Effect of Stocking Density on Growth and Water Quality for Largemouth Bass Micropterus salmoides Growout in Ponds

Juvenile largemouth bass Micropterus salmoides , trained to accept artificial diets, were stocked into six 0.04-ha ponds at stocking densities of either 6,175 or 12,350 fish/ha. Fish were fed a floating custom-formulated diet, containing 44% protein, once daily to satiation for 12 mo (May 1994–May 1995). At final harvest, the total yield of fish was significantly greater (P < 0.05) and feed conversion ratio (FCR) was significantly lower, for bass stocked at the higher density (4,598 kg/ha and 2.3, respectively) than when stocked at the lower density (2,354 kg/ha and 3.3, respectively). There was no significant difference (P > 0.05) in average weight, length, or survival of bass stocked at the two densities. Averaged over the study period, there were no significant differences (P > 0.05) in total ammonia-nitrogen (TAN), nitrite-nitrogen, or un-ionized ammonia concentrations in ponds in which bass were stocked at the two densities. These data indicate that largemouth bass of the size used in this study are amenable to pond culture at densities of at least 12,350 fish/ha and that higher stocking densities may be possible.     

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.     

Evaluation of a Barrier Confinement System for Channel Catfish,Ictalurus punctatus,Production

An in‐pond confinement system to separate channel catfish, Ictalurus punctatus, by size within a single pond provides an opportunity for improved growth of understocked fish in ponds with larger market‐sized fish. A barrier of polyvinyl chloride–coated galvanized wire mesh was constructed in five 0.10‐ha earthen ponds to partition the pond into one‐third and two‐third sections, while five other 0.10‐ha ponds were left as traditional open ponds for a control. To evaluate catfish performance in this confinement system, fingerlings (25 g) were stocked at 14,820/ha into the smaller one‐third section of the barrier and carryover fish (408 g) at 2580 kg/ha into the larger two‐third section of the barrier. The control ponds were stocked with the same sizes and numbers of fish in a traditional earthen pond without a barrier. Yield, survival, feed conversion ratio (FCR), growth, and economics were compared between treatments. Fingerling yields were greater in the barrier system that allowed fingerlings to be separated physically from larger carryover fish. There were no differences in yield of carryover fish, survival, FCR, or growth between the control and the barrier ponds. Partial budget analysis revealed a positive net change of $367/ha or $38,125 for a 104‐ha catfish farm (at a market price of $1.54/kg of additional stockers produced). The value of the greater weight of understocked fish produced in the barrier system was greater than the annualized cost of installing the barrier, for farmers raising fish in multiple batch. Thus, on an experimental basis, the confinement system was economically profitable; however, trials on commercial farms are needed to evaluate performance on a larger scale.     

Effects of Pond Renovation on White River Crayfish,Procambarus acutus acutus Production

Abstract

The effects of renovation on the production of white river crayfish, Procambarus acutus acutus were evaluated in ten 0.1-ha earthen ponds. The bottoms and levees of five ponds were reshaped with heavy equipment prior to planting sorghum-Sudan grass forage during the de-watered phase of the culture cycle. Five non-renovated ponds served as a control. The mean total length (TL) of the crayfish harvested from renovated ponds was significantly larger than those crayfish harvested from non-renovated ponds. The renovated pond harvest contained an estimated 43.2% carryover crayfish (>95 mm TL) in comparison to 7.6% in the harvest from non-renovated ponds. By weight, carryover crayfish constituted an estimated 69.3% of the harvest from renovated ponds, compared to 21.0% from non-renovated ponds. No difference was observed in the harvest between treatments; however, the low proportion of young-of-the-year crayfish in the renovated pond harvest may adversely impact future production.     

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.     

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.     

Pond production of Pacific white shrimp,Litopenaeus vannamei,fed grain distillers dried yeast

The objective of this study was to demonstrate the feasibility of four diets formulated to contain increasing levels (0, 50, 100 and 150 g kg^?1 of diet) of grain distillers dried yeast (GDDY) in production diets for Litopenaeus vannamei, reared in outdoor tanks or production ponds. The production pond trial was carried out in 16, 0.1‐ha ponds using four replicates per diet. Juvenile shrimp (38.1 ± 4.26 mg, initial weight) were stocked at 30 shrimp m^?2 for a 16‐week period. The same four diets and a commercial reference diet were offered to shrimp maintained in outdoor tanks over a 12‐week period. A total of 20 tanks were stocked with juvenile shrimp (3.05 ± 0.22 g, initial weight) obtained from production ponds at a density of 30 shrimp per tank (40 shrimp m^?2). At the conclusion of these trials, mean final weight ranged from 19.77 to 23.05 g, yield ranged between 4760 and 5606 kg ha^?1, survival ranged from 69.6% to 89.4%, and feed conversion ratio (FCR) was between 1.02 and 1.23. Shrimp reared in the outdoor tanks confirmed the results of the pond trial. Mean final weight ranged between 18.12 and 18.97 g, survival ranged from 93.3% to 98.3%, and FCR was between 1.25 and 1.29. In both trials, there were no significant differences regarding mean final weight, FCR and survival among dietary treatments. Based on this study, GDDY up to 150 g kg^?1 of diet can be used in L. vannamei commercial feed formulation.     

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.     

The effect of varying dietary protein level on the growth, food conversion, protein utilization and body composition of tropical catfish Mystus nemurus (C. & V.) cultured in static pond water system

Tropical catfish, Mystus nemurus (C. & V.) (25.89 ± 0.7 g) were stocked semi-intensively in 0.03-ha earthen ponds at the rate of 10 000 ha”^-1 and fed six iso-energetic practical diets ranging from 27% to 50% protein for 8 weeks. Each diet was fed in three replicate ponds twice daily to satiation. Experimental fish were also reared extensively, in control ponds, without supplementary feed. Fish fed the 42% protein diet had the highest standing crop, weight gain and protein utilization values and the differences from other diets were statistically significant (P > 0.05). Protein efficiency ratio (PER) decreased as dietary protein increased. The experiment indicated that natural food organisms contributed to some degree if not significantly to the catfish production. Weight gain, food conversion ratio (FCR). PER and SGR (specific growth rate) indicated that a 42% protein diet with digestible protein-to-energy ratio (D/E) of 27.57 mg kj^_1 produced maximum growth in the static pond system.     

Nursery rearing of the Asian catfish, Clarias macrocephalus (Günther), at different stocking densities in cages suspended in tanks and ponds

Growth and survival of hatchery‐bred Asian catfish, Clarias macrocephalus (Günther), fry reared at different stocking densities in net cages suspended in tanks and ponds were measured. The stocking densities used were 285, 571 and 1143 fry m^?3 in tanks and 114, 228 and 457 fry m^?3 in ponds. Fish were fed a formulated diet throughout the 28‐day rearing period. Generally, fish reared in cages in ponds grew faster, with a specific growth rate (SGR) range of 10.3–14.6% day^?1, than those in cages suspended in tanks (SGR range 9–11.3% day^?1). This could be attributed to the presence of natural zooplankton (copepods and cladocerans) in the pond throughout the culture period, which served as additional food sources for catfish juveniles. In both scenarios, the fish reared at lower densities had significantly higher SGR than fish reared at higher densities. In the pond, the SGR of fish held at 228 and 457 m^?3 were similar to each other but were significantly lower than those of fish held at 114 m^?3. The zooplankton in ponds consisted mostly of copepods and cladocerans, in contrast to tanks, in which rotifers were more predominant. Per cent survival ranged from 85% to 89% in tanks and from 78% to 87% in ponds and did not differ significantly among stocking densities and between rearing systems. In conclusion, catfish nursery in cages suspended in tanks and ponds is density dependent. Catfish fry reared at 285 m^?3 in tanks and at 114 m^?3 in ponds had significantly faster growth rates than fish reared at higher densities. However, the desired fingerling size of 3–4 cm total length for stocking in grow‐out culture can still be attained at stocking densities of 457 m^?3 in nursery pond and 571 m^?3 in tanks.     

Evaluation of alternative pond production systems for raising largemouth bass,Micropterus salmoides

This study evaluated three different pond‐based production systems for raising largemouth bass, Micropterus salmoides, for the food fish market, using nine 0.04‐ha ponds. Treatments included traditional ponds (TP), intensively aerated ponds (IAP), and split‐pond systems (SPS). TP and SPS ponds were aerated at 9.3 kW/ha, while IAP was aerated at 18.6 kW/ha. TP was stocked at 7,500 fish per ha (three replicates per treatment), and the other two production systems (SPS, IAP) were stocked with 12,500 fish per ha. Feed‐habituated advanced fingerlings (128 ± 47.6 g mean individual weight) were cultured for 157 days. Fish were fed a formulated diet (42% protein, 16% lipid) four times a day, feeding with a maximum allowance of 3% of total body weight and readjusted to the initial body weight biweekly. Fish raised in the SPS displayed a significantly lower specific growth rate, lower individual final weight, and lower weight gain, but the biomass gained was significantly higher than TP but not IAP. Final biomass gained was 50% higher in the SPS and IAP than in the TP. Survival rate and feed conversion ratio were not significantly different among treatments and ranged from 71 to 79% and 1.64 to 2.14, respectively.     

Effects of 28% Protein Diets Differing in Quality on Channel Catfish Performance,Processing Traits,and Production Economics in a Multi-Batch System

Three 28% protein feeds (premium, standard, or a low-cost diet) were fed to channel catfish in a pond study to compare growth, production, and costs as a follow up to similar work with 32% protein feeds. Twelve 0.1-ha earthen ponds at the University of Arkansas at Pine Bluff (UAPB) Aquaculture Research Station were stocked with carryover fish (0.39 kg mean weight) at 5,860 fish/ha and fingerling catfish (mean individual weight of 15.4 g) at 12,500 fish/ha. Total yield (gross and net) did not differ between fish fed the premium as compared to the standard diet, but that of the premium diet was significantly higher than that of fish fed the low-cost diet. The feed conversion ratio (FCR) did not differ between fish fed the premium and standard diets, but was lower than the FCR of fish fed the low-cost diet. There were no differences found in processing yields among treatments. Given the lower cost of the 28% standard diet and yields equivalent to those of the 28% premium diet, the 28% standard diet was economically preferable to the other diets tested.     

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.     

Effect of Dietary Protein Concentration and Feeding Rate on Weight Gain,Feed Efficiency,and Body Composition of Pond-Raised Channel Catfish Ictalurus punctatus1

Two experiments were conducted in earthen ponds to evaluate the effect of dietary protein concentration and feeding rate on weight gain, feed efficiency, and body composition of channel catfish. In Experiment 1, two dietary protein concentrations (28% or 32%) and four feeding rates (≤ 90. ≤ 112, ≤ 135 kg/ha per d, or satiation) were used in a factorial arrangement. Channel catfish Ictalurus punctatus fingerlings (average size: 27 g/fish) were stocked into 0.04-ha ponds at a rate of 24,700 fish/ha. Fish were fed once daily at the predetermined maximum feeding rates for 282 d (two growing seasons). In Experiment 2, three dietary protein concentrations (24, 28, or 32%) and two feeding rates (≤ 135 kg/ha per d or satiation) were used. Channel catfish (average size: 373 g/fish) were stocked into 0.04-ha ponds at a rate of 17,300 fish/ha. Fish were fed once daily for 155 d. In both experiments, five ponds were used for each dietary treatment. Results from Experiment 1 showed no differences in total feed fed, feed consumption per fish, weight gain, feed conversion ratio (FCR), or survival between fish fed diets containing 28% and 32% protein diets. As maximum feeding rate increased, total feed fed, feed consumption per fish, and weight gain increased. There were no differences in total feed fed, feed consumption per fish, or weight gain between fish fed at ≤ 135 kg/ha per d and those fed to satiation. Fish fed the 28% protein diet had a lower percentage carcass dressout and higher percentage visceral fat than fish fed the 32% protein diet. Dietary protein concentrations of 28% or 32% had no effect on fillet protein, fat, moisture, and ash. Feeding rate did not affect FCR, survival, percentage carcass dressout, or fillet composition, except fillet fat. As feeding rate increased, percentage visceral fat increased. Fish fed at ≤ 90 kg/ha per d had a lower percentage fillet fat than fish fed at higher feeding rates. In Experiment 2, dietary protein concentration or maximum feeding rate did not affect total feed fed, feed consumption per fish, weight gain, FCR, or survival of channel catfish. Feeding rate had no effect on percentage carcass dressout and visceral fat, or fillet composition. This was due to the similar feed consumption by the fish fed at the two feeding rates. Fish fed the 24% protein diet had lower carcass dressout, higher visceral fat and fillet fat than those fed the 28% or 32% protein diet. Results from the present study indicate that both 28% and 32% protein diets provide satisfactory fish production, dressed yield, and body composition characteristics for pond-raised channel catfish fed a maximum rate of 90 kg/ha per d or ahove.     

Production and Processing Trait Comparisons of Channel Catfish,Blue Catfish,and Their Hybrids Grown in Earthen Ponds

Fingerling HS‐5 channel catfish, Ictalurus punctatus, NWAC 103 channel catfish, D&B blue catfish, Ictalurus furcatus, HS‐5 female channel × D&B male blue catfish F₁ hybrids, and NWAC 103 female channel × D&B male blue catfish F₁ hybrids were stocked into twenty‐five 0.04‐ha earthen ponds at 12,500 fish/ha and grown for 277 d. Fish were fed daily at rates from 1.0 to 3.0% biomass based on feeding activity and temperature and adjusted weekly assuming a feed conversion ratio (FCR) of 1.8 and 100% survival. At harvest, 40 fish from each pond were sampled, and all other counted and weighed. Mean survival, growth rate indexes (a), FCR, and skin‐on fillet percentages were not significantly different. Mean harvest weights and net production were higher for HS‐5 channel and its hybrid than for the NWAC 103 channel, NWAC 103 hybrid, and D&B blue catfish, partially because of their larger mean stocking weights. D&B blue catfish was more uniform in size than NWAC 103 channel and NWAC 103 hybrid. D&B blue catfish was the easiest to seine. HS‐5 hybrids and NWAC 103 hybrids had lower mean head percentage and a better processing yield than their parent channel catfish.     

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.     

Preliminary Comparisons of the Native Penaeus setiferus and Pacific P. vannamei White Shrimp for Pond Culture in South Carolina, USA

Two pond experiments were conducted at the Waddell Mariculture Center to compare production characteristics of the native Penaeus setiferus and Pacific P. vannamei white shrimp in South Carolina. In 1985, 7–9 day old postlarval P. setiferus were stocked in one 0.1 and one 0.25 ha ponds, while P. vannamei of the same age were stocked in one 0.1 and one 0.25 ha ponds, while P. vannamei of the same age were stocked in one 0.1, one 0.25, and one 0.5 ha ponds. Both species were stocked at 12 shrimp/m². The shrimp were fed a 25% protein commercial food and harvested by draining after 147 d. Sarvival in all ponds was > go%, but growth and production of the P. setiferus were considerably lower than values obtained for P. vannamei: 12.8 g and 1,555 kg/ha/crop for P. satiferus versus 19.7 g and 2,477 kg/ha/crop for P. vannamei. In 1989, duplicate 0.1 ha ponds were stocked with P. setiferus and P. vannamei at 60 shrimp/m², and two additional 0.1 ha ponds were stocked with P. setiferus at 40/m². The P. setiferus postlarvae were produced at the Waddell Center from captive-reared and wild South Carolina brood stock. Rearing procedures involved paddlewheel aeration (10 hp/ha), regular water exchange (averaging 16–21%/d in all ponds), and use of a 40% protein feed. Due to the availability of postlarvae, the various treatments were stocked at different times. Both P. setiferus treatments were reared for 145 d, while the P. vannamei were reared for 165 d. P. setiferus at the 40/m² density attained mean size, survival, and standing crop biomass at harvest of 13.5 g, 97.5% and 5,259 kg/ha/crop, respectively. The 60/m²P. setiferus treatment was stocked 2 wk earlier and yielded 15.2 g mean weight, 87.5% survival, and 7,995 kg/ha/crop at harvest. The P. vannamei 60/m² treatment, which was stocked 3 wk earlier than any of the P. setiferus, produced mean size, survival and standing crop biomass at harvest of 17.1 g, 69.5% and 7,187 kg/ha/crop. Both survival and production levels would have been higher had not one replicate experienced a partial mortality due to a feeding accident. The 1989 study yielded what is thought to be the highest production levels yet achieved with P. setiferus in pond culture. These results suggest that P. setiferus may be a viable alternative to P. vannamei for intensive cultivation in the continental U.S. when P. vannamei are unavailable. Further evaluation of this potential is needed.     

Comparisons of Two By-Products and a Prepared Diet as Organic Fertilizers on Growth and Survival of Larval Paddlefish,Polyodon spathula,in Earthen Ponds

Two agro-industrial by-products, rice bran (RB) and distillers dried solubles (DS), and a prepared diet (PD) were evaluated as organic fertilizers for the production of juvenile paddlefish in nine 0.02-ha earthen ponds over a 40-day culture period. Paddlefish yield from ponds fertilized with RB (209 kg/ha) was significantly greater (P≤0.05) than that from ponds fertilized with DS (129 kg/ha), but it was not significantly greater than yields from ponds fertilized with PD (258 kg/ha). Fish survival from ponds fertilized with PD (79%) was significantly higher than from ponds fertilized with RB (55%) or DS (50%). There was no significant difference in survival between ponds fertilized with RB and DS. Secchi disk visibilities in ponds fertilized with RB were significantly lower than in ponds fertilized with DS and PD. Relatively low Secchi disk visibilities in RB-fertilized ponds were because of a brown stain or coloration which reduced sunlight penetrationa and growth of filamentous algai, not observed in Ds- or PD-fertilized ponds. Larvae congregated in areas where PD was being applied, whcih suggested direct feeding on PD. Paddlefish did not respond when RB and DS were applied to ponds. Cost per juvenile paddlefish raised in ponds fertilized with RB was $0.004, cheaper than $0.011 for fish raised in ponds fertilized with PD or DS. Rice bran is the recommended agro-industrial by-product to raise juvenile paddlefish greater than 120 mm total length based on improved fish yields, pond water quality, and lower cost per fish. The prepared diet may be used not only as an organic fertilizer, but also as a supplemental feed.     

Effects of Stocking Density on Growth of Tilapia nilotica Cultured in Cages in Ponds

Reported maximum carrying capacities of Tilapia nilotica reared in cages are Iow ranging from 10 to 70 kg/m³. This may be related to total numbers of caged fish reared in a body of water and not simply density per cage volume. An experiment was conducted to demonstrate such effects.
Sixteen cages in a 0.77 ha pond were stocked with T. nilotica at either 250, 500, 750, or 1,000 fish/cage for a total of 12,987 fish/ha. One cage in each of four 0.13 ha ponds was stocked with either 250 or 1,000 fish/cage for a total of 1,923 or 7,692 fish/hectare, respectively. Fish were fed a 32% protein diet at equal rates for 169 days. In the 0.77 ha pond, yield per cage was positively correlated with stocking density, while individual mean weights were negatively correlated with stocking density. However, among equal densities per cage between ponds, fish in the 0.13 ha ponds gained about 26% more than in the 0.77 ha pond. An interaction of the effects of density per cage volume and per pond area may have occurred.     

Production Characteristics of Rainbow Trout,Oncorhynchus mykiss and Brook Trout,Salvelinus fontinalis Under Seasonal Pond Conditions

Abstract

The production characteristics of juvenile rainbow trout, Oncorhynchus mykiss and brook trout, Salvelinus fontinalis were compared under winter pond conditions. Juvenile rainbow trout (55.1 ±1.5 g) and brook trout (28.9 ±0.4 g) were stocked at a density of 8,750 fish/ha into six 0.04-ha ponds. After 163 days, survival, growth, and feed conversion were similar (P >0.05). The results of this study suggest that brook trout may attain growth rates similar to rainbow trout under winter pond conditions in temperate regions of North America.