南美白对虾苗淡化养殖的主要技术措施

南美白对虾是生长在海水中的优良虾品种，通过淡化驯养，可在内陆淡水中正常生长。2004年，广丰县南美白对虾养殖基地养殖南美白对虾300亩，5月13日、5月25日两批虾苗淡化成活率很低，通过总结前两批的淡化经验，改进了淡化技术，6月15日、7月3日两批的虾苗淡化成活率达80～90％。现将南美白对虾苗淡化的主要技术措施介绍如下。     

南美白对虾(Penaeus vannamei)池养技术初探及经济效益分析

根据南美白对虾能适应低盐度海水的特点,采用“逐步淡化”法,在两口面积各为２０００ｍ＾２的池塘中饲养,１１０ｄ后收获成虾１０２９．６ｋｇ,产量达到２５７．４ｋｇ／１０００ｍ＾２,平均规格７３．６尾／ｋｇ,成活率５０．５４％,千平方 米纯利为９０７５元。试验表明,南美白对虾适宜于上海地区推广养殖。     

南美白对虾淡化养殖试验

南美白对虾在人工配制0．5‰盐度的淡水水体经过120d半封闭养殖，成活率达到50％，0．4hm^2池塘产量达到1260kg，而在0．25‰以下的成活率仅10％－29％。南美白对虾淡化养殖的盐度最低应保持在0．5‰。     

南美白对虾池塘淡水养殖试验

1999年在广西水产研究所中试基地进行了南美白对虾池塘淡水养殖试验。在600cm^2的淡水池塘中投放平均全长2．35cm的淡化虾苗2．5万尾,经70d饲养,生产成虾98kg,平均亩产量108．9kg,成虾平均全长9．59cm(最大为10．6cm),平均体长8．34cm(最大为9．4cm),平均体重7．73g(最大为11．5g),养殖成活率为50．7％。     

南美白对虾二级淡化试验

近年来，南美白对虾在北方的养殖面积不断扩大，并从沿海向内陆发展，由海水养殖向淡水养殖迈进。虾苗淡化是南美白对虾在淡水地区养殖成功的一个重要环节。一般育苗场为了自身经济利益，降低风险，很少将虾苗淡化到1‰以下，通常淡化到7‰左右甚至更高就作为淡化苗出售(因为7‰左右盐度的虾苗运输成活率高)。这种虾苗在进入淡水池塘养殖前必须经过进一步淡化才能保持较高的成活率。我们于2003年6月13日在从辽宁省盘锦市大洼县引进虾苗，随机取样，进行了二级淡化试验。现将淡化情况报告如下。     

池塘循环海水高效养殖技术探索

池塘循环海水高效养殖是一种正在探索中的新的集约化养殖模式，2000年进行的南养白对虾高产养殖试验，对虾平均亩产达到1040公斤/亩，最高达到1482公斤/亩，平均成活率为82.3%，铒料系数1.57,亩利润3.72万元。结果表明池塘循环海水高效养殖在技术上是可行的。     

南美白对虾虾苗淡化技术

南美白对虾在海水养殖条件下病害较多，养殖过程中使用药物品种多、剂量大，导致药物残存量较高。而在淡水条件下养殖该品种，能使引起南美白对虾的红体病、白斑病的病毒及引起其它疾病的细菌几乎不能存活，因而淡水养殖南美白对虾，生长快、个体大、病害少。最近几年，我省普遍养殖南美白对虾，亩产量徘徊在100-150kg左右，经济效益较低。笔者在海南多年从事各种对虾的人工工厂化育苗以及南美白对虾、斑节对虾虾苗的淡化和高位池塘精养对虾工作，并对我省淡水养殖南美白对虾进行了三年调查研究，认为造成低产低效的最主要原因是虾苗淡化方法简单粗糙，淡化成活率极低，甚至入池后1个月内存活率不足10％。     

南美白对虾双茬淡化养殖技术研究

研究采用南美白对虾塑料大棚保温三级淡化暂养技术等措施,实现南美白对虾池塘双茬淡化养殖。养成期间水质情况良好,水温平均（26±3）℃,pH值约8．5左右,溶氧量5．6m叽以上,氧氮约0．20mg/L,亚硝酸氮0．02m班左右,每667m^2养殖产量达426．7kg,养殖效益高达4186．7元。结果表明,采用南美白对虾双茬淡化养殖技术,延长了对虾生长期,提高了池塘利用率和经济效益,具有较好的推广价值.     

南美白对虾淡化养殖在西安取得成功

经过两年的引进试验，２００２年，南美白对虾池塘淡化养殖在西安市获得成功，平均亩产达到３６８．１千克左右，开创了西安市水产养殖的新纪元。２０００年，西安市开始在现代农业综合开发区渔场进行少量引进试验。２００１年，由西安市科学技术委员会立项，委托西安市水产工作站负责，于２００１～２００３年开始引进及淡化养殖试验。当年，选择现代农业综合开发区第一、二渔场和“西安市地热资源利用中心”罗非鱼养殖场进行试验，实现平均亩产７５千克。去年，市水产技术推广部门加大了南美白对虾淡化养殖推广力度，在养殖技术、养殖规模…     

南美白对虾养殖的生态学管理技术探讨

南美白对虾淡化养殖技术在鲁西盐碱池塘获得很大成功。通过几年实践，在抓高产的同时，我们致力于探索对虾养殖的池塘生态学管理技术，目的是为了更加充分利用池塘生态系中物质能量流动规律，提高虾苗下塘成活率，把池塘生物能量更大限度地发掘出来，逐步实施生态养殖，获取绿色水产品，取得经济效益、生态效益双收，倡导渔业和谐生产。茌平县有低洼盐碱池塘800hm^2（1．2万亩），属黄河故道，池塘蒸发量大，盐度大多在1～32．间，而南美白对虾经淡化的虾苗正适宜这个盐度。     

Effect of Stocking Weight and Stocking Density on Production of Hybrid Striped Bass (Sunshine) in Earthen Ponds in the Second Phase of a 2-Phase System

Sunshine bass from Phase I or pond production were graded into two weight classes, 3 and 5 g, and stocked into experimental earthen ponds at a density of either 8,649/ha or 11,120/ ha in a 2 × 2 factorial design. After stocking, the fish were fed a commercially manufactured feed (43.0-45.5% crude protein) twice daily to satiation for 17 mo. At harvest, mean survival ranged from 67.4 to 84.8% but was highest for the fish stocked at 5g. Average production Tor ponds stocked at 8,649/ha and 11,120/ha, regardless of stocking weight, was 4,506 kg/ha and 5350 kg/ha, respectively. Production and percentages of assigned weight classes were not significantly different among treatments as a result of wide variation among replicates. Using size-dependent market prices assigned to the different harvest size groups, an economic analysis revealed gross receipts, variable costs, and total costs for the 11,120/ha 5-g treatment. Net returns were not significantly different among the four treatments due to large variation among replicates per treatment. These results confirm that the traditional phase II of pond production can be eliminated in favor of a direct stocking of phase I fish into a single production phase and economically competes very well with traditional three-phase growout management. The potential reduction in turnover time of production units achieved through the direct stock practice is an efficiency trait that should translate into significantly higher returns and a greater profit over the long term. Further reduction of stocking density combined with a stocking weight greater than 5 g should translate into greater proportion of larger, higher valued fish at harvest and a growout period of 18-20 mo, rather than the 24-30 mo traditionally needed for the combined phase II and phase III of production.     

Split Ponds Effectively Overwinter Golden Shiners

Baitfish producers have expressed interest in adopting the split‐pond production system. However, confining fish to 20% of the pond area in split‐pond systems effectively quintuples fish density within the culture unit as compared with densities in open ponds. Winter conditions are known to be relatively more stressful on smaller fish, and high densities within split‐pond culture units could increase losses. A 139‐d study was conducted during the winter to compare the production of golden shiners, Notemigonus crysoleucas, in traditional earthen ponds and split ponds at two densities. Golden shiners were stocked at 646 kg/ha or 1292 kg/ha (ca. 370,500 or 741,000 fish/ha, respectively) into 12, 0.04‐ha, netted earthen ponds (six split ponds and six traditional). Feeding rate, nightly aeration hours, and daily circulation hours were reduced when water temperature decreased. At harvest, net yields were significantly lower in the split ponds as compared with traditional ponds at each density (53 and 113 kg/ha less in the low‐ and high‐density split‐pond treatments, respectively). Estimated survival was high (>87%) and did not differ among treatments. Results showed that, although net yield was reduced, small baitfish could be successfully overwintered in split‐pond culture units in preparation for the spring crappie market.     

The Effect of Understocking Density of Channel Catfish Stockers in Multiple-Batch Production

A multiple-batch study was conducted using stocker catfish (0.09 kg/fish) and carryover fish (0.39 kg/fish) to look at the effects of different stocker densities on fish production. Twelve 0.1-ha ponds were stocked with 7,400; 11,120; or 14,825 stockers/ha, and equal weights of carryover fish (2,268 kg/ha). Fish were fed once daily to apparent satiation with a 32% protein floating feed and aerated with a single 0.37-kW electric paddlewheel aerator. No significant differences were detected for gross, net, and net daily yields, growth (g/d), or survival. Sub-marketable yield (<0.57 kg) increased as stocking density increased. However, marketable yields (≥0.57 kg) were not affected by density. Carryover fish in high-density ponds had a significantly lower (P < 0.05) mean weight at harvest, but mean stocker weight was not different across densities. Economic analysis found breakeven prices increased and net returns decreased with increased stocking density when sub-marketable fish were not considered as revenue. The study indicated the possibility that stockers compete with large carryover fish, particularly at higher densities.     

Intensive Culture Potential of Penaeus vannamei

Tank and pond rearing studies were conducted to assess the potential for intensive culture of Penaeus vannamei in South Carolina. Postlarvae were stocked in intensive nursery tanks at 500/ m². Growth and survival were compared for shrimp reared in control fiberglass tanks and in tanks with artificial substrates (fiberglass screen). Addition of substrate improved survival (82% versus 58%), but not growth. Juvenile shrimp (mean weight, 1.3 g) from the nursery trial were stocked into 6 m diameter tanks at densities of 10, 20 and 40/m². Growth rate was inversely related to stocking density, with mean sizes of 33.9, 32.5, and 26.7 g attained at the low, medium, and high densities respectively after 168 days. At harvest, standing crop biomass averaged 225.6, 442.0, and 685.4 g/m² for the three densities. To further test the intensive culture potential, two 0.1 ha ponds were stocked with hatchery-reared postlarvae at densities of approximately 40 and 45/m². The ponds were managed intensively using paddlewheel aerators and water exchange averaging 16–17%/day. The ponds were harvested after 138 and 169 days and yielded 6,010 kg/ha of 16.7 g (mean weight) shrimp and 7,503 kg/ha of 17.9 g shrimp, respectively. Average production was 6,757 kg/ha with a food conversion of 2.51. These data suggest good potential for intensive pond culture of P. vannamei in South Carolina and other areas of the continental United States.     

POND STUDIES ON GULF KILLIFISH (Fundulus grandis) MARICULTURE

Investigations concerning spawning, hatching, and grow-out of gulf killifish (Fundulus grandis) were conducted in 0.08-ha, brackish-water ponds at Alabama's Claude Peteet Mariculture Center during 1979. Adult gulf killifish stocked at 88,750 fish/ha and a 1:1 sex ratio in 3 spawning ponds deposited 499,777 eggs on 1,001 Spanish moss mats placed around pond margins between 1 March and 13 August. Rate of egg deposition was highest in March (4,103 eggs/day/pond) and lowest in July and August (36 eggs/day/pond). A total of 293,467 eggs and 416 mats transferred to 3 hatching ponds between 13 March and 8 May produced 219,921 juvenile killifish (75% survival) averaging 0.5 g at harvest on 6 June. Production and feed conversion in hatching ponds averaged 413.90 kg/ha and 1.9, respectively. Stocked on 6 June in 4 grow-out ponds each at either 250,000 or 370,000 fish/ha and fed either 2 or 3 times daily, the juvenile gulf killifish reached marketable size (2.4 g and 57 mm total length) in 49 days. Production in grow-out ponds averaged 658 kg/ha with 93% survival and 2.4 feed conversion. Analysis (2 × 2 factorial) of grow-out data indicated no significant differences for effects of densities and feeding on mean weights of fish at harvest.     

Production of the Australian freshwater silver perch, Bidyanus bidyanus (Mitchell), at two densities in earthen ponds

Silver perch fingerlings (mean weight 15.3 g) were stocked at densities of 21 000 and 7000 fish/ha in six 0.1-ha earthen ponds and cultured for 10 months. There were three replicate ponds for each density. Ponds were aerated for at least 11 h a day and water was added every 4 weeks to replace that lost by evaporation and seepage. Fish were fed a formulated diet containing 35% crude protein at 4% body weight per day for the first 4 weeks and at rates up to 3% thereafter. The mean annual production rate of 9819 kg/ha of fish stocked at 21 000/ha was significantly higher (P < 0.01) than the annual rate of 3699 kg/ha of fish stocked at 7000/ha. The maximum daily production and growth rates achieved in any pond over a 1-month period during summer were 97.7 kg/ha and 5.1 g/fish, respectively. Stocking density did not significantly (P > 0.05) affect survival rate (treatment means for 21 000 and 7000 fish/ha: 92.8 and 94.7%), daily growth rate (0.2–3.3 and 0.3–3.4 g/fish), weight at harvest (434.9 and 473.2 g), food conversion ratio (1.9:1 and 1.8:1) and cost of feeding ($A1.55 and $A1.47/kg), suggesting that higher stocking densities and production rates are possible. Water temperatures ranged from 11.1 to 30.0 °C. Significantly (P < 0.05) slower growth during December was associated with concentrations of NH₃-N up to 0.65 mg/l. The results demonstrate that silver perch is an excellent species for semi-intensive culture in static earthen ponds with the potential to form the basis of a large industry in Australia, based on high-volume, relatively low-cost production.     

Effect of Multiple-batch Channel Catfish, Ictalurus punctatus, Stocking Density and Feeding Rate on Water Quality, Production Characteristics, and Costs

To quantitatively define relationships among stocking densities, feeding rates, water quality, and production costs for channel catfish, Ictalurus punctatus, grown in multiple‐batch systems, twelve 0.1‐ha earthen ponds were stocked at 8,600, 17,300, 26,000, or 34,600 fingerlings/ha along with 2,268 kg/ha of carryover fish. Fish in all ponds were fed daily to apparent satiation using 32% protein floating feed. Temperature and dissolved oxygen in each pond were monitored twice daily; pH weekly; nitrite‐N, total ammonia nitrogen, and Secchi disk visibility every 2 wk; nitrate‐N, chlorophyll a, total nitrogen, total phosphorus, and chemical oxygen demand monthly; and chloride every other month. The costs of producing channel catfish at different stocking densities were estimated. There were no significant differences (P > 0.05) as a result of stocking density among treatment means of (1) gross or net yields, (2) mean weights at harvest, and (3) growth or survival of fingerlings (24–36%) and carryover fish (77–94%). Mean and maximum daily feeding rates ranged from 40 to 53 kg/ha/d and 123 to 188 kg/ha/d, respectively, and feed conversion ratios averaged 1.75. There were no differences in any feed‐related parameter as a result of density. Water quality variables showed few differences among densities at samplings and no differences when averaged across the production season. Yield of fingerlings increased as stocking density increased with significant differences between the two highest and the two lowest stocking densities. Breakeven prices were lower at the higher stocking densities as a result of the higher yield of understocked fish and similar mean individual fish weights produced at these higher stocking densities. Overall, varying stocking densities of fingerlings in multiple‐batch systems had little effect on production efficiency and water quality. Additional research on managing the population structure of carryover fish in commercial catfish ponds may be warranted.     

A Comparison of Black Drum, Red Drum, and their Hybrid in Saltwater Pond Culture

Hybridization has been used in aquaculture to produce fish that exhibit improved growth and survival over parent species. Previous studies produced an intergeneric hybrid by crossing female black drum Pogonias cromis with male red drum Sciaenops ocellatus . In the present study, the two parent species and their hybrid were simultaneously cultured in ponds for 9 mo. Two- to three-day-old larvae of each type were initially placed into three separate 0.1 ha ponds. After about 41 d, fingerlings of each type were transferred from the larval culture ponds to six 0.2 ha ponds. Two ponds each received 3,000 black drum, red drum or hybrid fingerlings. Fish were fed a commercial feed and harvested after about 230 d. At harvest, mean weight, mean total length, and production for the hybrids was 190 g, 245 mm, and 10.7 kg/ha/d, respectively; red drum averaged 142 g, 236 mm, and 7.0 kg/ha/d; and black drum averaged 144 g, 214 mm, and 10.6 kg/ha/d. Black drum survival was 94%, red drum survival was 63%, and hybrid survival was 72%. Hybrid growth was more rapid than either parent. A taste panel failed to identify differences in flavor between the three fishes. With similar flavor and faster growth, hybrid drum have potential for commercial mariculture.     

Threadfin Shad Dorosoma petenense Effects on Water Quality, Phytoplankton, and Channel Catfish Production in Ponds

Threadfin shad Dorosoma petenense are often stocked into commercial catfish ponds for biological control of algae. It is thought that the fish will alter the phytoplankton community, improve water quality, and enhance channel catfish production. Co-stocking of shad and catfish is a common practice, although there is limited information regarding the effects of threadfin shad on pond dynamics and catfish production. To evaluate the influence of shad in catfish ponds, this study was conducted in ten 0.04-ha experimental earthen ponds near Auburn, Alabama. All ponds were stocked in April with 600 fingerling channel catfish Ictal-urus punctatus (13,200/ha) with a mean length of 10.4 cm (4.1 in). Additionally, five of these ponds were randomly chosen and stocked with 70 adult threadfin shad (1,750/ha) weighing a total of 3.3 kg (16.5 kg/ha). At harvest in November, an average of 1,284 threadfin shad (32,100/ha), weighing a total of 55 kg (1,375 kg/ha) were collected from each shad pond. Water quality was improved with the addition of threadfin shad to channel catfish ponds. Mean total ammonia-nitrogen was significantly lower and less variable in the shad treatment. Observed mean nitrite concentrations, though not significant, were lower in the shad treatment. The phytoplankton community of the shad treatment had significantly higher density, more taxa, and smaller organisms. Pond water in the shad treatment had higher projected early morning dissolved oxygen levels requiring less aeration. Channel catfish had significantly higher survival in the shad treatment, furthermore, though not statistically significant, observed mean fish production was higher and feed conversion ratio was lower than in the no-shad treatment.     

Paddlewheel Effects on Shrimp Growth, Production and Crop Value in Commercial Earthen Ponds

The effects of continuous paddlewheel operation on shrimp growth, yield and crop value were studied in Hawaii. Six 0.4 ha earthen ponds were stocked with Penaeus vannamei at 25 postlarvae/m². Three ponds served as controls with no mechanical aeration or mixing. Each of the other three ponds had two 1 hp paddlewheel aerators (3.7 kw/ha) running continuously throughout the five month trial (29 April-8 October 1986). All other management factors were applied uniformly.
Daily water temperature and use were significantly different between treatments. Paddlewheel ponds had lower water temperatures (28.3 vs. 28.5 C) and lower water use (0.8% exchange per day vs. 2.2% exchange per day) than control ponds.
Faster shrimp growth in paddlewheel ponds was evident in week 8. At week 14, mean shrimp body weights and growth rates were significantly greater. Shrimp at harvest were 21.2 ± 2.6 g in paddlewheel ponds versus 15.3 ± 2.6 g in control ponds. Mean shrimp production was 2,852 ± 222 kg/ha in paddlewheel ponds compared to only 2,061 ± 558 kg/ha in controls. Mean crop value was $13,719 per pond per crop for paddlewheel ponds versus $9,111 for control ponds. Hence, paddlewheels afforded an increase of 42% in net crop value after subtracting purchase and operating costs.