetland strain) using a bath challenge method. Two infection doses were used, low (4.1 × 105 pfu mL−−1) and high (2.4 × 106 pfu mL−−1), with two replicates for each experiment. Bathing times were 1 h for the low dose and 5 h for the high dose. A maximum prevalence of infection (30%) was seen 2 weeks post-infection in replicate 1 of the low dose experiment and was accompanied by low tissue titres. The tissue titres dropped to an undetectable level by 4 weeks post-infection. In the high dose experiment, a high prevalence of infection was seen along with moderate titres in tissues as well as a marked pathological response. Both prevalence and intensity declined rapidly and the fish recovered. In the high dose experiment, faecal titres followed the same pattern as those in the tissues. The implications for the use of wrasse in the farming of Atlantic salmon are discussed.  相似文献   

20.
Abstract. An antigenic comparison of ten strains of infectious pancreatic necrosis virus (IPNV) and a single strain of European eel virus (EEV) revealed the presence of three distinct groups separable by cross-neutralization. The 1/ r value calculated from the formula r=√r1× r2 (Archetti & Horsfall 1950) was used to divide the virus strains into: group I, which included all six U.S.A. strains: Buhl, Idaho; Reno, Nevada; ATCC VR 299; Powder Mill, New Hampshire; West Buxton, Maine; and Cascade Locks, Oregon: group II, the European strains: ďHonnincthun, France; Sp Denmark; and Bonnamy, France: group III, Ab Denmark and EEV. The group II European strains of IPNV were more closely related to the group I U.S.A. strains than to those viruses in group III. European eel virus (EEV) was antigenically most closely related to the Ab strain of IPNV.  相似文献   

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