Bartholomew W. Green, Department of Fisheries and Allied Aquaculture, Auburn University, AL 36849-5419, USA
Zeinab El Nagdy, Hussein Heibicha, Ibrahim Shaker, Dia A. R. Kenawy, and Abdel R. El Gamal, Central Laboratory for Aquaculture Research, Agricultural Research Center, Abbassa, Abou Hammad, Sharkia, Egypt
31 October 1995, CRSP Research Reports 95-91
Abstract Experiments were conducted at the Central Laboratory for Aquacultural Research to 1.) evaluate and compare the performance of established PD/A CRSP pond management systems to Egyptians pond management systems and 2.) to assess the economic potential of different tilapia pond culture systems. Five management practices--Traditional Egyptian, Enhanced Egyptian, Feed Only, Fertilization then Feed, and Chemical Fertilization-- were tested in twenty 0.1-ha earthen ponds. Young-of-year Nile tilapia (Oreochromis niloticus) were stocked 20,000 fish/ha and fingerling African catfish were subsequently stocked 60 fish/ha to prey on tilapia offspring. Water quality variables were analyzed weekly for 17 weeks. The Free-Water Diel curve method was used to determine primary productivity on six occasions. Dissolved oxygen was measure with a polarographic dissolved oxygen meter at depths of 5 cm, 25 cm, 50 cm, and 75 cm. Economic potential and profitability were also evaluated using Enterprise Budget Analysis. Fertilization then Feed, Traditional Egyptian, and Enhanced Egyptian treatments, in decreasing order, were more economically viable and produced the greatest gross fish yields, net returns, and average rates of return on capital. These treatments had the highest values of production per man-hour per kilogram of feed and per Egyptian pound. In addition, these treatments achieved the highs margins between average prices and break even prices to cover total variable costs of total costs. Production trial results and economic analyses demonstrated sufficient incentive for the expansion of intensified pond culture in Egypt.
This abstract was excerpted from the original paper, which was published as CRSP Research Report 95-91 by the Program Management Office of the Pond Dynamics/Aquaculture Collaborative Research Support Program (PD/A CRSP).
Monitoring water quality for tropical freshwater fisheries and aquaculture: A review of aircraft and satellite imagery applications
Hillary S. Egna, Pond Dynamics/Aquaculture Collaborative Research Support Program, and Department of Geosciences, Resource Geography Program, Oregon State University, Corvallis OR 97331-1641 USA
9 January 1996, CRSP Research Report 96-92
Abstract Water quality in tropical fish ponds is generally evaluated without the assistance of remote sensing because of cost, cloud cover, and other constraints, but certain parameters such as suspended solid concentrations, colour, chlorophyll and temperature can effectively be monitored by aerial photography and satellite imagery. This paper reviews applications of remote sensing to tropical inland fisheries and aquaculture and includes applications from related disciplines. A brief assessment of new platforms and sensors is also presented. Remote sensing images may help to inform researchers and planners about water quality trends that are occurring over a broad area in which fisheries and aquaculture activities occur. However, the operational use of remote sensing in aquaculture remains largely experimental.
This abstract was excerpted from the original paper, which was published in Fisheries Management and Ecology 1, 1994:165-178
Co-culture of catfish (Clarias macrocephalus x C. gariepinus) and tilapia (Orechromis niloticus) in ponds
C. Kwei Lin, School of Environment, Resources & Development, Asian Institute of Technology, PO Box 2754, Bangkok, 10500 Thailand
James S. Diana, School of Natureal Resources & Environment, University of Michigan, Ann Arbor, MI 48109-1115
27 February 1996, CRSP Research Reports 96-93
Abstract The experiment was conducted for 122 days in central Thailand to test rearing of hybrid catfish in cages in earthen ponds, where tilapia (Oreochromis niloticus) was stocked to utilize the waste products derived from intensively reared catfish. Catfish fingerlings (13-17 g size) was stocked in plastic net cages at a density of 275 fish/m3. Six earthen ponds (250 m2-110 m3 each) were used to suspend the cages in two loading densities as experimental treatments: 800 and 1760 catfish/pond. Each loading density was replicated in 3 ponds. Each pond was stocked with 440 sex-reversed male tilapia of 6-7 g size in open water, giving the catfish and tilapia stocking ratios of 2:1 and 4:1, respectively. Catfish was fed twice daily at 3-10% body weight per day with commercial floating pellets containing 25-30% crude protein. Water quality was analyzed bi-weekly for concentration of dissolved oxygen, ammonia and chlorophyll a.
Results showed that there was no significant difference (p<0.05) in catfish growth rate and survival between the two loading densities. The mean weight gain of harvested catfish was 259.5 ± 34.5 g and 255.2 ± 8.4 g/fish, giving the net yield of 218.0 ± 26.8 kg and 391.5 ± 88.0 per pond in low and high loading density, respectively. Tilapia was harvested with mean weight of 172.3.±37.8 g and 297.5 ± 32.0 g/fish, and the net yield of 68.1 ±13.6 and 86.9 ± 27.2 kg/pond for low and high loading catfish density treatment, respectively. Chlorophyll a and total ammonia concentration differed greatly between the two treatments. Early morning dissolved oxygen (DO) declined steadily under both treatments over the culture period.
This abstract was excerpted from the original paper, which was published in Aquat. Living Resour., 8(4)1995:449-454
C. Kwei Lin, Agricultural and Food Engineering Division, Asian Institute of Technology, G.P.O. Box 2754 Bangkok, Thailand
1 April 1996, CRSP Research Reports 96-94
Abstract Experiments were conducted to assess the effects of polyculture on tilapia growth and to evaluate African catfish (Clarias gariepinus) as a predator control for unwanted tilapia offspring in a polyculture system. Three treatments were tested using nine 200 m2 earthen ponds. Ponds were stocked with male tilapia in treatment 1 (T1), mixed sex tilapia in treatment 2 (T2), and mixed sex tilapia and catfish in treatment 3 (T3). Fish were fed a commercial diet ration of 1.5% of body weight per day twice a day at 0900 hr and 1500 hr. Feed inputs, adjusted biweekly, were based on Nile tilapia (Oreochromis niloticus) biomass. Gut contents of African catfish were analyzed two weeks prior to temination of the experiment. Water quality parameters were estimated biweekly. Diel analysis of dissolved oxygen (DO), temperature, and pH were performed at three depths and six time intervals, and net primary productivity (NNP) was estimated using DO concentrations. A t-test was used to compare final fry biomass, daily weight gain (DWG) of Nile tilapia, net fish yield (NFY), and the diel variability of gut content. DWG and NFY were significantly higher for treatment T1 in which male Nile tilapia were stocked. Mean fry biomass for each treatment showed large fluctuations. Statistical analyses of two of the three replicates of T1, T2, and all three replicates of T3 indicated that T2 production was significantly greater than T3 production. Forty-seven percent of the sampled African catfish contained one of the following in the stomach or intestines: whole fish, partially digested fish, fish flesh, fish scales, fins, or bones; twenty-six percent of the African catfish had freshly ingested fry in the stomach. Biweekly variation in mean values for water quality parameters were comparable for each treatment. Tilapia production in polyculture with African catfish was significantly lower than the culture systems with either all male tilapia or mixed sex tilapia. African catfish predation of tilapia fry was sufficiently effective to serve as a population control for tilapia; however, active predation occurred only in semi-intensive culture systems where fish were fed their natural diet.
This abstract was excerpted from the original article which was published as CRSP Research Report 96-94 by the Program Management Office of the Pond Dynamics/Aquaculture Collaborative Research Support Program (PD/A CRSP).
Abdelmoez A. F. Abdalla, Aqua-International, P.O. Box 1171, Alma, MI 48801 USA
Clarence D. McNabb, Ted R. Batterson, Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824-1222 USA
21 June 1996, CRSP Research Report 96-95
Abstract Total ammonia nitrogen pathways in fertilized fish ponds stocked with Nile tilapia Oreochromis niloticus were investigated. Three fertilizer treatments were used in a field experiment in Thailand: weekly application of 500 kg dry chicken manure/ha (1.2 g N/m2), 44 kg dry chicken manure plus 24 kg urea/ha (1.2 g N/m2), and 500 kg dry chicken manure plus 280 kg urea/ha (14.3 g N/m2). Substantial quantities of ammonia were reduced from pond water in each treatment during daylight hours. Ponds lost 36-75% of the average total ammonia that was present in early morning during daylight hours. Losses to the atmosphere (flux) were relatively small, varying from 1-5% of the total diurnal ammonia reductions. Uptake by algae was the most important mechanism for removal of ammonia from pond water. Net primary productivity varied between treatments and increased with the increased availability of inorganic nitrogen. Increasing the total ammonia present in the early morning increased net primary productivity. Fish mortalities were 71% in ponds with the highest weekly nitrogen input (14.3 g N/m2) and were between 22 and 26% in the two treatment ponds with low weekly nitrogen input (1.2 g N/m2). Average maximum concentrations of un-ionized ammonia (0.6 mg/L at 1600 hours), and low dissolved oxygen (2.8 mg/L at 0600 hours) may have combined to increase mortality in ponds with high nitrogen inputs. In the highest nitrogen treatment, neither the uptake of ammonia by algae nor its volatization to the atmosphere reduced un-ionized ammonia concentration to a level safe for fish.
This abstract was reprinted from the original, which was published in The Progressive Fish-Culturist 58, 1996:177-123.
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