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.     

Polyculture of Macrobrachium rosenbergii and Notemigonus crysoleucas

A polyculture study was conducted in southwest Louisiana comparing production of Malaysian prawns, Macrobrachium rosenbergii , in monoculture and polyculture with Golden shiners, Notemigonus crysoleucas .
This test revealed stocking of shiners at 24.7/m² with prawns at 4.4/m² resulted in increased total pond production over monoculture of prawns at 4.4/m² with equal prawn yields in both systems and little increase in labor. Feeding rates were based on prawn biomass. Food conversion ratios ranged from 0.5 to 1.0 in polyculture and 0.9 to 1.1 in monoculture when total production was considered. Prawn production averaged 640 kg/ha in polyculture and 629 kg/ha in monoculture. Mean size of prawns was 19 g in polyculture and 20 g in monoculture. The polyculture of shiners with prawns added an average of 307 kg/ha of the bait fish to pond production.
Shiners did not compete seriously with prawns when stocked at these rates. This practice could result in added revenues to producers culturing these species together.     

Effects of manures and pelleted feeds on survival,growth, and yield of Penaeus stylirostris and Penaeus vannamei in Panama

Brackishwater ponds on the Pacific coast of Panama were stocked at 5/m² with wild-caught postlarval shrimp (0.05 g). Species composition at stocking was 56% Panaeus vannamei, 33% P. stylirostris and 11% P. occidentalis. Experimental treatments were: chicken manure (4500 kg/ha dry weight), cow manure (4500 kg/ha), 25% protein pelleted feed (790 kg/ha) and control (which received no nutrient input). Water was exchanged 5–10% daily throughout the 120-day production period during the 1982 rainy season. Average shrimp yields at harvest, by treatment, were: chicken manure, 262 kg/ha; cow manure, 218 kg/ha; feed, 386 kg/ha; and the control, 160 kg/ha. Average survival for each treatment was 50%, 76%, 58% and 77%, respectively. All P. occidentalis died during the production period. Survival was not significantly different among treatments (P > 0.05). Average weights or shrimp at harvest were 8.72g, 7.32 g, 12.07 g, and 5.98 g, respectively, for the treatments. Manures and feed significantly increased yield over the control (P < 0.002). Feed significantly increased yield over that of the manures (P < 0.0001), while yield for manures did not differ (P > 0.05). A partial budget analysis indicated that a net income for the feed treatment was higher than for chicken manure or cow manure treatments.     

Polyculture of the Giant Malaysian Prawn and the Golden Shiner in Southwestern Louisiana1

Juvenile prawns (Macrobrachium rosenbergii) were stocked at 37,050/ha and golden shiner (Noremigonus crysoleucas) fry at 321,100/ha into 16 earthen ponds at Rockefeller Wildlife Refuge, Grand Chenier, Louisiana. Four replicated treatments were tested: fed prawn monoculture, fed shiner monoculture, fed prawn and fed shiner polyculture, and unfed prawn fed shiner polyculture. The study lasted 149 days. There were no significant differences in growth between prawns fed in monoculture and prawns fed in polyculture (P > 0.05). However, fed prawns grew significantly larger (P < 0.05) than unfed prawns. Prawn survival in all treatments combined averaged 63%. Survival was significantly higher (P < 0.05) for fed prawns than for unfed prawns. Prawn yields averaged 533 kg/ha, when all treatments were combined. Yield was significantly higher (P < 0.05) for prawns grown with shiners and for prawns that received supplemental feed. Growth was significantly higher (P < 0.05) for shiners grown with fed prawns than for shiners grown with unfed prawns. Shiner survival averaged 33% and was significantly higher (P < 0.05) in monoculture than in polyculture. Yield for all ponds averaged 392 kg/ha, with no significant differences between treatments (P > 0.05).     

Preliminary Pond Production of the Red Claw Crayfish,Cherax Quadricarinatus,in the Central United States

The Australian red claw crayfish, Cherax quadricarinatus, has recently attracted attention as a potential candidate for aquaculture in the United States. This paper reports the first experimental yield trials of the red claw crayfish in the central United States. Two earthen ponds (0.30 and 0.31 ha) were stocked with juvenile red claw crayfish at either 3.5 or 7.0 crayfish/m². Crayfish were fed a diet of pelletized shrimp ration supplemented with corn silage. When stocked at 3.5/m₂, red claw crayfish grew from an average weight of 3.0 g to 27.0 g in 97 days; average survival was 79.6%; net yield was 653 kg/ha; and feed conversion was 1.4. When stocked at 7.0/m² red claw crayfish grew from an average weight of 4.1 g to 19.7 g in 99 days; average survival was 70.0%; net yield was 678.9 kg/ha; and feed conversion was 1.8. During the yield trial, temperatures were optimal for growth (25 to 33°C) 60% of the time. These findings are sufficiently encouraging to warrant further trials in locations with a longer growing season, in order to evaluate more fully the potential of the red claw crayfish as a candidate for aquaculture in the United States.     

Effects of Stocking Density and Monosex Culture of Freshwater Prawn Macrobrachium rosenbergii on Growth and Production in Concrete Tanks in Saudi Arabia

Abstract This study was conducted to evaluate the effects of stocking density and monosex culture on growth, survival, yield and feed conversion ratio of freshwater prawn Macrobrachium rosenbergii in concrete tanks. Juvenile prawns with an average weight of 1.8 g were stocked into triplicate tanks at densities of 5, 10, 15 and 20 prawns/m², grown for 168 d and fed a 34% tilapia diet. Stocking density had significant effect on prawns. Final mean body weight decreased with the increasing density, being highest at 5 prawns/m² (29.6 9). and lowest at 20 prawns/m² (17.4 g). Total yield increased from 135 g/m² (1,350 kg/ha) at a density of 5 prawns/m² to 261 g/m² (2,610 kg/ha) at density 15/m^z to 245 g/m² (2,450 kg/ha) at 20/m^z. Feed conversion ratios were high and ranged from 3.7 (5 prawns/m²) to 5.6 (20 prawns/m²).
In monosex culture of freshwater prawns stocked in triplicate tanks at a density of 5 prawns/m² for 112 d, the all-male population had the best growth performance and feed conversion ratio, followed by the mixed-sex and all-female populations. The all-male population had 99% marketable prawns (>20 g) with an average yield of 159 g/m² (1,590 kg/ha); the mixed-sex population had 90% marketable prawns and the yield was 135 g/m^z (1,350 kg/ha); and the all-female population had 75% marketable prawns with an average yield of 108 g/m² (1,080 kgha).     

Double-Cropping Malaysian Prawns,Macrobrachium rosenbergii,and Red Swamp Crawfish,Procambarus clarkii

Prawns, "Macrobrachium rosenbergii," and crawfish, "Procambarus clarkii," were alternatively grown in ponds to determine if they were compatible and if total production could be increased. Brood crawfish were stocked into replicated ponds at rates of 0,60, 120 or 180 kg/ha on 18 April. Water was removed to encourage burrowing. Following this, rice was planted as forage. Post-larval prawns (0.02 g) were stocked 3 July in all ponds at 17,500/ha. Prawns in half the ponds were fed and those in the other ponds were not. Ponds were drained from 7 to 11 October. Prawn production ranged from 157 to 248 kg/ha; survival ranged from 69% to 88%, and average size ranged from 11 to 7 g. There was no significant difference (P > 0.05) between fed and non-fed treatments. The ponds were reflooded and crawfish were harvested by trapping from 15 January to 15 May. The average yield of crawfish ranged from 746 to 1,266 kg/ha. Stocking rate had no effect of crawfish yields (P > 0.25). Total yield, with prawns and crawfish combined, ranged from 1,037 to 1,237 kg/ha. Overall, prawns and crawfish were compatible in rotation. Prawns were a good size for soft shell production during months when crawfish are not available for soft shell production.     

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.     

Evaluation of Various Concentrations of Dietary Protein and Animal Protein for Pond-Raised Channel Catfish Ictalurus punctatus Fed to Satiation or at a Restricted Rate

A factorial experiment was conducted to evaluate effect of dietary protein (28% or 32%), animal protein (0, 3, or 6%), and feeding rate (satiation or >90 kg/ha per d) on production characteristics, processing yield, and body composition of pond-raised channel catfish Ictalurus punctatus . Fingerling channel catfish (average weight: 55 g/fish) were stocked into 60, 0.04-ha ponds at a rate of 18,530 fish/ha. Five ponds were used for each dietary treatment. Fish were fed once daily to satiation or no more than 90 kg/ha per d for 147 d. Fish fed at a rate of >90 kg/ha per d consumed about 85% of the amount of feed consumed by fish fed to satiation. Dietary protein did not affect the total amount of feed fed, amount of feed consumed per fish, weight gain, feed conversion efficiency, or fillet protein. Animal protein had no effect on the total amount of feed fed, amount of feed consumed per fish, weight gain, or fillet protein and ash. Fish fed a diet containing 6% animal protein converted feed more efficiently than fish fed diets containing 0% and 3% animal protein. Fish fed to satiation daily consumed more feed, gained more weight, converted the feed less efficiently, and had a higher carcass yield, a higher level of visceral fat as compared to fish fed at a rate of >90 kg/ha per d. Feeding rate had no effect on fillet protein. Results from this study indicated that both a 28% and a 32% protein diet with or without animal protein provided the same growth rate of channel catfish raised in ponds from fingerlings to marketable size if feed is not restricted below a maximum rate of 90 kg/ha per d. Even though there were some interactions among the three factors evaluated, dietary protein levels of 28% to 32% and animal protein levels of 0% to 6% do not appear to markedly affect carcass yield and fillet proximate composition of pond-raised channel catfish.     

Effects of Stocking Density and Feed on Pond Production Characteristics and Revenue of Harvested Freshwater Prawns Macrobrachiurn rosenbergii Stocked as Size-Graded Juveniles1

A nursery-reared population of juvenile freshwater prawns (Macrobrachium rosenbergii) averaging 0.11 ± 0.058 g was size graded through a 4-mm bar grader producing a numerically 53% upper size population (0.25 ± 0.086 g). These were stocked into triplicate earthen ponds (0.04–0.07 ha each) at densities of 39,540, 59,300 and 79,100/ha, grown for 131 to 134 d, and fed a specially formulated diet. An additional three ponds were stocked at 39,540/ha and fed a commercial sinking catfish feed. Density had a significant effect on average whole body wet weight at harvest but no significant effect on either total yield, survival, or feed conversion. Mean wet weight was significantly higher for prawns stocked at 39,540/ha (34.3 g) than that for those stocked at either 59,300/ha (26.7 g) or 79,100/ha (263 g). The direct relationship between the percentage of small males and increasing density usually seen with ungraded populations was not evidenced in the size-graded populations. Average total yield ranged from 1,041 to 1,662 kg/ha for stocking densities from 39,540 to 79,100/ha. Differences in overall mean wet weight resulted from differences in mean wet weights for orange claw and no claw males and berried and open females, not from differences in morphotype distributions. These differences resulted in significantly higher percentages of tails within the larger count categories and higher revenues for prawns stocked at 39,540/ha. Feed type had no significant effect. Projected net revenues suggest that prawns need to be marketed and sold as a whole product.     

The Effect of On-Farm Production of Various Sizes of Stocker Caffish Ictalurus punctatus on Farm Profitability.

Abstract— The effect of on‐farm production of various sizes of stocker catfish Ictalurus punctatus on farm profitability was compared to profitability of understocking fingerlings directly into multiple‐batch growout production. Vat‐graded catfish averaging 9 × 2 g (10 cm total length) and 27× 8 g (15 cm total length) were stocked into eight 0.1‐ha ponds at 100,000 fingerlingdha. Fish were fed once daily to apparent satiation and harvested 210 d after stocking. There were no significant differences (P < 0.10) in yield, feed conversion ratio (FCR), and survival across treatments. Mean gross yield (× SD) was 9,469 × 852 kg/ha and 8,846 × 2,099 kg/ha; net yield averaged 8,531× 885 and 6,374 × 2,189 kg/ha; FCR averaged 1.8 × 0.1 and 2.4 × 0.7, and survival averaged 38 × 7% and 26 ×11% for the 10‐cm and 15‐m fingerling stocking treatments, respectively. While experimental survival was low, varying survival rates of stockers in the economic analysis did not affect selection of the most profitable stocking strategies. The 15‐cm hgerlings reached a size significantly larger (361× 81 g or 32.8 × 2.2 cm) than the 10‐cm fingerlings (255 × 28 g or 29.6 × 1.4 cm) (P < 0.07). Whole‐farm budgets were developed based on three sizes of farm (65, 130, and 260 ha) and eight production strategies involving the purchase of different sizes of fingerlings for either understocking growout ponds (6,12, or 37‐g fingerlings) or to grow into stockers (114,135, 176, 255, or 361 9). Purchasing 37‐g advanced fingerlings for multiple‐batch production was the most profitable strategy for the three sizes of farm. The second most important profit‐maximizing strategy for larger farm sizes was single‐batch production with 255‐g stockers produced on‐farm, but purchasing 12‐g fingerlings to stock into multiple‐batch production was the second most profitable strategy for the smallest farm. Sensitivity analysis indicated that the results were robust to variation in survival, prices, and other production characteristics. Risk analysis indicated that purchasing 37‐g advanced fingerlings for multiple‐batch production was associated with the lowest levels of economic risk for growout production.     

Growth and Survival of the Australian Red Claw Crayfish Cherax quadricarinatus at Three Densities in Earthen Ponds

Australian red claw crayfish Cherax quadricarinatus were cultured in nine 0.02-ha earthen ponds at densities of l/m², 3/m² and 5/m² for 158 d. Average weight at stocking was 3.2 g. All ponds were provided with a combination of hay and corn silage at a rate of 500 kg/ha per month and a commercial crayfish ration fed at 5%, decreasing to 2% of estimated biomass/d during the growing season. Overall survival rate was 72%, and did not differ among treatments. Final yields and average weights varied significantly with stocking density. Red claw averaged 67 g with an average pond yield of 475 kg/ha at l/m². At 3/m² and 5/m², red claw averaged 48 g and 38 g, respectively, and yielded 1,020 kg/ha and 1,422 kg/ha, respectively.     

Evaluation of Distillers Dried Grains with Solubles as an Ingredient in Diets for Pond Culture of the Freshwater Prawn Macrobrachium rosenbergii

Distillers dried grains with solubles (DDGS) were evaluated as an ingredient in practical diets for pond culture of the freshwater prawn Macrobrachium rosenbergii . Juvenile prawns averaging 0.66 ± 0.47 g were stocked into nine 0.02 ha ponds at 19,760/ha. Three isonitrogenous diets (29% crude protein) containing 0, 20, or 40% DDGS were fed to shrimp in triplicate ponds. Average yield, survival, individual weight, and feed conversion did not differ significantly ( P > 0.05) among treatments. When averaged over the three diets, results were: yield, 833 kg/ha; survival, 75%; individual weight, 57 B; and feed conversion, 3.1. It appears that DDGS is a suitable ingredient for use in practical diets for freshwater prawns at levels of up to 40% of the total formulation, when prawns are stocked at the densities used in this study.     

Use of Alfalfa Hay, Compared to Feeding Practical Diets Containing Two Protein Levels, on Growth, Survival, Body Composition, and Processing Traits of Australian Red Claw Crayfish, Cherax quadricarinatus, Grown in Ponds

Juvenile red claw, Cherax quadricarinatus, were obtained from a commercial supplier and stocked into twelve 0.04‐ha ponds with an average water depth of approximately 1.1 m at a rate of 1100 red claw per pond (27,170 red claw/ha). Mean stocking weight (±SD) was 6.25 ± 3.0 g. Three replicate ponds were randomly assigned to each of the four treatments. In Treatment 1 (TRT1), red claw were stocked into ponds to which dried alfalfa hay (forage) was added at a rate of 500 kg/ha/mo; Treatment 2 (TRT2) consisted of red claw being fed a prepared diet containing 13% protein; in Treatment 3 (TRT3), red claw were fed a diet containing 13% protein at which had dried alfalfa hay been added at a rate of 500 kg/ha/mo; and in Treatment 4 (TRT4; control), red claw were fed a complete diet containing 28% protein. Water quality measurements were made three times weekly for dissolved oxygen and temperature (am , pm ), pH, total ammonia nitrogen, nitrite, and alkalinity averaging 7.17 mg/L, 8.96 mg/L, 25.5 C, 27.3 C, 8.68, 0.39 mg/L, 0.012 mg/L, and 106.5 mg/L, respectively. After 113 d, the final mean weight of red claw fed TRT3 was significantly (P < 0.05) higher (68.10 g) compared to that of red claw fed hay only (49.40 g) but not different from red claw fed TRT2 (56.03 g) and TRT4 (62.10 g). Likewise, red claw fed TRT3 had significantly higher percent weight gain (990%) compared to that of red claw fed hay only (690%) but not different from TRT2 (796%) and TRT4 (893%). Feed conversion ratio of TRT2, TRT3, and TRT4 and percent survival among all treatments did not differ significantly (P > 0.05), averaging 2.85 and 66.8%, respectively. Total yield of red claw fed TRT3 and TRT4 (968 and 952 kg/ha) was significantly (P < 0.05) higher compared to that of red claw fed hay only (617 kg/ha) but did not differ from red claw fed TRT2 (882 kg/ha). Tail meat yield of male red claw in TRT3 was significantly (P < 0.05) higher (17.3 g) compared to that of male red claw in TRT1 (12.7 g) and TRT2 (14.9 g) but not significantly different (P > 0.05) from male red claw in TRT4 (16.9 g). Tail meat yield of female red claw in TRT3 and TRT4 was significantly (P < 0.05) higher (14.2 and 13.9 g, respectively) compared to that of female red claw in TRT1 (10.5 g) and TRT2 (10.4 g). Tail muscle proximate compositions showed no significant differences (P > 0.05) in protein (wet weight basis) between males and females among treatments (diet) which averaged 16.2 and 14.6%; however, there were little to no significant differences in fat and ash between males and females among treatments. Results from this study indicate that pond‐cultured red claw stocked at 27,170 red claw/ha can be fed a practical diet containing 13% protein, with or without forage (alfalfa hay), compared to red claw fed a complete diet containing 28% protein; however, if alfalfa hay is added to the pond at 500 kg/ha/mo as the sole source of added nutrients, growth is reduced. Therefore, the use of alfalfa hay, in combination with a low‐protein pelleted diet may be a production method for pond‐grown red claw that may reduce costs for producers and thereby increase profits.     

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.     

Relative growth,survival and harvestability of bighead carp,silver carp,and their reciprocal hybrids

Growth and survival in the primary rearing phase (42 days) for bighead carp, silver carp, bighead × silver carp (BHC × SC), and silver × bighead carp (SC × BHC) in ponds and concrete tanks stocked at 370 500 fry/ha were studied. Mean survival for fishes in ponds was 93%, that in tanks was 73%. Yields among all fishes averaged 338 kg/ha. The growth rates of fishes in ponds were similar; in tanks, silver carp grew faster than the bighead carp.Growth, survival, and harvestability by seine during the secondary rearing phase (60-day duration) for the same groups of fish were studied. Fingerlings (0.9 g mean weight) were stocked in earthen ponds at 49 400 fish/ha and 98 800 fish/ha. Mean survival of fishes at low stocking rate was 77%, similar to that (71%) for the high stocking rate. Fish yields were similar at the low stocking rate. At the high rate, the BHC × SC yield (846 kg/ha) was greater than the SC × BHC yield (582 kg/ha). The BHC × SC and SC × BHC had greater mean weights at low stocking rate than at high stocking rate. The mean weights for bighead carp were similar at both rates. Bighead carp and the reciprocal hybrids were more easily harvested by seine than silver carp.     

Stable Isotopic Evaluation of the Relative Assimilation of Natural and Artificial Foods by Golden Shiners Notemigonus crysoleucas in Ponds

Stable carbon isotope ratios (δ¹³C) were used to estimate the relative contributions of natural and prepared feeds to the nutrition of golden shiners Notemigonus crysoleucas in ponds. Concurrent feeding trials were conducted in tanks (110 L) and ponds (0.04 ha) to determine the response of golden shiners to three isotopically distinct prepared diets both in the presence (pond) and absence (tank) of natural food. Seston was the primary indicator of the δ¹³C of natural foods available in the ponds, but δ¹³C's of free-swimming, unfed golden shiners provided an additional index. Fish receiving experimental diets were maintained in floating nets within the same ponds. After 6 wk, fish in tanks fed all three diets had acquired the diet label to some degree, while fish in ponds also tracked their respective feeds except for those fed diet 3. This diet contained a large amount of corn meal, which appeared to be poorly assimilated by golden shiners. The use of natural foods by golden shiners fed all three prepared feeds ranged from 40–83% and was inversely correlated with the relative assimilation of the prepared feeds.     

Monoculture of Indian freshwater prawn,Macrobrachium malcolmsonii (Milne Edwards)

The paper describes the growth and production performance of the Indian freshwater prawn, Macrobrachium malcolmsonii, in a monoculture system. At a moderate stocking density of 60 000 ha, survival of prawns ranged from 44.2 to 57.2%. Wide size variation was noted, with only 27.9–36.1% of the prawns attaining market size. Males grew faster than females, with average lengths and weights of 136–152 mm, 44–63 g and 124–135 mm, 31–38 g, respectively, recorded during multiple harvests in a 390-day growout period. By adopting a continuous culture system with periodic harvesting, total production of M. malcolmsonii reached 534.2–690.4 kg/ha with a 475.3–605.4 kg/ha marketable yield in 390 days.     

Intensive polyculture of common carp,Cyprinus carpio L., silver carp,Hypophthalmichthys molitrix (Val.) and black buffalo,Ictiobus niger (Raf.)

Intensive polyculture was carried out with common carp, silver carp and black buffalo fed a mixture of 60% pellets (with protein level of 25%) and 40% barley, along with mineral and organic fertilization. Two stocking patterns were tested. From pattern I, in pond 1 (total stocking density 4600 fish/ha), the yield of fish after 180 days was 3538 kg/ha, with standard weight (above 500 g), at a food conversion ratio of 2.36. From pattern II, in pond 2 (total stocking density 9200 fish/ha), the respective figures were 5022 kg/ha and 2.56.An economic comparison of several polyculture trials showed that buffalo fish (bigmouth and black) at a stocking rate of 2000 fish/ha, grown with common carp (2500 fish/ha) and silver carp (1200–1500 fish/ha), gave the best breeding and economic results (a profit of 962 levs/ha or 0.27 lev/kg). The buffalo fish have excellent organoleptic properties and are considered a delicacy favoured on the Bulgarian market.     

MALAYSIAN PRAWN CULTURE IN BRACKISH WATER PONDS IN LOUISIANA

Beginning on May 13, 1980, prawns were cultured at the Rockefeller Wildlife Refuge for 140 days from postlarvae and fed. Production in ponds receiving Ralston Purina Experimental Marine Ration #25 averaged 408 kg/ha, 619 kg/ha and 510 kg/ha for the respective replicated stocking densities of 2.5/m², 4.9/m² and 7.4/m². Average feed conversion factors were 1.0, 1.0 and 1.5. Average prawn weights at harvest decreased with increased stocking density and were 21 g, 17 g and 12 g, respectively. Production per pond ranged from 390 kg/ha to 832 kg/ha. An average of 77% of prawns stocked at 2.5/m² exceeded 115 mm TL whereas the stocking densities of 4.9/m² and 7.4/m² yielded only 32% and 31% over 115 mm. Extra postlarvae remaining after the stocking requirements for the feeding study were met permitting additional tests. Stocking rates selected for these additional studies were 1.2/m², 2.5/m² and 3.7/m². Prawns in these ponds received no supplemental feed and yielded harvests of 124 kg/ha, 224 kg/ha and 292 kg/ha, respectively. These treatments, the first two of which were not replicated, resulted in production similar to that of an earlier study of prawn production on natural forage in brackish ponds at this facility. Average prawn sizes at harvest were 18 g, 15 g and 12 g, and were inversely related to stocking densities.