Growth, Yield, Dressout, and Net Returns of Bighead Carp Hypophthalmichthys nobilis Stocked at Three Densities in Catfish Ictalurus punctatus Ponds

Abstract— Alternative fish species that can be cultured together with catfish Ictalurus punctatus provide an opportunity to diversify caffish farms. A 2-yr study was conducted in 0.10-ha earthen ponds to evaluate the effect of bighead carp (BHC) stocking density on growth, yield, dressout yield, and net returns. Initially, bighead carp (average weight of 22 g) were stocked at rates of 380, 750, or 1,130 fishha in ponds with catfish. Caffish were cultured under commercial conditions by stocking caffish at a density of 12,500/ha, aerating nightly and feeding at an average rate of 82 kgha per d. Stocking rates for 2-yr-old fish were reduced to 77, 260, and 435/ha in the second growing season. There were no significant differences among treatments ( P > 0.05) in summer growth of bighead carp in either year. Bighead carp stocked at 1,130 fishha had significantly higher yields than those stocked at 380/ha, but did not reach minimum market size of 2.2 kg during the first year ( P > 0.05). There were no significant differences ( P > 0.05) in caffish growth, yield, survival, or feed conversion ratios due to the bighead carp stocking densities. Partial budget analysis indicated that net benefits were positive for all three treatments over a range of prevailing prices of bighead carp. Bighead carp production in catfish ponds is economically feasible over a wide range of prices. Given the market risk of producing smaller fish at the higher density, the medium density is the preferred stocking density of fingerling bighead carp in catfish ponds.     

Growth, Yield, Dressout, and Net Returns of Bighead Carp Hypophthalmichthys nobilis Stocked at Three Densities in Fertilized Earthen Ponds

Abstract.— Bighead carp Hypophthalmichthys nobilis have been raised in the United States for two decades and sold through the livehaul market, but their profitability in monoculture has not been evaluated. Three studies were conducted in 0.10-ha earthen ponds to evaluate the effect of bighead carp stocking density on growth, yield, dressout yield. and net returns. Initially, bighead carp (average weight of 0.36 kg) were stocked at rates of 500, 320, or 130 fish/ha with three replicates of each treatment. Stocking rates for 2-yr-old fish (average weight of 2.45 kg) were reduced to 320, 220, or 130 fish/ha in the second year. Net yields of bighead carp stocked at 500 fish/ha (963 kg/ha) were significantly higher ( P < 0.05) than net yields at the 320 fishha density (771 kg/ha), and these were significantly greater ( P < 0.05) than net yields at 130 fish/ha (369 kg/ha) in the first growing season. Net yields in the second growing season were not significantly different ( P > 0.05) among densities. There were no significant differences ( P > 0.05) among treatments in yearly growth which ranged from 11–17 g/d in the first and from 6–13 g/d in the second growing season. Dressout percentages for whole-dressed, steak, shank fillet, and shank fillets with white meat only did not differ with stocking density ( P > 0.05). Enterprise and partial budget analysis indicated that monoculture of bighead carp in fertilized ponds is profitable only in the short run at average livehaul market prices, because revenues exceeded variable but not fixed costs. The negative net returns, when all costs were accounted for, indicated that it is not profitable to construct ponds solely for monoculture of bighead carp.     

POLYCULTURE OF THE FRESHWATER PRAWN (Macrobrachium rosenbergii) WITH TWO COMBINATIONS OF CARPS IN MANURED PONDS

A study was conducted to 1) evaluate the compatibility of prawns (Macrobrachiurn rosenbergii) with carps, especially the effect of the common carp (Cyprinus carpio); and 2) measure the ability of prawns to utilize the foods available in manured systems. Carps used were the silver (Hypophthalmichthys molitrix), bighead (Aristichthys nobilis), grass (Ctenopharyngodon idella) and common carp (Cyprinus carpio). Four ponds (0.09 to 0.17 ha) were stocked with silver, bighead and grass carps while common carp were stocked in only two ponds. Total fish densities were 8,600/ha where four carps were stocked, but only 6,200/ha when common carp were omitted. Post-larval prawns (wt 0.116 g) were stocked at densities of 17/m². Swine (approximately 60/ha of pond surface area) were housed on pond dikes so that fresh manure continuously entered each pond. Two lots of swine were fattened during the experimental period and loadings of swine manure were calculated based on hog size and feed consumption. Growth periods were 163 days for fish and 107 and 121 days for separate stockings of prawns. Gains in biomass by prawns averaged 714 kg/ha in ponds without common carp and 364 kg/ha in ponds containing common carp. Gains in biomass for both fish and prawns were 3,619 kg/ha (19.8 kg/ha/day) in ponds with common carp and 2,924 kg/ha (18.0 kg/ha/day) in those without common carp. Prawn survival was higher (X = 84.5% vs X = 72.5%), but final average weight of prawns was lower (2.64 vs 5.86 g) in the presence of common carp due to competition for food between common carp and prawns. Competition from carp is believed to have exerted less influence on prawn survival than predation on small prawns by larger, faster-growing prawns.     

主养草鱼池塘三种混养模式鱼类生长和效益的比较

为进一步提高我国广大池塘养鱼的产品质量、经济效益和改善其生态环境。本试验在武汉新洲973项目实验基地9个陆基鱼池中进行了三种不同混养模式鱼类生长和效益的比较研究,每种模式设3个重复。模式Ⅰ中放养草鱼、鲢、鳙和高背鲫;模式Ⅱ中放养草鱼、鲢、鳙、匙吻鲟和高背鲫;模式Ⅲ中放养草鱼、鲢和高背鲫。 结果表明：通过122d的养殖试验,模式Ⅱ中草鱼的生长不仅显著高于模式Ⅰ和模式Ⅲ（P<0.05）,而且其经济效益模式Ⅱ同样高于模式Ⅰ和模式Ⅲ。     

Intensive polyculture of common carp (Cyprinus carpio L.) and herbivorous fish [silver carp, Hypophthalmichthys molitrix (Val.), and grass carp, Ctenopharyngodon idella (Val.)]

Intensive polyculture of common carp and herbivorous fish (silver carp and grass carp) at high stocking densities and with intensive feeding with fodder and mineral and organic fertilization was carried out without mechanized aeration and automated feeding.Two stocking patterns were tested. The first, in Pond 1 (with an area of 2.5 ha), had the following stocking rates: one-year carp (C₁), 8000 fish/ha; one-year silver carp (S₁), 1500 fish/ha; and one-year grass carp (G₁), 200 fish/ha. The yield was 6292 kg/ha of standard consumer fish (C₁₊ 743 g, S₁₊ 944 g, and G₁₊ 1000 g) at a relatively low food conversion ratio (2.24) and high survival of all fish. Within the total yield, the two-year carp contributed 76%, the silver carp 21%, and the grass carp 3%. The second stocking pattern, in Pond 2 (0.25 ha), had the following rates: C₁, 8500 fish/ha; S₁, 2000 fish/ha; and G₁, 200 fish/ha, and produced a still higher total yield (6629 kg/ha) at a relatively low food conversion ratio (2.10). The two-year carp in Pond 2 contributed 88% of the total yield, and the herbivorous fish only 12% even though they accounted for 20% of the stock.Our results (Pond 2) are compared with other record yield experiments under similar conditions but including tilapia. At a total stocking rate of 10 700 fish/ha and without participation of tilapia, over a period of 186 days (as against 126 days in the other experiment), our experiments gave a total yield which was 347 kg/ha higher at a food coefficient 15% lower. The growth period was 60 days longer in our experiments but it included April and October when water temperature is much below the optimum and only 4% of the total amount of fodder was assimilated.     

Growth of Triploid and Diploid Bighead Carp,Hypophthalmichthys nobilis

Growth of second-year triploid and diploid bighead carp, Hypophthalmichthys nobilis, was compared in a 189- to 190-day yield trial; the fish were grown separately in 0.04-ha earthen ponds at 625/ha and were also grown communally in 0.05-ha earthen ponds at 640ha. When grown communally, bighead carp were polycultured with channel catfish, Ictalurus punctatus (7,50Oha), and grass carp, Cienopharyngodon idella (40/ha); when they were grown separately, they were polycultured with grass carp at 501ha. When cultured separately, diploids were longer (526 vs 499 mm) and heavier (1,645 vs 1,427 g) than the triploids at harvest, but the differences were not significant (P 5 0.05). When cultured communally, the diploids were significantly longer (519 vs 485 mm) and heavier (1,621 vs 1,321 g) than their triploid counterparts at harvest. Ploidy of all bighead carp was determined after fish were harvested, and 7.9% of the presumed triploids that were stocked separately were actually diploids. Growth of the triploids appeared to be acceptable for commercial use where diploid bighead carp are banned. The efficiency of producing triploid bighead carp must be improved if they are to be cultured in states where bighead carp are illegal.     

A comparison of growth, survival rate and number of marketable koi carp produced under different management regimes in earthen ponds and concrete tanks

To compare the growth performance of koi carp, Cyprinus carpio var. koi, produced in concrete tanks (2.13 × 0.91 × 1.22 m; capacity: 2,000 l each) and earthen ponds (9.1 × 6.10 × 1.07 m; capacity: 59650 l each), fish larvae (stocking size: 0.12 ± 0.008 g) were cultured for 11 weeks and individual weight gain, survival rate and number of marketable fish produced were compared among four management regimes for each culture system: (1) live zooplankton fed to fish larvae in ponds (PLF) and tanks (TLF); (2) application of poultry manure in ponds (PPM) and tanks (TPM); (3) application of cow manure in ponds (PCD) and tanks (TCD); and (4) a control treatment for ponds (PC) and tanks (TC), where a commercial feed was applied. There were three replicates for each treatment. Weight gain of koi carp was highest in the PLF treatment, followed in decreasing order by TLF, PPM, PCD, TPM, TCD, PC and TC treatments (P < 0.05). There was a significant difference in the survival of koi carp among the treatments, ranging from 67.83% in TC to 95.50% in PLF. The number of marketable fish produced was highest in the PLF treatment, followed in decreasing order by TLF, PPM and PCD treatments. However, none of the fish produced in the TPM, TCD, PC and TC treatments attained marketable size. Significantly higher (P < 0.05) values of pH and dissolved oxygen (for water samples collected weekly at 9 A.M.) were obtained in the live food and control treatments (for both tanks and ponds), compared to the manured treatments. The concentration of total alkalinity, BOD, PO₄-P, NO₃-N and specific conductivity were significantly higher (P < 0.05) in PPM and PCD, compared to other treatments. NO₂-N and NH₄-N values were significantly higher (P < 0.05) in TPM and TCD, than other treatments. The results suggest that introduction of live zooplankton into culture units result in higher growth of koi carp larvae compared to manure based systems. Earthen ponds appeared to be better alternative to concrete tanks for manure application through maintenance of better water quality due to their higher assimilatory capacity and greater abundance of plankton which resulted in better growth of cultured fish.     

Effect of density on survival and growth of cyprinid fish fry

One of the bottlenecks in Israel's cold water ornamental fish industry is the large loss of fish during the post-larval stage. As a first step towards increasing survival rates, the optimal stocking density in earthen ponds for fry of each species should be determined. The results of five consecutive experiments with fry of goldfish (Carassius auratus), common carp and koi (respectively, edible and ornamental morphotypes of Cyprinus carpio) are presented here. The experiments were run in 18 cages of 1 m³ and 0.8 mm mesh size placed in a 0.02 ha earthen pond, stocked at 50,100 and 200 fry per cage. The variables analyzed were growth rate, harvesting weight, biomass and survival. Equations to estimate growth rates under different conditions are given. The three fish types present different growth rates and survival patterns in relation to stocking density and season, which lead to different management implications. Koi can be stocked up to 2 million fry per ha without showing negative density effects. Goldfish should be stocked at low density (500,000–1 million fry per ha) in spring and at higher rate (2 million fry per ha) in summer. Common carp stocking density should be adjusted to obtain the required fish size at harvest.     

松浦镜鲤与长丰鲢食用鱼混养试验

2012年5-10月,在面积为0.19hm2的试验池1中放养体质量160g的松浦镜鲤（Cyprinus carpio Songpu）117,700尾·hm^-2,混养体质量160g的长丰鲢（Hypophthalmichthys molitrix）春片、乌子头和鳙（Aristichthys no-bilis）夏花鱼种。在面积为0.19hm2的试验池2中放养体质量149.5g的松浦镜鲤3,450尾·hm^-2,只混养鲢和鳙夏花,采用常规饲养方法。2012年10月2日,试验池1平均每hm2产鱼21,025.5kg,其中松浦镜鲤平均全长34.3cm,体质量1425g,产量18,294.0kg;长丰鲢春片平均体质量674g,平均产量1,816.5kg,长丰鲢夏花平均全长18.6cm,体质量112.4g,平均产量592.5kg;鳙夏花平均全长达12.1cm,体质量39.9g,平均产量322.5kg。试验池2平均每hm2产鱼3,069.0kg,其中松浦镜鲤平均全长35.0cm,体质量1225g,平均产量2,766.0kg;鲢夏花平均全长达11.3cm,体质量24.9g,平均产量130.5kg;鳙夏花平均全长达11.1cm,体质量35.1g,平均产量172.5kg。试验表明,高密度养殖的松浦镜鲤产量显著高于密度低时,长丰鲢夏花的出池体质量是普通鲢的4.5倍,特殊生长率（6.27%·d^-1）是普通鲢（3.5%·d^-1）的1.79倍。文中还讨论了松浦镜鲤养殖池的水质和技术特点。     

Rearing advanced fry of major Indian carp species in recirculatory-filtering ponds at Barrackpore,West Bengal

This paper describes an experiment using a recirculatory-filtering system operating in two rectangular cemented ponds (160 and 190 m², 1.5 m deep) to rear fry (25 mm–50 mm) of the major Indian carp species Labeo rohita (Hamilton) and Catla catla (Hamilton) to fingerlings (100 mm–125 mm). These operations were concluded in both the species in 32 days at stocking densities of 0.46 million/ha and 0.55 million/ha, and showed survival rates of 96.6% and 84.4% respectively. In the presently followed practices of modern fish culturists, corresponding operations in earth ponds usually take 90 days and have a stocking density of 0.2 million/ha with survival rates more or less similar to those obtained in the recirculatory-filtering system. If followed by industry, the technique described will enable production of major Indian carp fingerlings with great saving in time, the use of water and the space occupied by the production system. These advantages greatly enhance the economic viability of rearing carp fingerling in India.     

The culture-based fisheries in small, farmer-managed reservoirs in two Provinces of northern Vietnam: an evaluation based on three production cycles

In this paper the results of a study conducted on the culture‐based fisheries in small (ranging from 2 to 160 ha), farmer‐managed reservoirs in YenBai and ThaiNguyen Provinces in the northern highland region of Vietnam, for the production cycles of 1997/98, 98/99 and 99/00 are presented. The small reservoirs are leased to small farmers by the provincial authorities for fishery activities, and all lessees adopt culture‐based fisheries when fingerlings of grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), common carp (Cyprinus carpio) and mrigal (Cirrihinus mrigala) are stocked between March and mid‐April each year and harvested, using large seine nets, after approximately 11–12 months. The mean yields from reservoirs in YenBai and ThaiNguyen Provinces in 97/98, 98/99 and 99/00 production cycles were 251, 332 and 253, and 331, 372 and 210 kg ha^?1 respectively. There were major differences in the fish productivity in the reservoirs in the two Provinces, and in a reservoir between culture cycles. The stocking strategies appeared to be rather ad hoc, being determined by the availability of seed stock and the financial status of the lessees. Accordingly, there was no apparent consistent trend in the improvement of yields from the culture‐based fishery practice throughout the growth cycles. The fish yields in reservoirs in each Province were significantly related to reservoir area (exponentially) and to mean weight of stocked fish and conductivity (logarithmically). Of the stocked fish, the highest returns were obtained with mrigal and bighead carp, which collectively contributed > 50% to the harvest. The return from common carp was the lowest. The mean growth rate of grass carp (2.7 g day^?1), followed by bighead carp (2.0 g day^?1) was the highest in reservoirs in YenBai Province, bighead carp (4.0 g day^?1) followed by grass carp (3.2 g day^?1) was the highest in ThaiNguyen Province. The seed stocked on average accounted for 65% and 48% of the total operating costs in YenBai and ThaiNguyen Provinces, and the mean cost:benefit ratio of the culture‐based fishery in the two Provinces was 0.35 and 0.37 respectively. The culture‐based fishery on average contributed about 28% to the gross income of a farmer lessee.     

Effects of feeding rates on growth and production of Nile tilapia, common carp and silver carp polycultured in fertilized ponds

Abstract In an attempt to identify appropriate feeding rates for multispecies of fish raised in fertilized earthen ponds, the present work was conducted over a 19‐week experimental period to establish the growth performance, production and body composition of Nile tilapia, common carp and silver carp fed 0.0%, 0.5%, 1.0%, 3.0%, 5.0% biomass and to apparent satiation (treatments). Twelve ponds were stocked with a similar number and weight of each fish species. Two ponds were assigned to each of the treatments, and a 25% protein pelleted fish feed was used to feed fish at the specified rate of feeding. At the end of the experiment, growth, weight gain, survival, yield and body composition of fish groups were affected by the treatments. The economic effectiveness also varied among treatments. The most conspicuous attribute of the feeding rates was its lack of influence on growth (g day^?1), weight gain (g per fish), yield (kg ha^?1) or body composition of silver carp. The results of whole‐body proximate analysis indicated that various feeding rates had either an irregular pattern or no effects on the protein and ash gain per 100 g of fish body weight (bw) gain. The most notable exceptions were significant (P < 0.05) increases in body fat and gross energy gains in Nile tilapia, common carp and silver carp accompanied by decreases in percentages of moisture (but not in silver carp) as feeding rate increased. Among the six different feeding levels, feeding to apparent satiation (feed amount was equivalent to 2.67% of fish bw day^?1) appeared to be optimal, as it significantly (P < 0.05) supported the highest fish production, income and net profit compared with all other treatments except for the 3% feeding level, for which the differences in those measurements were comparable.     

Effects of Feeding Diets with and without Fish Meal on Production of Channel Catfish,Ictalurus punctatus,Stocked at Varying Densities

ABSTRACT

Animal protein, generally fish meal, has traditionally been used in the diet of channel catfish. However, our previous research indicates that animal protein is not needed for growing stocker-size catfish to food fish when the fish are stocked at densities typical of those used in commercial catfish culture. Whether this holds when fish are stocked at high densities is not known; thus, we conducted an experiment to evaluate the effect of feeding diets with and without fish meal to channel catfish stocked in earthen ponds at different densities. Two 32% protein-practical diets containing 0% or 6% menhaden fish meal were compared for pond-raised channel catfish, Ictalurus punctatus, stocked at densities of 14,820, 29,640, or 44,460 fish/ha. Fingerling channel catfish with average initial weight of 48 g/fish were stocked into 30 0.04-ha ponds. Five ponds were randomly allotted for each fish meal level?×?stocking density combination. Fish were fed once daily to satiation for two growing seasons. There was a significant interaction between stocking density and fish meal for net production; net production increased in fish fed a diet containing fish meal compared with those fed an all-plant diet at the highest stocking density, but not at the two lower stocking densities. Net production of fish fed diets with and without fish meal increased as stocking density increased. Viewing the main effect means, weight gain decreased and feed conversion ratio increased for fish stocked at the two highest densities, and survival was significantly lower at the highest stocking density. Visceral fat decreased in fish at the two highest stocking densities. Body composition data were largely unaffected by experimental treatment except for a reduction in percentage filet fat in fish at the highest stocking density, and fish that were fed diets containing fish meal had a lower percentage fillet protein and a higher percentage fillet fat. It appears that at stocking densities two to three times higher than generally used, animal protein (fish meal) may be beneficial in the diet of channel catfish. In regard to stocking densities, high stocking results in higher overall production, but the average fish size decreased as stocking density increased.     

The effect of stocking different ratios of common carp, Cyprinus carpio L., and tilapias in polyculture ponds on production characteristics and profitability

Production characteristics and profitability of three carp-tilapia stocking ratios (1:1, 1:2 and 1:5) were compared in a semi-intensive polyculture system. The. experiment was carried out at the same total stocking density of 1 fish m², in nine 1000-m² earthen ponds. Common carp, Cyprinus carpio L., and a tilapia hybrid, Oreochromis niloticus (L.) x 0. aureus (Steindachner), were stocked at a joint density of 900 fish per pond, while grass carp, Ctenopharyngodon idella (Cuvier & Valenciennes), and silver carp, Hypophthalmichthys molitrix (Valenciennes), were each stocked at 50 fish per pond in all treatments. Mean harvested weights of both common carp and the tilapia hybrid were markedly decreased upon the increase in density of their own species. Survival of all four species was over 80% in all three carp-tilapia stocking ratios. The differences in relative profitability of the three carp-tilapia stocking ratios did not exceed 10% on the basis of 1991 prices. However, based on 1994 prices, relative profitability of the 1:2, and particularly, the 1:5 carp-tilapia stocking ratio were 35% and 41% higher than the 1:1 ratio, respectively. This was because of the increase in the price of large carp and tilapia of all sizes, and a decreases in the price of small carp.     

A non‐classical biomanipulation experiment in Gonghu Bay of Lake Taihu: control of Microcystis blooms using silver and bighead carp

A non‐classical biomanipulation experiment was carried out in Gonghu Bay of Lake Taihu in 2009. Silver and bighead carp were stocked in a large fish enclosure to control cyanobacterial blooms. Water quality, plankton abundance, and the intracellular and extracellular microcystins (MCs) in lake water were investigated monthly in 2009. The concentrations of nitrogen nutrients were significantly lower in the fish enclosure than in the surrounding lake, while phosphorus (especially total phosphorus) concentration was higher in fish enclosure. During the blooming period, Cyanophyta contributed to more than 90% of the phytoplankton in the surrounding lake, whereas it represented only 40–80% in the fish enclosure. The phytoplankton and crustacean zooplankton biomasses and the zooplankton/phytoplankton ratios were all significantly lower in the fish enclosure than in the lake. This result suggested that silver and bighead carp can effectively suppress the phytoplankton biomass with the initial stocking density of 7.5 g m^?3 for silver carp and 1.1 g m^?3 for bighead carp, despite a simultaneous decrease in the grazing pressure of the zooplankton on the phytoplankton. During the blooming period, the intracellular and extracellular MCs in the fish enclosure were reduced by 93.8% and 69.8% compared with the surrounding lake. MCs content varied from 0.34 to 18.8 ng (mean 4.8 ng) MC‐LReqg^?1 wet weight in the muscle sample of silver and bighead carp in the experimental enclosure, which suggested that these fish were safe to consume for human. However, the long‐term effects of MCs on aquatic ecosystem and on public health cannot be overlooked.     

太湖梅梁湾大型生态控藻围栏内鲢鳙的生长特征

富营养化湖泊围栏养殖鲢（Hypophthalmichthys molitrix）、鳙（Aristichthys nobilis）控制蓝藻水华在生物操纵示范中得到了广泛应用。在2004和2005年,研究了太湖梅梁湾生态修复区内大型生物控藻围栏中鲢鳙的季节生长特征,分析了影响其生长的因素。结果表明,鲢鳙生长受养殖密度的影响...     

The effect of fish density and species combination on growth and utilization of natural food in ponds

Abstract. Interactions between bottom-feeding fish (common carp, Cyprinus carpio L., and hybrid tilapia) and a filter feeder (silver carp, Hypophthalmichthys molitrix (Valenciennes)) in polyculture were studied in fertilized ponds with no supplementary feeding. The silver carp were stocked at two densities: 1300 and 2600/ha. Growth rate and yield of each of the species were also compared with those in polyculture of bottom feeders alone, and in a monoculture of silver carp alone, at the same densities. The consumption of natural feed as melabolizable energy (ME) was calculated by the energy balance (requirement for maintenance and growth divided by the utilization efficiency).
Increasing the density of silver carp reduced proportionally their own growth rate, due to the limited amount of food. Above a density of about 1000/ha, silver carp inhibit the growth rate of common carp and tilapia. This inhibition was small at 1300 silver carp/ha, but considerable at 2600/ha. However, the presence of bottom feeders increased the growth rate of silver carp at both densities. Calculated natural food consumption showed that growth interactions between species were brought about through the availability of food. The synergistic effect of the bottom-feeding fish on the silver carp is assumed to be due to the upwelling of bottom nutrients to the upper layers of water by the burrowing of the fish in the mud. Combined yield of all species in the polyculture was highest at the density of 1300 silver carp/ha (2116 kg/ha in 156 days). At 2600 silver carp/ha the inhibition of growth rate of silver carp itself, reduced total yield as compared with the lower density.     

太湖梅梁湾大型生态控藻围栏内鲢鳙的生长特征

富营养化湖泊围栏养殖鲢(Hypophthalmichthys molitrix)、鳙(Aristichthys nobilis)控制蓝藻水华在生物操纵示范中得到了广泛应用。在2004和2005年,研究了太湖梅梁湾生态修复区内大型生物控藻围栏中鲢鳙的季节生长特征,分析了影响其生长的因素。结果表明,鲢鳙生长受养殖密度的影响很大,鲢在养殖密度低的2004年和养殖密度高的2005年的日均增重分别为6.07 g和4.30 g,鳙则分别为11.29 g和5.09 g。鳙的生长速度比鲢快,但受密度影响的程度比鲢大。从季节变化来看,鲢属于单峰型生长,生长速度和水温显著正相关;而鳙一年中呈现出2个生长高峰期,分别在5～6月和9～10月,夏季爆发的蓝藻水华对鳙的生长速度有所抑制。为使当年投放的鱼苗在年底能达到出售的商品规格,太湖梅梁湾水域围栏养殖鲢鳙的初始鱼苗投放密度应低于12 g/m3。     

Percid Pond Production Techniques

Tremendous variation in survival and growth of percid fry stocked in ponds was addressed through manipulation of amounts and kinds of fertilizers added and stocking densities of fish. Ponds were filled with water from nearby eutrophic lakes less than one week prior to stocking. Survival in these ponds averaged 64%. whereas ponds filled one month before stocking averaged only 14%. Optimal inorganic fertilization was identified as weekly restoration to 600µg N/L (NH4 +NO₃) and 30µg P/L as PO₄ ^-3. Organic fertilization gave variable results and water qualities. In one experiment, low organic fertilization alone (28 kg alfalfa meal/ha/week) provided survival and growth comparable to optimal fertilization with inorganic nutrients. Although similar in results, inorganic fertilization was more cost effective than the alfalfa meal. Low fish predation from low stocking or survival allowed Daphnia to overgraze algae. This resulted in a crash in both algae and zooplankton in the ponds. Doubling the initial stocking density increased harvests from 150.000 to 300,000 fish/ha and increased yield from 45 to 100 kg/ha.     

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.