Production of Nile Tilapia Oreochromis niloticus and Freshwater Prawn Macrobrachium rosenbergii Stocked at Different Densities in Polyculture Systems in Brazil

Abstract.— The effect of stocking prawns Macrobrachium rosenbergii at increasing densities in ponds with Nile tilapia Oreochromis niloticus reared at low density was evaluated. Twelve 0.01-ha earthen ponds were stocked with 1 tilapia/m² and 0, 2, 4, or 6 postlarvae prawn/m². Three replicates were randomly assigned to each prawn density. Postlarval prawns were stocked a week prior to tilapia juveniles and both were harvested 175 d after the beginning of the experiment. Tilapia final average weight, survival, production, and food conversion rates did not differ significantly among treatments ( P > 0.05); the averages were 531 g, 67%. 3,673 kg/ha, and 1.91, respectively. Prawn survival rates did not differ for the three stocking densities (mean 90%). However, final weight and production were significantly different ( P < 0.05) as follows: 34.0, 23.0, and 14.7 g and 639, 909, and 818 kg/ha, respectively for 2. 4, and 6 prawns/m² densities. Stocking densities up to 6 prawn/m² did not affect tilapia production and required neither additional feeding nor significant changes in management. The polyculture system allowed an increase in total production with the same amount of supplied feed, thus improving the system sustainability.     

Effect of population density on the growth, feed and protein conversion efficiency and biochemical composition of a tropical freshwater catfish, Mystus nemurus (Cuvier & Valenciennes)

Abstract. Six groups of tropical freshwater catfish, Mystus nemurus (Cuvier & Valenciennes)(mean weight. 20·45 ± l·5g), were reared in 0·34m³ fibreglass tanks at different stocking densities (105, 195, 285, 375, 465 and 555 specimens/m³ water) for 84 days. The objective of the study was to determine the effect of various stocking densities on the growth, nutrition, biochemical composition and survival of M. nemurus. The lowest growth rate appeared in fish at the highest density and the highest was observed in fish stocked in moderate density of 285 and 375 fish/m³ water. Fish production was also lower at relatively low stocking densities of 105 and 195 fish/m³. Food conversion ratio (FCR), protein efficiency ratio (PER) and biochemical composition of M. nemurus indicate that there exists an optimum stocking density which lies between 285 and 375 fish/m³.     

Use of night-lights to attract food organisms into tropical marine fish cages

Abstract. A 91-day cage trial was conducted with juvenile seabass, Lates calcarifer (Bloch), and grouper, Epinephelus tauvina (Forskal), to ascertain the capacity of kerosene pressure lamps and fluorescent electric lamps as night-lights above the cages to attract pelagic food organisms into the cage and consequently sustain the survival and growth of the cultured fish. The experiment was conducted using 1×1×1·5m floating cages with three different net mesh sizes (1, 13, and 19mm) and four fish stocking densities (seabass—10, 20,30 and 40/m³; grouper —10/m³). A positive growth response and survival was observed with seabass and to a lesser extent with grouper with increasing net mesh size and decreasing fish stocking density. At the lowest tested density of 10 fish/m³ seabass survival increased from 5·0 to 95·0% and total cage fish biomass increased from −95·1% to +56·9% with an increase in net mesh size from 1 to 19mm over the 91-day culture trial, respectively. The results are discussed in relation to the current commercial marine finfish cage farming practices employed in Indonesia.     

Production of Oreochromis niloticus (L.) and ecosystem dynamics in manured ponds of three depths

Abstract. During three 5-month experiments in Thailand, earthen ponds of approximately 370m2 surface area were stocked with male Nile tilapia, Oreochromis niloticus (L.), fingerlings of 4–12g weight at densities of 0·5 to l·6fish/m². Stocking and fertilization (with chicken manure, urea and TSP) in triplicated depth treatments of 0·6,1·0 and 1·5m were proportional to pond volume in two experiments (wet and dry seasons) and to pond area in the other (dry season).
Depth showed no direct effect on fish yields of 0·9–6·3t/ha/year, on survival rates of 66 to 98%, nor on final individual weights of 96–313 g/fish. Greater yields were obtained from deeper ponds when they received proportionally greater stocking and fertilizer inputs. Inputs per unit area were the most important factor accounting for yield variation.
Temperature, dissolved N and P, and suspended solids showed little or no relation to depth treatments. Time-averaged chlorophyll concentrations and photosynthetic production of dissolved oxygen were greater in treatments receiving greater inputs of nitrogen per unit pond volume.
Deeper ponds produced the greatest areal yields of fish, when fertilized in proportion to their volumes. Shallow ponds produced fish and dissolved oxygen at least as efficiently per unit input as did deep ponds, which is consistent with models of photosynthesis-depth relations.     

The food and feeding of tropical marine fishes in floating net cages: Asian seabass, Lates calcarifer (Bloch), and brown-spotted grouper, Epinephelus tauvina (Forskal)

Abstract. A 156-day cage feeding trial was conducted with fingerling seabass, Lates calcarifer (Bloch), and grouper, Epinephelus tauvina (Forskal), so as to test six different dietary feeding regimes, namely no exogenous feeding (NF), frozen fish (FF), commercial shrimp finisher pellet (SP), in-house prepared dry pellet RDI (RDI) and RD2 (RD2), and an in-house prepared moist pellet (frozen fish: diet Rd1, 40:60 mixture w/w — code MP). Seabass fed FF and MP displayed the best growth response, with fish (30/m³) growing from an initial weight of 8·9g and 8·5g to a final weight of 285·5g and 257·5 g in 156 days, with a food conversion ratio of 3·77–5·10 (dry matter basis 1·15 – 1·95), and with a survival of 93·3 and 93·3% respectively. Similarly, grouper fed FF and MP also displayed the best growth response, with fish (30/m³) growing from an initial weight of 23·8 g and 25·8g to a final weight of 471·7g and 388·7g in 156 days, with a food conversion ratio of 3·53–4·16 (dry matter basis 0·89–1·06) and 1·73–2·96 (dry matter basis 1·06–1·80), and with a survival of 90 and 98·3% respectively. The results are analysed from an economical viewpoint and discussed on the basis of other published studies.     

Semi-Intensive Commercial Grow-Out of Penaeus vannamei Fed Diets Containing Differing Levels of Crude Protein During Wet and Dry Seasons in Honduras

Shrimp were grown under ideal management conditions during two distinct seasons of the year at stocking densities used most often in Honduras with the objective of evaluating the usefulness of high protein diets. A randomized design in 2 × 2 factorial arrangement was used to test a diet composed of either 20 or 40% crude protein in earthen ponds that were stocked with juvenile Penaeus vannamei at 5 to 11/m². The study was repeated during wet and dry seasons. Dietary protein level had no significant effect ( P > O .05) on survival, yield, or average weight of shrimp at either density during either season. Higher stocking rates yielded significantly greater shrimp production during both seasons. Mean shrimp weight in high density ponds was significantly lower than mean shrimp weight in low density ponds during the wet season, but there was no significant weight difference because of stocking density during the dry season. Mean survival was significantly lower at the higher stocking rate during the dry season. Net income was negative during the dry season, particularly at the high stocking density. Mean production was 240% greater in the wet season than in the dry season. Diets offered P. vannamei stocked at 5 to 11/m² should contain no more than 20% protein, regardless of season. Higher dietary protein levels increase costs and waste nitrogen without resulting in greater shrimp yields. The high stocking density might increase profitability in the wet season, but long term sustainable production may be more feasible at lower stocking rates because of reduced nutrient wastes.     

Effect of stocking density on growth and survival of Oreochromis niloticus (L.) fry in the hatchery

Abstract. The effect of stocking density on growth and survival of Oreochromis niloticus (L.) fry was evaluated. O. niloticus fry (average weight, 10·56 ± 0·28mg and average length. 9·09 ± 0·05nim) were stocked in 2–1 tanks at 2, 5, 10, 15 and 20 fry/1 and reared for 33 days post fertilization, at 30°C (±1°C). Mean lengths, mean weights, and specific growth rates were found to be significantly lower ( P < 0·05) at the higher stocking densities. The coefficient of variation for the five stocking densities was significantly ( P < 0·05) different. Condition factors, however, were not significantly ( P < 0·05) different and survival was high at all density treatments. These data suggest that the culture of O. niloticus is feasible at the density groups tested but 5–10fry/I is recommended for fry culture in the hatchery, if a more uniform size is desired.     

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.     

Bioenergetic modelling of effects of fertilization, stocking density, and spawning on growth of the Nile tilapia, Oreochromis niloticus (L.)

Abstract. A bioenergetic growth model was developed to examine the integrated effects of fertilization, stocking density, and spawning on the growth of tilapia, Oreochromis niloticus (L.), in pond aquaculture. The analyses showed that growth rates increase with higher levels of organic fertilization up to 500kg/ha/week. Growth rates increased with added food rations in ponds, reaching a maximum growth of 2-07g/day at about 44–48 days after stocking. Fish growth rates decreased with increased levels of stocking density. The stocking density for optimal growth is 1fish/m²; the optimal density for total harvesting weight and fish size is 2 fish/m². Model sensitivity analysis indicated that tilapia growth is most sensitive to catabolism (metabolism) and anabolism (synthesis) coefficients, both of which are geometrically related to the fish body weight. Food assimilation efficiency (b) and the food consumption coefficient (h) have a modest effect on fish growth. Spawning in grow-out ponds can have a major effect on fish growth.     

Effects of Stocking Density, Salinity, and Light Intensity on Growth and Survival of Southern Flounder Paralichthys lethostigma Larvae

Four separate studies were done on Southern flounder Paralichthys lethostigma larvae during first feeding and metamorphosis to determine the effects of stocking density, salinity, and light intensity on growth and survival. One study used stocking densities of 10, 20, 40, and 80 fish/L during first feeding; the second study compared the growth and survival of larvae stocked at 20 and 33 ppt; and a third experiment evaluated stocking densities of 1/L and 3/L under two different light intensities (1,600 lux vs 340 lux) during metamorphosis. The fourth experiment tested the effects of different salinities (0, 10, 20 and 30 ppt) on larval growth and survival during metamorphosis. Growth and survival (overall 6.9%) were not significantly different ( P > 0.05) for stocking rates up to 80/L. Larvae placed into 20 ppt salinity had survival through first feeding similar to that of larvae raised at 33 ppt. During metamorphosis, light intensity had no effect ( P > 0.05) on growth or survival, but fish stocked at 3/L had significantly lower ( P < 0.05) survival than fish at 1/L. Complete mortality of larvae occurred at 0 ppt. Growth and survival past metamorphosis were not significantly different ( P > 0.05) at 10, 20 and 30 ppt, but unmetamorphosed fish did not survive to day 60 at 10 ppt. Based on these results, practical larviculture of Southern flounder may require a two-step process with high stocking rates (80 fish/L) through first feeding and lower densities (1/L) through metamorphosis. Fingerling production in fertilized nursery ponds might he possible at salinity as low as 20 ppt.     

Overwintering tilapia, Oreochromis spilurus (Günther), fingerlings using warm underground sea water

Abstract.
The study was conducted to develop guidelines for high-density overwintering of tilapia in tanks using warm underground sea water. Seawater-acclimated fish of 20 g were stocked in 36 tanks at 250, 500 and 750/m³. Water flow was regulated at 0.1 and 0.2 l/kg fish/min. Fish were fed at the rates of 0.75% and 1.0% of biomass per day.
After 135 culture days, the mean individual weight gain and specific growth rate decreased, whereas feed conversion increased significantly ( P <0.0001) with the increase in stocking density. The condition factor at 500 and 750 fish/m³ was significantly lower ( P <0.0005) than at 250 fish/m³. However, stocking density had no significant effect on the survival rate. Significantly better specific growth rate, condition factor and feed conversion were observed at a water flow rate of 0.2 l/kg fish/min than at 01 l/kg fish/min. Significantly higher mean individual weight gain, specific growth rate, and survival rate were observed at 1.0%/day than at the 0.75%/day feeding rate. The findings indicate that the optimum stocking density for overwintering tilapia in tanks using warm underground sea water is 750 fish/m³ with a water flow rate of 0.1 l/kg fish/min and a feeding rate of 0.75%/day.     

密度对网箱养殖硬头鳟生长及经济效益的影响

本文主要研究密度对网箱养殖硬头鳟Oncorhynchus mykiss存活和生长的影响。在水温8.2~19.1℃下,将体质量1.02 kg的硬头鳟鱼种养殖在5m×10m×6m网箱中,网箱放置在松花江上游的松山水库中,密度分别为5尾/m~2(Ⅰ组)、8尾/m~2(Ⅱ组)、11尾/m~2(Ⅲ组)和14尾/m~2(Ⅳ组),投喂粗蛋白含量为42%、粗脂肪22%的颗粒饲料,常规养殖。145d的养殖表明:网箱养殖的放养密度对硬头鳟的生长有一定影响。第Ⅳ组鱼的存活率显著低于其他3组(P0.05);放养密度为5~11尾/m~2时硬头鳟的生长与密度呈正相关,大于此密度范围则呈负相关。第Ⅲ组鱼的终末体质量、日增重、增重率、利润和利润率显著高于其余3组(P0.05);4个密度组硬头鳟的产量随放养密度增加而递增。本试验表明:网箱养殖硬头鳟的放养密度为11尾/m~2较适宜。     

A study of the optimum stocking density and feed rate for school prawns Metapenaeus macleayi (Haswell) in some Australian brackish water farming ponds

A stocking density experiment was conducted in 18 experimental enclosures within a single 0.11 ha pond. As stocking density increased in the range 6.1–21.2 prawns/m², school prawn growth declined while survival rate was unaffected and total harvest (final biomass) increased. A simple economic analysis indicated that the optimum stocking density for juvenile school prawns was 19.1 prawns/m². In a similar experiment the effects of feeding school prawns with a pelleted diet at a range of supplementary feed rates (0–12.5% of prawn biomass/day) were investigated. The optimum feed rate in terms of growth was approximately 5% of biomass/day. However the optimum feed rate, in terms of the economic return index used, varied depending on the estimated cost of the diet.     

Effects of Diffused Aeration and Stocking Density on Growth, Feed Conversion, and Production of Florida Red Tilapia in Cages

The effects of four levels of diffused aeration (0, 6, 12, and 24 hours/day) and two stocking densities (400 and 600 fish/m³) on the culture performance of caged Florida red tilapia were evaluated in 1 m³ cages in a 2 ha watershed pond on St. Croix, U.S. Virgin Islands. Fish obtained a nutritionally-complete (36% protein), floating feed from demand feeders for 143 to 146 days. Diffused aeration had no significant ( P > 0.05) effect on fish growth, survival, feed conversion, and production in cages. Combined across all levels of diffused aeration, fish stocked at 400/cage had a greater growth rate (2.21 vs. 1.97 g/day), larger final body weight (370 vs. 335 g), and a lower feed conversion ratio (1.69 vs. 1.80) than fish stocked at 600/cage ( P < 0.05). The final biomass of fish stocked at the higher density (181 kg/m³) was greater than at the lower density (140 kg/m³). The enhancement of water exchange rates by diffused aeration did not increase tilapia growth rate or production in cages.     

Appropriate Timing of Supplemental Feeding for Production of Nile Tilapia, Silver Carp, and Common Carp in Fertilized Polyculture Ponds

In an attempt to identify appropriate times for initial application of supplemental feed in polyculture fertilized fish production earthen ponds, a study was conducted for 19 wk to establish the growth performance, yield, survival, and body composition of Nile tilapia, common carp, and silver carp as influenced by four different feeding regimens (treatments). The four treatments were: 1) supplemental feeding beginning at onset of the experiment (T-I) (control treatment); 2) 6-wk delay of feeding after fish stocking (T-II); 3) 13-wk delay of feeding after fish stocking (T-III), and 4) no supplemental feed application (T-IV). Two ponds were assigned to each treatment and each pond was stocked with a similar number and weight of each fish species. A commercial pelleted fish feed (25% protein) was used to feed fish in T-I, T-II, and T-III at 3% of their body weight, twice a day. At the end of the experiment, fish species (except for silver carp) in T-II showed weight gain, growth rates, and yields significantly higher than fish in T-III or T-IV. Also, the total fish production and net profit in T-II were significantly higher than in T-III or T-IV. Fish species in T-II showed weight gain, growth rates, survival rates, and yields similar to those of T-I (control treatment) with no significant differences. The amount of feed consumed by fish in T-II was reduced by approximately 7.3% compared to that consumed by fish at T-I. Moreover, there was increase in th net profit in T-II by 4.8% over that achieved in T-I. Therefore, T-II appears to be the most appropriate among the tested feeding treatments and recommended for use in order to achieve the best growth, production, and net profit.     

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.     

Effect of initial age variation on production of Florida red tilapia fry under intensive, brackishwater tank culture

Abstract. Growth and survival were compared among uniform- and mixed-age groups of Florida red tilapia fry during sex reversal in brackishwater (12ppt) tanks, under commercial-scale hatchery conditions. Three treatment groups of post-yolksac (i.e. free-swimming) stage fry of different age compositions were compared: (1) 100% fry collected at the free-swimming stage (FSF); (2) 100% fry obtained through artificial incubation of eggs and non-swimming sacfry (ENS); and (3) a mixed group consisting of 50% of each type (FSF+ENS). Fry were stocked into 530–1 cylindroconical tanks at a density of seven fish/l (3700/tank) and reared on an androgen-treated diet for 30 days. While specific growth rates (range = 17·1–17·8% body weight/day) did not differ (P > 0·05) among treatments, significant (P < 0.05) differences were observed for survival and feed conversion ratio (FCR). ENS showed highest survival (76·8%) and lowest FCR (1·14), FSF showed intermediate survival (59·2%) and FCR(l·33), while the mixed-age group (FSF+ENS) showed lowest survival (38·5%) and highest FCR (1·70). Under all treatments, a majority of fry losses were attributed to cannibalism. A highly significant ( P < 0·001) negative regression between survival and coefficient of variation of initial weights (CV = SD/) indicated that cannibalism was reduced by minimizing age/size variation at stocking. The CV of initial weight may be a useful parameter for predicting fry survival under intensive tank culture.     

Preliminary study on the production of the tilapia, Oreochromis spilurus (Günther), cultured in seawater cages

Abstract. A preliminary study was conducted to assess the performance of the tilapia, Oreochromis spilurus (Günther), cultured in seawater cages at different stocking densities during the nursing and rearing phases. The stocking densities tested were 200, 400 and 600 fish/m³ during the nursing phase and 100, 200, and 300 fish/m³ during the rearing phase.
In both growth phases, no significant differences (P>0.05) were observed among the different stocking densities on the mean individual final weight, daily growth rate, feed conversion ratio and survival rate. Yields in cages stocked with 400 and 600 fish/m³ during the nursing phase, however, were significantly (P<0.05) higher compared with cages stocked with 200 fish/m³. No significant differences (P>0.05) were observed between 400 and 600 fish/m³. A density of 600/m³ is therefore considered to be optimum for the nursing phase.
Yields of cages during the rearing phase increased significantly (P<0.01) with the increase in stocking density. After grading the fish, however, no significant differences (P>0.05) were observed when only fish bigger than 150g were considered. The occurrence of exophthalmia (cataract) was observed in two of the four replicates at the highest stocking density (300 fish/m³) during the rearing stage. Therefore, a stocking density of 200 fish/m³ is considered optimum for the rearing phase.     

Seasonal production of rainbow trout, Oncorhynchus mykiss (Walbaum), in ponds using different feeding practices

Abstract. In temperate regions of North America, the culture of rainbow trout, Oncorhynchus mykiss (Walbaum), in ponds is constrained to the period mid-November to early April by water temperature. Feeding practice may influence production time. The effects of three feeding practices on growth and body composition of rainbow trout raised in ponds during a 142-day winter growth period were investigated. Feeding practices were (1) hand-feeding to satiation, (2) feeding according to a fish size/water temperature chart, and (3) feeding by demand feeder.
Fish fed to satiation consumed 66% more diet than fish fed according to a feeding chart and 163% more than fish fed by demand feeders. Fish fed to satiation had significantly higher (P < 0·05) weight gain, harvest weight, specific growth rate, and protein gain with no significant increase (P > 0·05) in percentage body fat or feed conversion ratio (FCR) compared to the other two treatments. Survival percentage did not differ significantly (P > 0·05) between treatments. These data indicate that by using satiation feeding, marketable size rainbow trout can be produced in temperate region ponds without increases in percentage body fat or FCR.     

Utilization of cocoa-pod husk in low-cost diets by the clariid catfish, Clarias isheriensis Sydenham

Abstract. Clarias isheriensis Sydenham fingerlings (60·42 ± 1·13g) were fed for 180 days with pelleted diets in which maize was progressively replaced with graded levels (0, 15,30,45%) of cocoa-pod husk meal (CPHM). There was a decline in growth rate with increase in dietary CPHM level, though this was not significantly different (P < 0·05). Differences in feed conversion, nutrient digestibility and carcass characteristics among different dietary treatments were also not significant (P > 0·05). Fish mortality was low (< 2%) in all dietary treatments tested. Lack of significant difference in growth performance and nutrient utilization indicated that CPHM could be incorporated into low-cost diets for C. isheriensis up to the 30% level.
In a second experiment, three feeding regimes of 15% CPHM diet were tested with C. isheriensis fingerlings (60·81 ± 1·87g) over 180 days and results showed no significant (P > 0·05) differences among the feeding regimes tested, with regards to growth, feed conversion and fish yield. This suggests that the growth of C. isheriensis from fingerling to adult size (≥ 200g) can be satisfied in one single feeding equivalent to 3% body weight per day.