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1.
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   

2.
This study investigated the effects of estrogens on sexual differentiation in sea bass (Dicentrarchus labrax L.), a gonochoristic marine teleost that under culture conditions has a histologically sexual undifferentiated period that covers most of the first year of life, after which most individuals develop as males. Sea bass that had no noticeable histological sign of sex differentiation were fed estrogens at two doses (5 or 10 mg kg-1 food) and for different periods ranging from 48 to 426 days post fertilization (DPF). Exposure to the synthetic estrogen 17-ethynylestradiol (EE2) at 10 mg kg-1 food from 60 to 260 DPF, including the sensitive period to equivalent doses of synthetic androgens previously determined for this species (126-226 DPF), significantly (p < 0.05) more than doubled the number of juvenile females to 80%, compared to the control value of 33%, and completely suppressed gonadal development in the remaining 20% of the population. This suggests that the period during which sea bass gonads exhibit high sensitivity to androgens is also very sensitive to estrogens. A comparable exposure to the natural estrogen estradiol-17 (E2) resulted in 13% of the fish having suppressed gonadal development, but induced 57% of the fish to develop gonads with germinal tissue of both sexes, suggesting a pivotal role for E2 during this sensitive period. Earlier exposure to EE2 at 10 mg kg-1 food from 48-88 DPF, significantly (p < 0.05) increased the number of females to 62% from 36% in the control group, allowing for the normal testicular development in the remaining fish. In contrast, a later chronic exposure (226-426 DPF) to E2, at either 5 or 10 mg kg-1 food, starting when the gonads showed no sign of sexual differentiation but past the critical sensitive period, had no effect on the resulting overall sex ratios, indicating that after this period responsiveness of the gonads to estrogens decreases as gonadal sexual differentiation progresses. However, the consequences of this apparently innocuous exposure were later manifested in adults, exemplified by a significant dose-dependent reduction in the number of mature males at 626 DPF, coinciding with the second reproductive season, the time when males normally reach sexual maturation in cultured sea bass. This suggests that chronic exposure to E2 past the critical sensitive period may not affect the sex ratio, but could result in alterations in the male reproductive organs. This was later verified by histological analysis which revealed a significant (p < 0.05) dose-dependent reduction of the surface of the testicular lobules in the remaining males that did not mature. Together, these experiments illustrate both readily observable and subtle effects of estrogens on sex proportions, gonadal morphology and maturation rates, providing evidence that estrogen exposure can have delayed action in a teleost in a manner similar to the effects described for mammalian species. The possible existence of effects of this latter type in adult fish could be considered when evaluating the consequences of deliberate or accidental exposure to estrogens or putative estrogenic chemicals, particularly if such exposure had taken place during sex differentiation.  相似文献   

3.
Monosex populations can be a valuable management tool in culture of larger size largemouth bass (>400 g). In this study, we investigated the effective mode and duration of oestrogen and androgen administrations to produce monosex largemouth bass populations. The experiment consisted of nine treatments. In oral administration groups, we fed 40-day-old fry either 200 mg of an oestradiol-17β (E2) kg−1 diet or 60 mg of a 17α-methyltestosterone (MT) kg−1 diet for 30, 45 or 60 days. In bath treatments, we immersed fry in a 1 mg MT L−1 solution for 5 h a day on three or six occasions. For control treatment, we fed fry an ethanol-treated diet for 45 days. The frequency of females in the control group was 53.1%. Oral administration of E2 at all durations resulted in slight increases in the frequency of females (59.8–70.5%). Both modes of androgen administration at all durations were ineffective in altering phenotypic sex. The experimental results of our study indicated that male differentiation passed the point of being completely and functionally influenced by exogenous oestrogens, while female differentiation had already taken place and was no longer responsive to exogenous androgens in 40-day-old (33.5 mm) largemouth bass fry.  相似文献   

4.
The annual profile of plasma vitellogenin (VTG) and 17ß-estradiol (E2) levels, as well as gonadal development and spawning characteristics were investigated in captive female sea bass (Dicentrarchus labrax). Endocrine and gonadal changes were studied in fish reared under natural conditions or exposed to manipulated photothermal cycles. In natural conditions of photoperiod and temperature, sea bass spawned from February through March (East coast of Spain, 40°N 0°E). One or two months of constant long-days (15L/9D) in a constant short-day photoperiod regime (9L/15D) all-year-round, given early in the year (March and March–April), advanced spawning by 3 months. The same treatment applied later in the year (September–October) delayed spawning by 1 month, compared to controls.In all groups, changes in plasma VTG levels were correlated with E2 levels, oocyte growth and spawning time. In control females, VTG was low (<100 ng ml-1) during the summer, until its first surge in plasma 4 months before the beginning of spawning. The VTG (3.1 ± 0.3 mg ml-1) and E2 (4.1 ± 0.5 ng ml-1) levels showed a single annual peak during late vitellogenesis, the time of the highest proportion of vitellogenic oocytes in the ovary. Constant high levels of VTG (1–1.4 mg ml-1) and E2 (1.6–1.9ng ml-1) were maintained during the entire spawning time, together with the presence of vitellogenic oocytes, suggesting the existence of several waves of oocyte growth in the ovary and thus, several spawns per female. Endocrine profiles and oocyte development in fish exposed to constant photoperiods were similar to controls, but were shifted in time in relation to the displacement of the spawning time. In the fish showing advanced spawns, the duration of the gametogenic proces was compressed when compared to controls. The differences observed in the evolution of the reproductive-related factors in the advanced groups, which were exposed to a reduction in temperature to 15°C, suggest an influence of the temperature in the early stages of the reproductive cycle in sea bass.  相似文献   

5.
In this study, we evaluated the effect of diets with various concentrations of estradiol-17β (E2) on the feminization, growth and survival of juvenile fat snook. Over a 45-day period, the juveniles were fed with five diets containing 0, 25, 50, 75 and 100 mg E2/kg feed. Three replicates were run for each diet. After this hormonal treatment, the fishes were transferred to 1-m3 net cages, where they remained for 12 months. During this period, they were fed a commercial diet without added hormones. During the feminization, the control fish grew more than those in the other treatments, and the survival rates did not differ significantly among the treatments. At the end of the experiment growth did not differ among the treatments. In the control treatment, 80.85 % of the fish were male, and the females were significantly larger than the males. All of the treatments with E2 produced 100 % females. No intersex fish were found in this study. This research showed that it is possible to obtain 100 % fat snook females using feeds with 25 mg E2/kg for 45 days without impairing the growth or survival of the fish.  相似文献   

6.
Abstract. An investigation was undertaken to study the effect of 17α-methyiteslosterone (17-MT) on the sex reversal and growth of tilapia, Oreochromis spilurus (Günther), in brackish water (3–5 ppt) and sea water (40 ppt). Seven experiments were performed; four in brackish water and three in sea water. Yolk-sac fry (1 or 3 day age) were immersed (7 or 24 h/day) in water containing hormone at a concentration of 0–10mg/l for 4–25 days. The swim-up fry were subsequently fed either normal or hormone-impregnated diets (30–70 mg/kg) for another 35 days starting from first feeding. The growth and SGR of fry were better in groups which received hormone both in water and food as compared with water or food alone. Immersion In 5–10 ppm (24 h/day) brackish water solution for 5 days did not bring any change in growth or sex ratio. However, immersion in sea water solution for 25 days (7 h/day) at a concentration of 1 ppm induced positive growth but no change in sex ratio. Higher doses either did not affect or reduced growth and SGR but induced higher percentages (77–83%) of males. Complete masculinization (100%) was observed only in brackish water when fish were immersed in 2·5 ppm solution for 4 days (24 h/day) and later fed 50 mg/kg in diets for 35 days. These results were further confirmed when the immersion schedule was modified to 10 days (7 h/day) and feeding 50–70 mg/kg hormone. It can be concluded from these studies that in brackish water complete masculinization of O. spilurus is possible through immersion in 5·0 ppm for a minimum of 75 h followed by feeding with 50 mg/kg food for a minimum of 40 days starting from first feeding.  相似文献   

7.
The tambaqui Colossoma macropomum is the most important native fish in Brazilian aquaculture. Females are almost 20% heavier than males and therefore are more profitable. Based on this information, we tested four different concentrations (20, 40, 80, and 120 mg/kg diet) of oestradiol (E2) offered during 6 weeks to tambaqui larvae and analysed their efficiency in producing female monosex batches of the species. The study was performed in two independent tests, using different genetic backgrounds (broodstocks). All treatments increased the percentage of females in the population, but only the highest E2 dose was “free” of males in both tests. All treated groups contained intersex individuals (when sex inversion is not complete). Plasmatic E2 concentration was similar between treated and non‐treated fish 60 days after the treatment in fish treated with 20, 40, and 80 mg E2/kg diet. However, tambaqui treated with a 120 mg E2/kg diet showed lower E2 plasma concentration in comparison with the control group. Last, we chlorinated the water to ensure the environmental integrity of the study. Three days after chlorination, the water was completely free of any oestradiol residue (analysed by high‐performance liquid chromatography).  相似文献   

8.
Juvenile stellate sturgeon Acipenser stellatus were intraperitoneally injected with estradiol-17β (E2; 0 and 5 mg/kg fish) to investigate the possibility of sex reversal and also determine the changes in biochemical parameters. Five-month-old fish (40.9 ± 1.1 g) were injected every 3-week interval during a 190-day trial. At the termination of the experiment, final weight and other growth parameters including weight gain and specific growth rate, hepatosomatic and viscerosomatic indices were not affected by repetitive injection of E2. Hematological features of E2-treated fish showed significant reductions in number of red blood cells, hemoglobin concentration, hematocrit value and mean corpuscular hemoglobin (P < 0.05), but no significant changes were observed in number of white blood cells, mean corpuscular volume and mean corpuscular hemoglobin concentration (P > 0.05). Calcium, phosphorus, glucose, triacylglycerol, cholesterol, total protein and estradiol concentrations were significantly increased in fish injected with E2 (P < 0.001). Plasma progesterone and testosterone levels were noticeably lower in fish injected with 5 mg/kg E2 rather than the control fish (P < 0.001). Histological observations of gonads showed that all fish injected with 5 mg/kg E2 apparently feminized, while 66.6 % of the control group was female. These results revealed that the injection of E2 is an effective method for feminization of stellate sturgeon without having significant inhibitory effects on growth and survival.  相似文献   

9.
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   

10.
European sea bass (Dicentrarchus labrax) fry vaccinated orally via bioencapsulation in Artemia nauplii or by bath method exhibited better performance than control fish in terms of growth, food conversion and resistance to stress. The comparable survival between vaccinated and non-vaccinated animals suggests that vaccination methods are not stressful. The present study shows that oral vaccination can be used to enhance growth in fish fry.  相似文献   

11.
Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha–1 to the total yield of 1,700 kg ha–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha–1, while in marine cages, yields ranged from 4–10 kg m3. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.  相似文献   

12.
The silver perch, Bidyanus bidyanus (Mitchell 1838), displays sexual dimorphism in size, with females reaching larger maximum size than males. In an attempt to produce all‐female populations, larvae at 30 d posthatching were fed an estradiol‐17β (E2) diet at dosages of 0, 60, and 120 mg/kg for 30 d. Histological examination of gonads revealed that all E2‐supplemented diets resulted in significantly higher (P < 0.05) feminization rates (97.22–100%) than did the control (39.69%) but with no difference between the two E2 diets (P > 0.05). Female and male gonads were observed in fish fed the 60 mg E2/kg diet. No significant differences were observed in the survival rate, weight gain, gonad weight and length, specific growth rate (SGR), or gonadosomatic indexes, except for gonad length and SGR at the end of the experiment. Although the ovary length of fish fed the 60 mg E2/kg diet was significantly shorter than that of the control groups, no abnormalities were detected. In contrast, fish fed 120 mg E2/kg grew faster than the other fish and showed sexual dimorphism. Our results suggest that supplementation of E2 at 60–120 mg/kg diet could be applied to establish all‐female populations of silver perch.  相似文献   

13.
This study was conducted to evaluate the efficacy of β-glucan and selenium supplements to the diet on increasing survival of hybrid striped bass Morone chrysops X M. saxatilis exposed to Streptococcus iniae. A 2 × 2 × 2 factorial design was employed by including purified casein/gelatin-based diets and practical menhaden fish meal-based diets with supplement! of either β-glucan from barley at 0 and 0.1 % of diet or sodium selenite at 0 or 0.2 mg/kg diet or a combination of these supplements. All diets were formulated to meet the nutritional needs of hybrid striped bass with the exception of selenium. The purified and practical basal diets contained 0.03 and 1.03 mg Se/kg, respectively, and the diets supplemented with sodium selenite had an additional 0.07 mg Se/kg on average. Juvenile hybrid striped bass initially averaging 2.44 ± 0.17 g/fish were fed the eight experimental diets in triplicate 110-L recirculating aquaria for 6 wk, after which they were immersed in a bath of S. iniae at 6.2 × 106 CFU/mL for 2 h and monitored for 21 d. Weighi gain and feed efficiency were significantly (P < 0.05) affected by diet type and selenium supplementation, with fish fed practical diets and those supplemented with selenium having the greatest values. Supplementation of β-glucan to the purified or practical type diets did not significantly affect survival of fish after experimental infection. The most notable difference (P < 0.0001) was in the comparison of diet type; the survival rate of fish fed the practical diets was 75% compared to 35% for those fed the purified diets. Dietary supplementation of β-glucan did not enhance disease resistance in the present study. Fish fed menhaden fish meal-based diets were significantly more resistant to 5. iniae in comparison to the those fed the purified diets. Thus, nutritional influences on disease resistance of hybrid striped bass were evident in this study and warrant further investigation.  相似文献   

14.
This study compared co-feeding zooplankton (ZP, mixed copepods and mysids) and formulated diets (FD) supplemented with L-tryptophan (TRP) on the survival and growth of grouper and sea bass fry nursed in brackish water ponds. Grouper (84 fry m?3) and sea bass (150 fry m?3) were reared for 30 days and 60 days, respectively, in net cages within two separate 743 m2 nursery ponds. Five treatments (with three replicates each) were compared (P < 0.05): FD-1 = ZP + basal FD (no added TRP, but containing 0.29% endogenous TRP); FD-2 = ZP + (FD 0.58% TRP); FD-3 = ZP + (FD 1.22% TRP); FD-4 = ZP + (FD 2.50% TRP); and FD-5 = minced fish (Sardinella sp.) + basal FD (no additional TRP). TRP supplementation in grouper diets produced no significant affect on growth but increased survival at rates of 0.58% and above. TRP supplementation at 2.5% (FD-4) produced significantly better sea bass growth than other diets but had no affect on survival. Zooplankton improved both survival and growth in both grouper and sea bass juveniles compared to the minced fish diet, and may be a practical and lower cost alternative to indoor nursing.  相似文献   

15.
Commercial tilapia production is dependent on monosex culture, commonly obtained through the inclusion of an androgen in the diet for a brief period soon after hatch. To determine a minimum effective dose and identify the problems associated with over‐dosing, Nile tilapia Oreochromis niloticus fry were fed diets containing methyltestosterone (MT) at rates up to 1200 mg kg?1 of diet for 28 days. The minimum effective dose for ≥95% males was 14 mg MT kg?1 diet. Percent phenotypic males increased as the rate increased from 3.75 (80%) to 30 mg kg?1 MT (99%). Methyltestosterone given at rates of 120 mg kg?1 or more reduced efficacy but did not result in a reduced frequency of males relative to that of non‐treated fish. The term ‘paradoxical feminization’ does not adequately describe the observed sex ratios, where no fish were feminized but the efficacy of MT at high doses to masculinize females was reduced. At 1200 mg MT kg?1, the frequency of females (48 ± 1%) was not different from that in the non‐treated population. The mechanism for the reduced efficacy is not clear and is not adequately explained as an aromatization of androgen to oestrogen response.  相似文献   

16.
The egg yolk precursor, vitellogenin (VTG), was purified from blood plasma of striped bass by chromatography on hydroxylapatite or DEAE-agarose. The fish were first implanted with estradiol-17β (E2), which induced vitellogenesis. A rabbit antiserum (a-FSPP) raised against plasma from mature female striped bass, and then adsorbed with mature male plasma, was used to detect female-specific plasma protein (FSPP) in the chromatography fractions. Striped bass VTG (s-VTG) was collected from the peak fraction that was induced by E2, reacted with a-FSPP, and contained all detectable phosphoprotein. It appeared as a single band (Mr ≂ 170,000) in SDS-PAGE or Western blots using a-FSPP, and as a pair of closely-spaced phospholipoprotein bands in native gradient-PAGE, suggesting that there is more than one circulating form of s-VTG. The relationship of s-VTG to the yolk proteins was verified using a-FSPP. The antiserum reacted with the main peak from gel filtration of saline ovary extracts, and it specifically immunostained the two main bands in Western blots of the extracts and the yolk granules of mature oocytes. The amino acid composition of s-VTG was similar to that of VTG from other fish and Xenopus. A radial immunodiffusion assay for s-VTG was developed using a-FSPP and purified s-VTG as standard. The s-VTG was not detected in blood plasma of males, immature females, or regressed adult females, but plasma s-VTG levels were highly correlated with plasma E2 and testosterone levels, and oocyte growth, in maturing females. The results indicate that the maturational status of female striped bass can be identified by s-VTG immunoassay.  相似文献   

17.
Abstract. High rate of feminization was achieved by oral administration of diethylstilbestrol (DES) and ethynyloestradiol (EES) to gonadally undifferentiated Oreochromis mossambicus (L.) and O. mossambicus × O. urolepis hornorum Trewavas all-male hybrid. All-female groups were produced at doses > 10mg/kg DES and >50mg/kg EES, when fry immediately after yolk-sac absorption were fed hormone-treated feed ad libitum. The critical period for feminization was about one week. Treatments longer than 10 days did not result in a higher proportion of females, and treatments starting later than one week after yolk-sac absorption were not effective. Optimal derived protocol was applied to O. aureus (Steindachner), resulting also in complete feminization.  相似文献   

18.
The phenomenon of incidental sex reversal was observed in experiments originally designed to determine the importance of feeding duration and feed quality in the optimization of masculinization and feminization treatments of Oreochromis niloticus (L.) fry by oral application of hormones. Four separate experiments were conducted: (1) masculinization and (2) feminization using three feeding durations and (3) masculinization and (4) feminization using three alternative feed mixtures. Masculinization experiments incorporating 17 α-methyltestosterone (MT) into the feed at 40 mg kg?1 were applied to putative monosex male progeny whilst feminization treatments were applied to putative all female fry using diethylstilboestrol (DES) at 1000 mg kg?1. Treatments were applied outdoors in small cages suspended in 900-l circular concrete tanks with a flow through rate of 1-l min?1. Replicate cages for all treatments and the controls in each experiment were reared together in the same tank. Only the first experiment produced significant differences in sex ratio, with the control treatment producing a slightly lower proportion of males than the three MT treatments at different durations. The most significant finding was that in all experiments the sex ratio of the control differed significantly from expectations and in all but experiment 1, did not differ from those of the treated fish in which sex reversal had clearly been effected. It appears likely that incidental sex reversal occurred in the control fish as a result of the accumulation of active metabolites from the treated fish and/or leachates from uneaten food given to fish in the same water body. The results are discussed in the context of improving the efficiency and safety of hormonal sex reversal treatments.  相似文献   

19.
Water quality in sea-cages, and metazoan ectoparasites on bass, Dicentrarchus labrax (L.), and bream, Sparus aurata L., were sampled at two fish farms in south-west Greece over 2 years. The seabed and marine life around the cages of one farm was surveyed using scuba. The most frequent and abundant parasites were the monogeans Sparicotyle chrysophrii and Furnestinia echeneis on the gills of bream, and Diplectanum aequans on the gills of bass. The copepod Caligus minimus occasionally occurred in the buccal cavity of bass, but only in low numbers. Prevalence and abundance of parasites increased with bass size but F echeneis levels decreased with bream size. There were no other clear relationships between water quality, parasite levels and fish size. Ammonia varied seasonally with sea temperature, and with oxygen levels below 6 mg 1-1 on many occasions, it is possible that fish suffered stress from a combination of high ammonia and low oxygen conditions. There was no accumulation of waste food or faeces below the cages at the one farm surveyed, but there were thousands of wild fish, including mullet (Mugilidae), Spicara sp. and Diplodus spp., present around the cages. Water quality may be improved by changes in farm management, such as reducing stocking densities below the present 16 kg nr-3. Oxygen should be monitored at the cages on site daily. How comparable environmental conditions and impacts, and parasitization are at other bass and bream sea cage farms is unknown.  相似文献   

20.
Australian bass Macquaria novemaculeata were challenged by immersion with nervous necrosis virus (NNV) at different ages and under controlled conditions to investigate factors affecting disease expression. Fish challenged at 3 weeks of age with 103 TCID50/ml and higher doses developed clinical disease; a lower dose of 102 TCID50/ml resulted in incidence below 100% and 101 TCID50/ml was insufficient to cause infection. Additionally, fish were challenged at 5, 6 and 13 weeks of age at 17 and 21°C to assess the role of the age of the host and water temperature on disease expression. Although Australian bass challenged at all ages had evidence of replication of NNV, only those challenged at 3 weeks of age (20 and 24 days post?hatch [dph]) developed clinical disease. Higher water temperature had an additive effect on disease expression in larvae challenged at 24 dph, but it did not affect the disease outcome in older fish. Finally, isolates of NNV derived from fish with clinical or subclinical disease presentations caused similar cumulative mortality and clinical signs when larvae at 24 dph were challenged, suggesting that agent variation was not responsible for variation in clinical presentation in these field outbreaks of NNV infection.  相似文献   

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