Length
1 metre = 1.09 yard = 3.28 feet = 39.37 inches
1 inch = 2.54 cm. 1 foot = 30.5 cm 1 kilometre = 0.62 miles
1 mile = 1609 m = 1760 yd = 5280 feet
1 fathom = 1.83 m = 6 feet
Weight
1 kilogram = 2.2 pound = 35.3 ounce 1 ounce = 28.35 grams
1 1b = 0.454 kg. 1 U.K. Ton = 2240 1b = 1016 kg
1 short tone = 2000 1b. 1 metric ton = 1000 kg = 2200 1b.
Area
1 metre2 = 1.196 yd2 = 10.76 feet2
1 hectare = 10,000 m2 = 2.47 acre = 11,960 yd2
1 mile2 = 640 acres = 259 ha = 2.59 km2
1 acre = 0.404 ha = 4840 yd2 = 4047 m2
Volume
1 metre3 = 1.31 yd3 = 35.3 feet3 = 220 U.K. gal = 1000 litres
1 ft3 = 6.2 U.K. gal. 1 U.S. gal = 0.83 = 0.13 ft3 = 3.79 litres
1 U.K. gal = 0.16 ft3 = 4.55 1. 1 acre foot = 1234 m3
1 U.S. bushel = 0.03523 m3
Flow
1 U.K. gal/min = 7.58 × 10-7m3/sec
1 million gal/day (mgd) = 694.4 gmp = 1.86 cusecs
1 cusec = 1 ft3/sec = 0.0028 m3sec (cumec)
Velocity
1 metre/sec = 3.6 km/h = 3.28 ft/sec = 2.237 miles/hr = 1.943 knots
1 knot = 0.5144 m/sec
Pressure
1 standard atmosphere = 760 mmHg = 1.013 bar = 14.7 lb/ft2= 1.03 kgf/cm2
1 standard atmosphere = 29.2 inHg = 33.89 ft H2O = 1.013 × 105Pascals (Pa).
1 bar = 1.0 × 105Pa.
Volumetric Conversion Factors
From | To | Multiply By | From | To | Multiply By |
mg% | ug% mEg/1 ug/m1 | 1000 (10/eg.wt.) 10 | wt% | g/1 oz/gal oz/ton* fine ppm ug/m1 | 10 p 1.335 p 326.7 10 10,000 10,000 p |
ug% | mg% mEg/1 ug/m1 | 0.001 (0.01/eg.wt.) 0.001 | |||
mEg/1 | mg% ug% ug/m1 | 0.1 × eg. wt. 100 × eg. wt. eg. wt. | ppm | g/1 oz/gal oz/ton* fine ug/m1 wt% molar | 0.001 p 0.0001335 p 0.03267 0.001 p 0.0001 (p/100 × atomic wt.) |
g/1 | oz/gal mg/1 ug/m1 wt% | 0.1335 1000 1000 0.1 | |||
ug/m1 | mg% ug% mEg/1 g/1 ppm wt% oz/gal oz/ton* fine molar | 0.1 100 (1/eg.wt.) 0.001 (1/p) (1/10,000 p) 0.0001335 (0.03267/p) (1000/p) (1/1000 × atomic wt.) | |||
oz/gal | g/1 ug/m1 wt.% | 7.491 7491 (0.7491/p) | |||
oz/ton* | ppm wt% fine | 30.61 0.003061 0.03061 | |||
fine | oz/ton* wt% ppm | 32.67 0.1 1000 | |||
molar | ug/ml ppm | 1000 × atomic wt (1000 × atomic wt/p) |
Definition of Compound Units
Power, Energy, Heat
1 Joule = 1 watt second = 9.48 Btu = 2.39 × 10-4 kcal
Water heat capacity = 4.2 j/kg °C
Density
1 g/1 = 1 kg/m3 16 kg/m3 = 1 1b/ft3
Filter flow
1 gpm/ft2 (U.K.) = 2.94 m3/h/m2 = 1440 gpd/ft2
1 gpm/ft2 (U.S.) = 2.44 m3/h/m2
Loading (mass per unit area)
1 1b/ft2 = 4.89 kg/m2
Miscellaneous
1 Newton = 1 mkg/sec2 (m × a)
1 Joule = 1 m2kg/sec2 (f × 1)
1 ft1bf/sec = 1.356 W
1 ft/sec2 = 2.58 × 10-5m/sec2
O2, NH3, NO2, BOD, Suspended Solids, PV, pH, H2S, PO4P
The following are abreviated versions of the full methods of analysis used in most laboratories. As such, they are acceptable for most field determinations for aquaculture use, provided there are no interfering ions, but for detailed experimental work, the following sources should be consulted (see book list).
Standard Methods for Water and Waste Water Examination APHA/AWWA - the basic “bible” for water chemistry, but incomplete coverage of seawater methods.
Methods for Physical & Chemical Analysis of Fresh waters, Gulterman et.al 1BP handbook No. 8
• a good practical guide for freshwater analysis.
A Practical Handbook of Swawater Analysis, Fisheries Research Board of Canada, Bulletin 167. the “bible” for sea water analysis.
Water Analysis, Mackereth, Heron and Talling, FBA Scientific Publication No. 36.
Note should be made of the accuracy of the method employed in terms of the information required. For many routine aquaculture purposes, appropriate checks of a feq parameters, such as O2, pH, NH3, solid critical to the health and survival of the fish, will suffice. Other cases, such as nutrient budgets in ponds, waste output by fish, require more careful examination. (see Table 4). In all cases, sampling and storage procedures exert a considerable influence on the accuracy of results.
Table 4
IDEAL SAMPLING REQUIREMENTS
PURPOSE | PARAMETERS | FREQUENCY | |
1) | Commissioning new systems recycle systems etc. | O2, NH3, NO2, pH, CO2, solids | Twice daily, with 24-hr runs at 2 hr max interval |
2) | Routine operation, recycle systems, heavily loaded open flow | As above | Check feeding twice daily if load changes |
3) | Routine operation, openflow intensive systems, at medium stock density | As above, also BOD, NO3 PO4 if discharge regulations | Weekly plus O2, NH3 at low flow/high temp. period |
4) | Experimental intensive ponds | O2m NH3, CO2, pH Secchi disk PO4NO3 Chloraphyll | Daily with 24 hr runs check feeding |
5) | Routine operation,intensive ponds | As above | Weekly, plus extra during high loading |
6) | Freshwater cages | O2, NH3, CO2,pH, Secchi disk | Weekly plus O2NH3 checks during high loading |
7) | Seawater cages | O2 salinity | Weekly, plus exceptional tide/rainfall periods |
8) | Hatcheries | O2, NH3, NO2, CO2, pH, solids, salinity (if seawater) | Daily, check also during feeding |
9) | Effluent aquaculture | As for (3), plus specifics assoc. with the combined process (eg. Chlorine, metals) | Daily, plus checks during effluent changes |
NOTE : Temperature and weather conditions should normally be recorded daily at a standard time; a min/max. thermometer may also be used. Generally the more heavily loaded and the more untried the system, the greater the frequency of sampling required.
SAMPLING AND STORAGE
The method and frequency of sampling are important in the use that can be made of the results for aquaculture purposes. As most aquaculture systems are composed of many variable biological and chemical processes, concentrations of water quality parameters can vary considerably in a short time. Similarly, once a sample is taken, changes can continue to take place within the sample, and it is essential to perform the analyses as soon as possible, or proserve the sample by some suitable means. The stability of sample depends on the level of microbiological activity in the water, and the chemical stability of the substance to be analysed : Table 2 shows typical procedures
PARAMETER | SAMPLING | STORAGE |
O2 | Immediate, avoid splashing, agitation | Add first two Winkler reagents if minimal organic matter |
NH3, NO2, NO3 Organic C | Immediate, at least within 2 hrs | Freeze, or add 5 ml/litre 2MH2SO4 |
Organic solids CO2, pH, HCO3-, hardness, alkalinity | As above | 5 ml/litre CHCL3 |
PO4-P, dissolved organic P | As above | CHCL3 or H2SO4 as above Do not use soda-glass |
Trace elements | 5ml/litre NHO3 |
Always record sampling method, sampling time, and storage method used. Note also the importance of obtaining a clean, representative sample of the water to be tested - wash the sample container out at least twice, with the water to be sampled, before sampling.
Worked Example
25 g of pelleted diet was fed to a single fish over a 5 week test period. The initial weight of the fish was 10 g (wet weight), and at the end of the 2 week test period was 25 g (wet weight).
Calculation:
Amount of food fed | 25 g |
Initial fish weight | 10 g |
Final fish weight | 25 g |
Food conversion over experimental test period = 1.66
Worked Example and Growth Rate Checks
Specific Growth Rate =
Worked Example
Specific Growth Rate (%) = 1.460
The following guidelines should be adhered to whenever possible:
Never mix newly introduced fish to the farm with established stocks of fish without carrying out health checks and quarantine procedures.
Never mix broodstock from different sources without quarantine and prophylactic treatment.
Never mix broodstock with fry or fingerlings. Adults are often resistant to organisms which cause disease in younger fish.
Wherever possible remove wild fish from the water source and from pond prior to stocking.
Health Checking
Wherever possible samples of newly introduced fish should be subjected to examination for disease organisms and then given treatment baths if necessary. For further advice on health checks contact N.I.F.I.
Quarantine
New stocks of fish should be isolated whenever possible until health checking and prophylactic treatment has been carried out.
Use all chemicals for Disinfection and Treatment with the greatest CAUTION. Use protective clothing and avoid contact with eyes and skin.
Chemicals for Disinfection
1. For Utensils
Iodophors. Soak in a dilute solution of 1–2% iodine after removal of dirt by scrubbing. The solution may be sprayed onto all surfaces. The chemical should be thoroughly removed by rinsing before stocking. FAM, Wescodyne and Betadyne from VANODYNE INTERNATIONAL are most commonly used. Use according the manufacturer's instructions. These iodophors have the advantage of being bacteriocidal and viracidal.
Chlorine. A concentration of 200 ppm chlorine for 30–60 minutes is effective. It is, however, corrosive. Chlorox contains 5.25% hypochlorite (HTH, or High Test Hypochlorite, and contains a 65% Chlorine concentration).
Roccal. This is a quaternary ammonium compound and is a useful disinfectant for nets and equipment. It is most effective in alkaline water at 1–2 ppm for 1 hour. NB. It is more toxic in soft water.
Formalin. This can be used for nets or surface disinfectant at about 1000 ppm.
2. For Tanks and Ponds
Earth ponds should be drained if at all possible between stocking. The action of DRYING and SUNLIGHT has an excellent disinfectant action.
Chemical disinfection ponds is also best undertaken when ponds are dry or when water is at its lowest level. Less chemical is thus required. A concentrated solution of the disinfectant can be sprayed on the bottom and this is subsequently diluted when ponds are filled.
Chemical Disinfectants for Ponds
Calcium Oxide (Quicklime). This is usually added to the bottom and sides of drained but wet ponds as a solid at a rate of 150–200 kg/ hectare. Use with extreme caution.
Calcium Hydroxide (Slaked lime, hydrated lime). This is used in the same way as Calcium Oxide ie. sprinkle on sides and bottom of drained or wet ponds at the same rate of application. Use with extreme caution.
Calcium hypochlorite (HTH) (70% available Chlorine). This should be used at a rate of 10 ppm available Chlorine or 10–12 g per cu. metre. Sprinkle or spray into wet ponds and leave for several days so that the chlorine slowly disappears. Chlorine can also be neutralised with Sodium Thiosulphate. Use with extreme caution, dangerous to eyes nose etc.
3. For Eggs
Eyed eggs may be treated safely with the following chemicals:
Iodophors. A 10–15 minute dip in 50–100 ppm Iodine in water buffered to pH 7.0–8.0.
Malachite Green. Zinc-free malachite is useful to control Saprolegnia fungus on eggs at a rate of 2–5 ppm as a bath treatment for 1 hour.
Removal of Predators and Pests
1. Wild Fish
Wild fish which may carry disease or predate young fish should be removed from the ponds prior to stocking and from the water source. Hydrate lime or chlorine is usually effective. Otherwise Rotenone may be used. Emulsifiable rotenone is most easy to use and contains 5% rotenone. It is a liquid and requires no mixing before application. For normal pond use 0.5–1.0 ppm is sufficient.
2. Piscivorous Birds
Feeding by these birds at the ponds should always be avoided wherever possible. Apart from loss of fish stocks, many harbour parasites which can be passed on to the fish.
3. Molluscs
Many molluscs, particularly snails, contain parasites which can be passed on to the fish. Unless fish which feed specifically on snails are being stocked into the ponds, snails should always be removed.
Copper sulphate is effective at 0.1 ppm in soft water and 2.0 ppm in hard water. Copper sulphate also kills algae in the water and may result in deoxygenation.
Molluscicides such as Frescon and Bayluscicides are excellent for clearing molluscs but are very toxic to fish. Use according to manufacturer's instructions only in the absence of fish.
Useful conversions:
1 ppm = 1 mg/litre = 4.5 mg/gallon = 28.3 mg/cu.ft.
1 cu. metre = 1000 litres
1 gallon = 4.55 litres
1 gallon weighs 10 lg (4.53 kg)
1 litre weighs 1 kg (2.2 lb)
Example 1
A pond of dimensions approximately 50 m × 50 m × 2 m is to be treated with Dipterex to control crustacean ectoparasite infection. Dipterex is available as a 50% active solution.
Volume of pond | = | 50 × 50 × 2 = 5000 cu.m. |
= | 5000 × 1000 litres | |
Dose-rate | = | 0.25 ppm Dipterex |
= | 0.25 mg/litre | |
= | 5000 × 1000 × 0.25 mg | |
Quantity needed | = | ![]() |
= | ![]() | |
= | 1.25 kg Dipterex |
Dipterex is provided in solution at 50%. As 1 litre of solution weighs 1 kg but this is only half-strength, a total of 1.25 × 2 = 2.5 litres of 50% Dipterex will be needed to treat the entire pond.
Treatment is carried out by diluting the Dipterex further and spraying onto the entire surface to ensure even dispersal.
Example 2
Clarias are being on-grown in a large pond system. Sample weighing has revealed that the average size of each fish is 500 gm and the total stock to be treated number approximately 20,000. Fish are being fed at 10% body weight daily. The fish are suffering Aeromonas infection and are to be treated with Oxytetracycline at a dose-rate of 7 g/100 kg fish/day for 10 days.
Total weight of fish to be treated | = | ![]() |
= | 10,000 kg | |
Amount of antibiotic needed | = | ![]() |
= | 700 g/day |
To ensure efficient feeding, fish will be fed at half the normal rate i.e. 5% body weight daily.
\ | Total food fed daily in 5% of 10,000 kg |
= 500 kg | |
\ | 700 g of antibiotic will be added to 500 kg food daily for |
10 days. |