首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
The effect of extended photoperiods on growth and age at first maturity was investigated in 166 (79 females and 87 males) individually tagged Atlantic halibut Hippoglossus hippoglossus and in 114 (50 females and 64 males) individually tagged turbot Scophthalmus maximus. The halibut were reared at 11 °C on four different light regimes from 10 February to 6 July 1996: simulated natural photoperiod, (LDN), continuous light (LD24:0), constant 8 h light and 16 h darkness (LD8:16) and LD8:16 switched to continuous light 4 May 1996 (LD8:16–24:0). From 6 July 1996 to 9 February 1998 the LD24:0 and LD8:16–24:0 were reared together under continuous light and the LDN and LD8:16 together under natural photoperiod. The turbot were reared at 16 °C on three different light regimes: constant light (LD24:0), 16 h light:8 h darkness (LD16:8), or simulated natural photoperiod (LDN). After 6 months on the different photoperiods, the turbot was reared together on LDN for approximately 12 months until first maturation. Juveniles subjected to continuous light (halibut) or extended photoperiods (halibut and turbot) exhibited faster growth than those experiencing a natural photoperiod or a constant short day. Moreover, when the photoperiod increased naturally with day-length or when fish were abruptly switched from being reared on short-day conditions to continuous light, a subsequent increase in growth rate was observed. This growth enhancing effect of extended photoperiods was more apparent on a short time scale in Atlantic halibut than in turbot, but both species show significant long-term effects of extended photoperiods in the form of enhanced growth. In both species lower maturation of males was seen in groups exposed to extended or continuous light compared to LDN and this could be used to reduce precocious maturation in males leading to overall increase in somatic growth. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

2.
Abstract.— The use of 12–mo long, but phase-shifted advanced and delayed photoperiod cycles in the regulation of the reproductive cycle was investigated in captive-reared female striped bass Morone saxatilis during the 3-yr study in an attempt to control the timing of sexual maturation under simulated photoperiod conditions. Phase-shifted photoperiod cycles did not induce a full shift in oogenesis during the first year cycles, but did in the following years. Spawning time, indicated by maximum oocyte diameters, was advanced up to 4 mo in females maintained under the phase-shifted advanced photoperiod, and delayed up to 4 mo when they exposed to the phase-shifted delayed photoperiod, compared to the natural spawning time in Spring (March-May). Phase-shifted photoperiod regimes shifted the profiles of plasma testosterone (T) and estradiol (E2), corresponding to the shift of oogenesis in the respective groups. Significant increases in T and E2 levels occurred during the vitellogenic phase, and these levels peaked before the occurrence of maximum oocyte diameters. The studies demonstrate that phase-shifted photoperiod regimes can be used to control oogenesis, and have implications for ensuring the year-round supply of mature female striped bass, particularly in domesticated striped bass.  相似文献   

3.
The effect of extended photoperiods on growth and age at first maturity was investigated in 166 (79 females and 87 males) individually tagged Atlantic halibut. The halibut were reared at 11°C on four different light regimes from 10 February to 6 July 1996: simulated natural photoperiod, (LDN), continuous light (LD24:0), constant 8 h light and 16 h darkness (LD8:16) and LD8:16 switched to continuous light on 4 May 1996 (LD8:16–24:0). From 6 July 1996 to 9 February 1998 the LD24:0 and LD8:16–24:0 were reared together under continuous light and the LDN and LD8:16 together under natural photoperiod. Juveniles subjected to continuous light exhibited faster growth than those experiencing a natural photoperiod or a constant short day. Moreover, the results suggest an overall growth enhancing effect of continuous light in females, but not in males. No females matured during the trial, but the proportion of mature males differed between the photoperiod groups, with significantly fewer males maturing in groups reared at continuous light. Independent of photoperiod regime and maturation status, females were significantly bigger than males from 14 April 1997 onwards. Immature males were bigger than maturing males from 23 March 1996 onwards. As continuous light reduced maturation at age 2+ in males, this could be used to reduce precocious maturation in males.  相似文献   

4.
Ovulation and spermiation of maturing Pacific herring were accelerated using single injections of acetone-dried salmon pituitary extract (10 mg/kg), partially purified salmon gonadotropin (0.1 mg/kg and 1.0 mg/kg) and the mammalian gonadotropin-releasing hormone analogue des-Gly10 [D-Ala6] GnRH-ethylamide (0.02 mg/kg and 0.2 mg/kg). All treatments gave responses and were considered to have potential application for inducing ovulation and spermiation in Pacific herring.  相似文献   

5.
Plasma growth hormone (GH), insulin-like growth factor-I (IGF-I), and insulin were measured in two groups of Salmo salar L. during a one-year study. The fish were reared under either a simulated natural photoperiod (SNP) from January to December or a regime of continuous light from January to June, followed by SNP until December (LL/SNP). Plasma GH levels during spring were low, and lower in the LL/SNP fish (< 0.9 ng ml− 1) than in the SNP fish (> 1.9 ng ml− 1), although the LL/SNP grew better (0.8% per day) than the SNP fish (0.5% per day). Plasma IGF-I levels increased transiently from January (64.7 ng ml− 1) to maximum in late September in the LL/SNP (85.8 ng ml− 1) and in November in the SNP group (87.3 ng ml− 1). The ratio GH:IGF-I was lower in the LL/SNP group during spring when this group grew better than the SNP group.  相似文献   

6.
The effects of extended photoperiods, mimicking the longest day of the year, were studied in 1- and 2-year seabream. The photoperiod regimes started in late July, 36 and 39 days after the summer solstice and continued for 11 months, well beyond the natural reproductive season of December–March. Regime 1 (long day, 15.5L:8.5D), which used natural and fluorescent light, reduced the incidence of maturity in both year classes and females did not spawn although some gonadal development was observed. Among all 1-year sampled fish of regime 1, a maximum of 5% became spermiating males (March) and 5% reached the yolk granule stage of vitellogenesis (VO3; 250–400 μm diameter) by May. Among 2-year sampled fish of regime 1, 45% became spermiating males and 25% were females, which reached the advanced vitellogenesis stage (VO4; 400–600 μm) by April. Regime 2 (skeleton photoperiod), consisting of natural light and a 1.5-h pulse of fluorescent light during the period 14–15.5 h after sunrise, postponed gonadal development and spawning for up to 3 months. In this regime, a maximum of 80% of 1-year sampled fish were spermiating males in February and a maximum of 10% were VO3 stage females in March. In the sampled 2-year fish, the maximum levels were 50% spermiating males in February and 25% VO3 stage females in March. Control fish, which were exposed to the natural photoperiod (29°34′N), spawned during their natural season. The maximum levels for 1-year sampled control fish were 95% spermiating males and no females in December, while among 2-year sampled fish, maxima of 75% males in February and 45% VO4 stage females in November. Final average weights of photoperiod treated fish (1-year=430 g—regime 1, 400 g—regime 2; 2-year=582 g—regime 1, 518 g—regime 2) were significantly greater (p<0.05) than control fish (1-year=341 g; 2-year=476 g). Daily feed consumption (g/100 g fish) dropped from an average of 1.83 to 0.93 g for 1-year fish during August–December and from 0.88 to 0.54 g for 2-year fish during the same period. This was correlated with reduced autumn and winter water temperatures (26–20°C summer to winter change) and increased fish weight in all treatments. Daily feed consumption was also affected by the onset of spawning in the control and regime 2 (skeleton photoperiod) treatments of both 1- and 2-year fish. The efficiency of feed utilization (FCR) and protein and energy retention were all affected by the photoperiod regimes and followed the same pattern of decrease as weight gain, regime 1 (long day)>regime 2 (skeleton photoperiod)>control.  相似文献   

7.
Effects of temperature and photoperiod on the reproductive activity of a reef associated tropical damselfish Chrysiptera cyanea were evaluated under three phases with different environmental patterns, phase I (April–May; increasing water temperature and photoperiod), phase II (June–July; increasing water temperature and peak/decreasing photoperiod), and phase III (August–September; peak/decreasing water temperature and decreasing photoperiod). When the fish were reared at 20, 25, or 30°C under natural photoperiod, the reproductive conditions differed within and among the phases depending on experimental temperature and environmental patterns. From phases I through III, ovaries with vitellogenic oocytes were notable only at 25°C, whereas regressing and immature oocytes were noticed at 20 and 30°C. The fish underwent active spawning at 25°C, whereas no or few spawnings were observed at other temperatures. In phase III, there was a resultant prevention of decrease in the gonadosomatic index and disappearance of vitellogenic oocytes in the ovaries of fish under a long photoperiod (LD14:10) compared to those under a short photoperiod (LD10:14). These results indicate that a long photoperiod with a suitable range of water temperature is a principal determinant in continuity of reproductive activity and performance, and that a high temperature has a negative impact on their ovarian development.  相似文献   

8.
Haddock (Melanogrammus aeglefinus L.) were maintained on either simulated natural (SNP) or advanced, phase‐shifted photoperiods (ADV) and reproductive characteristics of female fish were measured throughout two reproductive cycles. By advancing the seasonal photoperiod 8 weeks, relative to ambient conditions, follicle development, peak levels of estradiol and initiation of spawning were all accelerated compared with fish maintained on an SNP. Profiles of steroid synthesis and follicular development were similar between the two groups but the spawning period was protracted by 40 days in the fish maintained on ADV. Ultrasound imaging proved to be an effective and non‐invasive tool for accurately assessing ovarian development throughout the reproductive cycle. These results suggest that photoperiod manipulation has significant potential for extending the availability of eggs and larvae for haddock aquaculture.  相似文献   

9.
Ninety sexually mature Cherax quadricarinatus females were exposed to various combinations of photoperiod and temperature for 2 months during the summer. Females were randomly assigned to either “winter” “semi-winter” or “summer” simulation treatments. In the “winter” treatment, crayfish were exposed to a simulated winter photoperiod (gradual decrease from 14L:10D to 10L:14D, 4 weeks at short day length followed by gradual increase to 14L:10D) and temperature (gradual decrease from 27 to 15 °C, held for 4 weeks, and then gradual increase to 27 °C). In the “semi-winter” treatment, crayfish were exposed to a simulated winter photoperiod and a summer temperature (27–29 °C). In the “summer” treatment, the crayfish were exposed to summer water temperatures and a photoperiod of 14L:10D. Following the 2 months of conditioning, the females were stocked for 7 months in small groups with males under environmental conditions similar to those of the “summer” treatment. All females were individually tagged and molting and spawning events were monitored. Females exposed to “semi-winter” conditioning in the summer, demonstrated a threefold increase in the rate of first spawning during the winter (December–February) compared with the other females. Crayfish breeders can easily implement these findings since shifting the breeding season into the winter only requires shortening of the photoperiod in the summer. The stocking of ponds in the spring with large nursed juveniles that hatched from eggs spawned in the winter, would allow the attainment of market size at the end of the limited growout season in temperate zones.  相似文献   

10.
Juvenile Atlantic halibut, Hippoglossus hippoglossus (initial weight (SD) 191.3 (±44.7)) g, were reared for 99 days at a constant temperature of 11°C and subjected to three different light regimes from 13 September to 21 December: continuous light (LD24:0), simulated natural photoperiod of Bergen (60°25′N, LDN) and constant 20 h light:4 h dark (LD20:4). The fish reared on the different photoperiod regimes differed in their growth patterns as juveniles exposed to long days, i.e. LD20:4 and LD24:0, exhibited faster growth than those experiencing a natural photoperiod. The LD20:4 group showed the highest average specific growth rate (0.72% body weight day?1), whereas fish on LDN displayed the lowest average specific growth rate (0.60% body weight day?1). The final mean weights of the LD20:4 and the LD24:0 groups were 15% and 12% higher than those of the LDN group. Dividing the duration of the experiment into three time periods shows that the LD20:4 and LD24:0 had a higher feed conversion efficiency (FCE) as compared with the LDN group during the first and the last period, while a reversed situation was observed in the second period. Our data indicate a larger variation in growth rates among individuals in the best‐performing groups (here LD20:4 and LD24:0). This may indicate that formation of size hierarchies is more pronounced in groups with more homogenous growth (here LDN). Overall, our findings indicate that extended light regimes result in faster growth and better feed conversion in juvenile Atlantic halibut. In line with findings on other flatfish species, this supports the concept that constant long day:short night or continuous light regimes should be used by the farmer in order to maximize growth and improve feed conversion in Atlantic halibut.  相似文献   

11.
The effects of artificial photoperiod regimes on reproductive patterns have been studied in several species, as have haematological parameters. However, information on how artificial photoperiods may affect blood components is scarce, especially under field conditions. We have assessed the effects of constant light [long day (LD) photoperiod: 24 h (light):0 h (dark)] on haematological parameters of cultured rainbow trout in Chile (Southern Hemisphere). In the initial stage (March up to June), two groups of fish were maintained under similar conditions and under the ambient (natural) photoperiod (NP). One group was then placed under the LD photoperiod regime for 2 months (June/July), following which it was returned to␣the NP (August–January); the control group remained under the NP throughout the experiment (March–January). All fish were assessed for haematological parameters and growth performance at various times during the experiment. During the initial stage, no differences were found between groups. However, at the end of the LD 24:0 period, the LD fish had increased haematocrit values and erythrocyte numbers and diminished mean corpuscular haemoglobin. After the LD fish had been returned to the NP, they developed secondary sexual characteristics and had a 40–44% decrease in the number of leukocytes.  相似文献   

12.
This study provides new and practical information to implement the use of photoperiodic manipulation for the control of the sexual maturation of Canadian 6+ Atlantic wolffish (Anarhichas lupus) and 3+ first-time spawners spotted wolffish (Anarhichas minor) from Canadian and Norwegian populations. Wolffish reproductive cycle (gametogenesis and oocyte maturation and spermiation) was monitored for 23 consecutive months. Control groups were held under a 12-month simulated natural photoperiod and treatment groups under an 8-month compressed photoperiod. Plasma sex steroid concentrations (estradiol-17β and 11-ketotestosterone), oocyte diameter growth, and milt production were assessed monthly. For all groups under study, fish subjected to the compressed photoperiod spawned 2–6 months earlier than the controls. Complete out-of-shift cycle was not achieved based on the completion of two reproduction cycles, and this is briefly discussed. Photoperiod treatment induced temporal shifts in sex steroid profiles, which are the likely mediators of altered timing of ovulation/final maturation. Photoperiod has a strong influence on the timing of wolffish maturation and could be used as an efficient and inexpensive tool to secure wolffish reproduction operations (year-round supply of egg and milt and/or timing with optimal temperature regimes).  相似文献   

13.
Haematological parameters are often used as health status and stress indicators in fish. However, information on the effects of artificial photoperiods on these parameters is scarce and ambiguous. The consequences of three different artificial photoperiod regimes [light/day 12 h:12 h (LD 12:12) for 150 days as controls; LD 14:10 and LD 24:0, both for an initial 60 days, and then LD 12:12 for the remaining 90 days] were evaluated in trout. In all fish the haemogram and the erythrocyte production index (EPI) were assessed at days 7, 14, 30 and 60 (phase 1) and at days 90, 120 and 150 (phase 2). At the end of phase 1, photoperiods LD 14:10 and 24:0 induced higher production of immature (late basophilic) erythrocytes (0.06–0.08 × 1012 cells/l, P < 0.05) and elevated EPI (young erythrocytes = 1.6 in LD 14:10, 2.25 in LD 24:0; late basophilic erythrocytes = 4.1–4.9 in LD 14:10, 3.3 in LD 24:0) than in controls (late basophilic erythrocytes = 0.02–0.04 × 1012 cells/l; EPI young erythrocytes = 0.2–1.0; EPI late basophilic erythrocytes = 1.4–2.7). During phase 2, only reduced numbers of lymphocytes and thrombocytes were observed at day 150 in the LD 14:00 group. An increase in the EPI (1.9) of control young erythrocytes was found at day 150.  相似文献   

14.
In order to evaluate manipulation of spawning time as a potential means to extend 0+ Atlantic salmon (Salmo salar) smolt production in Tasmania, Australia, female salmon were exposed to a natural/simulated natural (42°S) photoperiod or an advanced (L:D 9:15) photoperiod from the austral summer solstice (20 December) under natural or advanced (~ 6 °C below natural temperature) temperature conditions. In late summer (26 February) injections of a commercial LHRHa preparation or vehicle (propylene glycol) commenced. Regular ovulation checks were conducted and ova were fertilised using milt from LHRHa-injected males held under matching photo-thermal conditions. Plasma levels of 17β-estradiol (E2) and testosterone (T) were monitored and reproductive success (cumulative % ovulation, % fertilisation and % survival to the eyed-egg stage) was recorded. Ovulations commenced first (09 March) in LHRHa-treated fish that experienced advanced photoperiod and thermal regimes whereas sham-treated fish exposed to natural photoperiod and temperature conditions where the last to ovulate (22 May-08 June). Treatment-related sequential changes in the timing of ovulations were reflected by sequential advances in the timing of peaks in plasma levels of E2 and T. The fertilisation of ova from LHRHa-treated fish that experienced advanced photoperiod and thermal regimes was significantly reduced (~ 52%) relative to all other treatments (> 80%) but there were no significant treatment-related differences in the survivals of eggs to the eyed stage (~ 50-90%). Consequently, a maximum advance in the timing of median ovulation of 71 days and commercially acceptable eyed-egg yields were generated, demonstrating that combinations of photoperiod, thermal and hormone treatments may be employed to significantly extend spawning and thereafter increase the availability of 0+ smolts for grow-out.  相似文献   

15.
In order to study the possible interactive effects of salinity and photoperiod on growth, feed conversion, and blood chemistry in juvenile halibut, 2,604 (initial mean weight 26.8 g ± 0.2 SEM) juvenile halibut were exposed to six different combinations of salinities (13, 21, or 27‰) and photoperiods [continuous light, C and simulated natural photoperiod (65°N), SNP] for 129 days. Improved (10–20%) growth and 10–24% higher feed conversion efficiency were observed at low and intermediate salinities compared to the high salinity groups. Improved feed conversion efficiency (20%) and temporary growth enhancing effects (10%) of continuous light were observed, but effects faded out as day length in the simulated natural photoperiod group increased. No interactive effects of photoperiod and salinity on growth feed conversion or measured blood chemistry variables (blood sodium, pH level, haematocrit, bicarbonate content, and total carbon dioxide). It is suggested that juvenile Atlantic halibut should be reared at low and intermediate salinities and at continuous light, as this will improve growth and increase feed conversion efficiency.  相似文献   

16.
SUMMARY: Macronutrient self-selection patterns in rainbow trout and common carp, which were maintained in groups, were examined when both water temperature and duration of light phase gradually decreased. Three semipurified macronutrient diets composed mainly of protein (casein and gelatin; crude protein (CP) = 65%), fat (pollock oil and soybean oil; crude fat (CF) = 38%), or digestible carbohydrate (dextrin and gelatinized starch; crude starch (CS) = 57%) were offered to five groups of trout (20 fish/group, 51 g/fish) and carp (15 fish/group, 36 g/fish) using three self-feeders. A standard diet (ST) containing the three macronutrients at an appropriate ratio (CP = 47%, CF = 14%, CS = 25%) was also offered to three groups each by a single self-feeder. After an initial 3 weeks of experiencing a long photoperiod (14 h light : 10 h dark cycle) and high water temperature (trout, 17°C; carp, 25°C), the light phase and temperature were gradually decreased in the following 3 weeks to 10 h light : 14 h dark, and 8°C for trout and 13°C for carp, and feeding was continued for a further 3 weeks under low temperature and short photoperiod conditions. Growth and protein utilization parameters between the ST diet self-fed groups and macronutrient diet self-selection groups were not different ( P > 0.05) for both trout and carp. Trout preferred the high-protein diet (HP) to the high-fat and the high-carbohydrate diets ( P < 0.05) regardless of the changes in water temperature and photoperiod. Carp also preferred the HP diet ( P < 0.01) under the high temperature and long photoperiod conditions; however, this preference gradually disappeared with lower temperatures and shorter photoperiods. These results suggest that the most appropriate macronutrient ratios in carp diets change with environmental conditions.  相似文献   

17.
A specific immunoassay was developed for the quantification of testosterone (T) in sea bass plasma. Specific primary antibody against T was produced using an antigen BSA conjugated with T. The enzyme immunoassay (EIA) had a sensitivity of 5–0.009 ng ml–1 and 6.2% intra-assay variation; inter-assay variation was 9.5% for sea bass plasma. The effects of two different accelerating photoperiod regimes, compressed photoperiod (CO; 6 months), and constant short photoperiod (9L:15D) with a long photoperiod (15L:9D) in March (SLmar), on T plasma levels and sexual maturation were examined during the onset of puberty in male sea bass. Natural photoperiod (NP) and SLmar groups exhibited the highest T values in December (8.69±1.03 and 10.85±1.04 ng ml–1, respectively). However, SLmar group showed the first significant decrease in T plasma levels in January, two months earlier than the NP group, which presented elevated T levels until February. The CO group displayed two significant T peaks, one in October (8.90±1.60 ng ml–1) and the other in January (9.60±1.10 ng ml–1). Gonadosomatic index (GSI) in the NP and SLmar groups displayed the highest values from December to February (>2.5%). However, the SLmar group showed the first significant increase in GSI in November, one month before the controls, indicating a clear advancement of gonadal development with respect to the NP group. In the CO group, a bimodal pattern was observed with two peaks, one in October–November (1.30±0.25%) and the second in March–April (0.97±0.33%) (P<0.05). In NP group, the percentage of running males was about 80% from December to March while the percentage of running males in the SLmar group (70%) lasted only three months (December to February) decreasing (P<0.05) in March. In the CO group, spermiation began in October (60%), decreased during the next months, and increased again in March–April (30%) (P<0.05). These results indicate the advancement of puberty by either one or two months with respect to the control group in the SLmar and CO groups, respectively, and the presence of a second reproductive surge in the CO group. Collectively, these results suggest that exposure of fish to these photoperiod regimes may affect both the time of the onset of puberty and the pattern of gonadal development in prepuberal male sea bass.  相似文献   

18.
ABSTRACT: To study the influence of different photoperiod cycles on the metabolic rate and energy loss of fed and unfed adult tilapia Oreochromis niloticus (bodyweight 102–107 g) at 28°C, four photoperiod cycles (i.e. 3L : 3D, 6L : 6D, 12L : 12D, and 24L : 24D) were applied. A computer-operated respirometer with a closed tank was used so as to prevent water from condensing from the air or evaporating into the air. A photoperiod-mediated metabolic cycle was demonstrated during the routine state in which the metabolic rate was higher during the light phase compared with during the dark phase for all photoperiods. The combined effects of photoperiod and feeding episodes acted as a strong Zeitgeber (cue or synchronizer) for synchronizing the daily rhythm in fed fish. Fish exposed to short photoperiod cycles showed a higher metabolic rate and energy loss compared with those exposed to longer photoperiod cycles. Mean oxygen consumption in the fed and unfed fish were 295.7 mg/kg per h and 149.8 mg/kg per h, respectively, during the 3L : 3D period; 286.5 mg/kg per h and 143.3 mg/kg per h during the 6L : 6D period; 262.2 mg/kg per h and 130.3 mg/kg per h during the 12L : 12D period; and 238.3 mg/kg per h and 120.4 mg/kg per h during the 24L : 24D period. The highest post-prandial increase in energy loss was recorded during the 3L : 3D period (56.2 kJ/kg per day), followed by 55.1 kJ/kg per day during the 6L : 6D period, 50.7 kJ/kg per day during the 12L : 12D period, and 45.4 kJ/kg per day during the 24L : 24D period. The study's results demonstrated that the fish conserve energy when raised under longer photoperiod cycles.  相似文献   

19.
This study assessed the effects of two artificial photoperiods (LD 24:0 and LD 12:12) and three temperature regimes (9, 11, and 18°C) for 30 days on haematological parameters of trout (Oncorhynchus mykiss) kept in freshwater. Samples were taken at days 7, 14, and 30 during exposure to treatments. A higher mortality (22%) and lower oxygen concentration (<8.0 mg/l) were associated with the combination of photoperiod LD 24:0 and 18°C. The LD 24:0 photoperiod (independently of temperature) increased the haematocrit and the number of erythrocytes at days 7, 14, and 30 (P < 0.01). A temperature of 18°C (independently of photoperiod regimes) diminished the number of total leucocytes, lymphocytes and thrombocytes (P < 0.01). The LD 24:0 photoperiod (also independently of temperature) lowered the number of lymphocytes only after 14 days of experimentation (P < 0.01). Interaction between artificial photoperiod and temperature was only observed at day 14 for polychromatophils (P < 0.01). These results resemble the effects of stress caused by elevated temperatures and the application of continuous light photoperiods, indicating that survival risks may develop in trout farming when this combination is met.  相似文献   

20.
Caspian roach (Rutilus rutilus caspicus), a spring spawning teleost, were subjected to various photoperiod and temperature regimes to study the feasibility of shifting the timing of spawning for artificial propagation purposes. A total of 650 female reproductively mature R. rutilus caspicus were subjected to different photoperiod and temperature regimes including four light regimes (natural light (NL), 16 hr of light (L):8 hr of darkness (D), 9L:15D, 11L:13D), each affected by three temperature regimes (14, 20 and 24°C) for 70 days. Five fish per tank were randomly sampled on Feb. 10, Feb. 20, March 28, April 15 and April 30 (natural spawning time). Ovarian tissue sections were studied using light microscope and transmission electron microscope (TEM). The levels of 17‐β estradiol (E2) and 17α‐hydroxyprogesterone (OHP) were also measured in the serum samples. In late winter (March 28th), the gonadal maturation and spawning were accelerated in fish treated with the long day length (16L/8D) and warm temperature (20°C). While, the maturation of oocytes and spawning delayed in fish exposed to low temperature (14°C) and short day length (9L/15D and 11L/13D). Photoperiod seems to play a more important role in the ovarian development of the R. rutilus caspicus compared to temperature; since even among the fish treated with the lowest temperature (14°C), those exposed to a longer day length (16L/8D), matured and spawned earlier than the others. Considering that the earliest spawning occurred in R. rutilus caspicus treated with 16L/8D at 20°C and the latest spawning occurred in fish exposed to low temperature and short photoperiod, it can be concluded that temperature and photoperiod play an important role in accelerating oocyte maturation and spawning.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号