Fish Culture Site and Management

1. Fish Culture Site and Management Principles and Methods of Rehabilitating and Managing Mangroves and Other fish Culture Sites; Elements of Weather (5 Units) • Aquaculture - fishery operations involving all forms of raising and culturing fish and other fishery species in fresh, brackish and marine water areas.

2. TEMPERATUREMeasurement of heat. As fish are cold blooded their metabolism is temperature dependent. A fishes metabolism increases with temperature. All fish have an optimum temperature for growth and food conversion rate. This can vary between species and sometimes between strains of species. Fish will become increasingly stressed at temperatures out with their normal growth range and will cease to feed. In general oceanic marine species are more stenothermic than freshwater and coastal fish, as they have evolved to withstand the temperature changes of the ocean which are slower and less extreme than other environments. For species where the limits are unknown, it is wise to look at their natural environment and the temperatures that they regularly experience, and use these as a guideline. Sudden changes in temperature (even as low as 2oC) can stress fish. When fish are being transferred to water of different temperature, every effort should be made to reduce temperature shock to a minimum. Growth rates and egg development rates are governed by temperature. Optimum temperatures for some species are given below, however these should be regarded as guidelines only, as they can change with different developmental stages and acclimation.

3. Stenothermoc Fish that can only withstand small differences in temperature, the opposite of Eurytherm • Eurythermic Fish that can withstand large differences in temperature • Food conversion rate(F.C.R.) The ratio of the gain in the wet body weight of the fish to the amount of feed fed. The true F.C.R includes wasted feed and mortalities. The ratio, usually expressed as a true ratio (i.e. 1 : 1.5) is often quoted as a "rate" (1.5). Feed conversion ratios of less than 1 : 1 are possible with commercial diets, as the pellet being fed is a "dry" diet, and a high percentage of weight gained by the fish, is water trapped in the tissues and cells. Feed conversion ratios with commercial "dry" diets are typically in the region of 1 : 0.8 to 1 : 1.5. Ratios with wet diets are higher than this, and can be as high as 1 : 10.

4. Dissolved Oxygen Oxygen gas which is in solution (i.e. not that which is present in bubbles) Odourless, colourless gaseous element. Chemical symbol O. Atomic weight 16. Most abundant element in the earth's crust, forms 20.95% of earths atmosphere (by volume). Essential for all forms of aerobic life. Accelerates combustion in the prescience of a fuel source. It is therefore essential that items used near or in oxygen are non-combustible and grease free. Available "pure" (percentage purity usually quoted by supplier) in most countries, as either compressed gas or liquid. 1 m3 oxygen = 1.429kg at 20oC and atmospheric pressure. Boiling point : -183oC, melting point -218.4oC. Used in many farms to supplement the oxygen available in the water to enable more fish to be held in a given flow of water than would otherwise be possible. • Stratification - the separation of different "layers" of water by distinct boundaries. • Algal blooms and fish kills – results in lack of dissolved oxygen or poisoning by other toxins, especially where fish are held in cages at high stocking densities. stenohaline species with low range of salinity tolerance • Anoxic -Completely lacking in oxygen. • stocking densities

5. Diffusion - The movement of a substance from an area of high concentration to an area of low concentration. Turbulent diffusion, or mixing, results from atmospheric motions (wind) diffusing water, vapor, heat, and other chemical components by exchanging parcels called eddies between regions in space in apparent random fashion. Molecular diffusion, which operates in stagnant zones, such as at the bottom sediment-water boundary in a deep lake, occurs much, much more slowly and so is important only on a very small scale such as right at the bottom.

6. Turbidity The ability of light to penetrate through the water. Turbidity is caused by the sum of suspended solids particles and any dissolved chemicals in the water which may restrict the passage of light through the water. The most common method of measurement is by using Secci disc. Electronic meters are available for measuring, but these are only of use in aquaculture in green water systems as the sensitivity of the probes is generally not high enough for other waters. The turbidity of the water can affect aquaculture in a two ways ; 1.By limiting thefeeding capabilities of sight feeders (such as salmonids), 2. By restricting the light available to algae and plants in the water, causing them to die off or limit growth. The treatment of turbid water is dependant on the nature of the particles or chemicals that are causing it.  • Secchi Disc A circular disc, divided into quarters and painted alternately black and white. The disc is lowered on a rope of chain in to the water and used as a measure of water clarity. The depth at which the disc can no longer be seen is noted and used as a measurement value.

7. Green Water System A system in which fish are reared with phytoplankton and zooplankton. Many favour the green water system as a more natural method of rearing some species, especially marine fish and crustaceanlarvae which require live feed in the early stages of development. The system usually involves a static tank, with aeration to give water movement and prevent the tank from becoming stagnant. Algae is seeded into the tank from cultures and nutrients for the growth of algae may be added. Live feed animals are also added, which feed on the phytoplankton, and become prey for the fish. The system is largely unreliable with regard to accurately predicting end survival rates. Some believe that the presence of so many organics in the water has a probiotic effect which can enhance survival rates, but this is largely unproven. The term "Green water System" is not usually applied to ponds which are fertilised for extensive aquaculture, but this application may found in some texts. See also activated sludge, a type of green water system where all the nutrients are kept in suspension.

8. Algae    Algae are simple celled plants and (like all plants) contain chlorophyll. This traps energy from the sun and uses that energy to convert nutrients and carbon dioxide (which are dissolved in the water) into growth. When grown in a hatchery, the growing and multiplying algal cells are collectively known as a culture. The main form of algae that is of interest to aquaculture is collectively known as unicellular. These consist of free floating cells of algae which make the water look green or brown, depending on the colour of the algae. There are many different types of unicellular algae but only a few are nutritionally suited for good growth. These are divided into two types; flagellates, which can swim by the action of one or more flagellae and diatoms, which have an outer shell made of silica. Some of the more commonly grown species and their sizes are listed in the table. Other forms include filamentous, which are strand like colonies of algae, which usually form dense mats or clumps, and blue-green algae, more commonly referred to as cyanobacteria. As well as being grown for food for the fish and also as food for zooplankton, which are then fed to the fish, algae impacts on aquaculture in other ways. These include algal blooms, taints, oxygen depletion, supersaturation and fouling. 

9. Productivity In aquaculture - The capacity of a pond to produce cultivated fish. Measured in weight per area per annum. In general terms, it refers to the total weight of all organisms rather than just the cultivated fish. • Primary Productivity - productivity of the photosynthesizes at the base of the food chain in ecosystems. This refers to the yield of new biomass (plant) growth during a specified time period. The entire year’s accumulation is termed annual production. In the open water of lakes it is typically estimated by measured growth rates of phytoplankton (algae), either via O2 accumulation in light relative to dark bottles of lake water or by the uptake of added radioactive carbon dioxide in sealed bottles of lake water. • Food Web- Food chains hooked together into a complex interconnected web. • Food chains- The transfer of energy in the form of food. • Plankton – Tiny organisms consisting of phytoplankton and zooplankton. • Phytoplankton - the plant component of plankton.

10. Omnivorous – eat both plants and animals. • Metabolism - The chemical and physical processes continually going on in living organisms and cells, by which the energy is provided for cellular processes and activities, and new material is assimilated to repair waste. • Ecosystem - A biological community and the physical environment associated with it. • Primary producers- Organism which uses nutrients and sunlight to exist and does not prey on other organisms as a food source typically phytoplankton. • Ecological pyramid- Conceptual scheme whereby the amount of biomass or energy at each level of the food "chain" decreases as you move from primary producers through the different levels of consumers. • Herbivores- Animal that consumes vegetable and decayed organic matter as the principle constituent of diet. • Zooplankton-The animal component of plankton, consisting mainly of protozoa, rotifers, fish and insect larvae/eggs, small crustaceans. • Primary consumer portion of the zooplankton.

11. Secondary consumers, preying on other zooplankton • Planktivores- Animals that eat plankton; usually refers to fish that feed on zooplankton but can also refer to fish that graze on algae; includes invertebrate predators, such as the phantom midge. • Carnivores -An animal that feeds solely on other animals • Trophic - Classification of organisms according to their feeding relationships. • Omnivorous- Animal that eats both vegetable and animal matter as part of it's diet. • Consumers- Organisms that must eat other organisms for their energy metabolism; organisms that cannot produce new organic matter by photosynthesis or chemosynthesis (producers). • Algae - Simple single-celled, colonial, or multi-celled, aquatic plants. • Photosynthesis- The chemical process by which green plants make organic compounds from a combination of carbon dioxide and water in the presence of sunlight. The process of absorption of carbon dioxide by the plants during daylight hours (which results in the release of oxygen) is reversed during the hours of darkness, when the plants absorb oxygen and release carbon dioxide.

12. Respiration- The process by which animals and plants metaboliseorganic substances, breaking them down into simpler components which produce energy. In most plants and animals the process of respiration requires oxygen, and carbon dioxide and heat production are the end products. The exchange of oxygen and carbon dioxide between the body and the environment is termed external respiration in most animals this takes place at special organs such as gills or lungs and is assisted by respiratory movements (e.g. breathing). Respiration at a cellular level is called Internal (or tissue) respiration. • Anaerobic - does not require oxygen. • Aerobic - requires oxygen, producing carbon dioxide as a waste product. • Inorganic- Substances of mineral, not carbon origin. • Carbon dioxide- Produced as a result of respiration by the fish and other aerobic organisms (including plants) in the system. • Carbon dioxide has the effect of increasing the acidity of the water, it is present in three different forms in the water : CO2 (free carbon dioxide, which is the toxic form), HCO3- (bicarbonate ion, and CO3-- (carbonate ion). The concentration of each is dependant on the pH of the water. The table shows the effect of pH on the proportions of different forms of carbon dioxide in freshwater.

13. Organic- general term, loosely used (although not necessarily always correctly) to refer to any material which consists of live or dead cells, or carbon containing material which is capable of being broken down by biological means. • Photosynthesizers- organisms that produce their energy via photosynthesis. • Macrophytes- term that refers to leaved plants. • Acid - A solution that is a proton (H+) donor and has a pH less than 7 on a scale of 0-14. The lower the pH the greater the acidity of the solution. • Alkalinity - Acid neutralizing or buffering capacity of water; a measure of the ability of water to resist changes in pH caused by the addition of acids or bases and therefore, the main indicator of susceptibility to acid rain; in natural waters it is due primarily to the presence of bicarbonates, carbonates and to a much lesser extent occasionally borates, silicates and phosphates.

14. Liming • Carbohydrate - General term for compounds such as sugars, starches and cellulose. Contain carbon, oxygen and hydrogen. Most carbohydrates can be used as an energy source by animals, although some are difficult to digest (especially by carnivores) and so release only small amounts of energy to the body • Carbon - The essential building block of all organic compounds. Often needs to be added to the water (often in the form of methanol) to supply bacteria in denitrification filters. • Carbon Dioxide - Produced as a result of respiration by the fish and other aerobic organisms (including plants) in the system. The amount of carbon dioxide produced is directly proportionate to the oxygen consumed. For every 1g oxygen that is consumed, 1.4g carbon dioxide is produced. Carbon dioxide has the effect of increasing the acidity of the water, it is present in three different forms in the water : CO2 (free carbon dioxide, which is the toxic form), HCO3- (bicarbonate ion, and CO3-- (carbonate ion). The concentration of each is dependant on the pH of the water

15. Phosphorous - non metallic element. An essential element for living organisms, found in the tissues (especially bones and teeth) and cells. Present in fish feeds as a result of the inclusion of fish and other animal meals. Excreted by fish as a result of more phosphorous being available in the feed than the fish requires. In general 5-15g of phosphate are excreted per kg of dry diets fed to fish. • Carbonate minerals - A group of minerals containing the anion CO32- as the fundamental unit of their structure. Carbonate minerals are used for buffering water to increase the alkalinity. See also lime • Lime - is a generic term used to encompass a variety of compounds all of which are alkaline. The compounds differ in their pH values and their buffering capacities, a summary is given in the table. Lime is used to increase the pH of water, disinfect ponds and pond bottoms and oxidiseorganic matter that has built up in the sediments.  • Liming - The process of addition of lime to a body of water or a pond. • ammonia - The unionised form of ammonia (although sometimes used to express the total ammonia (i.e. unionised and ionised). Symbol NH3. Toxic to fish. See unionised ammonia for more details on toxicity. The amount of ammonia produced by the fish is approximately 0.03 x feed (for commercial diets).

16. Nitrate - Chemical symbol NO3 - Formed as a result of the breakdown of ammonia to nitrite and then to nitrate by bacteria (see nitrification). May also be present in watercourses through run-off from the addition of nitrate as fertiliser to agricultural land. Nitrate, along with phosphate form one of the critical chemicals that all plants require. • Zeolites - The exchange of ions from one medium (usually water or another liquid) to another medium (usually a solid). There are two types of ion exchange material, anionic and cationic. The former will exchange positive ions (as it has negative ions built into it's structure) and the latter will exchange negative ions (as it has positive ions built into it's structure). The most commonly used ion exchange in aquaculture is with the use of zeolite material (an inorganic polymer) in which positive ions are held within a silicate lattice. • Sodium hydroxide - Chemical symbol NaOH - Chemical sometimes used to raise the alkalinity and pH of the water. Easy to overdose due to the high alkalinity of the chemical, resulting in a very high pH and a fish kill through rapid pH change. • Nitrite - Chemical symbol NO2 - Toxic chemical formed during the oxidation of ammonia to nitrate by bacteria (se nitrification

17. Nitrobacter - Species of aerobic bacteria which converts nitrite to nitrate. One of the critical bacteria in biological filtration. Optimum pH range between 6.0 and 9.0, temperature 10oC - 34oC. • Nitrification - The oxidation of ammonia to nitrite and then nitrate by bacteria. pH (hydrogen­ ion concentration) pH is a measure of the acidic or basic (alkaline) nature of a solution. The concentration of the hydrogen ion [H+] activity in a solution determines the pH. Mathematically this is expressed as: pH = - log [H+] • ph is very importance in culturing an organism to determine if the area if it is toxic due to the run-off of agricultural ,domestic, industrial that may contain iron , aluminum, ammonia, mercury or other elements in order to live or grow. Hence , without knowing the ph level higher than the 5.5 the fish might be die. • pH in pond management is desired and tolerable of A pH range of 6.0 to 9.0 appears to provide protection for the life of freshwater fish and bottom dwelling invertebrates

18. The pH value is the negative power to which 10 must be raised to equal the hydrogen ion concentration. • Limiting pH Values Minimum Maximum Effects 3.8 10.0 Fish eggs could be hatched, but deformed young are often produced 4.0 10.1 Limits for the most resistant fish species 4.1 9.5 Range tolerated by trout--- 4.3 Carp die in five days 4.5 9.0 Trout eggs and larvae develop normally 4.6 9.5 Limits for perch--- 5.0 Limits for stickleback fish 5.0 9.0 Tolerable range for most fish--- 8.7 Upper limit for good fishing waters 5.4 11.4 Fish avoid waters beyond these limits

19. 6.0 7.2 Optimum (best) range for fish eggs--- 1.0 Mosquito larvae are destroyed at this pH value 3.3 4.7 Mosquito larvae live within this range 7.5 8.4 Best range for the growth of algae Nitrate-Nitrite Nitrogen • Nitrogen - N2 • Nitrate - NO3 • Nitrite - NO2 Nitrites can produce a serious condition in fish called "brown blood disease." Nitrites also react directly with hemoglobin in human blood and other warm-blooded animals to produce methemoglobin. Methemoglobin destroys the ability of red blood cells to transport oxygen. This condition is especially serious in babies under three months of age. It causes a condition known as methemoglobinemia or "blue baby" disease. Water with nitrite levels exceeding 1.0 mg/l should not be used for feeding babies. Nitrite/nitrogen levels below 90 mg/l and nitrate levels below 0.5 mg/l seem to have no effect on warm water

20. Nitrogen is one of the most abundant elements. About 80 percent of the air we breath is nitrogen. It is found in the cells of all living things and is a major component of proteins. Inorganic nitrogen may exist in the free state as a gas N2, or as nitrate NO3-, nitrite NO2-, or ammonia NH3+. Organic nitrogen is found in proteins and is continually recycled by plants and animals. Phosphorus Phosphorus is one of the key elements necessary for growth of plants and animals. Phosphorus in elemental form is very toxic and is subject to bioaccumulation. Phosphates PO4--- are formed from this element. Phosphates exist in three forms: orthophosphate, metaphosphate (or polyphosphate) and organically bound phosphate. Each compound contains phosphorous in a different chemical formula. Ortho forms are produced by natural processes and are found in sewage. Poly forms are used for treating boiler waters and in detergents. In water, they change into the ortho form. Organic phosphates are important in nature. Their occurrence may result from the breakdown of organic pesticides which contain phosphates. They may exist in solution, as particles, loose fragments, or in the bodies of aquatic organisms.

21. Rainfall can cause varying amounts of phosphates to wash from farm soils into nearby waterways. Phosphate will stimulate the growth of plankton and aquatic plants which provide food for fish. This increased growth may cause an increase in the fish population and improve the overall water quality. However, if an excess of phosphate enters the waterway, algae and aquatic plants will grow wildly, choke up the waterway and use up large amounts of oxygen. This condition is known as eutrophication or over-fertilization of receiving waters. The rapid growth of aquatic vegetation can cause the death and decay of vegetation and aquatic life because of the decrease in dissolved oxygen levels. Osmoregulation The process by which an animal maintains it's correct balance of salts and water in it's body. For example, marine fish are unable to osmo-regulate correctly in freshwater; in seawater their osmoregulation system discharges salt from the body and keeps water, but in freshwater they need to reverse this operation as salts are scarce and freshwater is plentiful. See diagram for processes in fresh and saltwater. The natural salts concentration in a fishes body is 10 parts per thousand. Some aquaculturists who farm euryhaline species, claim that maintaining their stock in systems at 10 parts per thousand salinity, reduces stress and promotes growth rates.

22. Diff and 'Oz' The permeability of the gills and gut and, to a lesser extent, the skin, which are all in close contact with the water, leads to a further challenge for aquatic animals. Diffusion or osmosis alone would eventually result in the fluid of a fish's body being identical to that of the surrounding water, just as a sugar cube, left in a hot cup of tea, would eventually fully dissolve and be spread evenly throughout the tea (by diffusion). If the fluid within the fish were to be dissolved thoroughly with the water surrounding it we would, I'm afraid, have a dead fish! But the composition of the body fluids is obviously different to the pond water and has to be maintained that way if the fish is to remain alive and healthy. So how does a fish manage to do this? What is it that keeps a fish's body fluids stable and different to the surrounding water? • Constant urination The body fluids of a freshwater contain more dissolved salts and ions than the surrounding water. As a result of this imbalance there is a constant influx of water into its body and a loss of salts and ions from the blood outwards. A similar effect occurs if you put a dried raisin or apricot into distilled water. There is a net influx of water molecules through the skin of the dried fruit and it swells up to look like a grape again. (Try it!) • The mechanism may seem complex but essentially a fish has to rid its body of excess inflowing water by constantly excreting a weak solution of urine. Fresh-water fish can urinate approximately 30 per cent of their body mass each day. Salts are removed from the urine before it is excreted (fish are not wasters, remember) and they are also actively taken up from the water by way of the gills in order to maintain internal salt levels.

23. Photosynthesis • The chemical process by which green plants make organic compounds from a combination of carbon dioxide and water in the presence of sunlight. The process of absorption of carbon dioxide by the plants during daylight hours (which results in the release of oxygen) is reversed during the hours of darkness, when the plants absorb oxygen and release carbon dioxide. This can lead to a reduction in the dissolved oxygen concentration of waters containing plant matter (algae or higher plant types) which culminates in a minimum concentration, which is usually experienced just before dawn. Even in comparatively clean waters, the effect of algae can reduce the dissolved oxygen concentrations to less than 80% saturated at dawn. It is important for all farmers to check, at varying times of the year, and during varying weather conditions, the extent of the fall of dissolved oxygen concentrations at dawn. This will then assist in predicting low oxygen levels and being able to take preventative action such as feeding early in the day so that the maximum oxygen demand by the fish occurs in the afternoon and evening, when there is plenty of oxygen available. An addition precaution is to install aeration or oxygenation devices on a simple timer so that they start when the oxygen is likely to be at it's lowest. The use of oxygen controllers is preferable, but the cost of such items often prohibits their use. In such circumstances, timers are an effective solution.

24. Stocking Density The weight or number of fish held per unit area or volume. Stocking densities depend on the species and it's tolerance to the stress of increased overcrowding. For example crustacean species will begin to fight, leading to the loss of limbs and reduction in market value if over stocked. Many finfish species will bite each other (particularly on the fins if overstocked. The effects of overstocking can be alleviated by attention to the water quality and also the feeding regimes. The accumulative effect of stresses on the fish, has lead to the realisation that high stocking densities can be tolerated by the fish if other stresses such as low dissolved oxygen, poor diet etc. are eliminated. It is by using this methods that some recirculation systems, which have total control over their water quality, can achieve efficient production at stocking densities of over 100kg/m3.

25. STRESS • Can be defined as "A stimulus acting on a biological system and the system reacting to that stimulus" Stress changes a biological system from one that acquires energy to one that uses it. Stress can be divided up into two types, acute (such as handling)  and chronic (such as continued poor water quality. Stress is cumulative, i.e. a fish that is suffering from low dissolved oxygen stress will increase stress levels if it is then handled. This is because all the stresses act in the same way which results in the release of plasma corticosteroids from the kidney. In addition to changing the body to one that starts using energy, rather than storing it, this also results in a suppression of the immune system and therefore the animal is at greater risk of disease. The level of Plasma corticosteroids in the body can remain high for longer than the period when the stress occurs, leading to effects from the stress several days after it has occurred. Stress is of paramount importance for a successful aquaculture system, stressors should at all times be kept to a minimum. • Corticosteroid - A general term for hormones produced by the adrenal glands.

26. Feed Rate The amount of food give to fish over a specified period of time. the most common way of expressing this is as percentage of the animals body weight per day. For example a 1000 gram fish, being fed 20g of food per day would be on a 2% feed rate [(20 / 1000 ) x 100)] Suspended Solids • Particles larger than 0.45 microns which are found in the water column. The maximum size of suspended solids is dependant on their specific gravity and the velocity and turbulence of the water. In turbulent waters large and heavy items can remain in the water column, however in slower moving and still waters, these items may settle to the bottom and are then not regarded as suspended solids. Feed Conversion ratio (F.C.R.) • The ratio of the gain in the wet body weight of the fish to the amount of feed fed. The true F.C.R includes wasted feed and mortalities. The ratio, usually expressed as a true ratio (i.e. 1 : 1.5) is often quoted as a "rate" (1.5). Feed conversion ratios of less than 1 : 1 are possible with commercial diets, as the pellet being fed is a "dry" diet, and a high percentage of weight gained by the fish, is water trapped in the tissues and cells. Feed conversion ratios with commercial "dry" diets are typically in the region of 1 : 0.8 to 1 : 1.5. Ratios with wet diets are higher than this, and can be as high as 1 : 10.