Study guide: Prawn and Crab Production Management

📋 Course Outline

1. Fiji Agricultural Trade
2. Trade Issues and Solutions
3. Green Economy and Careers
4. Internal Combustion Engine Principles
5. Engine Maintenance Systems
6. Farm Financial Management Tools
7. Farm Inventory and Labour Records
8. Cash Flow and Business Planning
9. Soil Nutrients and Fertility Evaluation
10. Biological Soil Fertility Testing
11. Soil Water, Moisture, and Air
12. Soil Chemical Properties and Management
13. Plant Breeding Principles and Importance
14. Breeding Types and Sustainable Farming
15. Organic Container Gardening Methods
16. Container Garden Management
17. Potential Crops in Fiji
18. Aquaculture Development in Fiji

📅 Key Dates

1. 1900three scientists rediscovered and publicized Mendel's findings after the paper had been largely ignored
2. 1954Tilapia mossambicus was introduced into ponds at Nacocolevu Agriculture Research Station to support pig diets, escaped into surrounding river systems, and later became both an animal-protein source and a pest to other cultured species
3. 1976the Naduruloulou Government Freshwater Station was established, and carp and tilapia from Lami were transferred there for breeding and release into major rivers
4. 1982the Raviravi farm became Fiji’s first commercial shrimp farm, initially working with Panaeus monodon and later introducing Panaeus stylirostris in 1984 after difficulties producing Panaeus monodon post-larvae
5. 1984–1989JICA assistance supported aquaculture research at Naduruloulou, including the introduction of silver and bighead carp and successful spawning of carp and the giant Malaysian freshwater prawn, Macrobrachium rosenbergii

📖 1. Fiji Agricultural Trade

🔑 Key Concepts & Definitions

• Import: a good or service brought into one country from another
• Export: a good or service produced in the home country and sold to another market

★ Must-know

• Fiji’s major exports include:
  • sugar
  • fish
  • coconuts
  • taro
  • copra
  • pawpaw
  • ginger
  • garments, mineral water and gold

• Fiji recorded a trade deficit of FJD$316 million in the agriculture crop and livestock sub-sector in 2015.

Further detail

• In 2015, the crop and livestock sub-sector’s import bill declined by 7% while domestic exports increased by 10%.

• In 2015, Fiji exported crop and livestock commodities to 46 destinations, with New Zealand dominant in quantity, and imported such commodities from 79 countries, with Australia dominant at 150 million kilograms.

💡 Memory Hook

Imports enter Fiji; exports leave Fiji and earn foreign currency.

📖 2. Trade Issues and Solutions

🔑 Key Concepts & Definitions

• Import substitution: a trade and economic policy that replaces foreign imports with domestic production to reduce foreign dependency

★ Must-know

• Trade facilitation simplifies and harmonises international trade procedures for collecting, presenting, communicating and processing data required for the movement of goods.

• The Fiji Biosecurity Services Division is the first line of defence for safeguarding Fiji by helping remove trade barriers, improve market access and control imported and exported goods.

• Improving Fiji’s trade requires increasing local production, using crop scheduling, developing high-value crops, strengthening organic production, providing technical support, engaging stakeholders and improving trade facilitation and market access.

Further detail

• Fiji adopted an export-oriented, outward-looking trade policy in 1989, and the Government allocated $1 million in 2016 to an export promotion programme intended to improve agricultural production and exports.

• Fiji’s trade agreements include MSG, PICTA, IEPA, SPARTECA and PACER, which address free trade, market access, duty-free exports, customs, standards and quarantine issues.

💡 Memory Hook

Better transport, regulation and production can reduce imports and increase exports.

📖 3. Green Economy and Careers

🔑 Key Concepts & Definitions

• Green economy: reduces environmental risks and ecological scarcities while pursuing sustainable development without degrading the environment
• Green job: employment or self-employment that genuinely contributes to a more sustainable world

★ Must-know

• The three pillars of green development are:

  • economic
  • environmental
  • social

• Green economy benefits include decent work and economic growth, affordable and clean energy, responsible production, climate action, clean water, reduced inequality and improved livelihoods.

Further detail

• Green job sectors include: agriculture and natural resource conservation, clean transportation and fuels, green buildings, pollution prevention and environmental cleanup, renewable energy and energy efficiency, green policy and direction, green funding

• Related careers include:

  • import-export specialist
  • compliance officer
  • logistician
  • marketing manager
  • farm equipment mechanic
  • farm manager
  • market analyst
  • soil scientist and hydrologist

💡 Memory Hook

Economy, environment, society: the three pillars of green development.

📖 4. Internal Combustion Engine Principles

🔑 Key Concepts & Definitions

• Internal combustion engine: an engine in which combustion, or the burning of fuel, takes place inside the cylinder

📝 Essential Points

📌 Internal combustion engines are classified by stroke number as two-stroke or four-stroke engines and by ignition type as spark-ignition or compression-ignition engines.

• 🔄 A four-stroke spark-ignition cycle consists of:
  1. intake
  2. compression
  3. power or ignition
  4. exhaust

• In a two-stroke engine, induction and compression occur together during the piston’s upward movement, while ignition and exhaust occur together during its downward movement.

📌 A spark-ignition engine uses a spark plug to ignite a petrol and air mixture, whereas a compression-ignition engine uses compressed hot air to ignite diesel sprayed by fuel injectors.

• In a compression-ignition engine, only air enters during induction, the air is compressed to approximately 650°C, diesel is injected and ignited during the power stroke, and burnt gases leave during exhaust.

💡 Memory Hook

Four-stroke order: intake → compression → power → exhaust

📖 5. Engine Maintenance Systems

★ Must-know

• The three main enemies are:
  • wear
  • dirt
  • heat

📌 Lubricants and bearings reduce friction and wear, filters prevent dirt from entering the engine, and cooling systems prevent damage from excessive heat.

📌 Water-cooled engines remove heat by circulating coolant through water jackets, whereas air-cooled engines remove heat by blowing air over fins or hot surfaces.

Further detail

• The main tractor systems requiring maintenance are:
  • fuel
  • air intake and exhaust
  • electrical
  • cooling
  • engine oil
  • hydraulic
  • grease-point
  • power-train

• A fuel system includes:
  • a storage tank
  • tubing
  • fittings
  • filters
  • a carburetor
  • fuel injectors

• A water-cooled system may include:
  • a water jacket
  • hoses
  • a radiator cap
  • a radiator
  • a water pump
  • a thermostat

💡 Memory Hook

Wear, dirt, and heat → lubrication, filtration, and cooling

📖 6. Farm Financial Management Tools

🔑 Key Concepts & Definitions

• Profit and loss statement: a financial statement that measures farm revenues and expenses over an accounting period, usually one year, and shows the resulting profit or loss
• Balance sheet: a statement of a farm’s financial position at a specific point in time, showing its assets, liabilities, and owner’s equity

★ Must-know

📐 Formula - Farm profit is calculated as total income minus total expenses: $\text{Profit} = \text{Total income} - \text{Total expenses}$.

📐 Formula - The balance sheet equation is $\text{Assets} = \text{Liabilities} + \text{Owner's equity}$.

📌 Current assets and liabilities are expected to be consumed or settled within 12 months, whereas non-current assets and liabilities extend beyond one year.

📐 Formula - Under the straight-line depreciation method, annual depreciation equals the purchase price minus salvage value divided by the asset’s useful life: $\text{Annual depreciation} = \frac{\text{Purchase price} - \text{Salvage value}}{\text{Useful life}}$.

Further detail

📌 The reducing-balance method charges higher depreciation in the earlier years of an asset’s life and progressively lower depreciation as the asset ages.

💡 Memory Hook

Profit and loss measures a period, whereas the balance sheet measures a point in time

📖 7. Farm Inventory and Labour Records

🔑 Key Concepts & Definitions

• Inventory: a complete listing of merchandise or stock on hand, work in progress, raw materials, finished goods and other farm resources, usually updated annually

★ Must-know

• Common farm inventories include:

  • livestock
  • fertiliser
  • stored stock feed
  • seed
  • machinery

• Accurate inventory records support accrual income statements, year-end balance sheets, income tax filing and planning, marketing decisions, credit applications and farm budgeting.

📌 Family labour consists of family members working on the farm, hired labour is employed for particular work, and permanent labour consists of full-time farm workers.

Further detail

• Labour records may include: employment commencement, promotion and transfer records, wage records, end-of-year payment records, attendance, absence and leave records, occupational retirement and provident fund records, sickness and maternity records, termination records, other staff records

• Labour records help farmers calculate wages, verify employment rights and benefits, track employment history and skills, reduce labour disputes, manage Fiji National Provident Fund payments and support employment claims.

💡 Memory Hook

Inventory tracks farm resources, whereas labour records track people and work.

📖 8. Cash Flow and Business Planning

🔑 Key Concepts & Definitions

• Cash flow plan: a strategic document that forecasts a business's cash inflows and outflows over several periods
• Business plan: a formal decision-making document that states a business's goals and objectives and explains how and when they will be achieved

★ Must-know

• 🔄 A cash flow plan is developed by: identifying start-up capital, determining capital sources, estimating monthly sales, estimating when sales will occur, calculating monthly expenses, transferring the information into the cash flow plan

• A cash flow plan helps a farmer evaluate the current and future cash position, plan financial operations, make short-term financial decisions, develop financial policies and assess loan repayment capacity.

Further detail

• In Farmer X's example, start-up operating costs total $185.00, beginning capital is $300.00, and the projected end-of-year cash balance is $1108.00 after deductions.

• A business plan may contain a cover page, table of contents, executive summary, owner information, business idea and market description, marketing plan, legal form, start-up capital, organisation and staff, operations and costs, financial plan and appendices.

💡 Memory Hook

Capital → sources → sales → timing → expenses → cash-flow plan

📖 9. Soil Nutrients and Fertility Evaluation

🔑 Key Concepts & Definitions

• Soil chemical properties: Soil chemical properties include nutrients, water, air, pH, cation exchange capacity and buffer capacity.

★ Must-know

📌 Macronutrients are required by plants in relatively large amounts and include nitrogen, phosphorus, potassium, calcium, magnesium and sulphur, whereas micronutrients are required in very small amounts and include boron, iron, manganese, copper, zinc, molybdenum, chlorine and cobalt.

• Plants require 18 essential nutrients: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, boron, copper, iron, manganese, zinc, molybdenum, chlorine, cobalt and nickel.

📌 Mobile nutrients can move within the soil or plant, while immobile nutrients cannot be readily translocated; deficiencies of mobile nutrients such as nitrogen commonly appear first in older leaves, whereas deficiencies of immobile nutrients such as calcium appear first in younger leaves.

• Soil fertility evaluation uses:
  • deficiency-symptom observation
  • soil testing
  • plant analysis
  • missing-element tests
  • field trials

Further detail

• 🔄 Soil sampling involves: dividing the field into similar sampling units, avoiding unusual areas, collecting representative portions at the appropriate depth, mixing approximately 20 equal portions into a composite sample, labeling the sample, sending the sample to a laboratory for analysis

💡 Memory Hook

Mobile nutrients show deficiency in older leaves, whereas immobile nutrients show it in younger leaves.

📖 10. Biological Soil Fertility Testing

★ Must-know

• Biological testing measures soil fertility by evaluating plant growth performance after fertilizer application.

• Field plot tests randomly assign selected fertilizer treatments to replicated areas of land to improve reliability and account for variation in soil and management.

• Azotobacter tests can determine soil content of:

  • lime
  • phosphorus
  • potassium

Further detail

• Recommendations from large numbers of field tests on well-characterized soils can be extrapolated to other soils with similar characteristics.

📌 Laboratory and greenhouse tests resemble field tests but are more rapid, use higher plants and small quantities of soil, and are widely accepted in developed and developing countries.

💡 Memory Hook

Field plots → greenhouse tests → microorganisms

📖 11. Soil Water, Moisture, and Air

🔑 Key Concepts & Definitions

• Water Holding Capacity: the ability of soil to retain water according to its pore capacity

★ Must-know

📌 Adhesion water is tightly held as a thin film around soil particles and is unavailable to plants, cohesion water is held in small capillary pores and is available to plants, and gravitational water moves rapidly through macropores and is generally unavailable.

📌 Field capacity is the water remaining 24–48 hours after saturation when gravitational water has drained, whereas permanent wilting point is the minimum moisture at which plants wilt and cannot recover their turgidity.

📐 Formula - Water content by weight is calculated as $\text{Water content}=\frac{\text{moist weight}-\text{dry weight}}{\text{dry weight}}$.

📌 Soil air and soil water have an inverse relationship: increasing soil water usually reduces aeration, while reducing soil water increases aeration.

Further detail

• Gravitational water drains from soil in approximately 2–3 days and can cause plants to wilt because it occupies air space needed to supply oxygen to roots.

• Plant root growth decreases when soil oxygen concentration falls below 10 percent, and soil gases move by diffusion influenced by texture, structure, water content, and compaction.

💡 Memory Hook

Adhesion binds water; cohesion supplies plants; gravity drains it

📖 12. Soil Chemical Properties and Management

🔑 Key Concepts & Definitions

• Soil pH: the negative logarithm of hydrogen ion activity in a solution
• Cation Exchange Capacity: the total amount of exchangeable positive charge that soil can adsorb at a specified pH
• Soil Buffer Capacity: the ability of soil to resist changes in ion concentration or pH, and clay minerals and humic acids provide good buffering

★ Must-know

• The ideal pH for most crops is 6.5–7, while the best pH range for soil microorganisms is 6–8.

• Major sources of soil acidity include: carbonic acid from respiration and precipitation, mineralization of organic matter, oxidation of nitrogen and sulfur, leaching, acidic parent materials, nutrient uptake, excess sulfur or ammonium fertilizers

• Low soil pH restricts nitrogen, sulfur, and molybdenum availability, can make phosphorus unavailable, and increases the solubility and toxicity of aluminium and manganese.

• High-CEC soils generally contain more clay or organic matter, retain more water and cations, and are less susceptible to nutrient leaching than low-CEC sandy soils.

Further detail

• Ions are lost from the soil pool through:

  • plant uptake
  • leaching
  • precipitation
  • secondary mineral formation
  • ion exchange

• Minimum tillage preserves more organic matter and increases soil fertility, CEC, and buffering capacity, whereas excessive tillage reduces organic matter and nutrient-holding capacity.

• Ammonium and ammonium-forming fertilizers such as urea decrease soil pH over time, while calcium, magnesium, potassium, and sodium in fertilizers slightly increase pH or cause no change.

💡 Memory Hook

Clay and organic matter increase exchange and buffering, stabilizing nutrients and pH

📖 13. Plant Breeding Principles and Importance

🔑 Key Concepts & Definitions

• Plant breeding: the art and science of changing plant traits to produce desired characteristics

★ Must-know

• Gregor Mendel explained how dominant and recessive alleles produce visible traits and can be passed to offspring, providing a major scientific insight into plant breeding.

• 🔄 Corn breeding followed these steps: artificially self-pollinate corn plants for generations, cross different self-pollinated lines, produce vigorous hybrid plants

• Plant breeding provides: food security through higher productivity and better yield stability, social benefits through more profitable varieties for poverty alleviation, economic benefits through drought resistance and reduced production costs, environmental benefits through lower pesticide dependence and more efficient water and nutrient use

Further detail

• Selected features included:
  • faster growth
  • larger seeds
  • sweeter fruits

💡 Memory Hook

Selection and genetic crosses → improved plant characteristics

📖 14. Breeding Types and Sustainable Farming

🔑 Key Concepts & Definitions

• Inbreeding: the production of offspring through mating between close relatives and repeated self-pollination
• Crossbreeding: the pollination or breeding of plants from different species, races, breeds, or varieties to produce a hybrid

★ Must-know

📌 Line breeding mates selected members of successive generations to maintain or fix desirable characteristics, whereas outbreeding introduces unrelated genetic material into a breeding line.

• 🔄 Artificial crossing involves: remove the male organs by emasculation, deposit selected pollen onto the female part, bag the flower to prevent contamination, allow fruit and seeds to develop if the cross succeeds

📌 Inbreeding increases homozygosity and uniformity but can reduce vigor and fertility, whereas outbreeding increases variation and heterozygosity and can mask disadvantageous recessive characteristics.

Further detail

• Crossbreeding can produce hybrid vigor, also called heterosis, and introduce traits or genes from one variety or line into a new genetic background.

💡 Memory Hook

Inbreeding fixes traits, whereas outbreeding increases variation

📖 15. Organic Container Gardening Methods

🔑 Key Concepts & Definitions

• Sustainable farming: farming that is economically viable, environmentally sound, protects public health, and uses non-renewable factors thoughtfully and effectively
• Urban agriculture: the growing, processing, and distribution of food and other products through plant cultivation and limited livestock raising in and around cities for local populations
• Permaculture: the development of agricultural ecosystems intended to be sustainable and self-sufficient through ecologically harmonious and efficient design
• Bio-intensive gardening: a sustainable organic method that achieves maximum yields from minimum land while increasing biodiversity and maintaining soil fertility

★ Must-know

📌 Organic container gardening grows plants without synthetic or chemical pest control, weeding, or fertilization by using natural methods and recyclable containers.

📌 Horizontal container growing places containers horizontally on the ground, whereas vertical container growing places containers upward to increase production where space is limited.

• The ten steps for growing organic vegetables in containers are planning the garden, selecting containers, preparing containers, preparing the soil medium, selecting crops, sowing or transplanting, controlling weeds pests and diseases, managing nutrients, managing water, and harvesting.

• For loam or alluvial soil, the ideal container mixture is $1:1:1$, consisting of one part soil, one part composted manure or household or agricultural waste, and one part sawdust, rice hulls, coconut coir dust, or sand.

• For clay soil, the ideal container mixture is $1:2:1$, consisting of one part clay soil, two parts composted manure or household or agricultural waste, and one part sawdust, rice hulls, coconut coir dust, or sand.

Further detail

• Seedlings are raised by filling a drained container with organic starting mix, covering seeds with ½ inch of soil, placing them in warmth and sunlight, watering regularly, and transplanting them after one to two pairs of true leaves form.

📌 Container vegetables should receive about five hours of sunlight each day, regular watering that keeps soil moist but not waterlogged, and well-composted manure or other organic material as a top dressing every two weeks.

💡 Memory Hook

Plan → select → prepare → plant → manage → harvest

📖 16. Container Garden Management

📝 Essential Points

• Container gardens require control of:

  • weeds
  • pests
  • diseases
  • nutrients
  • sunlight
  • water

• Pest, weed, and disease infestation is reduced by placing containers on covered ground, covering the ground with plastic sheets, hand-picking weeds, inspecting plants periodically, and planting repellents such as lemon grass (Coboi) and marigold around the garden.

📌 Organic vegetable plants should be top-dressed with well-composted manure or other composted materials every two weeks to maintain health and productivity.

• Organic container gardens should receive about 5 hours of sunlight each day because sunlight is required for photosynthesis and quality vegetable production.

📌 Container vegetables generally need watering once per day to keep the soil moist but not waterlogged, because waterlogged soil deprives roots of oxygen while dry soil can cause flowers and leaves to drop.

💡 Memory Hook

N-S-W: nutrients, sunlight, water

📖 17. Potential Crops in Fiji

🔑 Key Concepts & Definitions

• Paper Mulberry: a deciduous and dioecious shrub or tree usually growing 10 to 20 metres tall and used for food, fibre, and medicine
• Kuta: a freshwater reed whose stems are dried, flattened, and woven into fine mats, infant cradles, blankets, and traditional sashes

★ Must-know

• The potential-crop categories are:

  • vegetables: wild ferns, rourou, eggplant, and bele
  • shrubs: pandanus, water chestnut, and sago
  • ornamentals: jasmine, orchids, gardenia, carpet grass, and blue grass
  • tree crops: pawpaw, mangoes, heart of palm, and mulberry
  • weeds: seaweeds
  • grasses: duruka, Navua sedge, rice, spices, bamboo, and lemon grass
  • fungi: mushrooms

• Edible bamboo, paper mulberry, and mushrooms are identified as important potential crops in Fiji because demand from foreigners creates opportunities for local production and future exports.

• In Fiji, paper mulberry is propagated vegetatively from root shoots or stem cuttings because the introduced trees are male clones and do not produce seeds.

📌 Raw bamboo shoots contain cyanogenic glycosides, so fresh shoots must be thoroughly cooked before consumption because cooking destroys the toxins.

• Bamboo shoots are harvested by cutting them by hand below ground at the rhizome attachment, after which they are washed, weighed, packed in crushed ice, and optionally frozen for off-season sale.

• Kuta reeds are harvested after about 6 months, bundled, wrapped for four days and four nights, and then sun-dried for 5 days to obtain a golden-brown colour.

Further detail

• Paper mulberry bark is harvested 6 to 12 months after establishment, yielding 2400–2800 kg per hectare, and young trees are commonly coppiced every 6 months for tapa and paper production.

• Fiji has about 20 bamboo species, while approximately 1500 bamboo species occur worldwide, and the three bamboo growth types are monopodial, amphipodial, and sympodial, with sympodial bamboo found in Fiji.

• Eleocharis dulcis is the preferred Kuta species for mat production, and its stems contain transverse septa that are absent in Eleocharis ochrostachys and Eleocharis geniculata.

💡 Memory Hook

Mulberry gives fibre, bamboo gives shoots, and Kuta gives woven reeds

📖 18. Aquaculture Development in Fiji

🔑 Key Concepts & Definitions

• Estuary: an area between river and ocean environments where tides and inflows of freshwater and saline water create nutrient-rich conditions
• Muscle necrosis: a prawn disease characterized by whitish areas in the striated muscle of the tail and appendages that may enlarge and become reddish as the tissue decomposes

📝 Essential Points

📌 Commercial aquaculture in Fiji is intended to provide a long-term alternative to limited inshore fisheries, strengthen food security and income, create employment, increase foreign-exchange earnings, support research and training, and operate in an ecologically sustainable manner.

📌 Aquatic ecosystems are divided into marine ecosystems and freshwater ecosystems, with freshwater systems including lentic, lotic, and wetland environments.

• The main aquaculture environments and structures are: freshwater fish ponds, fish pens, fish cages, or rice paddies, brackish-water coastal fish ponds, marine fish cages or substrates such as stakes, ropes, and rafts

• Extensive freshwater prawn culture stocks post-larvae or juveniles at 1–4/m² and produces less than 500 kg/ha/year, semi-intensive culture stocks them at 4–20/m² with fertilization and feed, and intensive culture stocks them at more than 20/m² with continuous aeration and produces more than 5,000 kg/ha/year.

• The continuous system regularly stocks post-larvae and selectively harvests market-sized prawns, whereas the batch system stocks a pond once, grows the prawns to market size, and then drains the pond completely.

• Lower stocking rates generally produce larger average prawns, whereas higher stocking rates increase total productivity but produce smaller average prawns.

• Post-larvae should be stocked immediately after a pond is filled with filtered water, and transport bags should float in the pond for 15 minutes before release so the prawns acclimatize to the pond temperature.

• Routine management includes:

  • feeding
  • checking water quality
  • controlling pests, weeds, and predators
  • cutting grass on pond verges
  • monitoring water levels
  • keeping records

• Major predators and control measures include: other aquatic species, birds, snakes, humans, perimeter fences, dogs, lighting, and reliable watchmen, screens, netting, or string

📌 Cull-harvesting removes faster-growing market-sized prawns at intervals and leaves smaller or soft-shelled prawns to grow, whereas drain-harvesting removes the remaining prawns after the pond is drained.

💡 Memory Hook

Tilapia → carp → prawns → commercial shrimp farms

📊 Synthesis Tables

Green Development Pillars

Pillar	Documented benefits
Economic	Gross domestic product, economic diversification, green technology and decent work
Environmental	Resource efficiency, ecological limits, climate action and natural hazard management
Social	Livelihoods, decent jobs, knowledge capital and reduced inequality

Spark-Ignition and Compression-Ignition Engines

Feature	Spark ignition	Compression ignition
Fuel	Petrol	Diesel
Ignition	Spark plug	Compressed hot air and fuel injector
Induction	Air-fuel mixture	Air only
Typical pressure	Medium pressure	High pressure