How to Improve Fingerling and Shrimp Survival: Water Quality, Oxygen, Temperature, Density and Monitoring

Why young stock die: the usual causes

Fingerlings and postlarvae (PL) have small energy reserves and little tolerance for sudden change. On most farms, losses trace back to a short list: oxygen falling at night or after feeding, temperature or salinity shocks at transfer, ammonia or nitrite building up when biomass grows faster than the treatment or water exchange, handling stress, and infectious disease introduced with the stock or water. Survival is the result of all of these together, which is why one measurement is never enough.

Step 1 — Start with healthy, documented stock

• Buy from a hatchery that provides health certificates or test results required in your country, plus the batch origin.
• Record the batch, age or PL stage, count method and transport time for every delivery.
• Quarantine or observe new stock separately where your biosecurity plan requires it.

Step 2 — Acclimate gradually

Compare temperature, salinity and pH between the transport water and your tank or pond before release. Equalise them slowly; the hatchery's written acclimation guidance for that species and stage should set the pace. Record the readings and any deaths in the first 24–72 hours separately from later mortality.

Step 3 — Keep oxygen above the species' safe level at all times

Dissolved oxygen (DO) is usually lowest just before dawn in ponds and right after feeding in tanks. Measure at those times, not only at midday. Size aeration or oxygenation for peak biomass and feed load, and have a backup that works during a power cut. The aeration sizing calculator helps estimate demand before you request quotes.

Step 4 — Control temperature and salinity changes

Young stock tolerate stable conditions better than fluctuating ones. Note daily minimum and maximum temperature, and avoid large water exchanges with water of different temperature or salinity.

Step 5 — Match density to system capacity

Density is not a fixed number: the safe stocking level depends on oxygen supply, water treatment or exchange, feed quality and the operator's experience. Increase density only when your records show water quality stays stable at the current level. Use the stocking density calculator (finfish) and the biomass calculator to check the load your system must carry.

Step 6 — Monitor and record every day

What to record	When	Why
Dissolved oxygen	Pre-dawn, after feeding	Detects the lowest point
Temperature	Daily min/max	Shows stress and feeding response
pH, salinity	Daily or per your protocol	Detects drift and exchange errors
Ammonia, nitrite	Per your protocol, more often as biomass grows	Shows when treatment is overloaded
Feed given and left over	Every feeding	Appetite is an early warning
Deaths and behaviour	Every check	Survival by cohort and early alarm

Safety limits: when to stop and call a professional

This guide does not diagnose disease or recommend treatments. If you see a sudden rise in mortality, abnormal swimming, gasping at the surface, discolouration, or animals stop eating, first check oxygen and power, then contact a qualified aquatic animal health professional or veterinarian. Some diseases are notifiable: follow your national authority's reporting rules and the WOAH Aquatic Code. See also the fish-health first-response checklist.

Turning survival data into a project decision

If records show losses linked to oxygen, temperature control or water treatment capacity, the fix may be equipment or system design. Model the effect with the shrimp survival-profit calculator, then describe the problem and target in a project intake. FishMatch reviews it and contacts suitable suppliers for you.