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1.
This study investigated razor clam Ensis arcuatus culture from larval rearing to commercial size to assess it's aquaculture potential. Broodstock was spawned several times in hatchery facilities to demonstrate that larval availability is not a constraint for hatchery production. Larval culture lasted 20 days, showing an average survival of 14.35%. The razor clam seed reached a size of 28.5 mm at 4 months. Seed culture is feasible; however, it is constrained by the fact that razor clams need to be buried. Higher survival was observed when culturing razor clam seed with a substrate (82–83%), irrespective of the substrate grain size, while containers held without a substrate showed a significantly lower survival (56.5%). We showed that it is possible to rear E. arcuatus juveniles in bottles, with survival as high as 94–95% being achieved. The length increase of the hatchery‐produced E. arcuatus over 600 days was described by the equation Ln L=4.5+(?141.17/t), where L is length in mm and t is time in days. On‐growing showed adequate survival rates and it took 2–3 years to reach commercial size.  相似文献   

2.
In this study, the effects of different stocking densities on survival, injury and meat content of captive male red king crab (mean weight = 2.6 kg) were examined. The first experiment was carried out in square plastic tanks with stocking densities of 100, 150 and 200 kg m?3 for 56 days. In a second experiment, king crabs were kept at a stocking density of 60 kg m?3 and were either fed or not fed. Both mortality and occurrence of injuries increased significantly with increasing stocking density. In the highest density groups, mortality and frequency of injury was 17% and 14% respectively, compared with 5% and 4% in the 150 kg m?3 group. The percentage meat content was significantly lower at the final census compared with the initial census in all stocking density groups. In Experiment 2, there were no mortalities or injuries in either the fed or unfed treatments. The average percentage meat content increased in the fed treatment and decreased in the starved treatments. The results show that adult male king crab can maintain high survival rates at stocking densities up to 150 kg m?3 in holding facilities of the design used in the present study for periods up to 2 months. However, to reduce mortality and frequency of injury over this period densities as low as 60 kg m?3 and a holding system with a large bottom surface area are recommended.  相似文献   

3.
In this study the effects of different stocking densities on survival, injury and weight of captive male snow crab were examined. The first experiment (I) was carried out in square plastic tanks (700 L) with stocking densities of 100 (L), 150 (M) and 200 kg m?3 (H) for 30 days. In a second experiment (II) snow crabs were kept at a stocking density of 50 kg m?3 and were either fed (F) or not fed (S) for the same period of 35 days. The last experiment (III), was carried out with stocking densities of 25 kg m?3 for 21 days with two groups, one with inactivated claw and one without rubber bands, with three replicates per treatment. In the first experiment mortality (H = 27, M = 26 and L = 36%) and occurrence of injuries (H = 27, M = 20 and L = 16%) were high in all groups. The weight loss during the experimental period was; H = 15.3, M = 10.9 and L = 15.5 g, and was not significant different between the groups. In experiment II the mortality (F = 13% and S = 14%) and injuries were lower (F = 12% and S = 17%). The average weight increased in the fed treatment and decreased in the starved treatments. In the last experiment there was no mortality in any of the groups and the levels of injury were low (5% and 7%). The results show that adult male snow crab cannot be stored at densities equal to or higher than 25 kg m?3 for 3 weeks without risk of mortality.  相似文献   

4.
To evaluate effects of stocking density on welfare of Amur sturgeon (Acipenser schrenckii), an experiment was designed using three initial stocking densities in flow‐through tanks (LSD = 3.7 kg m?3, MSD = 6.9 kg m?3, and HSD = 9.3 kg m?3, respectively) for 60 days. Growth, body composition, and haematological and biochemical parameters were monitored. The mortality and feed conversion rate (FCR) were not affected by stocking density. However, the specific growth rate (SGR), final weight and weight gain in the HSD group were significantly lower than in the LSD and MSD groups. The hepatosomatic (HSI) and viscerosomatic indices (VSI) varied inversely with regard to stocking density. Stocking density did not affect crude protein levels in fish. In contrast, the total lipid level was significantly higher in the LSD group compared to the MSD and HSD groups. The levels of erythrocytes and haemoglobin were positively correlated with stocking density. Serum total bilirubin and urea in HSD group were significantly higher than in the LSD group while serum triglycerides showed opposite tendencies. Differences between treatments were not registered for glucose, total protein and albumin. In conclusion, higher stocking density resulted in increased immunosuppression and enhanced energy mobilization. The latter was necessary to enable Amur sturgeon to cope with crowding.  相似文献   

5.
The main objectives of this study were to approximate the maximum yield and evaluate size dispersion of stocker size largemouth bass, Micropterus salmoides reared in a semi‐closed recirculating system for 60 days. Fingerlings with an average body weight of 36.7 g were utilized for the study. An experimental system consisting of 18 square plastic tanks (165 L) equipped with a radial flow settler, a sump, a moving bed filter, a centrifugal pump, a rapid sand filter, a down‐flow oxygen saturator and a UV sterilizer was utilized for the trial. The system was operated semi‐closed, accounting for a daily exchange rate of 30–50% of total system water volume. Experimental stocking densities were 4.5, 9.1, 18.8, 36.5, 54.6 and 73 kg m?3 with three replicates per treatment. At the end of the experimental trial, largemouth bass showed acceptable feed conversion (1.00–1.48), specific growth rate (1.16–1.45% day?1) and survival rate (81.8–96.6%) in all treatments, displaying the highest performance at an initial stocking density range of 18–36 kg m?3. Based on a piecewise regression model with breakpoint analysis, maximum yield of largemouth bass fingerlings should not exceed 70 kg m?3. As stocking density increased, relatively more underweight fingerlings were produced with a higher uniformity of fatness.  相似文献   

6.
Growth of common sole Solea solea is negatively correlated to density, which affects productivity in culture and hence commercial success. Studies of individual feed intake were performed to examine growth and population dynamics at different densities. Three initial stocking densities: 1.0, 2.1 and 3.9 kg m?2 of individually tagged sole, referred to as low density (LD), medium density and high density HD), were examined during 145 days. Despite that tank productivity (g m?2 day?1), was highest for the HD group, the specific growth rate (SGR) decreased significantly with increase in stocking density. Individual size variation was similar between densities, indicating that growth was not associated with hierarchy and dominant behaviour. Individual data indicated that increased density reduced the growth potential of all individuals in a population. Individual feed intake was positively correlated to both fish size and individual SGR. Feed conversion ratio was likewise positively correlated to feed intake. The relative feed intake (g feed g fish?1) was not correlated to fish size at any density tested, but was significantly highest for the LD population. This explains a substantial part of the better growth in the LD group supported by indications of better utilization of the ingested feed.  相似文献   

7.
This article reports on the changes in gross biochemical and fatty acid composition of the razor clam Ensis arcuatus larvae throughout development. Protein was the largest component of dried larval tissues. The energy required for embryogenesis in E. arcuatus oocytes was obtained from stored proteins and carbohydrates, while total lipids increased significantly. Lipids and carbohydrates have an important role as energy contributors from day 1 to day 8. During larval development the strategy was to indistinctly store energy reserves (protein, lipid and carbohydrate) to surpass metamorphosis. During embryonic development there was a gain in fatty acids of neutral and polar lipids. A depletion of fatty acids in neutral lipids was observed from day 1 to day 8 in E. arcuatus larvae, mainly due to the decrease in 16:0 and EPA. NMID fatty acids were present in amounts similar to those of some PUFAs in polar lipids, especially 22:2NMID.  相似文献   

8.
Stocking density, representing a potential source of long‐term stress, is widely recognized as a critical factor in aquaculture husbandry. Atlantic salmon were reared at low‐density (LSD, ~9.80–18.41 kg m?3, initial to final density), medium‐density (MSD, ~19.62–36.96 kg m?3) and high‐density (HSD, ~28.79–53.54 kg m?3) stocking levels for 66 days to investigate the stress‐induced changes in fish growth and welfare. At the end of the trial, the salmon in HSD group showed significant lower final weight and higher ration level than those in MSD and LSD groups (P < 0.05). The salmon farmed in LSD group had higher special growth rate (SGR) and lower feed conversion ratio (FCR) (P < 0.05). However, stocking density could not affect the mortality, condition factor and coefficient of variation of salmon. The pectoral fin index of salmon in LSD group was significantly higher than that in HSD group (P < 0.05). Fifteen haematological and serum parameters were detected to assess the stress and welfare levels of salmon. The salmon farmed in HSD group had higher glucose (GLU) level and lower Cl?, haemoglobin (HGB) and red blood cell (RBC) concentrations (P < 0.05). Contrast to the pattern of superoxide dismutase (SOD) activity, the cortisol, maleic dialdehyde (MDA) and alkaline phosphatase (ALP) levels of HSD group were higher than those in other two groups (P < 0.05). All these findings will provide a reference for selecting suitable stocking density in Atlantic salmon farming industry.  相似文献   

9.
This study investigated the effects of manipulating carbon–nitrogen (C/N) ratio and fish stocking density on pond productivity: total heterotrophic bacteria counts, plankton biovolume and benthic macro‐invertebrates. Labeo victorianus juveniles were reared for 72 days in 18 hapas suspended in six ponds measuring 150 m2 at densities of 10, 15 and 25 fish m?2. Fish in hapas received a locally formulated and prepared feed containing 295 g kg?1 crude protein, and ponds were treated with a C/N ratio of either 10 or 20. All treatments were carried out in triplicate. Increasing C/N ratio from 10 to 20 increased phytoplankton by 13% and zooplankton biovolume by 25% in the water column (P < 0.001). Total benthic macro‐invertebrates biovolumes were also 30% higher (P < 0.05) with a C/N ratio of 20 compared to 10. Total heterotrophic bacteria counts increased both in water and sediment by 29% while net yield increased by 15% from 1534 (C/N 10) to 1821 (C/N 20) kg ha?1 72 day?1. C/N ratio of 20 and a stocking density of 25 fish m?2 led to the highest yield, survival, production and net benefits. It is suggested that polyculture may lead to better utilization of pond communities to further improve pond productivity.  相似文献   

10.
Genetic parameters and genotype by rearing density interactions for growth traits and survival were investigated in Litopenaeus vannamei. A total of 3626 shrimps from 40 families in two densities (low density, 80 shrimps m?2; high density, 160 shrimps m?2) were measured for four growth traits, body length, body weight, cephalothorax length and abdominal segment length. Variance components and genetic parameters for growth and survival were estimated using a two‐trait animal model or a threshold (probit) sire and dam model. The common environment effect was excluded because it could not be partitioned effectively, likely because of high heritability. The heritability for growth traits varied from 0.21 to 0.44, indicating a moderate level. For survival, the back‐transformed heritability () was 0.36 ± 0.06 and 0.22 ± 0.04 for the low and high densities respectively. There were no significant differences in heritability for growth traits and survival between the two densities (P > 0.05). High genetic correlations (0.94–0.98) between the two densities for growth traits indicated a low genotype by density interaction and ranking effect across the environments, which suggested that these traits were controlled mostly by the same genes over the two densities. Therefore, selection in a low‐density environment should produce desired correlated responses for growth at a high density. Genetic correlation (0.77 ± 0.09) between the two densities for survival was moderate and significant, which indicated that the genotype by density interaction effect was moderate and low for survival under the two densities. Our results provide crucial information for use in L. vannamei breeding programmes in China.  相似文献   

11.
In this work, we have assessed the effects of different stocking densities on the biometry, survival and physiological status of the wedge sole (Dicologoglossa cuneata), focusing on changes in the stress system and intermediate metabolism, with the aim of determining a stress indicator for chronic‐stress situations in this species. Wedge sole were kept at three different stocking densities (0.2, 0.4 and 0.8 kg m?3) for 197 days, and survival, growth, plasma metabolites, cortisol and enzymatic activities were assessed. Survival rates were the highest at low density, though growth did not vary significantly among treatments. Enzymatic activities, mainly in muscle, differed depending on stocking density. Liver hexokinase activity at low stocking density was the highest, while no differences were detected for the other enzymes assessed. In muscle, all enzymes significantly increased in activity with stocking density. We concluded that long‐term high stocking density culture significantly changed enzyme activities (hexokinase, glutamate dehydrogenase, glyceraldehyde 3‐phosphate dehydrogenase, and lactate dehydrogenase) in wedge sole muscle, although liver enzymes, plasma cortisol and metabolites did not vary significantly. Therefore, muscle enzymes, hexokinase and glutamate dehydrogenase, could be considered stress indicators for this species in chronic‐stress situations.  相似文献   

12.
Groups of adult sea bass were reared at either low (10 kg m?3) or high (50 kg m?3) stocking densities respectively for 84 and 116 days. To monitor the red muscle activity, about 20 fish from both densities were surgically implanted with EMG (Electromyograms) radio transmitters, after EMG calibration during exhaustive swimming exercise (Ucrit test). Blood samples and morphometric measurements were also taken. EMG showed that the muscle activity of fish reared at 50 kg m?3 was on average twofold higher than fish kept at lower density. Cortisol was significantly more elevated at higher density and haemoglobin, haematocrit and RBCC (red blood cells count) showed the same trend, while lysozyme decreased. Patterns for glucose and lactate were less clear. The results showed that the contemporary use of functional (EMG) and physiological (haematological and biochemical) profiles could give a more comprehensive view of the fish status validating the diagnosis of fish stress induced by culture practices.  相似文献   

13.
Scaling up the hatchery production of juvenile sandfish Holothuria scabra is constrained by limited hatchery space and the associated high operational costs. To shorten the hatchery rearing phase, ocean nursery systems like floating hapa nets have been used with good prospects but with limitations during rough sea conditions. In this study, the potential of bottom‐set trays (0.14 m2) as an alternative ocean nursery system for early sandfish juveniles (0.5 ± 0.1 cm) was evaluated. The effects of stocking density and presence of artificial substrates (AS) on the growth and survival were determined in a 60‐day field experiment. Average length and growth rates at lower stocking density treatment (100 individuals tray?1) were significantly higher (1.45 ± 0.22 cm; 0.03 ± 0.01 cm day?1) than at higher stocking density treatments (400 and 500 individuals tray?1) 0.95 ± 0.06 cm; 0.03 ± 0.004 cm day?1) with or without AS (p < .05) respectively. The coefficient of variation in length (CV) at high stocking densities were significantly higher than at low densities (p < .05) and growth rate was strongly negatively correlated with density. Survival was significantly higher (55% ± 9%) in trays with AS across all stocking density treatments than in trays without AS (34% ± 2%). Results suggest that AS may have reduced intra‐ and interspecific interactions, resulting to significantly lower growth variations and higher survival. The bottom‐set tray with AS can be a practical alternative ocean nursery unit for rearing early sandfish juveniles particularly when the sea surface condition is rough. With improved design and density management, survival and growth may be further enhanced.  相似文献   

14.
An experimental trial was conducted for 90 days to evaluate the growth performance, immunophysiological response of GIFT strain of Tilapia in biofloc‐based rearing system and to assess the relative percentage survival in 3 days after challenging with the virulent strain of Aeromonas hydrophila. Fingerlings with an average body weight 0.98 ± 0.06 g were stocked in triplicate at different stocking densities of 200 (SD1), 250 (SD2), 300 (SD3) and 350 (SD4) m?3 in biofloc‐based treatments and 150 (C) m?3 in control (clear water). Biofloc‐based units (SD1 and SD2) obtained significantly better (P < 0.05) growth performances at the end of the experimental period. Mean body weight of fish in biofloc‐based units showed a decreasing trend with increase in stocking density with 100% survival in all units including control. The stress parameters were significantly lower in biofloc‐based rearing units especially in treatments SD1 and SD2 as compared to the control. The fish from the biofloc‐based units (SD1 and SD2) possessed significantly (P < 0.05) higher immune status as compared to control and other biofloc treatments in terms of respiratory burst, serum lysozyme and myeloperoxidase activity. Relative survival percentages were significantly better in biofloc treatments with highest in SD1 and SD2 (83.33%) after challenge study. GIFT strain of Tilapia at higher stocking densities 200–250 nos m?3 can be taken as optimum stocking density whereas higher stocking densities up to 350 nos m?3 can be reared in the biofloc systems without compromising the growth and immunity.  相似文献   

15.
The total organic carbon (TOC) budget of the integrated aquaculture system of sea cucumber Apostichopus japonicus, jellyfish Rhopilema esculenta and shrimp Fenneropenaeus chinensis was investigated in a cofferdam (1.202 km2) for 13‐month field study. The results showed that the total input of TOC to the system was 498 300 kg year?1, of which photosynthesis accounted for 26.8% of input TOC. The TOC production of the sea cucumber was 3668 kg year?1, and that of the jellyfish and the shrimp was 714 kg year?1. The TOC utilization rate of the input TOC by sea cucumber production was 7.4‰, and that of the integrated system increased by 18.9% than that of sea cucumber monoculture model through integration with jellyfish and shrimp. The outflow TOC from the system was 336 600 kg year?1, which account for 92.7% of the inflow TOC. The integrated aquaculture system not only produce aquatic products, but also eliminate 7.3% of the inflow TOC, therefore, this system was not only a production system of aquatic products, but also an organic matter purification system for the coastal environment. The TOC utilization rate of the system can be probably improved by means of increasing stocking density of the sea cucumber and/or the shrimp.  相似文献   

16.
Sporeling and tissue propagation of agarophytic seaweed, Gracilaria fisheri, aimed to investigate the optimal shading colour for the preservation. This study was conducted under different shading colours indoor and outdoor experiments. The indoor experiment: tissues and sporelings of the seaweed were cultured in plastic chambers under fluorescent lights and were wrapped with white, green, blue and red colour PVC sheets of light intensity of 20 ± 1 μmol m?2 s?1. The outdoor tissues were cultured in the plastic tanks under different shadings of Saran sheets: white, green, blue and black covering the hoop‐houses with light intensity of 110 ± 10 μmol m?2 s?1. The results showed that different shading colours strongly influenced growth of G. fisheri sporelings and tissues but little effect on pigmentation. After 40 days, the highest growth rates of G. fisheri tissues and sporelings were found under red light with 1.44 and 1.89% day?1 respectively. There was no significant difference (P > 0.05) on pigment content of tissues indoor, whereas it was found that chlorophyll concentration of the sporelings under green light with 416.8 μg g?1 fresh weight was significantly higher (P < 0.05) than those in other treatments. After 8‐week culture, outdoor tissues showed the highest growth rate with 1.71% day?1 in the green hoop‐house. The study has found that G. fisheri cultivation was less influenced by epiphytes in the back hoop‐house with 15%. This study showed the feasibility of successful cultivation of G. fisheri sporelings and tissues.  相似文献   

17.
A 60 days feeding experiment was conducted to determine the effects of YK‐6 (a yeast culture feed supplement) on growth and immune responses of white shrimp, Litopenaeus vannamei and aquaculture environment in commercial scale farms composed of nine ponds. Three treatments (control, Diet 1 and Diet 2) were designed to contain YK‐6 levels of 0.0, 1.0 and 1.5 g kg?1 respectively. At the end of the test, the mean production of Diet 1 (0.649 ± 0.030 kg m?2) and Diet 2 (0.648 ± 0.033 kg m?2) were significantly higher than that of the control by 29.5% and 29.3% respectively. The feed conversion ratio decreased significantly by 12.3% (Diet 1) and 8.5% (Diet 2) compared with the control group respectively. The environmental indices indicate that the quality of water and pond sediment was improved. The endotoxin concentrations, the number of Vibrios and heterotrophic bacteria in the shrimp intestine of the treatment groups were significantly lower than that of the control, particularly in the later stage of the farming period. The YK‐6 extended positive effects on growth, improved sediment quality, reduced endotoxin in shrimp intestine, and enhanced activities of lysozyme and phenoloxidase.  相似文献   

18.
In a Biofloc Technology System (BFT), there is constant biofloc formation and suspended solids accumulation, leading to effects on water quality parameters that may affect the growth performance of cultured shrimp. This study aimed to analyse during biofloc formation the effect of different total suspended solids (TSS) levels on water quality and the growth performance of Litopenaeus vannamei shrimp in a BFT system. A 42‐day trial was conducted with treatments of three ranges of TSS: 100–300 mg L?1 as low (TL), 300–600 as medium (TM) and 600–1000 as high (TH). The initial concentrations of 100 (TL), 300 (TM) and 600 mg L?1 (TH) were achieved by fertilization before starting the experiment. Litopenaeus  vannamei juveniles with an average weight of 4.54 ± 1.19 g were stocked at a density of 372 shrimp m?3. Physical and chemical water parameters and shrimp growth performance were analysed. After 6 weeks, TSS mean concentrations were 306.37, 532.43 and 745.2 mg L?1 for, respectively, TL, TM and TH treatments. Significant differences (P < 0.05) were observed in TSS, settleable solids, pH, alkalinity and nitrite, especially between the TL and TH treatments. Similarly, differences (P < 0.05) were observed in the growth performance parameters, specifically final weight, survival, feed conversion and productivity. The water quality parameters at lower range of total suspended solids concentration (TL) treatment resulted in a better performance of L. vannamei in the BFT system. The maintenance at range of 100–300 mg L?1 TSS is thus important to the success of shrimp culture.  相似文献   

19.
We conducted large‐scale production trials in Seward, Alaska, USA to investigate effects of dietary astaxanthin supplementation on survival, growth and shell colouration of recently settled juvenile (C1–C4) red king crabs (Paralithodes camtschaticus). We supplemented a control diet of commercial crustacean feeds with astaxanthin, and fed these diets to juvenile king crabs at densities of 2000 and 4000 crabs m?2 for 56 days. We assessed survival and growth by counting crabs and individually measuring carapace width and weighing crabs at the start and end of the experiment, and quantified crab colour (hue, saturation, brightness) in digital photographs. Diets containing astaxanthin had higher survival, suggesting that astaxanthin may provide nutritional or immune system benefits. Crabs had lower hue, higher saturation and lower brightness values when fed diets containing astaxanthin, suggesting that red king crab colouration is plastic and responds to diet. Astaxanthin is likely an important dietary component for hatchery or laboratory reared red king crab juveniles, and should be considered for aquaculture and other rearing of this and possibly other crustacean species.  相似文献   

20.
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