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1.
We compared growth properties of spotted wolffish with initial mean weight (± SE) 3.65 (± 0.15) kg reared in shallow raceways at three different densities (50, 70, and 90 kg/m2, corresponding to approx. 170, 240, and 310 kg/m3) in a 447‐day‐long growth trial at ambient temperature (mean (± SD), 4.2 C ± 1.9). Growth in all three groups was comparable, but there was a trend toward higher growth at the highest density. Final mean weights (kg ± SE) were 4.90 (± 0.15), 4.80 (± 0.16), and 5.05 (± 0.11), at the 50, 70, and 90 kg/m2 density, respectively. Initially, growth rates were higher at the 90 kg/m2 density group compared to the two other densities, but overall growth rates were similar in all three groups. Feed conversion efficiency differed and was higher at the two highest densities compared to lowest density. The acid–base balance was influenced by the density treatment as there was a general trend toward higher partial pressure of CO2 and HCO in the 90 kg/m2 group. Calculated productivity increased almost linearly with increasing stocking density and was found to be 24, 42, and 66 g/m2/day at 50, 70, and 90 kg/m2, respectively. The results show that the optimum density conditions for farming large spotted wolffish, both with respect to growth rate, feed conversion, and productivity are at densities equal to or higher than 90 kg/m2.  相似文献   

2.
Respiration, calcification, and bio‐deposition of hybrid abalone, Haliotis discus hannai × Haliotis discus discus, fed on different foodstuffs have been measured to evaluate the effect of hybrid abalone culture on carbon source/sink in coastal areas. Fed with Laminaria japonica, Undaria pinnatifida, Gracilaria lemaneiformis, U. pinnatifida, and Ulva pertusa, alternated mutually, the carbon bio‐deposition rate of hybrid abalone was 24.29 ± 6.39, 65.40 ± 10.55, 21.48 ± 5.99, and 29.28 ± 6.47 µg/g/h, respectively. Hybrid abalone fed on U. pinnatifida had a higher carbon bio‐deposition rate compared to that fed on other foodstuff (P < 5%). Rate of CO2 released by respiration of hybrid abalone fed on the experimental foodstuff was 24.53 ± 8.57, 32.73 ± 7.99, 29.31 ± 6.39, and 33.67 ± 12.37 µg/g/h, respectively. Results indicated that calcification presented less relationship with body weight type of the foodstuff. The rate of CO2 released by calcification into seawater and atmosphere was 2.77 ± 1.89 and 6.53 ± 3.36 µg/g/h, respectively. The total rate of CO2 released because of bio‐deposition, respiration, and calcification processes was 16.19 ± 4.67 µg/g/h, while the total rate of carbon sequestered in shells and tissues was 8.94 ± 2.07 µg/g/h. The study revealed that hybrid abalone culture is a source of CO2.  相似文献   

3.
We revisit the empirical equation of Gislason et al. (2010, Fish and Fisheries 11 :149–158) for predicting natural mortality (M, year?1) of marine fish. We show it to be equivalent to , where L∞ (cm) and K (year?1) are the von Bertalanffy growth equation (VBGE) parameters, and L (cm) is fish length along the growth trajectory within the species. We then interpret K in terms of the VBGE in mass , and show that the previous equation is itself equivalent to a ?? power function rule between M and the mass at first reproduction (Wα); this new ?? power function emerges directly from the life history that maximizes Darwinian fitness in non‐growing populations. We merge this M, Wα power function with other power functions to produce general across‐species scaling rules for yearly reproductive allocation, reproductive effort and age at first reproduction in fish. We then suggest a new way to classify habitats (or lifestyles) as to the life histories they should contain, and we contrast our scheme with the widely used Winemiller–Rose fish lifestyle classification.  相似文献   

4.
Nitrogen excreted by aquatic animals mainly takes the form of metabolic wastes such as feces and ammonia, which is accumulated in the intensive aquaculture system and causes serious environmental contamination. So it is very important to determine the waste excretion characteristics of aquatic animals for the development of practical and nonpolluting land‐based aquaculture. Abalone has a unique feeding habit and feeding regime, different from those of finfish; abalone gnaw feed seaweed to produce feces and ammonia continuously. In this study, the rates of feces production and ammonia excretion of pacific abalone, Haliotis discus hannai, of three shell lengths (3, 5, and 7 cm) were investigated under three different temperature conditions (12, 16, and 20 C). All experiments were performed in triplicate in a semirecirculating aquaculture system. Feces were collected for 5 d, and ammonia concentrations (total ammonia nitrogen [TAN]) in the tank inlet and outlet were monitored every 4‐h interval for 24 h at the fourth day of the feces collection. The regressions for the weight‐specific feces production rate (g feces/kg abalone/d) and the weight‐specific TAN excretion rate (mg TAN/kg abalone/d) in relation to water temperature (T, C) and shell length (L, cm) were weight‐specific feces production rate = exp(1.575 ? 281.2/T2 – 0.142L), r2 = 0.9550, and weight‐specific TAN excretion rate = exp(5.052 ? 277.1/T2 ? 0.136L), r2 = 0.9598. Pacific abalone produced 108.3–111.7 g feces and excreted 3.83 g TAN/kg seaweed ingested (dry weight).  相似文献   

5.
The unnaturally dark pigmentation of cultured Australian snapper Pagrus auratus can be improved through dietary astaxanthin supplementation and by holding fish in tanks with a white background. The practical application of these laboratory‐based findings was examined with two experiments to establish if the advantages of transferring fish to light coloured tanks before harvest could be achieved on‐farm using white cages and to determine the effects of fish density on skin colour. For the first experiment, snapper (mean TL=29.7 cm) were transferred from a commercial snapper sea cage to black or white netted cages and fed diets supplemented with unesterified astaxanthin (supplied as Lucantin® Pink, BASF) at 0 or 39 mg kg?1 for 42 days. Skin colour was measured using the CIE (black–white), (green–red), (blue–yellow) colour scale. Snapper held in white netting cages became significantly lighter (higher ) than snapper held in black cages; however, values were not as high as previous laboratory‐based studies in which snapper were held in white plastic‐lined cages. Snapper fed astaxanthin displayed significantly greater and values, and total carotenoid concentrations after 42 days. In addition, total carotenoids were higher in fish from black than white cages. The second experiment was designed to investigate whether density reduced the improvements in skin colour achieved by holding fish in white coloured cages and whether cage colour affected stress. Snapper (mean weight=435 g) were acclimated to black cages and fed 39 mg kg?1 astaxanthin for 44 days before transferring to black or white plastic‐lined cages at 14 (low), 29 (mid) or 45 (high) kg m?3 for 7 days after which time skin colour, plasma cortisol and plasma glucose concentrations were measured. Skin lightness () was greater in snapper transferred to white plastic‐lined cages with the lightest coloured fish obtained from the lowest density after 7 days. Density had no effect on plasma cortisol or glucose levels after 7 days, although plasma cortisol was elevated in snapper from black cages. For improved skin colouration we recommend feeding unesterified astaxanthin at 39 mg kg?1 for approximately 6 weeks and transferring snapper to white plastic‐lined cages or similar at low densities for short periods before harvest rather than producing fish in white netting sea cages subject to biofouling.  相似文献   

6.
Pharmacokinetics and residue elimination of marbofloxacin (MBF) were studied in crucian carp (Carassius auratus, 250±30 g) kept at two water temperatures of 15 and 25 °C. Marbofloxacin concentrations in plasma and tissues were analysed by means of high‐performance liquid chromatography using an ultraviolet detector. The limits of detection were 0.02 μg mL?1, 0.02 μg g?1, 0.025 μg g?1, 0.02 μg g?1 and 0.025 μg g?1 in plasma and muscle, skin, liver and kidney respectively. Fish were administered orally at a single dosage of 10 mg kg?1 body weight in the PK group. The data were fitted to two‐compartment open models at both temperatures. At 15 °C, the absorption half‐life () and distribution half‐life (t1/2α) of the drug were 0.36 and 4.48 h respectively. The corresponding values at 25 °C were 0.23 and 0.87 h respectively. The elimination half‐life (t1/2β) was 50.75 h at 15 °C and 25.05 h at 25 °C. The maximum MBF concentration (Cmax) differed little between 15 (6.43 μg mL?1) and 25 °C (8.36 μg mL?1). The time to peak concentration was 1.74 h at 15 °C and 0.78 h at 25 °C. The apparent volume of distribution (Vd/F) of MBF was estimated to be 1.36 and 0.87 L kg?1 at 15 and 25 °C respectively. The area under the concentration–time curve (AUC) was 301.80 μg mL?1 h at 15 °C and 182.80 μg mL?1 h at 25 °C. The total clearance of MBF was computed as 0.03 and 0.05 L h?1 kg?1 at 15 and 25 °C respectively. After repeated oral administration at a dosage of 10 mg kg?1 body weight per day for 3 days, the results showed that the elimination half‐lives () of MBF from all tissues at 15 °C were longer than that at 25 °C. Therefore, water temperature is an important factor to be considered when deciding a reasonable withdrawal time.  相似文献   

7.
Two introduced abalone species are currently produced in Chile, red abalone Haliotis rufescens and Japanese abalone Haliotis discus hannai. However, red abalone accounts for 99% of total production, while the Japanese abalone has not adapted well to Chilean coastal waters. This study reports the hatching, growth and thermal tolerance performance in interspecific hybrids produced between red (R) and Japanese (J) abalone. Our results show that egg age and sperm concentration were critical factors to produce hybrids. The cross R♀ × J♂ showed a fertilization rate of 55.3 ± 3.5% using 20‐min‐old eggs and sperm concentrations of 14 × 106 cells mL?1, while the reciprocal cross (J♀ × R♂) was not successful. Further, larval development stages were similar in RR, JJ and RJ hybrid abalones. Among the experimental trials, settlement rate varied from 12.3% to 18.6% and final survival from 20.1% to 31.7%, being the RJ hybrid rates intermediate between parental species. The final shell lengths were similar between RR and RJ hybrids, but significantly higher in JJ abalones. In addition, thermal tolerance was ascertained due its pivotal role for the abalone physiology. Thus, RJ hybrids showed the highest HSP70 gene expression and offers new possibilities to expand Chilean abalone production in warm waters zones.  相似文献   

8.
This study was designed to assess the protective effects of dietary selenium (Se) on abalone Haliotis discus hannai Ino against the toxicity of waterborne copper (Cu). A 60‐day feeding trial was conducted in a static water system for abalone (initial weight: 3.17 ± 0.01 g) exposed to 0.02 mg L?1 of waterborne Cu. The animals were fed one of the three experimental diets with 0.10, 1.31 and 4.20 mg kg?1 of Se from Na2SeO3·5H2O respectively. Results showed that the abalone fed 1.31 mg kg?1 of dietary Se had the lowest Cu concentration in shell, muscle, mantle, gill, hepatopancreas and serum. Meanwhile, the significant lowest contents of malondiadehyde and protein carbonyl in hepatopancreas were also found in the treatment with 1.31 mg kg?1 of dietary Se (P < 0.05). In addition, this treatment had significant higher glutathione content and thioredoxin reductase activity in hepatopancreas (P < 0.05). However, the activity of Se‐dependent glutathione peroxidase (Se‐GPx) was significantly decreased in the treatment with 4.20 mg kg?1 of dietary Se (P < 0.05). In this treatment, the protein carbonyl content in hepatopancreas was significantly higher than that in the group with 1.31 mg kg?1 of dietary Se (P < 0.05). In conclusion, in terms of anti‐oxidation and Cu accumulation, the protective effects of dietary Se on abalone against waterborne Cu were dose‐dependent. The 1.31 mg kg?1 of dietary Se had this effect, but not 4.20 mg kg?1 of dietary Se. Moreover, the latter increased the oxidative stress in abalone exposed to the waterborne Cu.  相似文献   

9.
Feasibility of offshore co‐culture of abalone and sea cucumber was investigated in Northern China. Survival and growth of abalone, Haliotis discus hannai Ino, and sea cucumber, Apostichopus japonicus, co‐cultured in abalone cages from suspended longlines, in the offshore area, were examined. Abalone and sea cucumbers were co‐cultured at density ratios of both 3:1 and 6:1 for 1 yr. Abalone were fed with fresh kelp and no additional feed was given to sea cucumbers. Survival of abalone and sea cucumber was 100% for all treatments. Abalone and sea cucumber grew well; the body weight (BW) of abalone and sea cucumber was nearly doubled and had reached a commercial size. There were no significant differences in the growth rates for both abalone and sea cucumber between the two density treatments. The specific growth rate of BW of abalone (SGRbw) was highest in June, with a value of 0.536%/d. Growth rate of sea cucumber (SGRsc) was highest in December, reached 1.84%/d, with an annual average SGRsc of 0.182%/d. Results suggested that the offshore co‐culture of abalone and sea cucumber was feasible offshore. The co‐culture of abalone with sea cucumbers may provide an additional valuable crop without additional financial input.  相似文献   

10.
Pacific abalone (Haliotis discus hannai Ino) aquaculture is a thriving industry in China. This study describes a novel submerged cage culture system for abalone rearing in Fujian, South China. The cage consisted of five vertical slots that were oriented perpendicular to the flow of water. The slots were separated by six vertically connected plastic plates for abalone attachment and shelter at the bottom of the cage. Experiment 1 was designed to determine the appropriate stocking density at the start of the abalone sea‐based production cycle. Eight‐month‐old hatchery reared and size‐graded juveniles were transferred to the sea‐based culture system. For different stocking densities, shell length of juveniles obtained in this novel culture system on 2, 3.5 and 5 months, respectively, was compared with shell lengths obtained in a traditionally multi‐tier basket culture system. In Experiment 2, daily growth rates (DGRs) in shell length and biomass in terms of wet weight of 2‐year‐old abalones reared in cage and tiered basket culture systems were compared over a 6‐month period. Results of Experiment 1 showed that growth of abalone in the cage culture system is density‐dependent; the mean final shell length of juveniles obtained was 6.7–15.9% higher than in tiered baskets system even at the same initial stocking density. In Experiment 2, DGRs in shell length of 53.83–78.38 μm day?1 obtained in cage system were significantly higher than that in tiered baskets (P < 0.01). And in terms of wet weight biomass, it was 1.48–3.01 times higher in the cage system compared with the traditional system. Abalone survival was more than 87.5% in both culture systems in both experiments. Advantages of the newly established cage culture system included better growth performance of the animals reared and potential improvement of rearing conditions, such as improved water flow velocity and dissolved oxygen.  相似文献   

11.
Hybridization among abalone species has been suggested as a possible means to increase their growth rates for aquaculture. As a first step to test the usefulness of the hybrids of Japanese abalone species (Haliotis discus discus, Haliotis gigantea and Haliotis madaka) for aquaculture, we characterized the genetic background and gonad development of hybrids that were produced by artificial insemination. The hybrid status of the resulting offspring was confirmed by assaying 14 allozymes and by RFLP analysis of the 16s rRNA and cytochrome oxidase I (COI) regions of mtDNA using 13 restriction enzymes. Histological examination of the gonads of the hybrids was conducted in comparison with those of the parental species. Cross‐breeding among the three species was conducted successfully in all combinations although with lower fertilization rates (means of 1.3–60.8%) than the parental species (34.3–90%). Crosses between H. discus discus and H. madaka had higher fertilization rates (22.4–60.8%) than those involving H. gigantea (1.3–19.9%). The hybrids were ascertained by the presence of both parental genotypes at the LDH‐A, ME‐A, MDH‐A and GPI loci. The maternal origin of the hybrid mtDNA was confirmed by digestion with DdeI, TaqI, HpaII of the COI region. No polymorphism was observed in the 16S rRNA region. The hybrids had gonadal development and maturity stages similar to the parental species up to fully mature oocytes and sperm. They spawned upon stimulation and produced viable offspring with high fertilization rates and successful development to the juvenile stage in back‐ and homologous hybrid crosses.  相似文献   

12.
Effect of feeding regime on compensatory growth of juvenile abalone (Haliotis discus hannai) fed on the dry sea tangle (Laminaria japonica) was determined. Thirty juvenile abalone averaging 15.7 g were randomly stocked into 18 50‐L plastic rectangular containers each. Six treatments were prepared in triplicate: Abalone were fed the dry sea tangle once a day at a satiation level with a little leftover for 16 wk as the control (Con) and other abalone were fed the dry sea tangle once a day at a satiation level with a little leftover for 15 wk after 1‐wk starvation (S1 treatment), 14 wk after 2‐wk starvation (S2 treatment), 13 wk after 3‐wk starvation (S3 treatment), 12 wk after 4‐wk starvation (S4 treatment), and 10 wk after 6‐wk starvation (S6 treatment), respectively. A linear relationship between weight change of abalone and wk of starvation was observed: Y (Weight of abalone) = ?0.17X (Wk of starvation) + 15.89 (R 2 = 0.9462) (P < 0.0001). The highest survival of abalone was achieved in the S2 treatment, but not different from that of abalone in the Con, S1 and S3 treatments. Weight gain of abalone in the Con treatment was higher than that of abalone in the S4 and S6 treatments. Abalone fed on the dry sea tangle seemed to be able to achieve full compensatory growth up to 3‐wk starvation.  相似文献   

13.
A physiological study was performed to explore the effects in Sphoeroides annulatus (Jenyns 1842) juveniles of exposure to different salinities 10, 17, 23, 29, 35 and 41‰ on oxygen consumption rate (OCR), ammonium excretion rate (AER), the oxygen‐nitrogen atomic ratio (O:N), osmoregulation and Na+/K+‐ATPase expression. The OCR values ranged from 27.9 to 30.9 mg O2 h?1 kg?1, displaying a Type 1 response pattern Kinne (1977). AER ranged from 0.60 to 0.69 mg h?1 kg?1, and O:N values were from 53.12 to 59.26, indicating that the puffers use proteins and lipids as an energy‐substrate. Osmoregulation in S. annulatus was hyposmotic in salinities of 23, 29, 35 and 41‰ and hyperosmotic in a salinity of 10‰. The isosmotic point of the bullseye puffer was 356 mmol kg?1 (10.5‰). The enzyme expression analysis indicates that the fish acclimated to 41‰ had the highest Na+/K+‐ATPase expression level, whereas, the lowest expression level was found close to the isosmotic point. Na+/K+‐ATPase expression in the gills was found to have a U‐shaped relationship with environmental salinity. We conclude that the bullseye puffer is strongly euryhaline and can be cultivated in a wide range of environments that has important economic implications.  相似文献   

14.
In order to assess the potential of utilizing fouling macroalgae as feed for abalone Haliotis discus hannai, the species, biomass and total stock of fouling macroalgae attached on the aquaculture facility‐lines were investigated and assessed at Sungo Bay, China, in August 2007. The nutritional value of four fouling macroalgae (Codium fragile, Sargassum muticum, Ulva pertusa and Laminaria japonica) and one cultured macroalgae (Gracilaria lemaneiformis) as the diet of abalone was assessed by analysis of the chemical composition of the macroalgae and by measuring bioavailability and digestibility to abalone H. discus hannai under laboratory conditions in August 2007. The results showed that the biomass of fouling macroalgae at the two sites was 243.61 ± 26.23 and 1078.15 ± 50.28 g m?1 respectively. The contents of protein of G. lemaneiformis and C. fragile were 18.30% and 17.60%, respectively, which were significantly higher than the others. The five macroalgae were accepted by the abalone, and growth energies (P) and growth efficiency (%) were positive. However, significant differences were found among the different macroalgae. The growth efficiencies of abalone show a negative relationship with the levels of dietary lipid and a positive relationship with the protein contents. These results suggest that fouling macroalgae have a great potential to be used as diets of abalone.  相似文献   

15.
The growth rate of disk abalone, Haliotis discus hannai, energy consumption and changes in water quality were monitored in a pilot-scale recirculating aquaculture system (RAS) for 155 days. Baffles were installed in the RAS culture tanks to enlarge the attachment area and clean out solid waste materials automatically by hydraulic force only. The experimental disk abalones, of shell length 24.5 ± 0.5 mm, were cultured at three stocking densities, 700, 1300 and 1910 individuals/m2 bottom area, in triplicate. The abalones were fed with sea mustard, Undaria pinnatifida, once a week. The abalone feed conversion rates and daily growth rates ranged from 24.5 to 25.9 and 0.32 to 0.36%, respectively. Their daily shell increments and survival rates ranged from 67.7 to 78.6 μm/day and 87.6–92.2%, respectively. The growth in weight tended to decrease at a culture density of 1300 individuals/m2 bottom area, while shell increments and survival rates were acceptable at this density. The total power consumption for heating was 1185.4 kW, comprising 30.2% of the total power consumption, while the average water exchange rate was only 2.9% per day. The total ammonia nitrogen stabilized below 0.07 mg/L, after conditioning of the biofilter. The NO2−–N, NO3−–N and total suspended solid concentrations were also maintained within acceptable ranges for the normal growth of disk abalone. The use of the RAS with these newly designed culture tanks for disk abalone culture produced 1300 individuals/m2 bottom area with a water exchange rate of only 2.9% per day and used about one-tenth of the heat energy of a conventional flow-through system.  相似文献   

16.
温度胁迫对皱纹盘鲍生理和生化活动的影响   总被引：6，自引：2，他引：4  
为探讨温度胁迫下皱纹盘鲍(Haliotis discus hannai Ino)的响应机制,采用室内控温实验,通过设置4个温度梯度(5℃、10℃、20℃和25℃),设计温度骤变处理组(皱纹盘鲍从15℃暂养温度直接转移至各实验温度)和温度缓变处理组(0.5℃/12 h),分析温度剧烈变化和温度缓慢变化对皱纹盘鲍耗氧率和排氨率的影响及其差异性;并对高温和低温处理下皱纹盘鲍消化腺中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、酸性磷酸酶(ACP)和溶菌酶(LSZ)活性的变化情况以及不同组织(血细胞和肌肉组织)中Cu/Zn–SOD基因的表达状况进行了研究。结果表明,皱纹盘鲍耗氧率和排氨率随海水温度的升高而增加,20℃达到最高值;25℃骤变处理组与缓变处理组耗氧率和排氨率间存在极显著差异(P0.01)。5℃和10℃骤变处理组皱纹盘鲍氧氮比(O/N)同缓变处理组间存在极显著差异(P0.01)。在高温胁迫后的3 h,消化腺中SOD、CAT和LSZ活性达到最高,而ACP活性在胁迫6 h后达到最高(P0.01);低温胁迫显著降低皱纹盘鲍LSZ的活性,于胁迫9 h后达到最低(P0.01)。不同温度胁迫下,皱纹盘鲍血细胞和肌肉组织中Cu/Zn–SOD基因的相对表达量均表现上调,与对照组存在显著差异性(P0.05)。本研究表明,温度胁迫能显著影响皱纹盘鲍的生理和生化活动,这将有助于探讨皱纹盘鲍夏季高死亡率的原因,为皱纹盘鲍健康养殖提供一定的理论依据。  相似文献   

17.
The effect of dietary substitution of animal and/or plant protein sources for fishmeal on the growth and body composition of juvenile abalone was determined. Nine experimental diets in triplicate were prepared: Con, SM, PM, CM, SPM, MB, SM+CM, SM+SPM and CM+SPM diets. A 350 g kg?1 fishmeal was included in the Con diet, and the whole fishmeal was substituted with a 580 g kg?1 soybean meal (SM), 335 g kg?1 poultry meal (PM), 370 g kg?1 corn gluten meal (CM), 325 g kg?1 silkworm pupae meal dehydrated (SPM), 590 g kg?1 meat and bone meal (MB), the combined 290 g kg?1 soybean meal and 180 g kg?1 corn gluten meal (SM+CM), 290 g kg?1 soybean meal and 160 g kg?1 silkworm pupae meal dehydrated (SM+SPM) and 180 g kg?1 corn gluten meal and 170 g kg?1 silkworm pupae meal dehydrated (CM+SPM) diets respectively. All experimental diets were iso‐nitronic and iso‐lipidic. The survival of abalone fed with the SM and SM+SPM diets was higher than that of abalone fed with the CM, SPM, MB and CM+SPM diets. Weight gain of abalone fed with the SM+SPM diet was higher than that of abalone fed with all the other experimental diets, except for that of abalone fed with the SM+CM diet. The combined soybean meal and corn gluten meal (SM+CM) or silkworm pupae meal (SM+SPM) could be replaced with the whole fishmeal in the diet for abalone and improved its performance.  相似文献   

18.
Particle size distribution, organic content and the sinking velocity of bio‐deposits of abalone Haliotis discus hannai Ino were evaluated. The abalone was divided into three size classes according to shell length: Group B: 68.8 ± 2.8 mm, group M: 56.1 ± 2.3 mm and group S: 42.4 ± 2.8 mm. The faecal pellets had an amorphous shape, with a cross‐sectional area ranging from 0.01 to 2.64 mm2. The mean cross‐sectional area varied among the size classes: 0.59 (B), 0.21 (M) and 0.12 (S) mm2. The bio‐deposit organic content was similar among the groups (B: 18.3 ± 1.1%; M: 19.9 ± 0.9%; S: 19.3 ± 1.0%). Sinking velocity ranged from 0.5 to 2.3 cm s?1. Larger abalone tended to have larger and thus faster‐sinking faecal pellets. The median sinking velocity for groups B, M and S was 0.9, 0.5 and 0.7 cm s?1 respectively. The mean daily production rates for groups S, M and B were 2.8 ± 1.2, 3.4 ± 1.3 and 4.3 ± 1.8 g ind.?1 respectively. Bio‐deposit production rate estimated to be between 134.4 and 206.4 mg m?2 day?1 in the bay. Our results suggest that the pellet size was within the appropriate size range for filter‐feeding bivalves.  相似文献   

19.
To quantify the effects of serial‐use of water on abalone growth and feed conversion, this study describes water quality in a serial‐use raceway with seven passes. A flow index of 7.2–9.0 L h?1 kg?1 was estimated as the minimum value at which to grow 60–70 mm Haliotis midae, as weight gain (analysis of variance; F6, 14=13.9, P<0.0001) and feed conversion ratio (Kruskal–Wallis test; H6, 21=16.3, P=0.012) were significantly reduced at lower values. pH and dissolved oxygen concentration were positively correlated with the flow index (pH, r2=0.99; P<0.001; dissolved oxygen, r2=0.99; P<0.001), while free ammonia nitrogen (FAN) and nitrite were negatively correlated with the flow index (FAN, r2=0.99, P<0.001; Nitrite, r2=0.93, P<0.001). The concentration of nitrite increased throughout the experiment and may reflect the colonization of Nitrosomonas bacteria as water re‐use increased. Based on comparisons with growth and toxicity tests, it is suggested that low pH combined with growth‐limiting levels of FAN were the first variables limiting abalone growth in the serial‐use raceway.  相似文献   

20.
A 120‐day feeding trial was conducted to examine the effects of the ratio of dietary linoleic acid (LA, 18:2n‐6) to eicosapentaenoic acid (EPA, 20:5n‐3) on the growth and fatty acid composition of juvenile Haliotis discus hannai (initial shell length 10.23 ± 1.48 mm; initial body weight 0.13 ± 0.05 g) in a recirculation water system. Five semipurified diets with 35 g kg?1 total lipid were formulated to contain graded LA/EPA ratios (1 : 0, 0.75 : 0.25, 0.5 : 0.5, 0.25 : 0.75, and 0 : 1, respectively). Twenty‐five juveniles were stocked in a rearing unit, a plastic basket (20 × 20 × 10 cm), as a replicate, and there were three replicates for each dietary treatment. The results showed that abalone survival rates were generally high (90.1–98.3%) and independent of the dietary treatments. However, abalone growth was significantly affected by LA/EPA ratio (P < 0.05). The LA/EPA ratio of 0.25 : 0.75 (Diet 4) produced the highest weight gain rate (WGR, 416.3%), closely followed by the ratio of 0 : 1 (Diet 5, 412.9%), the ratio of 0.5 : 0.5 (Diet 3, 399.7%) and the ratio of 0.75 : 0.25 (Diet 2, 372.1%), but no significant differences were observed among these treatments. The abalone fed the diet without 20:5n‐3 (Diet 1) had the lowest WGR (Diet 1, 363.8%), which was significantly lower than that of Diet 4. Fatty acid profiles in abalone body reflected those of dietary lipids, especially for the polyunsaturated fatty acids. The contents of arachidonic acid (AA; 20:4n‐6) in abalone tissues were positively correlated with dietary level of 18:2n‐6 (P < 0.05). Similar correlation was also observed between the level of docosahexaenoic acid (DHA, 22:6n‐3) in abalone tissues and the level of dietary EPA. It is suggested that abalone, H. discus hannai, have the capacity to synthesize 20:4n‐6 from 18:2n‐6, and maybe 22:6n‐3 from 20:5n‐3.  相似文献   

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