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Effects of Temperature and Feeding Rates Upon Growth and Feed Conversion Ratios in Tilapia Stephen P. Kirkup Lori S. Marsh Graduate Research Associate Associate Professor Dept. of Biological Systems Eng. Dept. of Biological Systems Eng. Viginia Polytechnic Inst. and State Univ. Virginia Polytechnic Inst. and State Univ. George S. Libey Alan G. Heath Research Associate Professor Professor Dept. of Fisheries and Wildlife Science Dept. of Biology Virginia Polytechnic Inst. and State Univ. Virginia Polytechnic Inst. and State Univ. Charles W. Coale C. Gene Haugh Professor Professor Dept. of Agric. and Applied Econ. Dept. of Biological Systems Eng. Viginia Polytechnic Inst. and State Univ. Virginia Polytechnic Inst. and State Univ. Introduction Tilapia are ideally suited for culture in recirculating aquaculture systems. They are tolerant of poor water quality and low oxygen levels and breed prolifically. Although native to Africa and the Middle East, tilapia have been introduced in developing nations, such as South and Central America, Southeast Asia, Africa, China and the Philippines, as a dietary supplemental source of protein. Except for some of the southern most regions of the United States, tilapia cannot be over-wintered in ponds, and therefore have not been widely cultured in ponds in the US. But many of the same characteristics that make tilapia popular for pond and cage cultures throughout the world also make them ideally suited for recirculating aquaculture systems. In the United States and Canada, live tilapia command a premium price and thus have become a significant aquacultural product in major cities having large ethnic oriental populations. Recirculating aquaculture systems are ideally suited for serving these live tilapia markets, because they allow for year-round production and they can be located reasonably close to the market, thus reducing transportation costs, stress and moralities incurred during transportation. Several efforts have been made to analyze the economics of raising tilapia in recirculating aquaculture systems (Head and Watanabe 1995; Losordo and Westerman 1994; O’ Rourke 1996). Two of the largest costs in the production of tilapia are feed and fixed or overhead costs. Feed represents the largest of the variable costs. Losordo and Westerman estimate that feed accounts for approximately 21 percent of the total production cost, thus, any management practice that significantly improves the feed conversion efficiently 1
will have a large effect upon the cost of product. Fixed costs, which are an amalgamation of all costs that are independent of the rate of production, also represent a large part of the cost of production. In reality, most costs are a combination of a fixed and a variable component, and thus estimates of fixed costs will vary greatly depending upon which costs are considered fixed costs. Losordo and Westerman (1994) state that capital costs and depreciation of capital equipment account for approximately 34 percent of the total production cost, but these costs are just two of the larger fixed costs. Thus total fixed costs would represent a much larger percentage of the cost of production than the 34 percent noted previously. O’Rourke (1996) divided all of his costs into either fixed or variable, and calculated that fixed cost were 56 percent of total costs. Included in the list of fixed costs were wages, water, and maintenance, which usually would not be considered total fixed. It is fair to say however that fixed cost represent somewhere between 34 and 56 percent of total production costs. By definition, once a production facility is operational, fixed expenses remain constant. Fixed or overhead costs per unit of production change as the production rate changes, thus fixed costs as a percentage of total production costs can be reduced by increasing the production rate. The production rate for a given facility can be increased by either increasing the stocking density or the growth rate. While increasing stocking densities is an obviously attractive goal, there are physiological as well as engineering and physical limitations that limit the culture intensity. Stocking density has been shown to negatively affect growth rates in many species of fish, although the responses vary. Poorer growth rates have been associated with higher stocking densities of tilapia raised in ponds, irrigation ditches or cages (Coche 1982; Carro-Anzalotta and McGinty 1986; D'Silva and Maughan 1996; Yi et al. 1996; Siddiqui et al. 1989), but little research has be conducted on tilapia in recirculating systems. Huang and Chiu (1997) researched the effects of stocking density on growth rates on tilapia fry smaller than 10 g, and observed that increasing stocking densities had a significantly negative effect upon size, size variation and survival rate. Regardless, the effect of stocking density is beyond the scope of the experiments reported herein. For this research project, a density of 5 gallons per fish was selected to minimize the effects of crowding. Fish physiologists do not fully understand the biological mechanisms that control the growth rates of fish. Although there have been numerous mathematical models to describe the growth characteristics of fish, most of these models do not take into account such important factors as availability of food, food quality or the effect of environmental factors such as temperature. This has given rise to the scientific field of bioenergetics, which partitions the energy consumed into various metabolic processes including production or growth, and waste products. While the bioenergetic models account for changes in energy consumption, measuring each of the energy partitions is labor intensive, and are usually measured as a function of only one variable; thus ignoring the interactions with other biological factors. Bioenergetics provides a reasonable growth projection for fish in the natural environment, but its usefulness for describing growth in recirculating 2
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TABLE OF CONTENTS i Pages Symposium
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iii Pages Production of YY Male Til
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v Pages Special Session 2 - Volunte
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into the grow-out tanks. The airlif
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one above the other, reducing the
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nutritional requirements of summer
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Pump Functions The AMI Multi-Functi
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Introduction Commercial Application
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System Performance: Nine of these r
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electrical costs reduced by more th
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Nitrate, as the final product of th
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Culture conditions On August 1, 199
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surface area 740 m 2 /m 3 ). The co
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achieved a 750 mg/l decline in the
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ecomes possible without water repla
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tropical countries for tropical fis
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fastest absorption of nutrients fro
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Recirculation System Design; The KI
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The Japanese Aquaculture Market and
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Entrepreneurial and Economic Issues
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Our largest error though was in not
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Before You Invest. In my role as a
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are 590,000 kg/year. Prices, deprec
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Twenty-One Years of Commercial Reci
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have projects in the planning stage
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As the upward trend for seafood dem
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and the World Health Organization (
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Abstract not available at time of p
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increase the potential for bottlene
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Figure 1: Comparison of First, Seco
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Ecological and Resource Recovery Ap
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Acid mine drainage (AMD) is widespr
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and the polyphenol content (Northup
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References CAST. 1996. Integrated A
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Tilapia and Fish Wastewater Charact
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In comparison of gravity separation
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NY DEC Interaction. The owners of F
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O 2 Feed CO 2 Ammonia Figure 1. Gen
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The Hatchery The hatchery supports
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in crayfish populations, disappeara
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Table 2. Summary of average flows a
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depth decreases. Improvements in tr
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Perspective on the Role of Governme
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unprecedented in the growth of a ne
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with siting and the special equipme
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disease. We need to create environm
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Introduction Implications of Total
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The NOAA/DOC Aquaculture Initiative
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Future Directions for the NOAA/DOC
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’ Conduct research and help devel
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Information sources for aquaculture
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Tilapia is an important fish specie
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To determine the RSE of the examine
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Fig.1(a) Typical integrated olfacto
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Table 1. Relative stimulatory effic
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feeder control algorithms on a PC s
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Durant, M. D., Summerfelt, S. T., H
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The Effects of Ultraviolet Filtrati
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Table 1. The mean (N = 20) initial
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Introduction Evaluation of UV Disin
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Figure 1 Schematic of the experimen
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Table 1 Summary of the tested resul
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similar disinfection efficiency. Th
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(2) UV254 transmittance was an impo
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Materials and Method Schematic draw
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the amount of added increase by pro
Page 134 and 135: Oxygen Management at a Commercial R
Page 136 and 137: the outlet and inlet DO concentrati
Page 138 and 139: daylight hours averaged 0.5 kg DO/k
Page 140 and 141: At this time, the control (both tan
Page 142 and 143: yellow color, while the water in th
Page 144 and 145: Case Study: Genetic improvement of
Page 146 and 147: and human effort. This commitment m
Page 148 and 149: - Harold Kincaid works for the US F
Page 150 and 151: Figure 1. Production and selection
Page 152 and 153: Performance Comparison of Geographi
Page 154 and 155: Abstract Issues in the Commercializ
Page 156 and 157: The Salmon Example Salmon farming i
Page 158 and 159: Second, as the salmon farming indus
Page 160 and 161: Devlin, R.H., Yesaki, T.Y., Biagi,
Page 162 and 163: Introduction Removal of Protein and
Page 164 and 165: higher superficial air velocity gre
Page 166 and 167: Hydrodynamics in the ‘Cornell-Typ
Page 168 and 169: The ideal mean residence time was a
Page 170 and 171: A sample pellet-flushing test is sh
Page 172 and 173: tank’s dead time. When fish were
Page 174 and 175: Partial-Reuse Systems Ideally, the
Page 176 and 177: Figure 1. The partial-recirculating
Page 178 and 179: Table 1. Mean values (± standard e
Page 180 and 181: dioxide (1) and un-ionized ammonia
Page 182 and 183: Comparative Growth of All-Female Ve
Page 186 and 187: aquaculture systems, where the envi
Page 188 and 189: Figure 2. Growth relationships of y
Page 190 and 191: greater than the desired temperatur
Page 192 and 193: Figure 3. Cumulative feed consumpti
Page 194 and 195: 35 days into the experiment, and th
Page 196 and 197: C. Maximum specific feed consumptio
Page 198 and 199: of the fish used in this experiment
Page 200 and 201: Coche, A.G. Cage culture of tilapia
Page 202 and 203: Predictive Computer Modeling of Gro
Page 204 and 205: new studies begun. Daily water qual
Page 206 and 207: Development Rationale for the Use o
Page 208 and 209: Further, reduction in operating cos
Page 210 and 211: The operation of the MRBF is domina
Page 212 and 213: equired a high frequency of washing
Page 214 and 215: Several dramatically different hull
Page 216 and 217: support airlift applications. These
Page 218 and 219: Enhancing Nitrification in Propelle
Page 220 and 221: The last filter media used in this
Page 222 and 223: Table 2. Water quality analyses wer
Page 224 and 225: 1193.67 g-NO2 m -3 d -1 with the ni
Page 226 and 227: Biofilters Used in Recirculating Fi
Page 228 and 229: The Cyclone Sand Biofilter: A New D
Page 230 and 231: Marine Biotech (Beverly, MA) 2 has
Page 232 and 233: 120.0% 100.0% 80.0% 60.0% 40.0% 20.
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Nitrification Potential and Oxygen
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diffused aeration. The experiments
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It needs to be pointed out that the
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ammonia removal rate was low in the
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Tanaka, H. and Dunn, I. 1982. Kinet
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Ammonia removal activity was increa
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Ammonia Conc. (mg/NH 4 + -N/L) 12 1
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Antifouling Sensors and Systems for
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The Vic Thomas Striped Bass Hatcher
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Introduction In the Central Valley
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Each of the two recirculation syste
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Body injury rates (% of fish) to th
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usiness expectations and limited te
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needs of the endemic Murray-Darling
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sold (Gooley et al. 1999). The dist
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In response to the large levels of
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planning at the outset will, more t
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Table 1 Summaries of selected speci
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a) Photo courtesy of Neil Armstrong
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Information flow 1. Initial concept
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achieve continuous production, faci
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Solids Removal (9.71%) Electricity
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The Effect of Fish Biomass and Deni
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Marine Denitrification of Denitrifi
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(a) (b) (c) Nitrate conc. (mg NO 3
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6. Poxton, M. G. and S. R. Allouse.
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control unit. Two distinct advantag
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the many variables that are involve
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Filtration Recirculation systems re
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6. AERATION DEVICE: 6” airstones
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Piper, R.G., I.B. McElwain, L.E. Or
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carried out for both the 50 m 3 and
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possible to predict mean monthly ta
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Recirculation Systems for Farming E
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of this pilot-system will be evalua
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Figure 2. The main screen of the en
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What: What is your business structu
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should more than offset the costs o
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• Any other documents indicating
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production projects. Once these par
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A single discharge pipe works to re
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1. Oxygen recharge rates or the abi
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2.9.1.2. Measure ammonia. 2.9.1.3.
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Discharge pipe Number used within e
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Previous efforts by the Illinois De
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media. The water enters the filter
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Table 3: Summary of pro forma cash
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References Moss, S.M. (1999) “Bio
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Propagation and Culture of Endanger
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at a rate of 2 ft 3 /kg feed/d. Sod
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Modification of D-Ended Tanks for F
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MATERIALS AND METHODS All tests wer
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The single 100 ppm hydrogen peroxid
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The Potential for the Presence of B
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The main advantage for microorganis
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organism causes disease in humans,
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Bacteria No. of Facilities No. of D
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Assanta, M.A., Roy, D. and Montpeti
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Jones, K. and Bradshaw, S.B. (1996)
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Wilderer, P.A. and Characklis, W.G.
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systems (Egusa, 1981; Mellergaard a
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ecirculating system after mortality
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Fish Health Monitoring and Maintena
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disease problems. For tilapia, a sp
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The Role of Fish Density in Infecti
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This apparent interaction between t
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References Banks, J.L. (1994) Racew
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