Understand aquaculture efficiency
Be able to design basic aquaculture system, understanding
principles for spp selection, stocking needs, nutrient req’mts
Same PC principles apply as for other aspects of design
high oxygen is needed – SO greatest surface area is best; productivity of an aquaculture system is related to area rather than volume, since below two metres, very fish live because:
- less oxygen;
- less light
- less nutrient except in deposited soil and organic material
ie; can be mostly shallow, with deep spots for fish to escape in heat
An aquaculture pond can act as nutrient trap at bottom of system
Actually lose land, BUT Yield 4-20 times land system, because:
1 great diversity – wet soil trees on edge; permanent water levels critical; swamp plants ; emergents (bullrush); floating plants (water hyacinth); submergent plants
ii fish have greatest food-flesh ratio
iii temperature more consistent than surrounding land
Also: – aquatic env’mt can store more solar radiation than grasslands – convert this energy to fish flesh very efficient high protein.
– fastest growing landuse; best integrated with land systems – can yield between 250-1150kg protein/hectare
– water storage
– pest predator habitat – eg; frogs against mozzies
– microclimate and edge
– firebreak and control
SO,try to get 15% of land surface under water, at least during wet season!!!
Water from aquaculture pond is nutrient-rich, so any water used to irrigate plants is super-charged with a ‘soup’ of many nutrients valuable to plants. Win-win!
Why so efficient?
– cold-blooded , so don’t use up energy controlling body temp.
– fish weight supported by water, so more food energy for growth
– can be grown on waste, such as animal residues
– fish farming can be carried out on marginal land, making it productive
- ponds can add another use to existing facilities, such as irrigation dams;
- since aquaculture functions best in slightly alkaline water (7-9), if there is not a regular through-flow of water (in the case of a mostly rain-fed pond for example) acidity may increase especially if animals such as ducks or pigs are used to add fertility to the water as a symbiotic animal-fish system. This can reduce the productivity of the pond through high pH and over nutrification which deprives the water of oxygen.
- In such cases, the pond can be occasionally drained, planted with green manure which absorbs the high-nutrient level of the pond soil, and this can be used as fertilizer, complementing agriculture and increasing overall food prod’n
YIELDS; in terms of protein 4.05ha water > product than 80.9ha grazing
- nutrient water from fish and animals very rich (see above for problems associated with acidity; it has excellent pH level – best used for tree crops as may be too much N for vegetables
The city of Kalkutta in India produces over 20,000kg of fish PER DAY from its aquaculture. Not to mention the amount of other food produced. The system works – theoretically at least – on a series of lakes, each one functioning to treat the pollutants, reducing it to the point where it is healthy enough for edible fish. The first lakes produce biomass which grows biomass for reforestation, while extracting the heaviest pollutants. The next ones also produce vast amounts of biomass, plus fish and other aquatic species are introduced; this process continues, each system extracting more pollutants until the point that fishes which can only live in relatively clean water, survive. Thereafter productive edible aquaculture systems provide the 20,000 kg/day of edible fish plus aquatic edible plants. It’s all win from a pollution source to an abundance of many dimensions.
Factors in Setting up aquaculture ponds
* pH 7-9. Anything under 6.5 won’t be very productive. pH 7.5-8.0 is optimum, but will change at different times of year
- depth at least 2m in middle so fish can escape from heat. >2m is not valuable from a harvest perspective. Ideal temp 18-25degC.
* clear water. Hold large silver coin 450mm under water; if clearly seen, clear enough for fish. Turbidity reduces sun’s penetration and thus algal growth. Small amount of obscurity can inhibit predators. Gypsum will clear muddiness and help balance pH. 560kg/ha added in small quantities is effective in clearing murkiness
* available food required – grow your own food. New dam can be inocculated by taking a bucket of water from old dam to breed up plants and micro-organisms. Algal feeders need heavy manuring and algae needs sun. Grass eaters need water plants along the edges. Taro is an excellent feed with weeds in between. Mulch edge of new dam immediately to encourage edge plants and reduce erosion and run-off. if within 30deg of the Equator, mallee prawn does well. Suspend nets vertically in water to grow algae.
– some as runoff from agricultural land
– from leaves, other deitrus, insects falling from fruit & veg.
- manure from water birds and fish
- manure, scraps added directly; animals can be penned over pond
- pigeon coop standing in pond against fox attack
- floating chicken house;
- pig or cow house flowing into fish pond
– nutrient levels must be monitored, balanced by extra fish etc
– feeding sludge from bio-gas unit
– wild animals – bat nesting-box with rungs and bat shit in first
– bottom sludge should be slightly basic, but often acidic from manure etc – to correct, add lime , or periodically drain and grow high nutrient crop, leaving residue as nutrients in bottom of pond, and refill
* existing vegetation must be assisted to attract insects or drop feed into the dam. It also provides an immediate habitat for micro-organisms.
* size, number of fish and carrying capacity is related to surface area, NOT to depth of water or total volume. The ratio is of Size of Surface: Edge length.
- water level stability and water loss; top up if required. Oxygen levels are one of the most important factors. A reticulation system (running water, esp from height) or flow forms can help.
What are the main factors affecting your yields? Can you suggest ways to improve on this? Brainstorm.
Factors affecting yield
* Pond shape and shape
- longer the edge and greater the shallow area, more food available ; ie; crennelated edge, NOT straight sides or circular
Note also that the catchment area is vegetated fully apart from the small bare ground in foreground. Swales leading around the contour above the dam would greatly add to the catchment area if necessary
- different levels are important to provide range of habitats; large fish naturally move to deeper water and deep water ensures region of lower temps during summer months. Shallow water can carry weed growth which offers protection to small fish, and is source of large quantities of food, providing habitat for water fowl, and producing food crops such as water chestnuts, taro, and arrowhead ie; polyculture.
In case of lake losing water through evaporation or leakage, be sure to have a deep section lined with an impermeable membrane to hold water.
- allows for proper management practices, cleaning of the pond, removal of sludge for use as fertilizer, and complete harvesting of the fish if this is reqruired.* Screen
– at overflow essential to allow for drainage. Bottom slopes to outlet
– are should be managed in complementary ways, should be grassed to reduce muddiness of water, no sprays to be used and stock should be excluded.
– need to be provided for fish – tyres, terra-cotta pipes
* Pond Bottom
– very important in biology of the body of water; a good bottom is able to quickly recycle nutrients and make them available – if poor, bottom decay is slow. Gravel, clay and sand bottoms can be improved by the addition of organic matter such as stable manure, sewerage sludge or by sowing a green manure crop before filling dam with water.
Criteria for selection of plant and animal species
* Pond Size and shape– There is surface area, edge and depth which is suitable for certain species and affects their stocking rate amd available food supply.
– need to consider water temp, and max/min temps and overall geographic areas eg; inland, coast, mountains.
* Available Sunlight
– plant large species on the north (Nth hem) side of dam, since large trees on the south will obscure winter sunlight when it can be most important
– summer temp, wind speed & rainfall will interact. Water levels may need to be topped up
* Environmental Impact
– whether species can escape and become pests and also the interactions between species and symbiosis. Something needs to be known of the food chains in the water, and their inter-relationships. The more suited to their new habitats, the greater the growth rate.
– summer breezes will re-oxygenate the water – appropriate wind machines can be used to oxygenate water also. Perhaps plant wind funnels
* Water Quality
– amount of sediment, watershed and pollution(DDT 100 years in mud) – agricultural runoff -> increased weed growth and algal blooms
– 30m forest on catchment
* Before Stocking
– new dam should be allowed at least 3 months to settle and to allow establishment of a good food supply
Fish Stocking Rates
DO NOT stock low; the fish grow very big and are hard to catch. With very high stocking rates, the fish stay small
100 fish/surface acre without extra feeding
feed via pond fertilization – manures
When stocking ensure that there are no other fish, or eels. Eels can be trapped from empty dams by shaking in Derris Dust which asphyxiates them. After two weeks, the effects of the Derris Dust is gone.
Some fish like to breed under things or on floating rafts, logs and clay pipes
Shrimps like to hide in little things. They will dig holes in dam walls. They love living in beer cans (non-rust aluminium) suspended from a raft. Shrimps will eat worms. Big frogs eat prawns.
Freshwater mussels; can be grown on ropes and can filter 200 gallons of water per day (cleansing like kidneys). They also deposit phosphate.
Goldfish eat mosquitoes.
Different fish occupy different depths of water.
- Insectivorous fish occupy the surface water
- Herbivorous fish occupy the pond edges where there are grasses and other edge aquatic plants. Chinese say: “if you feed one grass carp well, you feed three other fish”.
- Fish which eat predominantly faeces occupy a medium depth
- Mud dwellers extract nutrient from deposited soil (eg; catfish – flesh tends to be ‘gritty’.
- So, ponds can be divided with suspended nets at appropriate depths to separate predator fish from others. Rafts with suspended netting can also be installed. Predator fish only get the little fish that swim by. Fish can also be separated completely in cages:
- In this way, many different species can occupy the same pond any problems arising of carnivorous fish over-eating other species and dominating.
- In marshes and wetlands make sinks to grow fish and prawns. This can also be done in mangroves.
Can have a main pond with small ponds around it.
Management of Fish
* Harvest smaller/medium sized fish (large for breeding
* Use traps,nets or line to catch fish
Lack of Oxygen occurs in hot weather,may occur after rain when organic matter such as animal manures, vegetable matter has been washed into dam. Decomposition of OM uses up oxygen. Sign of oxygen deficiency are dead fish or fish coming to surface gasping for air. Oxygen may be replaced by circulating water or, pumping it up and spraying back onto surface of water. IT CAN BE AVOIDED BY MAINTAINING A BETTER BALANCE IN THE FIRST PLACE.
A windmill – paddle floating on dam.
Air rippling on water will work.
Ducks swimming on the water.
Predators – Cormorants. Fish are quick to learn about safe retreats, not metal pipes or chicken wire as they release chemicals into the water. Abundance of forage fish or crustaceans (shrimps, goldfish) will ease predation pressures on dam fish.
Undesirable Fish – eels are problem (eat fingerlings -> reduce chances of establishing fish in dams). Removed using lights and baits of fresh meat.
Weeds – water hyacinth, but very good food supplement for cattle and pigs
– roots provide habitat for organisms eaten by fish etc
– good compost, mulch
– stems for basket weaving
* Never introduce water weeds unless sure of identity and characteristics
THE ESSENCE OF AQUATIC POLYCULTURE – AQUACULTURE
Each species of fish feeds on specific micro-organisms
Each species can’t use all available food eg; edge species (eg;mulberry) provides fruit, eaten in water by fish, on land by ducks, ducks manure the water, utilized as food by fish/ micro-organisms which feed fish; mulberry also feeds insects drop in water and eaten by fish, as is frass (excrement or other refuse of boring lavae). Leaves which fall in water are also eaten, especially by shrimp.
When food is not fully utilized, imbalances can develop with a drop in oxygen levels.
Good farm combinations are:
Fish and Pigs, Ducks, Domestic Waste, Agricultural Waste eg; rice, Industrial Waste eg; abattoirs, sugarbeet processing, Worm Farming
Fish wastes when there is only one species, can build to levels that foul water and inhibit growth
Limits overcome by stocking several species – match diff levels of food
When up to 6 spp fish, and waterfowl, are stocked, the predators of fish take no more than 15% of fish
Herbiverous fish perform a special function; Chinese say: “if you feed one grass carp well, you feed three other fish”. Grass carp consume massive quantities of partially digested materials, which directly feed bottom-feeding fish ie; common carp, and stimulate production in other parts of the food web. Grass carp can grow as much as 3-4kg/annum. (The Chinese use Mulberries particularly since they feed duck and fish on fruit and the leaves feed shrimp and grass carp).
Production can be increased three times with pig manure/sun/carp. Then water plants growth increased with nutrients from increased fish stocking & growth.
A SUCCESSFUL POLYCULTURE HAS A MIXTURE OF FISH, CRAYFISH, PLANTS, MOLLUSCS, WATER FOWL AND EDGE PLANTS
SEEPAGE areas can be used for mints, bamboo, and trees such as willows, pecans and poplars
There needs to be gradual shelving from ‘dry’ land to 1.2m
Taro->Chinese waterchestnut->Duck potato->Bullrush->Waterlily->Lotus->Indian Chesnut Sagitarria Cumbungi
– perennials and non-cultivated spp help consolidate and stabilize edge, and support insects -> pond and support livestock -> pond manure
– large evergreen to north, deciduous to south
– emergent plants at edge attract insects – add to pond floor: bananas, papaya, pineapple, mango, lychee, feijoa, blueberries, mulberries(add silkworms too), pecans, hazelnuts
Shrubs and Herbs: comfrey, sweet potato, lavenders, lemongrass, fragrant plants, millet, passionfruit, kiwifruit, tea tree
chinese water chestnut (Eleocharis)} 1sq.m. from 1 corm (8-9mths growth high pH – divide when harvesting
indian water chestnut (Trapa) } diff spp.
taro – Colocasia (shallow water or moist soil – good understorey; corm is carbohydrate, also young leaves and stems – steamed, well cooked to destroy calcium oxynate crystals, fermented into poi
kangong – water spinach (Ipomea) convulvulous, leaves very nutritious, and good livestock feed
bullrushes – whole plant is edible; roots eaten like potato
water cress Rorippa aquatica (daily picked with flow)
lotus (water lilies – roots, stems in salad, seeds like popcorn; grows to depth of 2.5m. Embed in ball of soft clay with shot poking out; drop in water.
arrowhead – leaves or root (arrowroot) – ground root to paste, dry for powder as thickener
Fodder grasses: comfrey, kikuyu, wandering jew, sugar cane
Fibre plants: bamboo, papyrus, NZ flax
Island vegetation: chose for controlling rampancy and as nests for birds
cane grass, pampas grass
* Keep plan and diary recording all tree/vegetation info – source, variety, neighbours etc
* Remember: after a few years, dam can be drained and terraces of sleepers etc put in place – excellent planting area for almost any crops
POLYCULTURE: combination of appropriate plant, water and fish spp for max yield, min space –
top – herbivores feed on algae
bottom – dwellers on mud
middle level – fish
Different order of ponds
different size ponds – different products
1. Tyre Pond – good in Zone 1
HOW? 1. Large tractor tyre (NOT radial steel mesh!), with one side-wall cut out, possibly with a serrated edge kitchen knife (hard work!), keeping blade wet, and exerting cutting pressure as you pull up. For radial tyre, use angle grinder with blade, or by drilling holes and cutting with bolt cutters. NB: Tyre not necessary!
2. Dig hole to depth required, slightly larger than tyre diameter. Spread 3cm layer of sand.
3. Lay large sheet of heavy duty plastic – enough for double layer wrapped generously around bottom and sides of tyre, and to line inside. Place tyre on top and plastic wrap. Spread 5cm layer of sand on bottom.
- Soil and composted material in tyre rim for deep water plants, with shallower ones in pots, placed on bricks to required level. Fill slowly
waterlily, taro, water chestnut (Guppies, goldfish against mozzies) Urban Situations
– water tubs, tyreponds, baths
– low maintenance, don’t need watering, weeding or mulching. Attracts birds , raises humidity around pond, good for subtropical plants such as papaya, provides habitat for insect predators (frogs,lizards). Plants are very ornamental.
Siting – needs full sun and low point looks more natural
Requirements – scavengers help establish natural balance, fish and water snails clean up rotting vegetation and algae, goldfish eat mosquito larvae and other insects. Plants and fish prefer mature water so do not empty pond unnecessarily and top up gradually.
Fertilizer – can be small amounts of compost or manure. Water lilies serve practical function by keeping oxygen in water by trapping it under lilypads.
Planting – containers are advantageous because water is clearer, it allows for easy harvesting of plants, easy repotting and division. The pond is easily cleaned. Use a clayey soil with compost or well rotted manure.
2. 4-5m across
– greater range of aquatic plants – eg; with steps
– fresh water prawns
– weed-eating fish (carp, catfish)
– household scraps, compost, manure
- some microclimate effect
3. 5-8m across
– all above, greater variety of fish (polyculture)
4. 1/4 acre
– semi commercial – commercial
– prawns/fish with ducks (feed ducks, manure feeds fish)
– ducks/fish forage themselves, ducks on plants, and emerging vegetation
– freshwater mussels
– need to hold in freshwater > 2hours to clean mud
– good filter system
– excrete phosphates into mud (periodic fertilizer)
– shells can be ground for liming pond, or fed to poultry as Calcium supplement
– in smaller pond, can cause pollution (by dying)
– dragon flies are indicator of good water health
5. Large ponds
– eel (world shortage) and fish rearing – hold eels from muddy ponds for 3 days before harvesting (bones high Calcium source)
NB: eels if stocked too high can destroy fish AND can cross country to get to stocked pond
SO may be better to raise in completely separated tanks, netted against escape!
– prawns farming (10lbs prawns cf. 1lb fish)
– eat leaves
– don’t like overcrowding – like to 2m depth
– need specific water temp (16-25deg) over 32deg will kill BUT can hibernate
BUT shrimps can cause dam leaks with rocky dam wall
AND eels eat ducks
yabbies like cloudy water’ (so ducks good)
many predators (birds, snakes etc) so need refuges
– sensitive to water pollution
6. Very large ponds
– edge vegetation for mulch
- fish and eels and prawns as wild harvest
Where to place pond(s)?
- Depends on where the water source is;
- relatively low maintenance after initial setting-up
- can be multi-functional depending on size (fish/irrigation/recreation/micro-climate influence)
- depends on size and shape of land
- high on the land offers greater potential for gravity-feed irrigation to gardens, fruiting trees, field crops when necessary
- low on land is last opportunity to trap and store soil and nutrients before it otherwise would flow out of the land.
Best is series of ponds – good for building up of nutrient – 4-7% increase in protein from pond compared with stream water
different system each pond (see example above of Kalkutta system for treating polluted water), but an suggestion is:
1st – reeds, ducks, geese (manure fertilizes water, but too high for fish)
nutrients trapped in plants – people, green mulch, fish protein
Azolla (water weed) – floating water fermentation – nitrogen fertilizer overflows to Pond 2
– high protein content – food and green manure, biogas digester, dried and stored as food
Duck weed doesn’t fert nitrogen, high biomass (40tonnes/ha/yr)
1st overflows to 2nd pond
polyculture of plant-eating fish – duckweed and azolla controlled by feeding
duck, geese, mussels, freshwater clams
2nd overflows to 3rd
polyculture including carniverous fish
Each pond should have capacity drain it empty, either by syphon system with pipe, or lock-pipe system.
If it can’t be topped up, then have floating raft and place plants in it. If raft is too high, can be weighed down with baskets of water lilies. Just add soil until raft floats at desired level, OR in case of raft with barrel flotation support, water can be added or subtracted to appropriate level for plants grown in raft. (See Diagrams Dam Construction Profile, and Drainage Pipe through Dam Wall, and Raft Island)
use sweet flavours to attract fruit flies, use honey and sugar 60% of fish food is insects. Can use a brick boiled in liver to attract blowfly family.
ADD one thing at a time to water, and observe what happens.
water-logged and shallow ponds /temp water
– edge between water and land systems
– very diverse 2-3000 useful marsh spp
– imp. as wildlife
– birds for insect control
– flood storage areas – absorb excess runoff, slowly release
– very important bee forage source
– used in treatment of human and industrial waste
– secondary effluent -> swamps -> nutrients and filter
– heavy metal (lead, mercury) temporarily trapped
– production of mulch and fertilizer
– high moisture content
– constant temp and high nutrients -> huge bio-mass
– equiv to seaweed as fertilizer
– grazing and stockfood (pigs, geese cattle)
– levels of limiting amino acid are lower though protein as high
– higher in calcium, potassium, magnesium, than land
– geese grazing with berry growing
– pigs originally forest and marshland foragers
– cattle forage during dry times, provided mud-pugging isn’t serious
Coppicing spp close planted (0.5m sq)
If land is small, and there is a large percentage of swamplands, this can be transformed into a chinampa system, in which the swampy land is trenched, with the material resulting from the deepening placed between each trench to form a mound which can be planted.
Aquaponics see http://en.wikipedia.org/wiki/Aquaponics
Aquaponics is another dimension of aquaculture especially appropriate for small-scale fish raising, with the added benefit of creating a closed-loop of nutrient cycle, with the fish providing the nutrient (through their faeces) for vegetable cultivation.
Of course a far more aesthetically pleasing system can be put together if space is not so important, but this is certainly a great example of stacking in practise!
Aquaponics is a valuable consideration as a recycling potential. These are small and large scale systems, in salt and in fresh water. They can be very simple, such as in the rice-fish systems of South East Asia, or more sophisticated and available as complete systems, at a price of course. Broadly speaking they consist of a series of components in which the water is filtered at various levels and recycled.
How it works (in brief):
- Fish are raised in a tank using a feed of commercial fish food (or by experimenting with various combinations of, for example, flaked grain and manure).
- The over flow of the fish tank (this water is highly enriched by fish faeces) flows through a filter removing solids unusable by plants;
- the ammonium in the faeces may be converted to nitrates by nitrification bacteria in this filter, before it;
- Flows into a tank or tanks in which a medium of substrate (sand, gravel, if not actually soil) supports the plants to be grown;
- the water at the bottom of the system is filtered again and pumped back to the fish tanks.
Since water is a significant factor, this both recycles the precious water, AND reduces water needed to grow the same vegetables outside in the soil. Not a bad result of win-wins, particularly in such a situation of water limitations.
Rearing tank: the tanks for raising and feeding the fish;
- Settling basin: a unit for catching uneaten food and detached biofilms, and for settling out fine particulates;
- Biofilter: a place where the nitrification bacteria can grow and convert ammonia into nitrates, which are usable by the plants;
Hydroponics subsystem: the portion of the system where plants are grown by absorbing excess nutrients from the water;
- Sump: the lowest point in the system where the water flows to and from which it is pumped back to the rearing tanks.
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