Shrimp Farming

Indian shrimp farming is concentrated in the coastal tracts of Andhra Pradesh, Tamil Nadu, Gujarat, West Bengal and Odisha, with production dominated by the Pacific white shrimp Litopenaeus vannamei following its introduction, and by the black tiger Penaeus monodon which preceded it and retains a place in certain systems and markets. The freshwater prawn Macrobrachium rosenbergii is farmed inland under quite different conditions and is included here because its husbandry shares much of the same logic.

The industry's history is instructive. Rapid expansion in the early years was followed by widespread viral disease that closed farms across whole districts, and the recovery was built on a specific set of changes: hatchery-produced postlarvae certified free of named pathogens, water treatment before intake, reduced or zero water exchange during the crop, and reservoir and settlement infrastructure inside the farm boundary. Those changes are the reason modern shrimp farming looks the way it does.

Shrimp is India's leading aquaculture export by value and a major source of coastal employment, spanning hatcheries, feed mills, farms, processing plants and cold chain logistics. A shrimp crop turns over in months rather than years, which means capital cycles quickly and both gains and losses are realised quickly.

It also matters as a technical discipline because shrimp farming forced the sector to take biosecurity seriously. The practices that are now standard in shrimp — certified seed, treated intake water, reduced exchange, crop records and disease reporting — were developed under commercial pressure after very large losses, and they transfer usefully to other species and systems where the consequences of failure have simply not yet been as visible.

Finally, the export market imposes requirements that reach back into farm practice: traceability of seed and feed, restrictions on antimicrobial use, residue testing and documentation. A farm that cannot produce a credible record of what it did cannot reliably sell into that market regardless of the quality of the animal it grew.

The moult cycle

Shrimp grow by shedding the exoskeleton and expanding before the new shell hardens. The animal is soft, vulnerable and largely defenceless during that window, and moulting draws heavily on calcium, magnesium and other minerals from the water. Mineral balance, and particularly the relationship between calcium, magnesium and potassium, therefore has a direct effect on moulting success — a consideration that becomes acute in low-salinity inland culture where the ionic profile of the water differs from diluted seawater.

A benthic animal

Shrimp live at the pond bottom, which is also where uneaten feed, faeces and dead algae accumulate. The sediment surface is where oxygen is lowest, where anaerobic pockets generate hydrogen sulphide, and where the animal spends its entire life. Pond bottom condition is not one factor among several in shrimp culture; it is the environment the crop actually occupies.

Postlarval quality

The crop begins with postlarvae, and their quality determines a large share of the outcome before the farm has done anything. Origin from a hatchery operating a specific-pathogen-free broodstock programme, screening for the relevant pathogens, uniformity of size, activity, gut fullness and response to stress testing are all assessable before stocking, and none of them can be corrected afterwards.

Aeration as life support

Intensive shrimp ponds depend on mechanical aeration continuously, not intermittently. Aerators supply oxygen and, equally importantly, create a circulation pattern that concentrates settleable solids into a central zone where they can be removed. Aerator placement is therefore a sediment management decision as much as an oxygenation one, and a power interruption at high biomass produces losses within a very short time.

Shrimp crops are managed by a small set of derived quantities, all of which depend on an honest estimate of how many animals are still alive.

Water chemistry in shrimp ponds turns on a few interacting variables. Alkalinity buffers the daily pH swing driven by algal photosynthesis; pH in turn governs how much of the total ammonia is present in its un-ionised, toxic form; and both alkalinity and mineral ratios affect moulting. In low-salinity inland ponds these relationships require deliberate management, because the water has not arrived with the ionic proportions of seawater.

The crop is decided before stocking. Pond preparation, water preparation and seed selection together determine most of the outcome, and the in-crop management that follows is largely about not losing what those three steps established.

1. Drain the pond fully, remove accumulated black sediment, and dry the bottom until it cracks, allowing organic matter to oxidise.
2. Lime according to the measured soil pH, and repair liners, dykes, central drains and aerator mountings while the pond is empty.
3. Fill through a reservoir where the water has been screened, settled and, where practised, treated and left to stand before transfer.
4. Establish a stable plankton bloom in the pond before stocking, so that early postlarvae encounter both natural food and a stabilised chemistry.
5. Select postlarvae on documented pathogen screening, uniformity, activity and stress-test response, and reject a batch that fails rather than negotiating on price.
6. Acclimate to the receiving pond's measured salinity, temperature and pH, over a period matched to the size of the difference to be crossed.
7. Feed conservatively at first and use check trays to establish the pond's actual consumption before increasing the ration.
8. Sample weight and observe animals routinely, adjusting the survival assumption downwards when tray behaviour and sampled counts suggest it.

Feed tray observation is the central daily practice. Trays report on consumption rate, on the health and gut fullness of animals that come to them, and on whether feed is being left in a pond where the operator cannot see the population. Trays are read after a fixed interval, and the next feed is adjusted from what they show rather than from a table.

Shrimp lack the adaptive immune response of vertebrates. They possess an innate immune system that can be supported by good nutrition and unstressed conditions, but they cannot be vaccinated and they do not acquire lasting immunity from exposure. This single fact explains why the entire industry is organised around exclusion: certified seed, treated water, controlled movement of people and equipment, and crop-to-crop disinfection.

The engineering considerations concentrate on the pond bottom and on power. Sediment management determines whether the animal's living surface stays aerobic, and it is influenced by pond shape, slope, liner choice, aerator placement and central drain design. Aerators must be positioned to sweep solids inward consistently rather than to create competing currents, and their number is set by peak biomass in the warmest month rather than by pond area.

Power reliability deserves separate treatment. In an intensive pond at high biomass the time between aeration stopping and serious loss is measured in a small number of hours at most, and shorter in hot weather. Standby generation with automatic changeover, tested under load rather than assumed functional, is the difference between an interruption and a crop failure.

Effluent is the third consideration. Shrimp ponds discharge water carrying suspended solids, nitrogen and phosphorus into coastal water bodies shared with other farms and with natural ecosystems. Settlement ponds, biological polishing and reduced exchange all limit that load, and in India discharge is subject to regulation under the coastal aquaculture authority framework.

• Treat the farm boundary as a real boundary: control vehicle and personnel movement, use dedicated equipment per pond, and disinfect anything that crosses between ponds.
• Never introduce untreated water directly into a production pond, regardless of how clean the source appears at the moment of intake.
• Read feed trays every feeding and let them, not a feed chart, determine the next ration.
• Monitor dissolved oxygen through the night at peak biomass, because that is when demand is highest and photosynthetic supply is absent.
• Track alkalinity, pH range and mineral ratios rather than single spot values, particularly in low-salinity ponds where moulting depends on them.
• Keep a complete written crop record — seed source and screening, feed lot numbers, water chemistry, treatments and mortality — because both diagnosis and market access depend on it.
• Plan an emergency harvest threshold in advance, so that the decision to take a partial crop early is a prepared option rather than a panic.

• Build reservoir and settlement capacity into the farm layout from the beginning, since the water path cannot be redesigned once ponds are constructed.
• Buy seed on documented screening and hatchery practice, and maintain the relationship with a hatchery whose programme can be inspected.
• Use a nursery phase where the farm can support it, because it improves early survival and gives a far better count entering grow-out.
• Size aeration for peak biomass in the warmest month and provide standby power with automatic changeover, tested on load at regular intervals.
• Manage the pond bottom actively through aerator placement, central drainage and, between crops, full drying and sediment removal.
• Follow the regulatory framework for coastal aquaculture registration, effluent and antimicrobial use, and keep the documentation that demonstrates it.
• Adopt a farm-level crop calendar and coordinate fallow periods with neighbouring farms sharing the same creek, because disease does not respect a boundary fence.
• Chill immediately at harvest and keep the cold chain unbroken, since quality lost in the first hour cannot be recovered downstream.

Genetic improvement has changed shrimp farming more than any single piece of equipment. Domesticated lines selected for growth rate, and separately for tolerance of specific pathogens, are the basis of the specific-pathogen-free supply chain, and they explain why current production is possible at densities that would have been untenable earlier. The trade-off is a dependence on a small number of broodstock sources, and the recognition that pathogen-free is a statement about the animal's history rather than a property it retains once it enters an unprotected pond.

Recirculating and near-zero-exchange shrimp systems represent the other direction of development. By treating water inside the farm rather than exchanging it, they reduce both the disease entry route and the effluent load, and they permit production away from the coast. The cost is energy, capital and a much narrower margin for operational error, since a closed system has no dilution to fall back on when something goes wrong.

The commercial frontier is a question of crop strategy rather than technology. Partial harvesting to relieve density and capture size premiums, multi-phase production using nursery and transfer stages, and shorter crops accepting a smaller animal in exchange for reduced disease exposure are all rational responses to the same underlying fact: risk in a shrimp pond accumulates with time and with biomass, so the optimum is rarely the largest animal the pond could theoretically produce.