Growth performances for monoculture and polyculture of hatchery‐reared juvenile spotted babylon,Babylonia areolata Link, 1807, in large‐scale earthen ponds

This study was conducted to determine the feasibility of growing out hatchery‐reared spotted babylon juvenile (Babylonia areolata) in earthen ponds. The growth, survival and water quality for monoculture of spotted babylon were compared with the two polyculture trials with sea bass (Lates calcarifer) or milkfish (Chanos chanos). This study provided good results for growth and survival of spotted babylon in earthen ponds. The mean body weight gain of snails held in the monoculture was 5.39±0.08 g, and 4.07±0.16 and 4.25±0.11 g for those held in the polyculture with sea bass or milkfish respectively. Food conversion ratios (FCR) were 2.69, 2.96 and 2.71 for snails held in the monoculture and polyculture with sea bass and milkfish, respectively, and the final survival rates were 84.94%, 74.30% and 81.20% respectively. There were no significant differences in each parameter of water quality among the treatments but significant differences among the culture period were present (P<0.05). Salinity and total alkalinity showed the greatest changes during the culture period for all treatments. Seawater temperature, pH, dissolved oxygen, nitrite–nitrogen and ammonia–nitrogen gradually changed over the culture period for all the treatments. The present study indicated the technical feasibility for monoculture and polyculture of B. areolata to marketable sizes in earthen ponds.     

Combined effects of water exchange regimes and calcium carbonate additions on growth and survival of hatchery-reared juvenile spotted babylon (Babylonia areolata Link 1807) in recirculating grow-out system

To determine a suitable culture environment to maximize growth and survival, the hatchery‐reared juvenile spotted babylon, Babylonia areolata, were held in plastic rearing tanks at four calcium carbonate additions of 0, 100 and 300 g tonne^?1, and four water exchange regimes of 0‐, 15‐, 30‐ and 60‐day intervals in a recirculating grow‐out system for 120 days. The results clearly showed that growth was greatest between water exchange regimes of 15‐ and 30‐day intervals and all calcium carbonate additions, with water exchange regimes of 0‐ and 60‐day intervals resulting in poor growth. Final survival was highest between water exchange regimes of 15‐ and 30‐day intervals, and all calcium carbonate additions, with water exchange regimes of 0‐day intervals and all calcium carbonate additions resulting in high mortalities. This study showed that water exchange regimes had a stronger influence on the growth of juvenile B. areolata than calcium carbonate additions. It is recommended that B. areolata juveniles be maintained within the water exchange regimes range of 15–30‐day intervals and at calcium carbonate additions between 0 and 500 g tonne^?1, providing optimum conditions for production of this species in a recirculating grow‐out system.     

Pilot study on polyculture of juveniles spotted babylon, Babylonia areolata, with milkfish, Chanos chanos, to marketable sizes using large-scale operation of earthen ponds in Thailand

Growth, production and economic analysis was performed for the polyculture of juveniles spotted babylon, Babylonia areolata, and milkfish, Chanos chanos, to marketable sizes using a large‐scale production of earthen ponds in Thailand. The analysis was based on actual cost and production data from a pilot commercial‐scale farm. A total farm area of 0.8 ha was comprised of 0.3 ha grow‐out earthen ponds, a 0.4 ha seawater reservoir, and a 0.08 ha accommodation and office. Each pond was stocked with spotted babylon juveniles of 0.3 g initial body weight at a density of 200 snails m^?2, and they were harvested at a 7‐month period, at an average body weight of 4.6 g for a total yield per production cycle of spotted babylon and milkfish of 9875 and 6875 kg ha^?1 respectively. Based on farm data and harvest data used in this study, initial investment requirement was estimated to be $4837. The ownership cost and operating cost per production cycle were $2241 and $18 501 respectively. Total cost per production cycle was $20 742. The cost of producing spotted babylon marketable sizes in this grow‐out farm design was $6.56 kg^?1. The enterprise budgets based on the price of spotted babylon at a farm gate in 2003 of $9.00 kg^?1 results in gross return, net return, return to capital and management, and return on investment of $31 190, $10 448, $12 689 and 2.62 respectively. Milkfish was not calculated for any returns because they were less than marketable sizes.     

Effects of water exchange regimes on growth, survival and shell normality of the hatchery reared juvenile spotted babylon (Babylonia areolata Link 1807) in a recirculating seawater system

Growth, survival and shell normality of hatchery reared juvenile Babylonia areolata were examined at four water exchange regimes of 0, 15, 30 and 60 day intervals in a recirculating seawater system over a 120 day experimental period. Higher body weight gains and shell length increments were observed in snails held at water exchange of 15 day intervals, especially when compared with those held at water exchange of 60 and 0 day intervals (P < 0.05). Water exchange affected the final survival of B. areolata. At the end of the experiment, final survival rates were 65.47 ± 0.66%, 87.48 ± 0.67%, 86.34 ± 0.92% and 78.50 ± 3.26% for snails held in the water exchange treatments of 0, 15, 30, and 60 day intervals, respectively, and those of shell abnormality were 97.65 ± 1.04%, 93.09 ± 2.34%, 97.08 ± 1.18% and 96.71 ± 1.84%, respectively. The present study concluded that water exchange regimes of the recirculating system influenced growth, survival, shell normality and water quality of the recirculating culture system for this species.     

换水率和密度对刺参生长和水质的影响

为探究日换水率(0、10%、20%、30%和100%)和养殖密度[0.980±0.008、1.760±0.005、2.810±0.007和(3.640±0.006)kg/m3]对刺参(Apostichopus japonicus)生长率和养殖水质的影响,养殖试验首先在非循环水养殖条件下,测定各组刺参综合特定生长率(ISGR)及养殖水体中氨氮及亚硝酸盐氮质量浓度。结果显示,日换水率为10%和20%处理组的ISGR分别达到每天(1.330±0.161)%和(1.410±0.182)%,显著高于其他处理组;密度养殖试验证明,随着养殖密度的增加,ISGR逐渐降低,分别达到每天(0.610±0.500)%,(0.570±0.030)%,(0.560±0.045)%和(0.320±0.040)%,各组换水率及养殖密度组水体中氨氮及亚硝酸盐氮均在安全浓度范围内波动;养殖结果显示,循环水养殖试验组刺参的ISGR高于非循环水养殖组,可达(0.130±0.007)%,且氨氮及亚硝酸盐氮质量浓度在0.020 mg/L以下,而非循环水养殖的分别积累到(0.600±0.015)mg/L和(0.076±0.002)mg/L。研究表明,在换水率15%,养殖密度(2.810±0.007)kg/m3的循环水养殖条件下,可以保证水体水质稳定,刺参生长良好。     

Growth trials for polyculture of hatchery-reared juvenile spotted babylon (Babylonia areolata) and sea bass (Lates calcarifer) in a flow-through sea water system

Juvenile spotted babylon (Babylonia areolata) and sea bass (Lates calcarifer) were cultured in 11.5‐m³ indoor rearing tanks supplied with flow‐through of ambient natural sea water over a 120‐day experiment. Each species, stocked at the following densities for the following treatments, was tested with three replicates per treatment: 5000 B. areolata per tank (Treatment 1); 200 L. calcarifer per tank (Treatment 2); and 5000 B. areolata plus 200 L. calcarifer per tank (Treatment 3),. The average growth (length and weight), feed conversion ratio and total production of spotted babylon and sea bass from Treatment 3 were not significantly different from those of Treatment 1 and 2 (P > 0.05). Average survival rates for both spotted babylon and sea bass exceeded 95% for all treatments.     

Growth and water quality for growing-out of juvenile spotted Babylon, Babylonia areolata, at different water-exchange regimes in a large-scale operation of earthen ponds

Growth and water quality for growing-out of juvenile spotted Babylon, Babylonia areolata, were determined at three water-exchange regimes of 7-, 15- and 30-day intervals in large-scale operation of earthen ponds over a 5-month period. Results showed that growth was significantly different among the water-exchange treatments (P < 0.05). The higher body weight gains and shell length increments were observed in snails held at water exchange of 7- and 15-day intervals when compared with those held at water exchange of 30-day intervals. At the end of the experiment, average body weight gains were 4.22, 3.73 and 2.77 g for snails held in water-exchange treatments of 7-, 15- and 30-day intervals, respectively, and 16.63, 15.04 and 13.78 mm for those of shell length increments, respectively, The average final survivals were 83.60, 80.90 and 74.20% for snails held in water-exchange treatments of 7-, 15- and 30-day intervals, respectively. Seawater temperature, salinity, pH, dissolved oxygen, nitrite–nitrogen and ammonia–nitrogen had gradually changed throughout the culture period for all water-exchange treatments. With one exception, the total alkalinity showed the greatest changes during the culture period for all water-exchange treatments ranging from 58.67–97.50 mg/l.     

饥饿及恢复生长对方斑东风螺抗氧化体系的影响

在(25.8±1.7)℃条件下,测定了方斑东风螺(Babylonia areolata)不同饥饿期(7d、15d、25d、40d)后再投喂(30d)过程中足肌、肝胰脏的抗氧化体系相关指标变化。结果显示,分别饥饿25d和40d时幼螺两组织丙二醛(MDA)含量较对照组均显著升高;饥饿25d前,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GPx)活力较对照组逐渐增强,当禁食达40d时却显著减弱;谷胱甘肽硫转移酶(GST)活力饥饿状态下先略上升后下降,肝胰脏、足肌中分别于饥饿25d和40d时显著降低;谷胱甘肽还原酶(GR)活力及谷胱甘肽(GSH)含量随禁食延长均呈下降趋势。恢复生长后,除饥饿40d组GR活力及肝胰脏MDA水平较对照呈差异显著外,该组其余指标及其他各处理组相应指标均恢复至或接近对照组水平。结果表明,饥饿胁迫下螺体抗氧化体系虽被激活,但仍处于一定的氧化应激状态,提示幼螺养成中禁食时间不宜超过25d,且SOD、CAT与GPx活性可作为螺体饥饿胁迫状态的指示参数。     

Effects of stocking density on growth, yield and profitability of farming Nile tilapia, Oreochromis niloticus L., fed Azolla diet, in earthen ponds

Two consecutive experiments were conducted to study the effects of stocking density on growth, food utilization, production and farming profitability of Nile tilapia (Oreochromis niloticus) fingerlings (initial mean weight: 16.2 ± 0.2 g) fed Azolla, as a main component in diet. In experiment 1, fish were hand‐fed twice daily with three isonitrogenous (28.5% crude protein) and isocaloric (14.5 kJ g⁻¹) diets A30, A35 and A40 containing 30%, 35% and 40%Azolla, respectively, for 90 days. Diets were formulated by mixing Azolla with locally available by‐products. No significant differences were found in growth parameters and production (P>0.05). Total investment cost was significantly higher with A30 (P<0.05), but same profitability values were obtained with all diets (P>0.05). In experiment 2, three stocking densities, 1, 3 and 5 m⁻², were assigned to three treatments T₁, T₂ and T₃ respectively. Fish were hand‐fed twice daily with diet A40. The final mean weight (89.53–115.12 g), the mean weight gain (0.81–1.10 g day⁻¹), the specific growth rate (1.90–2.20% day⁻¹) and the apparent food conversion ratio (1.29–1.58) were affected by stocking density, with significant difference (P<0.05) at 5 m⁻², compared with the other densities. Stocking density did not affect survival rate (P>0.05). Yield and annual production increased with increasing stocking density, ranging from 7.10 ± 0.90 to 25.01 ± 1.84 kg are⁻¹ and 28.79 ± 3.66 to 101.42 ± 7.48 kg are⁻¹ year⁻¹, respectively, with significant differences between all densities (P<0.05). Higher stocking density resulted in higher gross return and lower cost of fish production, with significant variations (P<0.05). The net return increased with increasing stocking density (P<0.05). However, both densities of 3 and 5 m⁻² produced the same profitability values. On the basis of growth values and economic return, it was concluded that Nile tilapia could be raised at a density of 3 fish m⁻² with A40 to improve production and generate profit for nutritional security and poverty alleviation in rural areas.     

Economic analysis of a pilot commercial production for spotted babylon, Babylonia areolata (Link 1807), of marketable sizes using a flow-through culture system in Thailand

This article examines the economic considerations involved in the production of spotted babylon (Babylonia areolata) in Thailand. A financial analysis of the construction and operating costs of a pilot commercial production of spotted babylon of marketable sizes is provided, based upon proven practical techniques and production data for a flow‐through growout system. The investment required for a spotted babylon growout hatchery producing 990 kg per year is estimated to be US$4528.8. The annual cost of operating such a hatchery is estimated to be US$4624.1. The cost of producing 990 kg of marketable‐size spotted bablyon with a survival rate of 95% is estimated to be US$4.91 per kg of snails produced. Cash flow analysis showed that a constant selling price of US$5.8 kg^?1 results in positive cash flow by year 4. The proposed enterprise is marginally feasible if cost can be considerably reduced by targeting production and integrating hatchery and growout operations.     

Effect of stocking density on growth performance,survival, production,and financial benefits of African sharptooth catfish (Clarias gariepinus) monoculture in earthen ponds

ABSTRACT

The present on-farm study assessed the effect of different stocking densities on growth, production, and financial benefits of African sharptooth catfish (Clarias gariepinus) in earthen ponds for 180 days. Low stocking density (LSD), medium stocking density (MSD), and high stocking density (HSD) of 3, 6, and 9 fish m^?2, respectively, were tested. C. gariepinus stocked at LSD and MSD showed significantly higher weight gain, specific growth rate, and final mean weight than those cultured at HSD (P < .05). There was a significant linear relationship between the stocking density and the yields and financial variables (P < .05). Net fish yields were significantly higher for C. gariepinus reared at HSD and MSD than those stocked at LSD (P < .05). Similarly, C. gariepinus raised at MSD and HSD generated significantly more profit than those cultured at LSD (P < .05). Results demonstrated that farmers can achieve high net yield and financial benefits by stocking C. gariepinus at HSD of 9 fish m^?2.     

方斑东风螺水泥池养殖不同底质的生长与存活试验

为了解方斑东风螺水泥池养殖适宜的底质,水泥池底铺设不同底质进行对比试验。结果表明：在池底铺沙情况下,添加10%海泥或添加1%的贝壳,不影响方斑东风螺的正常生长与存活,体重、壳高生长速度分别是23.7～25.1mg/d和105.3～110.4μm/d,不同池生长、存活无明显差异;底沙添加海泥达到30%时,初期东风螺的生长受到不良影响,但随着换水次数的增加,逐渐趋于正常;池底不铺沙时体重生长速度为10.0mg/d,仅为其他池的39.8～42.2%,存活率仅为其他池的65.1～67.6%。认为东风螺水泥池养殖必须铺沙,底沙可适当含泥,含泥量不高于10%。     

Effect of stocking density and photoperiod on growth and survival in cultured early juvenile pot‐bellied seahorses Hippocampus abdominalis Lesson, 1827

The effect of stocking density and photoperiod on Hippocampus abdominalis was examined in this study. Stocking densities of 45, 30, 15 and 5 seahorses 3 L^?1 were tested on newborns. Growth and survival were independent of stocking density. A second stocking‐density experiment aimed to remove the effect of an early mortality experienced in experiment 1 using older juveniles at 25, 15 and 5 seahorses 3 L^?1. There were no differences in the parameters measured. Also, the effect of photoperiod was investigated on seahorses cultured under 24:00, 16:08 and 08:16 (L:D) photoperiods. A single Artemia meal was delivered at 10:00 hours. Survival and body growth in 16:08 and 08:16 hours were higher than in 24:00 hours. In a second experiment, seahorses were cultured in the photoperiods and conditions described for experiment 1, except they were fed twice the amount in two meals delivered at 10:00 and 16:30 hours. The seahorses in 16:08 hours showed better growth than the other treatments, but there were no differences in survival. These results suggest that early juvenile H. abdominalis can be cultured at higher stocking densities than previously reported, without compromising growth and survival, and when feeding was not limiting, grew better in an extended photoperiod (16:08) but not in 24:00 hours.     

水温和养殖密度对大鳞鲃幼鱼的生长影响

分别进行水温和密度对大鳞鲃(Barbus capito)幼鱼的生长影响实验,旨在探索大鳞鲃适宜的放养密度和生长温度。水温实验设计为6个梯度值15℃、18℃、21℃、24℃、27℃、30℃,幼鱼初始体重为9~12 g,投喂75 d后,结果得出:在水温15~27℃时,随着温度的升高,终末体重会逐渐增加,27℃时最大值为(44.47±9.54)g,水温达到30℃时,终末体重开始下降。24℃、27℃和30℃组体重增长无显著差异,但温度达到30℃时,体重变异系数最大,为(29.82±11.36)%。密度实验设计为4个梯度值20 ind/m3、15 ind/m3、10 ind/m3、5 ind/m3,幼鱼初始体重为0.6~0.7 g,投喂60 d后,结果得出:随着放养密度的下降,体重增长的速度越快。体重、特定增长率、日增重变化在密度为5 ind/m3时最高,密度10 ind/m3与15 ind/m3没有显著差异,达到20 ind/m3时会显著下降。综合考虑,大鳞鲃适宜的养殖温度在24~27℃,静水池塘的放养密度建议在15 ind/m3左右。     

密度胁迫对凡纳滨对虾稚虾免疫指标及生长的影响

将体长为（3.59±0.26）cm的凡纳滨对虾（Litopenaeus vannamei）按1 800尾.m-3、1 500尾.m-3和1 200尾.m-3的密度分别饲养在注水0.3 m3的圆形玻璃纤维桶（容量为0.5 m3）中30 d,检测了基本水质因子、对虾肝胰腺和肌肉组织中的酚氧化酶（PO）活力、超氧化物歧化酶（SOD）活力、抗菌活力（Ua）、碱性磷酸酶（AKP）活力、体质量增长和成活率,研究了不同放养密度对凡纳滨对虾稚虾免疫指标及生长的影响。统计分析发现,试验过程中水体理化因子均在适宜范围,各处理间水质因子的差异不显著;对虾的PO活力、Ua和AKP活力均随着密度的增加而降低,SOD活力则反之;对虾的体质量增长、体质量特定增长率和成活率随着密度的增加而降低,成活率差异显著（P〈0.05）。结果表明,凡纳滨对虾（体长〈4.8 cm或体质量〈1.2 g）在密度为1 200～1 800尾.m-3时,密度胁迫可明显影响其免疫指标和生长。     

Growth and production performance of threatened snakehead fish,Channa striatus (Bloch), at different stocking densities in earthen ponds

Production trials of threatened snakehead fish (Channa striatus) were carried out under different stocking densities in earthen ponds of Bangladesh. The average weight and length of the fingerlings during stocking was 17.63 ± 1.23 g and 13.21 ± 0.52 cm. Fingerlings were stocked at 5000 ha^?1 in treatment‐1 (T₁), 6250 ha^?1 in treatment‐2 (T₂) and 7500 ha^?1 in treatment‐3 (T₃) respectively. Fish in all the experimental ponds were fed with supplementary feed comprising of fish meal (30%) and mustard oilcake (70%) at the rate of 3–6% of estimated body weight two times per day. In addition, trash fish were supplied at the rate of 2–3% of the estimated biomass on each alternate day. In situ water quality parameters of the pond were within the suitable range for fish culture. The growth and survival of fingerlings were significantly higher in T₁ than in T₂ and T₃. The food conversion ratio was significantly lower (P<0.05) in T₁ than in T₂ and T₃. The estimated gross and net production of fish was higher in T₁, followed by T₂ and T₃. Overall, the highest growth, survival and production were obtained from T₁. Therefore, it could be concluded that of 5000 fingerlings ha^?1 is the most suitable stocking density for culturing C. striatus under a monoculture system in the earthen ponds for better production.     

Combined effects of temperature,salinity and rearing density on growth and survival of juvenile ivory shell,Babylonia areolata (Link 1807) population in Thailand

The ivory shell, Babylonia areolata (Link 1807), has been exploited as an important aquaculture organism along the southern China coast. In order to obtain optimal culture conditions for ivory shell juvenile, the central composite rotatable design was used to estimate the combined effects of temperature, salinity and rearing density on accumulated growth rate (AGR) and survival rate (SR). The results showed that the linear effects of temperature and rearing density on both growth and survival were highly significant (P < 0.01), but there was no significant effect on salinity (P > 0.05). The quadratic effects of temperature, salinity and rearing density influenced growth significantly (P < 0.01). The quadratic effects of temperature and salinity on survival of juvenile snail were significant (P < 0.01), the combined effects between the quadratic effect of temperature and the linear effect of rearing density influenced survival significantly (P < 0.01); the interactive effects of temperature, salinity and rearing density played a significant role in survival (P < 0.01). As can be seen from the above experimental results, the effects of temperature and salinity on growth and survival of B. areolata were strengthened with enhanced rearing density in a certain range and vice versa. By optimization using the response surface method, the optimal point was found at a temperature of 26.81°C, a salinity of 28.76 ppt and a rearing density of 527.07 ind m^?2. Under these conditions, the optimal AGR and SR were 36.84 mg day^?1 and 99.99%, respectively, with a satisfaction function value of 99.71%.     

Effects of diet, stocking density and environmental factors on growth, survival and metamorphosis of clam, Paphia malabarica (Chemnitz) larvae

A series of experiments were conducted to evaluate the effects of diet, stocking density and environmental factors on the growth, survival and metamorphosis of short neck clam Paphia malabarica larvae. These experiments examined the following factors: diet [ Isochrysis galbana , Nannochloropsis salina and a mixture of I. galbana and N. salina (1:1 w/w)], stocking density (1, 3, 5 and 7 larvae mL⁻¹), light intensity (unshaded, partially shaded and fully shaded) and water filtration (unfiltered and sand filtered). Results indicated that N. salina could replace 50% of I. galbana as a food source for the clam larvae with an increase in growth, survival (47.2%), metamorphosis (33.5%) and early settlement. Larval growth decreased significantly with increasing stocking density. A density of 1–3 larvae mL⁻¹ appeared to be optimal for normal growth of clam larvae. Neither diet nor stocking density used in the study had a significant effect on larval survival. Under partially shaded (light intensity=1000–5000 lx) and fully shaded (light intensity <1000 lx) conditions, larval growth was significantly faster than under direct sunlight (unshaded). Larvae grew significantly faster in the unfiltered water than in the filtered water.     

Effects of temperature, stocking density and diet on the growth and survival of juvenile Mithraculus forceps (A. Milne Edwards, 1875) (Decapoda: Brachyura: Majidae)

Mithraculus forceps (A. Milne Edwards) has demonstrated a great potential for ornamental aquaculture and the present study tests the effects of temperature, stocking density and diet on the survival and growth of M. forceps juveniles. For 28 days post metamorphosis (DPM), the newly metamorphosed juveniles were reared at two temperatures (25±0.5 or 28±0.5°C), stocked at five densities (1, 5, 15, 30 or 60 crabs ring⁻¹; approximately 226, 1132, 3395, 6791 or 13 581 crabs m² respectively) and fed with commercial pellets (CP), microalgae (Amphora spp.), live newly hatched Artemia nauplii (NHA), frozen Artemia nauplii (FNHA), or combinations of each of these diets with NHA. At the end of the temperature experiment, carapace width of the crabs cultured at 28°C was significantly larger than the crabs reared at 25°C and average intermolt period was significantly shorter. Increased stocking density had a negative effect on survivorship and growth. Survivorship at the end of the diet experiment was significantly different between the crabs not fed, fed with CP and Amphora and the crabs fed with the other diets. Between the diet treatments, the crabs fed with NHA+Amphora were significantly larger than the ones fed with NHA+FNHA, NHA, FNHA and NHA+CP, and these in turn larger than ones fed with Amphora.     

养殖密度对毛蚶幼虫生长及存活的影响

为探讨毛蚶(Scapharca subcrenata)幼虫养殖的最佳密度,本研究设定了5个不同的放养密度(2、5、8、14、20 ind/m L),养殖实验从D型幼虫阶段一直持续到幼虫完成附着变态。实验结果表明,随着放养密度的增加,水体氨氮浓度、亚硝酸盐浓度显著升高(P0.05);幼虫密度为20 ind/m L时,分别达到最大值0.089 mg/L和0.008 mg/L。溶解氧浓度则随幼虫密度的增大呈现下降的趋势,幼虫密度达到14、20 ind/m L时,显著低于其他密度组(P0.05)。幼虫的生长速率随放养密度的增加显著下降,5~8 ind/m L为幼虫最佳生长密度。幼虫的存活率也随着放养密度的增加显著下降(P0.05),当幼虫的放养密度为20 ind/m L时,存活率仅为35%。放养密度为8 ind/m L时,幼虫的附着密度最大,且在附着基下层的附着密度显著高于中层和上层(P0.05)。同时,随着放养密度的增加,幼虫附着变态的时间被延长,附着变态规格也显著减小(P0.05)。因此,综合考虑各种要素,规模化苗种生产中幼虫的培育密度控制在5~8 ind/m L较为适宜。