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1.
Abstract. The effect of oral administration of 17α-methyltestosterone (17-MT) to Oreochromis spilurus (Günther) in brackish water (3-5 ppt) was studied in terms of masculinization, growth, food conversion efficiency (FCE), specific growth rate (SGR) and survival rate. A 38-day hormone treatment followed by 205 days of normal diet yielded a higher percentage of males, differing significantly from the normal 1:1 ratio. The highest proportion of males (90-3%) was in the replicates given 70 mg/kg of 17-MT. After the hormone treatment phase, no effects were observed on growth, FCE, SGR and survival rate. At the end of the experiment (243 days), the treated groups showed significant increases in growth, SGR and FCE. The 50 mg/kg replicates showed the highest growth and SGR, and the 70 mg/kg groups the highest FCE. The maximum survival rate was in the controls, and the minimum in the 50 mg/kg groups. It can be concluded that the androgen-induced sex reversal in O. spilurus is comparable to that in other tilapia species. However, further studies should be carried out to determine the optimum dose and duration to achieve 100% masculinization.  相似文献   

2.
The effect of size and acclimation period to full-strength sea water was investigated using the mortality, growth, chloride cell proliferation and plasma Na concentration in four size groups (0.03-1.6 g mean initial weight) of mixed-parentage, sex-reversed, all-male fry and fingerlings of Oreochromis spilurus spilurus Günter obtained from University of Stirling. The fish were transferred from fresh water to sea water (36.6%0) through a continuous salinity increase during a 48, 72 or 120 h acclimation period. Survival was high in all groups, although the smallest fish (0.03 g) showed significantly higher mortality than the larger fish. The acclimation regime had no effect on growth rate, but 120 h acclimation gave highest final weight in the newly released group. Regardless of acclimation period, size and plasma Na concentration during the acclimation period, the plasma Na level stabilized within 12 h after full salinity in the two largest size groups. Ovoid voluminous chloride cells proliferated in all groups during the acclimation period, and numbers stabilized with stable salinity. It is concluded in this study that O. spilurus spilurus can successfully be acclimated to sea water with a gradual continuous acclimation period of 48 h, even as newly released fry (0.03 g). However, an acclimation period of 120 h gave the highest final weight for this size group.  相似文献   

3.
Abstract  The short-term tolerances of northern pike, Esox lucius L., fry reared in a freshwater hatchery, to salinity were examined in the laboratory. Survival of two size groups of pike fry (mean length 21 ± 2 mm SD and 37 ± 4 mm SD) was examined over 72- to 96-h periods at 9–14 ppt salinity in combination with temperatures of 10, 14 and 18 °C. A parametric survival model found a significant correlation between survival of pike fry and temperature and salinity, respectively. L C50 values after 72 h were between 11.2 and 12.2 ppt, being lowest at 10 °C. Pike fry did not survive more than 13 ppt. Mortality at 12 ppt was significantly faster at 18 °C than 10 or 14 °C. Moreover, mortality was higher and faster for large than for small pike fry at 12 ppt and 14 °C. These results imply that pike raised in fresh water can survive stocking into brackish waters below 11 ppt at least for a short time.  相似文献   

4.
A study was conducted on Oreochromis spilurus (Günther) fry (9.0 mm) in sea water (38-40%o) to evaluate the effects of three doses (40, 70 and 100 ppm) of a synthetic oestrogen, 17α-ethynyloestradiol (17-EE) on the feminization, specific growth rate (SGR), food conversion efficiency (FCE), condition factor (CF) and survival rate. The fry were fed a hormone-impregnated diet for 42 days, followed by a hormone-free diet for another 77 days. At the end of the experiment (119 days), successful feminization was obtained in all groups treated with 17-EE. The dose of 100 ppm was the most potent one and induced 92.2% sex reversal. At the end of the hormone-treatment phase (42 days), all groups treated with 17-EE and the untreated controls showed no significant differences in growth, SGR, FCE, CF, and survival rate. After 119 days, a significant difference was detected only in the mean body weight and total length where the EE-100 group had the highest values. However, this was due to the low survival rate in this group (37.5%) and not to any possible anabolic effect of 17-EE. The findings of this study indicate that seawater sex reversal of O. spilurus is possible and 100% sex reversal could be achieved by slightly increasing the dose and/or duration of the treatment.  相似文献   

5.
在水温10.2~12.4℃、p H 7.8~8.0、盐度24~28条件下,将平均体质量为(45±5)g的仿刺参Apostichopus japonicus饲养在室内养殖池的网箱中,投喂蛋氨酸硒添加量分别为0mg/kg、0.2mg/kg、0.4mg/kg、0.6mg/kg、0.8mg/kg和1.0mg/kg的6组饲料。饲养60d后,测定仿刺参的特定生长率(SGR)和体壁中常规营养成分含量。结果表明:当蛋氨酸硒添加量为1.0mg/kg饲料时,仿刺参的特定生长率、粗蛋白、粗灰分含量最大,较对照组分别高155.56%、5.65%和2.9%(P0.05),而仿粗脂肪含量最低,较对照组低10.61%(P0.05)。  相似文献   

6.
The effects of stocking density and feeding levels on larval survival, growth rates, feed utilization efficiency and body composition of Nile tilapia (Oreochromis niloticus L.) fry were investigated in two consecutive experiments. In experiment 1, swimup fry (0.016 g average body weight) were stocked in 20‐L fibreglass tanks, in a closed, recirculating indoor system, at five stocking densities (3, 5, 10, 15 and 20 fry L?1) and fed a larval test diet (40% crude protein) to apparent satiation, three times a day, for 40 days. Fish survival, percentage weight gain and specific growth rate (% SGR) were negatively correlated with stocking density. The best performance was achieved at 3 fry L?1. However, no significant differences in growth parameters were found between 3 and 5 fry L?1. Body composition was not significantly affected by stocking density. In experiment 2, fry (0.016 g average body weight) were stocked at 5 fry L?1, and fed a larval test diet (40% crude protein) at six feeding levels (10%, 20%, 25%, 30% and 35% BW day?1) and to satiation, three times a day for 40 days. Fish growth rates and survival were extremely poor at 10% feeding level, and improved significantly with increasing feeding levels up to 30%, and levelled off with further increase in feeding levels. On the contrary, feed conversion ratio (FCR) and protein production value (PPV) were negatively correlated with feeding level. The lowest feeding level (10%) produced significantly lower body lipid and higher protein and ash than other feeding levels. The present results suggest that the optimum stocking density and feeding level of Nile tilapia fry are 5 fry L?1 and 30% per day respectively.  相似文献   

7.
A 4‐week growth trial was conducted to compare the effects of different feeding strategies of dietary immunostimulants on the growth, immunity and resistance against Vibrio splendidus of sea cucumbers Apostichopus japonicus (Selenka). Six feeding strategies were set, including feeding immunostimulants‐free diet continuously (control), feeding dietary β‐glucan (1.25 g kg?1 diet) continuously, feeding dietary mannan‐oligosaccharides (MOS; 2.00 g kg?1 diet) continuously, feeding β‐glucan 2 days followed by MOS 5 days alternately, feeding β‐glucan 5 days followed by MOS 2 days alternately and feeding β‐glucan 7 days followed by MOS 7 days alternately. The sea cucumbers fed immunostimulants showed higher specific growth rate (SGR) and lower cumulative mortality than control (P < 0.05). When sea cucumbers were fed with β‐glucan continuously, total coelomocytes counts and superoxide anion were significantly higher than control on the 4th day (P < 0.05). However, these two immune parameters were not significantly higher than those in control after the 18th day (P > 0.05). While sea cucumbers continuously fed MOS, these two immune parameters were not significantly higher than control until the 15th day. All immune parameters of the sea cucumbers fed with β‐glucan and MOS alternately were significantly higher than those in control during the experiment (P < 0.05). The sea cucumbers fed with β‐glucan 7 days followed MOS 7 days alternately showed the highest SGR and second lowest cumulative mortality. It was suggested that this feeding strategy is most suitable for sea cucumbers.  相似文献   

8.
This paper reports the triiodothyronine’s (T3) effects on the early growth and survival of piracanjuba (Brycon orbignyanus) produced from fertilized eggs hormone exposed. The study was carried out in two phases. In the first phase, eggs divided in 6 batches were immersed in T3 solutions: 0.01; 0.05; 0.1; 0.5 ppm; 1 ppm and control (no T3). After a 15-min immersion, eggs were transferred to incubators where larvae were kept up to 72 h after hatching. Larval weight, length and yolk sac volume were determined every 12 h. Sixty and 72 h after hatching, larvae exposed to 0.5 ppm T3 were significantly heavier than the others, and those exposed to 1 ppm T3 showed the lowest weight. The yolk sac absorption was not affected. In the second experimental phase, the resulting fry from the first phase were stocked into 3 boxes per treatment (5 larvae L−1) and fed with plankton, fish larvae and feed prepared in the hatchery (48% CP) in the first 3 days, plankton and feed from the 4th to the 10th day and only feed in the next (last) 5 days. Fry weight, length and specific growth rate were determined at 1, 5, 10 and 15 days. Survival was calculated in the last day. In the 15th day, fry length did not differ among treatments but the weight of the control group was higher. Higher survival in the T3-treated groups suggested lower predation among fry. The results allowed us to conclude that there was no expressive effect of T3 on the growth, but it improved the survival of the piracanjuba progeny.  相似文献   

9.
The purpose of the current study was to examine seasonal changes in seawater tolerance and growth performance of anadromous Arctic charr (Salvelinus alpinus L.) held at the same temperature (8°C) during winter and summer. Charr (20–27 cm), previously reared in freshwater under natural photoperiod, were transferred either directly (DT) from freshwater to seawater (35 ppt), from freshwater to brackish water (20 ppt), or were gradually adapted (GT) to seawater over a period of 10 days. Control fish were held in freshwater. Feed intake and osmoregulatory ability were then monitored on three occasions during the following 59 days. Two experiments were carried out, one during winter (December–January) and the other during summer (June–July). In both experiments fish mortality was low. Plasma osmolalities recorded in fish transferred to seawater were within normal ranges, but osmolalities on day 10, were significantly lower in summer (313 mOsm/kg (DT), 328 mOsm/kg (GT)) than in winter (323 mOsm/kg (DT), 352 mOsm/kg (GT)). In winter, feed intake and growth rates were high in fish kept in fresh and brackish water, but charr transferred directly to seawater ate little and lost weight. Fish that were gradually adapted to seawater occupied an intermediate position. During summer the observed differences in feed intake were small and all fish had relatively high growth rates. These results suggest that Arctic charr display seasonal changes in feed intake and growth performance that parallel seasonal changes in hypoosmoregulatory capacity. The ability to survive and hypoosmoregulate in full strength seawater does not, however, seem to be a particularly good indicator of successful seawater adaptation with respect to the ability to display high rates of feed intake and growth. During winter, a gradual transfer to seawater appeared to lead to improved feeding and growth compared to direct transfer.  相似文献   

10.
The effects of 5 mg/L of dissolved manganese on juvenile mulloway at salinities of 5, 15 and 45 ppt were determined by comparing their survival, growth and blood plasma and organ chemistry with those of fish grown at the same salinities without manganese addition. Survival of mulloway at 45 ppt in the presence of 5 mg/L of manganese (73 ± 13%) was significantly lower than all other treatments, which achieved 100% survival. Those fish grown in water without manganese exhibited rapid growth, which was not affected by salinity (SGR = 4.05 ± 0.29%/day). Those fish grown at 5 ppt and 45 ppt in the presence of manganese lost weight over the 2-week trial (SGR − 0.17 ± 0.42 and − 0.44 ± 0.83%/day, respectively), whilst those at 15 ppt gained some weight (SGR 1.70 ± 0.20%/day). Manganese accumulated in the gills, liver and muscle of the fish and significant differences in blood plasma chemistry were observed. Blood plasma sodium and chloride of fish exposed to manganese were significantly elevated in hyperosmotic salinity (45 ppt) and depressed at hyposmotic salinity (5 ppt) compared with unexposed fish at the same salinity; consistent with manganese causing apoptosis or necrosis to chloride cells. We did not, however, observe any gill epithelial damage under light microscopy. Blood plasma potassium was significantly elevated at all salinities in the presence of manganese and liver potassium and glycogen reduced. These findings are consistent with manganese interfering with carbohydrate metabolism.  相似文献   

11.
The nitrifying activity of the filter bed of aquaria was monitored in hypersaline conditions. Salinity was raised in 5 ppt steps from normal sea water to 126 ppt in a course of 35 and 41 days. Twenty grey mullet fry (Chelon labrosus and Mugil cephalus) were used in two 53 l aquaria. Daily monitoring of total ammonia–nitrogen (TAN), nitrite, nitrate ions, and pH was performed. After an initial peak of TAN (0.65 mg/l), total ammonia stabilized at safe low levels (0–0.2 mg/l). Nitrite exhibited more peaks at levels of about 10 mg/l, lasted for 3–8 days but they also subsided to almost zero afterwards. Nitrate finally stabilized at levels around 100 mg/l. The water was alkaline, with pH fluctuating in the region of 8.2–8.8. These findings indicate that the filter bed may be effectively conditioned for hypersalinity and that fish may be safely maintained in the aquaria.  相似文献   

12.
Abstract. Three experiments were conducted to evaluate the potential for culturing tilapia in tanks and raceways with flowing sea water (39-41 ppt salinity) in Kuwait. In the first and third experiments, fingerling tilapia were grown for 7 to 8 months under ambient conditions. In the second experiment, larger (50-100g initial weight) male tilapia were grown for 6 months. Growth and mortality rates were determined.
Oreochromis aureus (Steindachner) grew the slowest and survived poorly. O. spilurus (Günther) and O. aureus × O. spilurus hybrids had the best survival and moderate growth rates. A red tilapia from Taiwan grew the fastest but had high mortality rates during winter. O. spilurus and the hybrid were best suited for seawater culture under ambient conditions in Kuwait.  相似文献   

13.
Abstract. The eggs and yolk sac fry of the mouth brooding tilapia. Oreochromis mossambicus (Peters), were artificially reared in an experimental hatchery system at different temperatures. The hatchability, embryonic development of eggs and growth of yolk sac fry were studied under controlled conditions. It was shown that the upper lethal temperature for O. mossambicus eggs was above 40°C and the lower lethal temperature between 11°C and 17°C. For yolk sac fry these values lay between 34 and 40°C and 17 and 20°C respectively. Fry survival between 24·3 and 34·0°C was near to 100% while al 20°C it was less than 60%. The somatic growth rates of fry at temperature between 20 and 34·5°C up to 10 days post hatch are presented and were found to differ significantly. At 34·6°C a negative SGR was recorded during the period 6–9 days post hatching, but, during the first 6 days, the SGR at this temperature was more than four times higher than at 20°C. At the elevated temperatures, the utilization of yolk is faster and the loss of weight observed was due to starvation. This should be taken into account when incubating under artificial rearing condition so that initiation of exogenous feeding is timed most appropriately.  相似文献   

14.
Broodfish were reared for 6 months in underground brackish water (11 ppt), and the quality of eggs and semen was evaluated in comparison to broodfish held in fresh water. Fry produced by the broodfish in brackish water (S) and freshwater (F) were then reared in different salinities (1, 4, 7, and 10 ppt). Broodfish successfully matured and spawned in underground brackish water, and gonad quality was better than of the broodfish in fresh water (p < 0.01). Growth indices of fry produced by both groups decreased with increasing salinity (p < 0.01). Survival was not affected by the salinities tested. Underground brackish water can be used as a source to induce successful sexual maturation and to produce high-quality gonads.  相似文献   

15.
Along the Atlantic coast black sea bass occur from the Gulf of Maine to Florida and support important commercial and recreational fisheries. Interest in commercial production of black sea bass has increased in recent years due to high demand and limited seasonable availability. Efforts towards large-scale production have been hampered by a high incidence of early larval mortality. Two of the most important environmental variables affecting hatchery production of marine finfish larvae are temperature and salinity. In the wild, larval black sea bass are found in waters with temperatures of 12–24 C and salinity levels of 30–35 ppt. Studies were conducted to define the temperature and salinity ranges that support growth and development of black sea bass during early life stages. Three developmental phases were investigated: 1) fertilization to hatch: 2) hatch through yolk sac absorption: and 3) during the initial exogenous feeding stage (5–14 days post hatch: DPH). Fertilized eggs were obtained by manual spawning of fish following administration of LHRHa. Fertilized eggs were transferred to 300-mL glass Petri dishes or 500-mL beakers to assess the effects of salinity and temperature through hatch and yolk sac absorption, respectively. To determine environmental effects on growth and survival during initial exogenous feeding 400 actively feeding larvae were cultured in green water and fed enriched rotifers for a 9-d period. For investigation of the effect of salinity, sea water (35 ppt) was diluted gradually to 15, 20, 25, and 30 ppt and maintained at 21 C. For examination of the effect of temperature, seawater was adjusted from 21 C to 12, 15, 21, 27, or 30 C at a rate of 3 C/h. No eggs hatched at 12 C or when salinity was maintained at 0 or 5 ppt. Hatching was uniformly high (≥ 85%) at temperatures between 15 and 27 C and at salinities ≥ 15 ppt. Survival through yolk sac absorption was greatest at temperatures between 18 and 27 C and at salinities ≥ 20 ppt. Survival through first feeding stage was highest at temperatures ≥ 18 C and 30 ppt salinity. Larval growth through first feeding was not significantly affected by salinity level but did increase with rearing temperature. The results indicate that survival and development of black sea bass during early life stages are most favorable at temperatures >18 C with salinity levels approaching full strength seawater.  相似文献   

16.
Abstract. Cyprinid herpesvirus 1 (CHV) or Herpesvirus cyprini was virulent for carp, Cyprinus carpio L., fry following 1 h immersion in water at 20 °C. Cumulative mortality for carp fry was 86–97% in 2-week-old common carp, 20% in 4-week-old fancy carp, and 0% in both 8-week-old common and fancy carp. The virus did not produce mortality in fry of crucian carp, grass carp or other cyprinids. It was also oncogenic in carp, inducing papillomas to the extent of 55% among both common and fancy carp fry. The neoplasms appeared 5–6 months after carp had been exposed to the virus by immersion and recurred at an incidence of 83% in carp 7·5 months post-desquamation of the tumour. The CHV was reisolated from all moribund fish and from all survivors. It also induced papillomas at an incidence of 13% in adult mirror carp and at 10% in adult fancy carp 5 months after intraperitoneal inoculation of 105 TCID50 ml-1 fish. The virus was rcisolated only from the ncoplastic tissue and not from internal organs. The neoplasms were normally located on fin, skin or mandible, at the intraperitoneal inoculation site. Specific fluorescence for CHV antigen was frequently detected in the gills, liver, kidneys and intestine of 2-week-old fry from 3 to 21 days following challenge with CHV. It was found in greater concentrations in experimentally induced papillomata on 2-week-old carp fry survivors examined 24 weeks after challenge than in naturally occurring neoplasms.  相似文献   

17.
ABSTRACT:   Compensatory growth, feeding rate, feed efficiency and chemical composition of juvenile black rockfish (mean weight 1.43 g) were investigated for 35 days after a 14-day feed deprivation treatment under four feeding conditions: one group continuously fed (control) and the other three groups fasted for 5 days (F5), 10 days (F10) and 14 days (F14). All fasted fish were re-fed from day 15. Only F5 achieved the same body weight as the control, indicating that complete compensation occurred in F5. The specific growth rate (SGR) of F5 was the highest at day 21 and then decreased thereafter, showing higher values than the control at days 21, 28 and 42. In contrast, although SGRs of F10 and F14 were higher than that of the control during the whole refeeding period except day 21, they did not catch up the control in body mass, indicating that only partial compensation occurred in F10 and F14. The feeding rate (FR) of all groups except F14 changed in a pattern similar to SGR (Spearman's rank correlation, r s > 0.9), suggesting that SGR varied depending on FR. Similar feeding efficiencies (FEs) were found in the four groups and they did not vary significantly during the whole refeeding period, suggesting that FE was not the factor affecting SGR. At day 14, the ratios of lipid to lean body mass in F10 and F14 were lower than those in the control and F5, and there was no difference between the control and F5. At day 49, however, only F14 showed a lower value than the other three groups, and there was no difference among the three groups. These results indicate that juvenile black rockfish fasted for 5–14 days can exhibit compensatory growth after refeeding, but timing and degree vary depending on the duration of feed deprivation.  相似文献   

18.
Abstract. The endangered Australian freshwater fish trout cod, Maccullochella macquariensis (Cuvier), was the subject of a captive breeding programme to produce fry for reintroduction into the wild. Trout cod broodfish were maintained in earthen ponds for up to 5 years and underwent gonadal maturation each spring but did not spawn in the ponds. Infestations of the protozoan parasite Chilodonella hexasticha caused the death of at least 21 broodfish. Mature fish, removed from ponds when water temperatures had reached or exceeded 16°C, had a higher proportion of atretic oocytes and fewer fish spawned successfully compared to fish removed at lower temperatures. Ovulation was induced by a single injection of 1000–3000 iu/kg HCG. Between 1188 and 11338 eggs ranging from 2·5 to 3·6 mm in diameter were stripped from individual fish. Hatching commenced on days 5–9 and continued for up to 10 days (at 15·5–23°C). Larvae commenced feeding on days 21–25. Trout cod larvae were grown out to fry (363.3–48.6mm total length [TL]) in fertilized fry rearing ponds then released. Between 1986 and 1989, 8420 trout cod fry were released into several sites in the upper Murray River and upper Murrumbidgee River, and reports indicate that released fish are surviving.  相似文献   

19.
实验设置1.0%,1.5%,2.0%,2.5%,3.0%五个不同投饵率水平,在水温30℃的条件下,选取同一种饲料,对规格为3.67±0.30g的花鳗鲡黑仔苗进行40d的生长实验。结果表明,投饵率对花鳗鲡黑仔苗的相对增重率、特定生长率、饲料转化率均有显著性影响（p〈0.05）,花鳗鲡黑仔苗生长的适宜投饵率是2.0%;在此投饵率下,花鳗鲡黑仔苗的饲料转化率为（47.39±1.17）%,特定生长速率为（1.08±0.03）%/d,相对增重率为（52.49±1.04）%,存活率为100%。  相似文献   

20.
We investigated the feminization of bluegill and black crappie by short periodic immersions in an aqueous estradiol‐17β (E2) solution. Bluegill fry (13.8 mm) were immersed in a 1 mg L?1 E2 solution every 5 days on three occasions over an 11‐day period. In the positive control treatment, the same cohort of fry was fed 200 mg kg?1 E2 diet for 45 days. Two different size (26.1 and 20.1 mm) but the same age (45 days old) black crappie fry were immersed in the same concentration of E2 solution for 5 h a day every 3–5 days on 10 occasions between 45 and 86 days post hatch. Both modes of E2 administration were effective to induce feminization in bluegill. Feeding fry E2 impregnated diet for 45 days yielded 99.3% female populations from a 38.8% female experimental population. Only three short‐time E2 immersions of fry over a much shorter treatment period also produced 76.9% female populations. E2 immersions had no effect on sex ratios of larger black crappie fry and produced variable levels of feminization (60–82% female) in smaller black crappie fry. Results of the present study showed that feminization in both species can be achieved by periodic immersions of fry in a 1 mg L?1 E2 solution with no adverse effects on survival. Yet, further researches on timing and intensity of immersion treatments are still needed for optimization of the procedures.  相似文献   

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