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1.
Two experiments were conducted in order to determine the appropriate age and stocking density of vundu catfish Heterobranchus longifilis at the weaning time. In the first experiment, five triplicate groups of 100 larvae (initial mean weight=3.4 mg) per aquaria were stocked from first feeding [day 3 post‐hatch (p.h.)] to day 30 p.h., and then weaned, on days 3 (W3), 5 (W5), 8 (W8) and 14 (W14), and an unweaned group (An). Significant differences were observed in growth, survival, cannibalism, coefficient of weight variation and body composition among larvae weaned at different ages and the control group. The later the larvae were weaned, the better were the growth performances [final mean weight: from 65.1 to 201.1 mg and specific growth rate (SGR): from 11.0 to 15.2% day?1] and the survival (from 36.5% to 74.3%). The experiment with stocking densities of 5, 10, 25 and 50 larvae L?1 showed that increasing the stocking density decreased growth performances and weight variation but improved the survival rate of larvae. The best growth performances (SGR=13.4 and 11.4% day?1) with the lowest survival rates (70.3% and 77.3%) were observed in larvae stocked at densities of 5 and 10 larvae L?1 respectively.  相似文献   

2.
A high rate of sibling cannibalism is one of the principal obstacles in the rearing of larvae and juveniles of the African catfish Clarias gariepinus. This paper examines the underlying behavioural components of agonistic behaviour under culture conditions. Ten day old catfish larvae were stocked at 30 larvae l–1 in three tank designs with different surface areas and equal volumes. Stocking densities were 1.2, 0.6 and 0.3 fish cm–2 bottom surface. Growth did not differ between treatments. The highest mortality over 30 days was recorded at the medium density (0.6 larvae l–1). Fish stocked at this density showed the highest rate of aggression, while there was no difference in aggression between the highest and the lowest stocking densities. The results indicate that stocking density should be at least as high as 1.2 larvae cm–2 bottom surface area to obtain high production at best survival rates.  相似文献   

3.
Manipulation of stocking densities (10, 20, 30, 40 and 50 larvae L?1), each with or without the presence of shelter was conducted to determine the effects on survival, cannibalism and growth performances of larval bagrid catfish Mystus nemurus (Valenciennes 1840) from 2 to 14 days after hatching. This study revealed that stocking density significantly affected survival, cannibalism, total length, feed intake, specific growth rate and final weight of bagrid catfish larvae. Significantly higher survival was observed at moderate stocking density of more than 20 but less than 50 larvae L?1. Survival was significantly low beyond this threshold and was the lowest at 10 larvae L?1, coincides with the highest cannibalism. Total length, feed intake, specific growth rate and final weight were significantly higher at 10 larvae L?1. Shelter significantly improved total length and feed intake. No significant effects of stocking density and shelter were observed on the apparent feed conversion ratio and coefficient of variation. There was also no significant interaction between stocking density and shelter in all parameters. This study suggests that bagrid catfish larvae could be cultured at more than 20 but less than 50 larvae L?1 with the availability of shelter for optimal larviculture condition.  相似文献   

4.
Four separate studies were done on Southern flounder Paralichthys lethostigma larvae during first feeding and metamorphosis to determine the effects of stocking density, salinity, and light intensity on growth and survival. One study used stocking densities of 10, 20, 40, and 80 fish/L during first feeding; the second study compared the growth and survival of larvae stocked at 20 and 33 ppt; and a third experiment evaluated stocking densities of 1/L and 3/L under two different light intensities (1,600 lux vs 340 lux) during metamorphosis. The fourth experiment tested the effects of different salinities (0, 10, 20 and 30 ppt) on larval growth and survival during metamorphosis. Growth and survival (overall 6.9%) were not significantly different ( P > 0.05) for stocking rates up to 80/L. Larvae placed into 20 ppt salinity had survival through first feeding similar to that of larvae raised at 33 ppt. During metamorphosis, light intensity had no effect ( P > 0.05) on growth or survival, but fish stocked at 3/L had significantly lower ( P < 0.05) survival than fish at 1/L. Complete mortality of larvae occurred at 0 ppt. Growth and survival past metamorphosis were not significantly different ( P > 0.05) at 10, 20 and 30 ppt, but unmetamorphosed fish did not survive to day 60 at 10 ppt. Based on these results, practical larviculture of Southern flounder may require a two-step process with high stocking rates (80 fish/L) through first feeding and lower densities (1/L) through metamorphosis. Fingerling production in fertilized nursery ponds might he possible at salinity as low as 20 ppt.  相似文献   

5.
Gulf killifish, Fundulus grandis, is a hardy marine baitfish with established rearing techniques in ponds and static pools, but there is little information about the use of recirculating aquaculture systems (RAS) for growing killifish.The current trial investigated the effects of stocking density on growth and survival of young killifish in RAS. Young fish (28-day posthatch) of 51.6 ± 0.9 mg (mean ± SE) were stocked at 2, 5, 8, and 11 fish/L in 31 L tanks in RAS with triplicate groups for 16 weeks. Cannibalism was a major problem in the study, which increased with increasing initial stocking density, affecting survival negatively. Survival decreased (P < 0.03) with increasing initial stocking density and culture period. At the end of the trial, the 2, 5, 8 and 11 fish/L initial stocking density reduced to 1.66, 1.42, 0.86, and 0.74 fish/L respectively. A significant linear relationship existed between the initial stocking density and weight (y = 0.077x + 2.3; R2 = 0.8; P = 0.003), whereas an inverse relationship occurred between initial stocking density and survival parameters (y = ?9.43x + 97.4; R2 = 0.89; P < 0.001). From the trial, the optimum density for culturing young of Gulf killifish in RAS appears to be around two fish/L.  相似文献   

6.
Two experiments were conducted to evaluate the initial stocking density in larvae of Bay snook, Petenia splendida, and Mexican mojarra, Cichlasoma urophthalmus, using a recirculation system. Five initial stocking densities (0.5, 1, 5, 10, and 20 larvae/L) were evaluated by triplicate for 45 d. Weight and total length (TL) were measured every 15 d, and fish production was calculated for each density. The larvae stocked at the lowest densities (0.5 and 1 larvae/L) presented the highest growth for both species: C. urophthalmus (0.78 g and 45‐mm TL, and 0.76 g and 45‐mm TL, respectively) and P. splendida (0.80 g and 52‐mm TL, and 0.79 g and 49‐mm TL, respectively). However, lowest fish production was recorded (35 and 69 fish per tank, respectively, for C. urophthalmus and 34 and 70 fish per tank, respectively, for P. splendida) compared with those at densities of 5, 10, and 20 larvae/L (336, 584, and 604 fish per tank, respectively, for C. urophthalmus and 341, 679, and 912 fish per tank, respectively, for P. splendida). The polynomial model for biomass production related to the stocking density shows that the optimum stocking densities for C. urophthalmus and P. splendida are 12 and 14 larvae/L, respectively.  相似文献   

7.
Abstract. The growth and survival of Clarias gariepinus (Burchell) fry was investigated at high stocking density. Significant increases in mean fry weight, and concomitant significant decreases in specific growth rate, were recorded over successive 5-day periods. Fry growth was negatively density dependent. Fry survival was in excess of 90% in all treatments. Increasing stocking density between 50 and 150 fish/l altered the pattern of mortality; non-cannibalistic deaths decreased significantly with increasing stocking density though cannibalism did not significantly increase. Periods of weaning fish onto larger feed particles were associated with temporarily increased rates of cannibalism.  相似文献   

8.
Heterobranchus longifilis larvae were reared over a 35 d period to evaluate the effects of stocking densities and feeding regimes on growth and survival. In experiment 1, larvae (12.3?±?2.1 mg) were stocked into glass aquaria at densities of 1, 2, 5, 10, 15, 20, and 25 larvae L?1. Larvae were fed on Artemia nauplii ad libitum. Significant variations in terms of growth performance and feed utilization occurred at all levels of density treatments. Specific growth rate (SGR), body weight gain (BWG), and feed efficiency (FE) of the larvae decreased significantly as density increased. However, survival rate increased with the increase of stocking density. In experiment 2, larvae (13.4?±?1.1 mg) stocked at a density of 15 larvae L?1, in the same conditions as experiment 1, were fed on three different regimes: Artemia nauplii; 35%?protein beef brain; and 35%?protein commercial catfish feed (CN+). SGR, BWG, and coefficient of variation (CV) of larvae fed on Artemia nauplii were significantly higher than those fed on beef brain and CN+. The survival rate of larvae fed on beef brain was significantly higher (88.40?±?9.75%) than those of Artemia (69.21?±?6.69%) and CN+ (40.40?±?6.22%). The results of this study suggest that the optimum stocking density is 15 larvae L?1 and the beef brain can be used as alternative feed to Artemia in rearing H. longifilis larvae.  相似文献   

9.
《水生生物资源》1998,11(5):335-340
Sibling juvenile vundu Heterobranchus longifilis reared at 27±1 °C under 12L: 12D were fed during the day, at night or over the entire 24-h cycle, for periods of 14–15 d. Nighttime feeding gave the highest growth rates, best feed conversion, lowest mortality, fewest losses due to cannibalism and least growth heterogeneity. The trends were seen in fish of all ages and weights (31–101 d and 0.3–30.0 g), but differences were significant only for the smallest fish that were reared at the lowest stocking biomass (< 3.5 g-L1). The effects of daytime and nighttime feeding were examined in 151-d old (85 g) juveniles stocked at different biomasses (3.4 and 13.6 g-L1). The growth of vundu was density-dependent, being impaired at low stocking density, but this was substantially mitigated under nighttime feeding. Rearing at high stocking density, feeding at night or in darkness, may act through similar mechanisms that involve changes in the level of aggressive behaviour. It is suggested that nighttime feeding in intensive catfish culture could be replaced by 24-h feeding under conditions of permanent darkness.  相似文献   

10.
Abstract.— Three experiments investigating larval stocking densities of summer flounder from hatch to metamorphosis, Paralichthvs dentalus, were conducted at laboratory‐scale (75‐L aquaria) and at commercial scale (1,000‐L tanks). Experiments 1 and 2 at commercial scale tested the densities of 10 and 60 larvae/L, and 10, 20, and 30/L, respectively. The laboratory scale experiment tested the densities of 10, 20, 30, and 40 larvae/L. Experiments were carried out in two separate filtered, flow‐through seawater systems at URI Narragansett Bay Campus (laboratory‐scale), and at GreatBay Aquafarms, Inc. (commercial‐scale). At both locations, the larvae were raised in a “greenwater” culture environment, and fed rotifers and brine shrimp nauplii according to feeding regimes established for each location. Water temperature was maintained at 21C (± 2) and 19C (± 1) for the duration of laboratory and commercial experiments, respectively. Experiments 1 and 2 at the commercial location were terminated at 42 and 37 d post hatch (dph), respectively, and the laboratory experiment lasted 34 DPH. Larvae initially stocked at 10/L grew to an average length of 14.3 and 14.4 mm, and were significantly larger (P < 0.05) than those stocked at 30/L (13.1 mm) and 60/L (11.7 mm) in commercial scale experiments I and 2, respectively. At laboratory scale, no significant differences in length were detected, although mean total length tended to decrease with increasing stocking density (average length of 14.2, 13.3, 12.7, and 12.7 mm for treatments of 10, 20, 30, and 40/L, respectively). Final survival percentage was not affected by stocking density in either commercial experiment, and was 61 and 40% for treatments of 10 and 60/L in Experiment 1, respectively, and 62, 59, and 56% for Experiment 2, respectively. Similarly, there was no significant difference in final survival percentage among treatments in the laboratory experiment, which averaged 59, 55, 56, and 37% for treatments of 10, 20, 30, and 40L. respectively. Since larval length was not different between the intermediate densities (20 and 30 Iarvae/L), and because high‐density rearing can produce a much greater numerical yield per tank, we recommend a density of 30 larvaen as an optimal stocking density for the hatchery production of summer flounder.  相似文献   

11.
Data on production of fingerling striped bass, Morone saxatilis, in 103 ponds at 17 hatcheries in 1988 were related to information on management practices and water qualities. Production was highly variable, with a median of 50,000/ha. No survival was evident in 12% of ponds; numbers harvested exceeded 250,000/ ha in 5% of ponds. Best survival resulted when larvae were stocked within 2 days after pond filling was started and at hatcheries with relatively low application rates of fertilizers during the prestocking interval. No survival was evident in ponds with pH >9.0 in the week after stocking. High pH's and probably toxic concentrations of un-ionized ammonia were related to water being in ponds for too long prior to stocking and to high applications of fertilizers. Examination of samples of larvae collected at stocking and the week after stocking documented a problem with swim bladder inflation. When larvae were stocked at D5 or D6 (Dl is day of hatch), inflation success averaged 91%: when stocked at ≥D7. inflation success averaged 60%. Measures proposed to improve production include: (1) Stock larvae prior to the critical period of swim bladder inflation(D4-D5). (2) Start filling ponds as close to stocking as is feasible (filling can be completed after stocking). (3) If the concentration of available nitrogen is low, apply no more than 300 µg/L of nitrogen in the prestocking interval. (4) Add phosphorus as needed, but avoid pH>8.5 until larvae are D14.  相似文献   

12.
The effect of stocking density on the survival and growth of pikeperch, Sander lucioperca (L.), larvae was examined in two consecutive experiments. In experiment I, 4-day-old larvae [body wet weight (BW): 0.5 mg; total body length (TL): 5.6 mm] were reared in 200-l cylindro-conical tanks in a closed, recirculating system (20 ± 0.5°C) at three stocking densities (25, 50 and 100 larvae l−1) and fed a mixed feed (Artemia nauplii and Lansy A2 artificial feed) for 14 consecutive days. At densities of 25 and 100 larvae l−1, growth rate and survival ranged from 2.7 to 1.9 mg day−1 and from 79.2 to 72.3%, and fish biomass gain ranged from 0.6 to 2.0 g l−1, respectively. There were two periods of increased larval mortality: the first was at beginning of exogenous feeding and the second during swim bladder inflation. In experiment II, 18-day-old larvae (BW: 35 mg; TL: 15.6 mm) obtained from experiment I were reared under culture conditions similar to those of experiment I, but at lower stocking densities (6, 10 and 15 larvae l−1). The fish were fed exclusively with artificial feed (trout starter) for 21 consecutive days. At densities of 6 and 15 larvae l−1, the growth rate and fish biomass gain ranged from 28.8 to 23.1 mg day−1 and from 2.0 to 3.3 g l−1, respectively. The highest survival (56.5%) was achieved at a density of 6 larvae l−1. Mortality at all densities was mainly caused by cannibalism II type behaviour (27–35% of total). In both experiments, growth and survival were negatively correlated and fish biomass gain positively correlated with stocking densities. The present study suggests that the initial stocking density of pikeperch larvae reared in a recirculating system can be 100 individuals l−1 for the 4- to 18-day period post-hatch and 15 individuals l−1 for the post-19-day period.  相似文献   

13.
Initial larval stocking density, prey density, daily prey ration and light conditions (light intensity and photoperiod) were tested for common dentex larval rearing under experimental conditions. Experiments continued until the first peak of larval mortality. The best results in larval survival were obtained with an initial stocking density of between 10 and 40 larvae L?1, fed with at least 10 rotifers mL?1, maintaining ratios of 500–1000 rotifers larva?1, with one or two adjustments of prey density per day. The use of more than 2000 rotifers larva?1 or three daily adjustments of live prey density had negative effects on larval survival. The best light conditions for common dentex larval rearing were found using a photoperiod of 24 h L:0 h D and an intensity of at least 3.4 μmol m?2 s?1.  相似文献   

14.
养殖密度对杂交鳢仔鱼生长与存活的影响   总被引：3，自引：2，他引：3  
在温棚水族箱中养殖杂交鳢仔鱼,养殖密度分别为0.5、1、2、4、8尾/L,共养殖15 d,试验结果表明:养殖密度在0.5～4尾/L之间,杂交鳢仔鱼的最终体重、特定生长率、日增重都随着养殖密度的增大而升高,当养殖密度为4尾/L时,三者达到最大值;进一步增加养殖密度,仔鱼的生长反而下降。高密度组(4、8尾/L)杂交鳢仔鱼个体生长速度离散度明显加大,仔鱼的成活率随养殖密度增加而下降。  相似文献   

15.
This research examined the effect of initial stocking density and feeding regime on larval growth and survival of Japanese flounder, Paralichthys olivaceus. Larval rearing trials were conducted in nine 50‐L tanks with different initial stocking densities combined with different feed rations (20 larvae/L with standard feed ration [LD], 80 larvae/L with standard feed ration [HD], and 80 larvae/L with four times the standard feed ration [HD+]). Larvae were stocked on 0 days posthatch (DPH) following hatching of the fertilized embryos. Larval total length (TL), survival rates, and final densities were observed on larval settlement (32 DPH) to evaluate larval rearing performance. At 32 DPH, there were no significant differences (p > .05) in TL or survival rates between the LD (46.5 ± 17.0%) and HD+ (40.3 ± 9.4%). The TL and survival rate of HD (23.1 ± 3.5%) were significantly lower than that of LD and HD+ (p < .05). However, the larval density of HD was significantly higher than that of LD (p < .05). HD+ achieved the best larvae production (32.27 ± 7.51 larvae/L), supported by sufficient food source, high water exchange, and proper water quality management (routine siphoning, surface skimming). The larval‐rearing protocols and larval development from hatching to metamorphosis is described in detail, with corresponding photographs taken during the experiment.  相似文献   

16.
Juvenile red king crabs (RKCs) Paralithodes camtschaticus have a strong tendency for cannibalism, which is an obstacle for seedling production. We investigated the effects of density-dependent cannibalism on the survival rate and on growth, and estimated the optimal stocking density. Four different stocking densities of juvenile first instar crabs were maintained in tanks (50, 100, 200 and 400 individuals per 100-l tank: bottom area was 0.25 m2) during the 209 or 216 days of rearing. The survival rate was affected by stocking density, elapsed days, and the interaction between these variables. Although carapace length, an index of body size, was also affected by density, elapsed days, and the interaction between these variables, the effect associated with density was quite small, suggesting that cannibalism did not intensely affect growth of juvenile crabs. We then estimated the initial stocking density that maximizes the number of survivors using parameters of analyses. Optimal initial stocking density was predicted as 416, 197 and 149 individuals per tank when the target size was assumed as 5.0, 10.0 and 15.0 mm, respectively. This estimation provides a baseline for seedling production in RKCs and could be further improved by considering other factors that affect survival and growth of RKCs.  相似文献   

17.
Cannibalism is one of the main causes of mortality in the culture of the mud crab Scylla paramamosain, particularly in the early post‐larval and juvenile stages when the densities of hatchery‐reared crabs may be very high before stocking into ponds or release into the wild for stock enhancement. In a series of experiments investigating cannibalism mitigation, the influence of stocking density, the effectiveness of sand substrate, brick and shell shelters and feed type were compared in culture of crabs from instar 1 for short nursery periods of 15–30 days. Inclusion of brick and shell shelters significantly increased survival over sand substrate alone. However, inclusion of shelters did not affect growth rates. In scaled‐up nursery production in lined‐ponds, with shelters, live Artemia biomass and fresh chopped shrimp or tilapia were found to be equally effective feeds for juvenile crabs stocked at a density of 70 m−2 from instar 1 and grown for 30 days [52–66% survival, 21.6–24.6 mm carapace width (CW)]. In an extended nursery period for a further 30 days, crabs of 22 mm CW, stocked at 30 m−2 in the same ponds, attained a final size of 34.5–36.2 mm CW with a survival of 64.3–67.0% using the same feeds.  相似文献   

18.
Pond-nursed pike-perch (Sander lucioperca) fry were trained to artificial diet and reared under controlled conditions maintained in aquaria using three stocking densities (1.25, 1.66 and 2.08 g/l). Two replicates per treatment were applied. The survival during the 4-week period of the experiment ranged from 44.2 to 49.6%. The majority of the losses were caused by cannibalism; only 8–14% could be attributed to natural mortality. Both cannibalism and natural mortality occurred in the first 2–3 weeks of rearing. The differences in the rate of cannibalism were independent of the stocking density. Natural mortality decreased with increasing density, consequently the highest survival was observed under the highest stocking density. Stocking density did not significantly influence growth, feed consumption and feed conversion ratio of the pike-perch fingerlings (p < 0.05).  相似文献   

19.
ABSTRACT

Catla, Catla catla, and rohu, Labeo rohita, fry were cultured at 6,667,8,333, and 10,000/m3 in 15-L aquaria in recirculating systems for 30 days. Larvae were fed with exogenous live plankton. Cultures at 6,667 and 8,333 larvae/m3 showed significantly (P <0.05) higher survival and growth than larvae stocked at 10,000 larvae/m3 for both species. Food was more efficiently used in low stocking density, as evident from the significantly (P <0.05) lower values of feed conversion ratio in lower density compared to those for high stocking density. Specific growth rate of both species was high in the early stage and gradually declined along with the ontogenic development. Dissolved oxygen level was higher in the low density system than in the high density one. Values of phosphate and COD increased during the experiment. Ammonia, nitrite, phosphate, and COD levels were significantly (P <0.05) higher in the 10,000 larvae/m3 density system than in the other two systems for both species. Considering the survival and growth of fish and values of water quality parameters, it appears that stocking density can be raised up to 8,333 larvae/m3 with a recirculating system for both catla and rohu.  相似文献   

20.
The hypothesis that intraspecific competition affects survival and growth during the culture and harvest at extensive/semi-intensive Penaeus vannamei shrimp ponds was evaluated. Thus, the effect of stocking density on the biomass, shrimp average weight, survival, and economic performance during the culture (133 days) and at the harvest of the P. vannamei shrimp was investigated in 400 m2 earthen ponds. In order to reduce the likelihood of infectious diseases, shrimp received preventive health treatments (probiotics and β-1,3/1,6-glucans) during all culture phases. In this way, the effect of density on the intraspecific competition for space/food was isolated. Ponds stocked at 6, 9, and 12 shrimp m?2 showed competition-dependent growth. Ponds stocked at 12 shrimp m?2 presented a mortality (12 %) between days 76 and 99. Competition, and accordingly individual growth reduction, could have begun at day 76 at a density of 5 shrimp m?2. Survival was significantly higher at 6 shrimp m?2 (84.2 ± 6.2 %) compared with the 12 shrimp m?2 (64.8 ± 12.4 %) treatment, while no significant differences in yield were observed between both treatments. Ponds stocked at 3 and 6 shrimp m?2 presented the best benefit–cost rates. The optimal shrimp density during the experimental culture was 5 shrimp m?2. Given the experimental conditions and considering the fraction of density-independent mortality observed, the optimum stocking density was found to be 6 shrimp m?2.  相似文献   

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