Commercial-Scale Production of Florida Red Tilapia Seed in Low- and Brackish-Salinity Tanks

Commercial-scale production of Florida red tilapia ( Oreochromis sp.) seed (eggs, sacfry, and fry) under methods that minimized freshwater usage was studied on Lee Stocking Island, Bahamas. Comparisons of seed production by broodstock held in low-salinity (LS = 5 ppt; mixed rain and ground water) and brackish-salinity (BS = 18 ppt; mixed ground and sea water) tanks (34 m²) showed that seed production over an 8 month period was significantly greater in LS (77.7 seed/m²/ day) than in BS tanks (47.4 seed/m²/day), with average proportion of brooding females and number of seed per clutch being greater in LS (26.9% and 763) than in BS tanks (19.8% and 643). While LS seed production was among the highest reported values for tilapias, BS production was within reported ranges for fresh and low-salinity tilapia hatcheries. Seed production per unit of low-salinity water (i.e., rain and/or groundwater) consumed in both LS (7,262 seed/m³) and BS (5,337 seed/ m³) tanks exceeded reported values. The results support the feasibility of commercial-scale production of Florida red tilapia seed under intensive methods and of salinities as high as 18 ppt in regions where fresh or low-salinity water resources are limited.     

Preliminary Observations on the Marketability of Saltwater-Cultured Florida Red Tilapia in Puerto Rico

A preliminary assessment of the marketability of saltwatercultured Florida red tilapia was conducted at a farm outlet store and at nine restaurants in Puerto Rico. Florida red tilapia were grown in six 0.2-ha ponds at 22.7 ± 1.2 (mean ± SE) ppt salinity by a commercial aquaculture enterprise in Dorado, northeastern Puerto Rico. Customers purchased 4,683kg of dressed-out fish (gilled, gutted and scaled) at $7.70/kg and 826kg of whole fish at $6.60/kg from a retail outlet store located at the aquaculture farm, and nine restaurants purchased 1,071kg of dressed-out fish at wholesale prices ranging from $4.96 to $5.18/kg. Farm outlet customers and restaurants preferred dressed-out fish between 454–567g and 567–580g, respectively. Prices paid per serving by restaurant customers for red tilapia ($7.00–$25.00) were similar to that paid for silk snapper Lutjanus vivanus , a popular marine food fish in Puerto Rico. Market surveys of customers at these outlets showed that 75–81% of the respondents were new consumers of red tilapia and that they rated red tilapia highly in taste, texture, freshness, and presentation and equal to or better than silk snapper. There was no effect ( P > 0.05) of age group or economic level on consumer responses. Survey participants stressed the need for product promotion, including a more markehriented name that emphasized the red color and that it was farm-raised in saltwater, to distinguish it from darkcolored, wild-caught freshwater tilapia. Local saltwater production of Florida red tilapia could help supply the market demand for fresh, marine fish in Puerto Rico if producers can meet the demand for quality, availability and price.     

Preliminary Investigations into the Socio-Economic Feasibility of Saltwater Cage Culture of Florida Red Tilapia in Haiti

The primary objective of this study was to investigate the socio-economic feasibility of saltwater cage culture of Florida red tilapia as a new production activity in Haiti. Market outlets and potential prices for saltwater-reared red tilapia in Haiti were examined. Availability and prices of inputs to production were considered. Although this information was collected in the context of Haiti, it is relevant to other developing countries when assessing the potential for a mariculture industry.
Two types of market outlets for saltwater-reared red tilapia were found to exist in Haiti. The predominant rural market sector treated red tilapia as a low-value species and paid an average price ($0.90/kg roundweight) similar to that for freshwater black tilapia. Urban specialty markets treated red tilapia as a premium quality fish and paid an average price ($2.20/kg cleaned) equal to that for snapper and grouper.
Comparison of production costs to potential market prices indicates that saltwater cage culture of tilapia is not economically feasible on an artisanal scale and is a high financial risk on a commercial scale. Break-even prices are higher than prices in the large rural market sector. No data exists to indicate sufficient demand in the smaller urban specialty market sector or export markets.     

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

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

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.     

The Effects of Salinity on Reproductive Performance of Florida Red Tilapia

The reproductive performance of yearling Florida red tilapia broodstock was studied in laboratory aquaria at salinities of 1 (freshwater), 9, 18, 27 and 36 ppt under controlled photoperiod (14 L:10 D) and temperature (28 C).
Spawning was observed at all salinities, although egg production per unit female weight at each spawn was significantly higher at 1 ppt than at higher salinities. An inhibitory effect of salinity on reproductive performance was evidenced by a trend toward lower fertilization, hatching, and survival of prejuveniles with increasing salinity. Fry production per unit female weight declined at salinities above 18 ppt. The results suggest that Florida red tilapia broodstock may be maintained under salinities as high as 18 ppt without impairing fry production, suggesting that hatchery production in brackishwater would be practical in areas where freshwater resources are limiting.     

Economics of cage culture in Puerto Rico

Abstract

Puerto Rico has been faced with a decline of fish stocks similar to other parts of the world. Offshore cage aquaculture might be an answer to this problem although there are many unanswered questions. This paper describes a project in Puerto Rico that assessed the economics of offshore cage culture for aquaculture. The first cage was placed in the water in February 2002 with a second one to follow shortly thereafter.     

Production Economics of Nile Tilapia (Oreochromis niloticus) Pond Culture in El-Fayum Governorate,Egypt

Econometric techniques were used to estimate a production function for tilapia pond culture in El-Fayum Governorate, Egypt, utilizing cross-sectional field data. Explanatory variables were feed, initial stocking weight, and pond size. The function was used to examine returns to scale, estimate the productivity of feed and initial stocking weight, and estimate the profit maximizing demand equations for feed and fingerlings. Diminishing returns to scale seem to exist for tilapia pond culture. Optimal economic stocking and feeding rates, yield, and profits for the whole sample were estimated at prevailing prices. Results indicated that producers were using stocking rates greater than the optimal by 36% to 115% and using insufficient feed by 8% to 22%. Investigation of the effects of changes in tilapia selling price and feed price on optimal stocking and feeding rates, yield, and profits showed that a change in tilapia selling price has greater effect on profits, yield, stocking, and feeding rates than a proportional change in feed price. Profits, feeding, and stocking rates are more sensitive than yield to changes in selling price, while feeding rate is more sensitive than stocking rate, yield, and profits to changes in feed price.     

Economic and Risk Analysis of Tilapia Production in Kenya

Commercial production of tilapia in Kenya has potential for expansion, but growth and development of the tilapia industry in Kenya will depend upon its profitability and the effect of associated risks. Data from pond experiments, on-farm trials, and farm surveys were used to develop enterprise budgets and a risk analysis for nine production scenarios. The nine scenarios include: 1) monoculture of sex-reversed male tilapia fed either rice bran, a pelleted experimental diet, or a pelleted pig finisher diet; 2) clarias monoculture fed with each of the three diets; and 3) tilapia-clarias (sex-reversed male fingerlings) polyculture fed with each of the three diets. Net returns/ha were highest for production with the pig finisher diet, with clarias in monoculture the highest followed by tilapia in monoculture and then the polyculture system. The lowest net returns/ha were obtained with clarias fed rice bran. Profitability was affected by feed cost and tilapia survival. Tilapia monoculture systems had lower probabilities of financial losses than either clarias monoculture or the polyculture system. Use of the pelleted diets also resulted in lower probabilities of financial losses. Lower yields from the rice bran feed scenario resulted in its greater sensitivity to fluctuating costs of rice bran and survival of tilapia.     

Growth, Survival, Yield, and Size Distributions of Freshwater Prawn Macrobrachium rosenbergii and Tilapia Oreochromis niloticus in Polyculture and Monoculture Systems in Puerto Rico

Abstract.— Tilapia and freshwater prawn production in Puerto Rico for monoculture and polyculture systems were compared. The experiment consisted of three treatments with three replicates each. The stocking rates for the prawn monoculture, fish monoculture and polyculture treatments were respectively: 7 prawns/m², 1 tilapia/M², and 7 prawns with 1 tilapia/ m². The mean stocking size for tilapia and prawn were respectively, 7–8 g and 1–1.3 g. After 145 d of culture, yields and mean weight of tilapia in monoculture and polyculture system were not significantly different. Total yields were 2,942 and 2,769 kg/ha, respectively. Mean weights were 348 g in monoculture and 331 g in polyculture. Yields and mean weight of prawns in monoculture and polyculture were significantly different. Total yields were 1,367 and 951 kg/ha, respectively. Mean weights were 55 g in monoculture and 31 g in polyculture. Total yield in polyculture was 3,720 kg/ha showing an increase over the production separately obtained in prawn and fish monoculture.     

Salinity During Early Development Influences Growth and Survival of Florida Red Tilapia in Brackish and Seawater

Growth of juvenile Florida red tilapin (1.57 g average weight) spawned and sex-reversed (monosex male) at salinities of 4 ppt and 18 ppt was compared at rearing salinities of 18 ppt and 36 ppt in 200 L aquaria under controlled photoperiod (12 L:12 D) and temperature (28 C). Growth was significantly higher for progeny spawned at 18 ppt than those spawned at 4 ppt under both rearing salinities with no difference observed between 18 ppt and 36 ppt.
In another experiment, growth of juvenile progeny (0.98 g average weight) spawned and sex-reversed at salinities of 2 ppt and 18 ppt was compared in 24 m³ outdoor pools at 36 ppt. When water temperatures exceeded 27 C, growth and survival were not significantly different between these groups. However, when temperatures fell below 25 C, growth and survival were significantly higher among progeny spawned at 18 ppt.
The results showed that progeny spawned and reared through early ontqenetic development in brackishwater are better adapted for growth in brackish and seawater and suggested that these fish may have higher resistance to cold-stress in seawater than progeny spawned in freshwater.     

红罗非鱼和尼罗罗非鱼正反交后代体色和生长性能的评价

用台湾红罗非鱼 (以下简称台红 )和吉富品系尼罗罗非鱼 (以下简称吉富 )进行杂交 ,观察正反杂交后代的体色分离和生长差异。结果表明 :(1)正反杂交子代的体色均出现分离 ,台红 (♀ )×吉富 (♂ )子代的体色以全红和花斑为主 ,两者的比例为 1∶1,吉富 (♀ )×台红 (♂ )子代中红色个体的比例为 83.8% ,优于红罗非鱼自行繁衍之后代。 (2 ) 12 2d网箱试验的结果表明 ,正反交子代及其亲本的日增重率由高到低依次为吉富 >反交〔吉富 (♀ )×台红 (♂ )〕 >正交〔台红 (♀ )×吉富 (♂ )〕 >台红。 4种鱼的生长速度存在极显著的差异 (P =0 .0 0 0 2 0 )。正交和反交子代的日增重率分别比台红提高 18.4 %和 2 4 .5 %。若考虑到种内的体色 ,日增重率存在极显著的体色间差异 (P =0 .0 0 2 3)。总之 ,反交子代具有红色个体比例高、生长速度快等优势 ,可应用于生产     

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.     

Effect of Using Low-Protein Diets in Semi-Intensive Pond Cage Culture of Tilapia,Tilapia rendalli (Boulenger)

ABSTRACT

An experiment was carried out to determine the effect of using low-protein diets on production of Tilapia rendalli in semi-intensive pond cage culture. This was carried out at Bunda College of Agriculture's fish farm, University of Malawi, where two 200-m² earthen ponds of 1-m depth were used for two months from February 2003 to early April 2003. Each pond had 6 cages of 1 m³ in size stocked with 15 fish, each 4.8 ± 1.2 g average weight and 6.7 ± 0.6 cm average length. Chicken manure was used as the organic manure applied at 500 kg/ha/wk and also acted as a control. All treatments were replicated three times. It was observed that fish growth was higher in the soybean meal-based diet, with final weight of 34.4 g, followed by sunflower cake, with final weight of 23.3 g. The lowest was 14.4 g in the chicken manure only, and cottonseed-based diet had final weight of 19.5 g. These results also agree with the specific growth rate (SGR) that ranged from 2.1%/day in the cages only fertilized with chicken manure to 3.6%/day in the soybean-based dietary treatment. The lowest feed conversion ratio of 1.2 was also observed in the soybean-based dietary treatment. This suggests that the use of lower protein diets that contain soybean would produce better results and may increase yield when combined with fertilization, as evidenced by high fish survival rates of more than 93% in all treatments.     

Economic Analysis of Nile Tilapia (Oreochromis niloticus) Production in Tanzania

In Tanzania, Nile tilapia culture is a promising aquaculture enterprise. Information on production costs could assist fish farmers in economic and financial planning. Economic profitability of small‐scale Nile tilapia production in Tanzania is analyzed using a model that simulates individual fish growth and takes into account fish population dynamics in the pond. The results suggest that the current practiced mixed‐sex tilapia culture without predation is not economically sustainable. Extension efforts should be geared toward developing a Nile tilapia production system that is based on a hand‐sexed all‐male tilapia. Meanwhile catfish can be introduced in ponds to control overcrowding in mixed‐sex tilapia culture without predation. Studies to determine optimal pond sizes, availability of feed, and a quality fingerling supply chain are also fundamental for developing a sustainable Nile tilapia production system in Tanzania. Under improved Nile tilapia production systems, returns are high enough to justify investment through borrowed capital from formal institutions.     

Effect of Feeding Rate on Growth and Feed Conversion of Florida Red Tilapia Reared in Floating Marine Cages

An experiment was conducted to investigate growth, survival and feed conversion of Florida red tilapia reared in floating cages in seawater under different feeding regimens. Twenty-four cages (1 m³) were anchored in a sea pass on Great Exuma, Bahamas, and each was stocked with 300 juvenile, monosex males (10 g mean weight). Growth was monitored every 14 days for 84 days. Fish were fed daily a floating pelletized diet (32% protein) at 4 programed rates representing 50, 70, 90, and 110% of the estimated satiation rate, ad libitum , and by demand feeders, with each treatment comprised of 4 replicate cages.
Final mean weight was significantly lower for the 50% treatment (94.1 g) than for all other treatments (range = 121.8–155.7 g). Final mean biomass per cage ranged from 24.2 to 39.4 kg/m³, and survival ranged from 98.2 to 99.8%.
Mean specific growth rate was significantly lower under the 50% programed feeding treatment (2.42%/day) than for all other treatments (range = 3.15–3.56%/day) while feed conversion ratios (dry weight/wet weight) were significantly lower under the 50% (1.57) and 70% (1.68) programed feeding treatments than under all other treatments (range = 1.98–2.26). Thus, maximum growth was achieved at feeding rates near satiation while feed conversion was improved at lower feeding rates. Under demand feeding, growth and feed conversion were not significantly different than those of the ad libitum , 100%, and 90% treatments.     

Production of Australian Red Claw Cherax quudricarinatus in Polyculture with Nile Tilapia Oreochromis niloticus

Abstract— Australian red claw crayfish Cherax quudricarinurus were cultured in monoculture and in polyculture with male Nile tilapia Oreochromis niloricus in nine 0.02-ha earthen ponds. Red claw with an average weight of 7 g were stocked in all ponds at 2/ m². Tilapia with an average weight of 19 g were stocked in six ponds at either 0.5 or 1/m². A sinking 32% fish diet and dry alfalfa hay was provided to all ponds as feed and forage. After 135 d, red claw survival was similar (19–24%) in all treatments while average weights were 76 g in monoculture and 48 g in both polyculture treatments. Lower than expected survival was a result of stress caused by poor shipping conditions. Tilapia survivals were similar (84–90%) in all ponds and had an average weight of 403 g when stocked at 1/m² and 444 g when stocked at 0.5/m². Red claws are generally considered non-aggressive, especially when compared with other clawed crustaceans. This lack of aggressiveness is suggested as a cause for decreased growth in polyculture with tilapia.     

不同盐度下3种罗非鱼的Na+-K+-ATPase活性比较

在盐度为0、10、20、30时测定了萨罗罗非鱼(Sarotherodon melanotheron)、尼罗罗非鱼(Oreochromis niloticus)和以色列红罗非鱼(Oreochromis sp.)鳃和肾中Na+-K+-ATPase活性。结果表明:(1)不同盐度对不同组织的Na+-K+-ATPase活性有显著影响,鱼的品种及其他交互作用对Na+-K+-ATPase活性均无显著影响;(2)在实验盐度范围内,无论是鳃和肾,萨罗罗非鱼、尼罗罗非鱼和以色列红罗非鱼的Na+-K+-ATPase活性均随盐度的升高而增高;3种罗非鱼中,萨罗罗非鱼的Na+-K+-ATPase活性随盐度的升高增大最为剧烈,以色列红罗非鱼次之,尼罗罗非鱼最小;低盐度时尼罗罗非鱼的Na+-K+-ATPase活性相对较高,高盐度时萨罗罗非鱼的Na+-K+-ATPase活性相对较高,Na+-K+-ATPase的活性与罗非鱼的耐盐能力有着一定的联系;(3)盐度大于7.19和11.94时,萨罗罗非鱼鳃中的Na+-K+-ATPase活性分别开始高于以色列红罗非鱼和尼罗罗非鱼;盐度大于18.42时,萨罗罗非鱼肾中的Na+-K+-ATPase活性开始高于尼罗罗非鱼;(4)除了在盐度20和30中的尼罗罗非鱼及盐度30的以色列红罗非鱼,是肾中的Na+-K+-ATPase活性高于鳃外,其他均为鳃中的Na+-K+-ATPase活性高于肾,肾中Na+-K+-ATPase活性在不同盐度之间的变化较鳃剧烈;罗非鱼的鳃比肾在渗透压调节上起的作用更大。     

罗非鱼简易大棚越冬保种技术

报道了用简易大棚进行罗非鱼越冬的技术措施,包括大棚的选址与建设、进棚越冬鱼的选择要求、进棚时间、密度掌握、消毒办法以及进棚后的管理——温度调节、水质调节、饵料投喂、疾病防治提出具体方法。