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Table 1 Commercially important species in inland water cage and pen farming

SpeciesCountriesClimateType of feedingLotic/LenticCage/Pen
SalmonidsRainbow troutEurope, North America, Japan, high altitude tropics (eg Colombia, Bolivia, Papua New Guinea)TemperateIntensive. High protein (40%)LenticFloating cage
Salmon (various species) smoltsEurope, North America, South America, JapanTemperateIntensive. High protein (45%)LenticFloating cage
CarpsChinese carps (Silver carp, grass carp, bighead carp)Asia, Europe, North AmericaTemperate - tropicalMainly semi-intensive, although also extensive (Asia) and intensive (Europe, North America)Lotic and lenticCages and pens
Indian major carps (Labeo rohita)AsiaSub-tropical - tropicalSemi-intensiveMainly lenticMainly cages
Common CarpAsia, Europe, North America, South AmericaTemperate - tropicalMainly semi-intensive, although also intensiveMainly lenticMainly cages
Tilapias(O. mossambicus, O. niloticus etc)Asia, Africa, North America, South AmericaSub-tropical - tropicalMainly semi-intensive, although also intensiveMainly lenticMainly cages
CatfishesChannel catfishNorth AmericaTemperate - sub-tropicalIntensiveLenticFloating cages
Clarias spp.Southeast Asia, AfricaTropicalSemi-intensiveLotic and lenticFloating cages
SnakeheadsChanna spp.
Ophicephalus spp.
Southeast AsiaTropicalSemi-intensive/intensiveLotic and lenticFloating cages
Pangasius spp. Southeast AsiaTropicalSemi-intensiveLenticFloating cages
Milkfish Southeast AsiaTropicalSemi-intensiveLenticPens

Table 2: Advantages and limitations of cage fish culture technique (from Balarin and Haller, 1982)

Possibility of making maximum use with the greatest economy of all the available water resourcesDifficult to apply when the water surface is very rough therefore location restricted to sheltered areas
Helps reduce the pressures on land resourcesBack up food store hatchery and processing units necessary therefore requires strategic location
Possibilities of combining several types of culture within one water body, the treatments and harvests remaining independent 
Ease of movement and relocation 
Intensification of fish production (i.e. high densities, optimum feeding results in improved growth rates and reduces length of rearing period)Need an adequate water exchange through the cages to remove metabolites and maintain high dissolved oxygen levels. Rapid fouling of cage walls requires frequent cleaning
Optimum utilisation of artificial food for growth, improves food conversion efficienciesAbsolute dependence on artificial feeding unless utilised in sewage ponds. High quality balanced rations essential. Feed losses possible through cage walls
Easy control of competitors and predatorsSometimes important interference from the natural fish population, i.e. small fish enter cages and compete for food
Ease of daily observation of stocks allows for better management and early detection of disease. Also economical treatment of parasites and diseasesNatural fish populations act as a potential reservoir of disease or parasites and the likelihood of spreading disease by introducing new cultured stocks is increased
Easy control of tilapia reproduction 
Reduces fish handling and mortalitiesIncreased difficulties of disease and parasite treatment
Fish harvest is easy and flexible, and can be complete and of a uniform productRisks of theft are increased
Storage and transport of live fish is greatly facilitatedAmortisation of capital investment may be short
Initial investment is relatively smallIncreased labour costs for handling, stocking, feeding and maintenance

Table 3: Theories proposed to explain floating and stationary Fish Attraction Devices (FAD's), and their applicability to inland water cage and pen structures.

1.Use as cleaning stations where external parasites of pelagic fishes can be removed by other fishes-
3.Creates shadow areas in which zooplankton become more visible*
4.Provides substrate for egg laying-
5.Drifting object serves as schooling companion-
6.Provides spatial reference around which fishes could orient in an otherwise unstructured environment*
7.Provides shelter from predators for small fishes**
8.Attracts larger fishes because of presence of smaller fishes**
9.Acts as substrate for plant and animal growth, thus attracting grazing fishes**

from M. Seki, 1983. Summary of pertinent information on the attractive effects of artificial structures in tropical and subtropical waters. Unpublished administrative report of the Southwest Fisheries Center, Honolulu. 49 p.

Table 4: Predators reported from cage and pen fish farms. Data taken from Salmon and Conte (1982), Martin (1982) and Ranson and Beveridge (1983)

Predator Country
Snakes(Natrix sp)
USA, Europe
USA, Europe
USA, Europe
USA, Europe
SE Asia1
USA, Europe
SE Asia1
USA, Europe, SE Asia1
USA, Europe

1 From personal observation

Table 5: Summary of the results from studies of the environmental impacts of intensive cage fish culture in various countries

Bull Shoals Reservoir, Arkansas, USA Built 1961-rainbow trout channel catfish blue catfish∼205  5 yearsincrease: NH4, total-P, green algae, diatoms, protozoa, game & coarse fish
decrease: secchi disc
build up: faecal material under cages
O2, temp, NO3, NO2, turbidity, CO2, pH, alkalinity, conductivity, blue-green algae, rotifers, desmids.Changes localised in bay where cages sitedHays, 1982
White Oak Lake, Arkansas, USA Reservoir, built 19601083 hachannel catfish∼150  2 yearsincrease: turbidity, alkalinity, total-P, PO4-P, organic N, BOD, bacteria, zooplankton, benthic invertebrates, primary production.
decrease: dissolved 02, NO3, chlorophyll a
temp, CODCages localised near outflowEley et al, 1972
Crystal Lake, Arkansas, USA24 hachannel catfish rainbow trout∼91 yearincrease: turbidity, PO4 -P, NO3, NO2, phytoplankton, zooplankton, oligochaetes, fish populations
decrease: culicids
temp, O2, pH, NH43 sampling sites chosenKilambi et al, 1976
Lake Hartwell, South Carolina, USA24,300channel catfish0.15  5 monthsincrease: local fish populations-Small, experimental cages. Only effects on fish community studiedLoyacano and Smith, 1976
Lake Keowee, South Carolina, USA7,300channel catfish0.4312 monthsincrease: local fish populations-Small, experimental cages. Only effects on fish community studiedLoyacano and Smith, 1976
Lake Glebokie, Poland47.3 harainbow trout∼18  5 yearsincrease: C, total-P, total N-Only C, P, and N budgets examinedPenczak et al, 1982
Dgal Wielki, Poland93.9carp and tench-  4 yearsincrease: BOD, suspended solids, P content of seston decrease: O2PO4, NH4, NO3-Korycka and Zdanowski, 1980
Lake Skarsjon, Norway310 harainbow trout20  3 yearsincrease: total-P, and in sediments total-P, total-N, O2 consumption decrease: redox potential in sedimentstotal-P, NH4, NO3 & NO2, Kjeldahl-N in waterWork concentrated on sedimentsEnell, 1982
Lake Byajon, Norway140 harainbow trout153 yearsincrease: total-P, and in sediments total-P, total-N, O2 consumption decrease: redox potential in sedimentstotal-P, NH4, NO3 & NO2, Kjeldahl-N in waterWork concentrated on sedimentsEnell, 1982

Table 6: Extensive cage tilapia production figures from the Philippines

LakeDateCage size (m)Stocking Density ( m-3)Size at stocking (g)Culture Period (months)Size at Harvest (g)Production (kg m-3 month-1)Reference
Bunot198020 × 25 × 54-42500.24Alvarez, 1981
Laguna de Bay1978  5 × 10 × 3 -
10 × 20 × 5
4–8∼14–51000.07–0.18Mane, 1979
Sampaloc198310 × 10 × 9 -
25 × 20 × 9
1.6–2.012.5–16.06–9225–3000.05–0.08Guerrero, 1983
Taal198310 × 5 × 350-41001.25Guerrero, 1983
Bato1983-50-41601.90Job Bisuña, pers. com.
Buluan1982–3  5 × 10 × 510∼152000.40Oliva, 1983

Table 7: Life span of various materials used in temperate and tropical cage and pen construction (modified from IDRC/ SEAFDEC, 1979)

MaterialsLife expectancy in fresh waters
Bamboo and logs
1–2 years
Metal drums
0.5–3 years
Rubber tyres*
5+ years
Used plastic drums
1.2+ years
Styrofoam- covered
5+ years
 - not covered
2+ years
10+ years
PVC Pipes
5+ years
Spherical buoys - aluminium
10+ years
 - plastic
5 years
Aluminium cylinders
10+ years

* Polystyrene filled

Table 8: The relative supply and demand of elements required by plants and algae and derived from soils and rocks (lithosphere) of the catchment area (from Moss, 1980)

Element(1) Ratio of amount of element to that of phosphorus in the lithosphere(2) Ratio of amount required of element to amount required of phosphorus in plants and algaeRatio of (1) to (2)
  Na  32.5
  Mg  22.2
  P    1.0
  K  19.9
  Ca 39.5
  Mn     0.90
  Fe 53.6
  Co    0.02
  Cu    0.05
  Zn    0.07
  Mo        0.0014

Table 9: N:P ratios (by weight) in a range of freshwater bodies

Data baseNo.Ratio % above ratioReference
Lakes and reservoirs from all over the world54>5:1
total-N:total P
 85Schindler, 1978
European and North American lakes and reservoirs89>7:1
inorganic N:PO4 -P
 85OECD, 1982
Shallow water bodies in Europe and North America70>7:1
inorganic N:PO4-P
 95Clasen, 1981
Reservoirs in Missouri and Iowa, USA 6>7:1
 99Hoyer and Jones 1983
Lakes off the Pre-Cambrian Shield, Canada22>12:1
 95Prepas and Trew, 1983
Kenyan lakes 8>9:1
total N:total-P
100Kalff, 1983
Southern African man-made lakes25>7:1
 68Walmsley and Thornton, 1984 (in press)

Table 10: Dietary phosphorus requirements of fish, expressed as percentage weight of diet (after Beveridge et al, 1982).

    SpeciesRequirement      Source
Anguilla japonica0.29%Arai et al, 1975
Salmo trutta0.71%McCartney, 1969
Salmo salar0.30%Ketola, 1975
Salmo gairdneri0.70–0.80%Ogino and Takeda, 1978
Oncorhynchus keta0.50–0.60%Watanabe et al, 1980a
Cyprinus carpio0.60–0.80%Ogino and Takeda, 1976
Ictalurus punctatus0.45–0.80%Andrews et al, 1973; Lovell, 1978
Chrysophrys major0.68%Sakomoto and Yone, 1980
Oreochromis niloticus0.90%Watanabe et al, 1980b

Table 11: Ranges and mean values (%) of total-P content of commercially available salmonid diets in the U.K. Data based on the analysis of feeds produced by six manufacturers.


Data from Tacon and De Silva (1983).

Table 12: Total-P content (% wt.) of carp and tilapia diets used in intensive culture in various parts of the tropics

(a) Tilapias

CountryDietP content of ingredients (%)P in diet (%)
PhilippinesDIET 1   
75% rice bran (‘cono’)  0.410.311.30
25% fish meal  3.970.99
DIET 2   
65% rice bran (‘cono’)  0.410.271.32
10% copra meal  0.600.06
25% fish meal  3.970.99
Central African Republic82% Cottonseed oilcake  1.050.861.29
  8% Wheatflour  0.110.01
  8% Cattle blood meal  0.290.02
  2% Bicalcium phosphate20.000.40
Ivory CoastDIET B1   
65% Rice polishings  1.320.861.19
12% Wheat middlings  0.830.10
18% Peanut oilcake  0.500.09
  4% Fishmeal  3.580.14
  1% Oyster shell  0.07-
DIET B2   
61% Rice polishings  1.320.811.29
12% Wheat middlings  0.830.10
18% Peanut oilcake  0.500.09
  8% Fishmeal  3.580.29
  1% Oyster shell  0.07-
DIET B3   
65% Rice polishings  1.320.861.30
12% Wheat middlings  0.830.10
18% Cottonseed oilcake  1.100.20
  4% Fishmeal  3.580.14
  1% Oystershell--
DIET B4   
15% Brewery waste  0.530.081.51
15% Maize bran  0.800.12
15% Rice bran  0.430.65
12% Wheat middlings  0.830.10
38% Cottonseed oilcake  1.100.42
  4% Fishmeal  3.580.14
  1% Oyster shell--
UK ( 35g fish)  5% Brown fishmeal  3.970.201.25
  3% Hydrolysed feathermeal  0.700.02
  5% Meatmeal  1.400.07
  4% Soybean meal  0.670.03
10% Groundnut meal  0.500.05
20% Cottonseed meal  1.050.21
37% Rice bran  0.410.15
10% Dried distillers sol.--
  2% Vitamin premix--
  4% Mineral premix13.100.52

(b) Carps

CountryDietP content of ingredients (%)P in diet (%)
EuropeDIET 1   
25% Soybean meal     0.630.161.03
10% Fishmeal     3.580.36
10% Meatmeal     1.400.14
5% Lucerne meal  -  -
25% Rice bran     0.430.11
20% Rice polish     1.320.26
5% Distillers solubles  -  -
DIET 2   
25% Soybean meal     0.630.160.94
10% Fishmeal     3.580.36
10% Meatmeal     1.400.14
20% Wheat middlings     0.830.17
5% Lucerne meal  -  -
25% Rice bran     0.430.11
5% Distillers solubles  -  -
USA46% Fishmeal     3.581.653.09
28% Wheat middlings     0.830.23
7% Rice bran     0.430.03
5% Wheat bran     1.270.06
5% Soybean seeds     0.630.03
4% Yeast     1.670.07
1.5% Corn gluten     0.470.01
0.5% Vitamin premix00
0.5% Mineral premix   13.100.66
0.5% Sodium chloride00
2% Potassium phosphate  17.640.35

Tilapia diet formulations from Coche (1982), Jauncey and Ross (1982). Carp diet formulations from Pearson (1967) and NRC (1977). P content of feedstuffs from NRC (1977) and Santiago (1983).

Table 13: Recommended food particle sizes for salmonids and tilapias. The term ‘crumb’ refers to round particles, whereas ‘pellet’ refers to cylindrical (1 ≤ 3d) particles. Sizes refer to particle diameter (d).

(a) Trout (b) Tilapias  
Fish sizePellet sizeFish sizePellet size
0.40.3–0.6crumbFry first 24 hrsliquifry*
3–91.5–2.0  0.5–1.00.5–1.5
  9–202.0–3.0    1–301.0–2.0
  9–201.5pellet   20–1202.0pellet
20–402.0 100–2503.0

* Tilapia data from Macintosh (1984), Macintosh and De Silva (1984), Jauncey and Ross (1982). Trout data from Ewos-Baker.

Table 14: Summary of data from Glebokie Lake, Poland (Penczak et al, 1982). Units in kg, and total losses (F + C + U; see p. 41 for terminology) calculated assuming mortalities were not removed from the lake.

 Generation 2Generation 3
 (June 1976–Dec. 1977)(Jan. 1978–Dec. 1978)
Fish Production27,53411,000
total-C losses16,708  9,701
total-P losses     507     291
total-N losses  2,094  1,296
C losses per kg trout production  0.607  0.890
P losses per kg trout production  0.019  0.026
N losses per kg trout production  0.076  0.118

Average (Gen. 2 and Gen 3) C losses per kg trout production = 0.748
P losses per kg trout production = 0.023
N losses per kg trout production = 0.097

Table 15: Feed Conversion Ratios (FCR's) for various intensive trout and tilapia diets. The composition of tilapia diets are detailed in Table 12

(a) Trout
Feed Brand/TypeFeed FormCrude Protein Level (%)Culture SystemFCRReference
Commercial, variousPellets, dry, sinking40–41Ponds1–3:1Edwards, 1978
Ponds1–28:1Templeton & Jarrams, 1980
EWOS, T-4DPellets, dry, floating47%*Tanks0.94:1Ketola, 1982
AbernathyPellets, dry, sinking-Tanks1.19:1Ketola, 1982
Purina Trout ChowPellets, dry, floating40Cages2.09–3.26:1Kilambi et al, 1976
Pellets, dry, sinking  40*Cages1.59–2.73:1Templeton & Jarrams, 1980
(b) Tilapia
Feed Brand/TypeFeed FormCrude Protein Level (%)Culture SystemFCRReference
Philippines, Diet 1Mash, moist, sinking24.2Cage2.57:1Guerrero, 1980
Philippines, Diet 2Mash, moist, sinking24.3Cage2.58:1Guerrero, 1980
Central African Republic DietPellets, sinking-Cage3.20:1Coche, 1982
Ivory Coast Diets B1 + B4Pellets, dry, sinking20–25Cage2.0–2.40:1Coche, 1982

* Estimated

Table 16: Theoretical calculations of total-P released into the environment during intensive cage culture of trout and tilapia.

(a) Rainbow trout

Phosphorus content of commercial trout pellets 1.50%a
∴ 1 tonne feed contains 15.0 kg

Food Conversion Ratio (FCR) = 1.0:1,Pfood = 15.0 kg
  FCR = 1.5:1,Pfood = 22.5 kg
  FCR = 2.0:1,Pfood = 30.0 kg
  FCR = 2.5:1,Pfood = 37.5 kg

Phosphorus content of trout = 0.48% wet weight of fishb = 4.8 kg tonne fish-1

∴ Phosphorus release to environment (Penv):-

   1.0:1 FCR = 15-4.8 = 10.2 kg tonne fish prod-1
1.5:1 FCR = 22.5-4.8 = 17.7 kg       "       "       "
2.0:1 FCR = 30.0-4.8 = 25.2 kg       "       "       "
2.5:1 FCR = 37.5-4.8 = 32.7 kg       "       "       "

(b) Tilapia

Phosphorus content of compounded feeds (see Table 12)  1.30%
∴ 1 tonne feed contains13.0 kg
Food Conversion Ratio
(FCR) = 2.0:1
Pfood = 26.0 kg
Pfood = 32.5 kg
Pfood = 39.0 kg
Pfood = 45.5 kg
Pfood = 52.0 kg

Phosphorus content of tilapia = 0.34% wet weight of fishc = 3.4 kg tonne fish-1

∴ Phosphorus release to environment (Penv):-

2.0:1 FCR = 26.0-3.4 = 22.6 kg tonne fish produced-1
2.5:1 FCR = 32.5-3.4 = 29.1 kg       "       "     "
3.0:1 FCR = 39.0-3.4 = 35.6 kg       "       "     "

a = Average P content of commercial grower feeds used in Europe. Data from Tacon and De Silva (1983).

b = data from Penczak et al (1982)

c = P content of tilapia, estimated from Meske and Manthey (1983), assuming dry weight = 25% wet carcasse weight

Table 17: Total-P loadings associated with intensive land-based salmonid culture (modified from Beveridge et al, 1982)

(kg tonne fish production-1)
40.15PLiao and Mayo, 1972
15.70PSolbe, 1982
36.50 total-PWarrer-Hansen, 1982
10.95–113.15 total-PAlabaster, 1982
18.32 total-PSumari, 1982
9.10–22.77total-PKetola, 1982

Table 18: Food Conversion Ratios (FCR) of rainbow trout grown in cages and in ponds, using commercial dry pellets as food source

 FCR      Reference
Ponds1.00–3.00:1Edwards, 1978
1.28:1Templeton and Jarrams, 1980
1.20–1.40:1Stevenson, 1980
1.50:1Bardach et al, 1973
Cages2.09–3.26:1Kilambi et al, 1976
1.50–1.80:1Landless, 1980
1.59–2.73:1Templeton and Jarrams, 1980
1.50:1Enell, 1982
1.60–2.00:1Coche, 1978a
3.40–3.70:1Korycka and Zdanowski, 1980

Table 19: Summary of [P] predictive models (r = correlation coefficient; S.E. = standard error)

Model typeModelData BasePerformanceReference
Vollenweider, 197668 mid-western reservoirs, USAr = 0.64; S.E. = 0.39Mueller, 1982
32 Southern African reservoirs (42 observations)difference between predicted and observed: n = 42; x2 = 4.90; P 0.01Thornton and Walmsley, 1982
Jones-Bachmann, 197675 North American lakes Jones and Bachmann, 1976
68 mid-western reservoirs, USAr = 0.65; S.E. = 0.37Mueller, 1982
704 natural and artificial lakes in Europe and North Americar = 0.81Canfield and Bachmann, 1981
271 natural lakes in Europe and North Americar = 0.82Canfield and Bachmann, 1981
433 artificial lakes in Europe and North Americar = 0.82Canfield and Bachmann, 1981
704 natural and artificial lakes in Europe and North Americar = 0.77Canfield and Bachmann, 1981
Dillon-Rigler, 197418 Canadian lakes   -Dillon and Rigler, 1974
68 mid-western reservoirs, USAr = 0.86; S.E. 0.20Mueller, 1982
32 Southern African reservoirs (37 observations)difference between predicted and observed n = 37; x2 = 1.83; p < 0.001Thornton and Walmsley, 1982
OECD - 198287 lakes in Europe and North Americar = 0.93OECD, 1982
14 Nordic lakesr = 0.86OECD, 1982
18 Alpine lakesr = 0.93OECD, 1982
31 North American lakesr = 0.95OECD, 1982
24 shallow lakes and reservoirs in North America and Europer = 0.95OECD, 1982

Table 20: Tentative1 values for maximum acceptable [P] in lentic inland water bodies used for enclosure culture of fish

Water Body CategorySpecies CulturedTentative maximum acceptable [P]
TemperateSalmonid  60
TropicalCarp & tilapia250

1 see text ( and 4.6)

Table 21: Regression equations relating annual mean chlorophyll levels [chl] and peak chlorophyll levels to each other, and to mean in-lake total phosphorus concentrations [P]. N. B. Three equations are given for each relationship except the last (see text). Units = mgm-3.

(a) Relationships between [ch1] and [P]
(i)[ch1] = 0.61 [P].69n = 99;r = 0.75;S.E. = 0.335
(ii)[ch1] = 0.38 [P].86n = 88;r = 0.86;S.E. = 0.272
(iii)[ch1] = 0.28 [P].96n = 77;r = 0.88;S.E. = 0.251
(b) Relationships between and [P]
(i) = 1.77 [P].67n = 65;r = 0.70;S.E. = 0.375
(ii) = 0.90 [P].92n = 54;r = 0.86;S.E. = 0.296
(iii) = 0.64 [P]1.05n = 50;r = 0.90;S.E. = 0.257
(c) Relationships between and [chl]
(i) = 2.86 [chl]1.03n = 73;r = 0.93;S.E. = 0.199
(ii) = 2.60 [chl]1.06n = 72;r = 0.95;S.E. = 0.167

data derived from OECD (1982)

Table 22: Relationship between [chl] and ΣPP in some tropical lakes

Madden    6 mg m-3
600 mg O2 m-2h-1
Gliwicz, 1976
Chad  18 mg m-3
45 g O2 m-2d-1
Lemoalle, 1975
Victoria  44 mg m-3
7.4 g O2 m-2d-1
Talling, 1965
Naivasta Crater  45 mg m-3
4.9 g O2 m-2d-1
Melack, 1979
McIlwaine  93 mg m-3
3.9 g O2 m-2d-1
Robarts, 1978
Elementia  97 mg m-3
570 mg O2 m-2h-1
Melack, 1979
Castanho127 mg m-2
2.8 g O2 m-2d-1
Schmidt, 1973
George400 mg m-2
7.4 g O2 m-2d-1
Ganf, 1974, 1975

Table 23: Empirical models for calculating the sedimentation rate, ρ, retention coefficient, R (1/ρ), and the sedimentation coefficient, V, of phosphorus, for both general and specific categories of temperate water bodies

Model typeSize of data base ModelCorrelation coefficientSource
(a) General.
U.S. EPA data base & several European lakes and reservoirs
704σ = 0.129 (L/Z)0.549 0.81Canfield and Bachmann, 1981
*0.79Larsen and Mercier, 1976
σ = 0.94*0.79Jones and Bachmann, 1976
V = 2.99 + 1.7qs*0.73Reckhow, 1979
V = 5.3*0.71Chapra, 1975
73 0.79Larsen and Mercier, 1975
σ = 0.65 0.79Jones and Bachmann, 1976
R = 0.426 exp(-0.271qs)+0.574exp(-0.00949qs) 0.71Kirchner and Dillon, 1975
V = 11.6 + 1.2qs 0.68Reckhow, 1979
σ = 10/Z 0.68Vollenweider, 1975
V = 12.4 0.66Chapra, 1975
(b) Reservoirs.
North American
210σ = 0.114 (L/Z)0.589 0.83Canfield and Bachman, 1981
*0.80Larsen and Mercier, 1976
(c) Natural lakes151σ = 0.162 (L/Z)0.458 0.83Canfield and Bachmann, 1981
*0.80Larsen and Mercier, 1976
(d) Lakes with low flushing rates (qs < 10m)  53R = 0.201 exp (-0.0425qs)+0.574exp(-0.00949qs) -Ostrofsky, 1978

qs = areal water loading (mg-1)
ρ = flushing rate (volumes per year)
*  = coefficients recalculated by Canfield and Bachmann (1981) using their data base

Table 24: Diet of tilapias and carps commonly used in aquaculture (tilapia data modified from Jauncey and Ross, 1982)

O. mossambicusAdults omnivorous, but feed mainly on plankton, vegetation and benthic algae. Juveniles feed initially entirely on zooplankton.
O. niloticusAdults omnivorous, but feed predominantly on phytoplankton, and can utilise blue-green algae. Juveniles consume wider range of food items.
H. molitrixAdults and juveniles feed largely on phyto-plankton, although they will ingest detritus and zooplankton, providing the particle size is within the range 8–100 μm.
A. nobilisAdults feed on larger phytoplankton, zooplankton and detritus particles within the size range 17- 3000 μm.

Table 25: Assimilation efficiencies (Aε) of tilapias feeding on various diets (modified from Bowen, 1982)

   Species      DietComponentA
O. niloticusMicrocystis sp.14C     70
Anabaena sp.14C     75
Nitzschia sp.14C     79
Chlorella sp.14C     49
Lake George suspended mattertotal C   43
O. mossambicusNajas guadalupensisdry wt.29
T. rendalliCeratophyllum demersumdry wt.53–60

Table 26: Increases in yields from lake fisheries in China, following the implementation of stocking and other management policies. Data from FAO (1983).

LakeSize (ha)Yield prior to stocking, etc.Yield subsequent to stocking, etc.%increase in yield
Baitan Hu, Hubei400450 kg ha750 kg ha   67
Xi Hu, Zhejiang559  35 kg ha536 kg ha 1431
Dianshan Hu, Shanghai6,670  48 kg ha  75 kg ha   56
Tai Hu, Jiangsu226,700  24 kg ha  56 kg ha   133

Table 27: The relationship between gross areal photosynthetic rates and fish yields from seven suburban lakes near Wuhan, China (data from Liang et al, 1979). Efficiencies of energy transfer (fish yield/primary production) are based on a conversion factor of 0.375 for photosynthetic O2 production → photosynthetic C production (APHA, 1980), and a fresh fish C content of 10% (Gulland, 1970).

LakeGross photosynthetic
rate (g C m-2y-1)
Gross fish yield
(g m-2y-1)
Net fish yield
(g m-2y-1)
Gross efficiency
Net efficiency
South Lake   219 45  312.01.4
Temple Lake   561 31  130.50.2
East Lake   589 26  220.40.4
Ink Lake   712 91  771.31.1
Yu's Lake1,0131941661.91.6
Tea Leaf Bay1,2462632452.12.0
Inlet Bay1,9164464292.32.2

Table 28: Conversion efficiencies of ΣPP to annual fish yield (Fy), for water bodies of different productivities. Conversion efficiencies for lakes and reservoirs with ΣPP ≤ 2500 g C m-2y-1 have been derived from Fig. 25, whilst for those with ΣPP > 2500 g C m-2y-1, yields have been assumed to lie on the upper portion of the logistic curve described by Liang et al (1981).

% conversionto fish yield
<10001 – 1.2
1000–15001.2 – 1.5
1500–20001.5 – 2.1
2000–25002.1 – 3.2
2500–30003.2 - 2.1
3000–35002.1 - 1.5
3500–40001.5 - 1.2
4000–45001.2 - 1.0
>4500∼ 1.0

Table 29: Feeding practices of 70 cage operators at Lakes Buhi and Bato, Camarines Sur, Philippines (after Escover and Claveria, 1984, in press)

AType of feedLake BuhiLake Bato
 Rice bran
Rice bran and dried shrimp
Rice bran and “irin-irin”
Rice bran and coconut meat refuse
Rice bran, corn and “irin irin”
No feeding
BMethod of feeding  
 Broadcast (dry feed)
Broadcast (wet feed)
Broadcast combination wet and dry
Do not feed
CFrequency of feeding  
 Once per day
Twice per day
Thrice per day
Once per week
Twice/Thrice per week
Four-Ten times per week
Once/Twice per month

Table 30: Total-P content and P loadings1 of various feedstuffs commonly used as supplementary feeds in semi-intensive tilapia culture. FCR values refer to O. mossambicus. Data from Jackson et al (1982), NRC (1977), and Balarin and Hatton (1979).

content (%)
FCRtotal-P loading
(k tonne-1 fish culture)
Rice bran0.41--
Copra meal0.60--
Brewery waste0.5312.6063.38
Soya meal0.67  3.0416.97
Groundnut meal0.64 4.9128.02
Cottonseed meal1.01 2.6923.77

1 P loadings calculated as:- total-P fed per tonne fish - total-P content per tonne fish harvested

Table 31: Summary of problem areas associated with the predictive models discussed in the text

Method of CultureProblem Solution
 (a) Intensive Culture Setting of desirable/acceptable water quality criteria-Research into the relationship between mortality of farmed fish, and envirinmental conditions in cages.
-Research into the feedback effects of qualitative changes in the plankton community on cultured fish
-Study of the economics of risk at high production sites
  Estimation of waste production-Research into the nature and bioavailability of wastes, with particular emphasis on diet formulation and manufacture, and the influence of temperature and fish size on feed utilisation and waste composition
-Research into the effects of harvesting schedule (continuous/quantum cropping) on waste output
 Estimate of impact-Research into impacts in different types of inland water body (deep/shallow, N-limited/P-limited, oligotrophic/eutrophic/dystrophic, tropical/temperate, etc.)
(b) Extensive CultureEstimates of conversion efficiencies-Studies on predation efficiencies of planktivorous species under varying conditions (temperature, turbidity, different algal and zooplankton species, etc.)
-Research into the effects of increased predation on one particular trophic level
-Research into the effects of stocking density on predation efficiency and food utilisation
-Research into poly- versus monoculture in enclosures
-Research into diet of cultured species in pens and cages
-Research into the design and siting of enclosures
(c) Semi-intensive cultureThe relationships between supplementary feed quantity and quality, and fish production-Research into the utilisation and nutritional role of materials used as supplementary feeds in pens and cages
-Studies on the effects of stocking density on diet

Table 32: Production of O. niloticus in cages and pens, without supplementary feeding*, in Cardona, Laguna de Bay, Philippines, 1982–83. Cages are 3–5m deep.

Method of cultureArea
Stocking density
(fish m-2)
Stocking period
Size at harvest
(g m-2month-1)
Cage138–29007.46.3119140Lazaga & Roa, 1983
Pen    1500020  4–6170–250833–850Guerrero, 1983

* In fact, limited amounts of feed were given to the caged fish

Table 33: Estimated potential for reduction in total-P wastes associated with intensive fish culture through various feed manufacturing and management options. Costs estimated as ranging from * (inexpensive) to *** expensive.

Option MethodCostReduction
Reduction of dust added to water body-Improved manufacturing (e.g. use of steam conditioning, increased mash transit time in steam conditioner, etc1)**  2%+
-Sieving of feeds by farm staff prior to use*
Reduction of pellet losses to the environment-Improved feeder design**10%+
-Careful siting of cages*
-Careful adjustment of feeding regime to prevailing environmental conditions*
Reduction of total-P load in wastes-Reduced P content in feeds**30%+
-Use of high digestibility diets*30%  
Removal of surplus P added to lake or reservoir during culture-Pumping and removal of wastes from under cages***?   
 -Removal of mortalities to site on shore*10%2
-Trapping and removal of escaped fish*    1.5%2
-Utilisation of wastes through combination with extensive culture??

1 see ADCP (1983)

2 these figures depend very much on extent of mortalities and number of escaped fish

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