How to Calculate Shrimp Biomass Accurately During Culture

How to Calculate Shrimp Biomass Accurately During Culture

Introduction

Accurate shrimp biomass calculation is one of the most important activities in successful shrimp farming. Whether you are farming Litopenaeus vannamei (Pacific white shrimp) or another shrimp species, knowing the estimated total weight of shrimp in your pond helps you make better feeding, water-quality management and harvest decisions.

Many farmers calculate feed based only on the age of the shrimp or the amount of feed given the previous day. However, shrimp growth, survival rate, stocking density and environmental conditions change throughout the culture period.

If biomass is overestimated, farmers may provide excess feed, increasing feed costs and organic waste. If biomass is underestimated, shrimp may receive insufficient feed, resulting in uneven growth and reduced production.

The goal is to estimate the actual standing shrimp biomass as accurately as possible and update the estimate regularly using sampling and survival information.

What Is Shrimp Biomass?

Shrimp biomass is the estimated total live weight of all shrimp currently present in a culture pond at a particular time.

It is usually expressed in kilograms (kg) or tonnes.

For example, if a pond contains an estimated 50,000 live shrimp with an average body weight of 15 grams, the estimated standing biomass is 750 kg.

Why Is Biomass Calculation Important?

Accurate biomass estimation helps farmers to:

Calculate daily feed requirements more appropriately.

Monitor shrimp growth and feed conversion ratio (FCR).

Estimate standing crop and potential harvest production.

Evaluate survival rate and changes in shrimp population.

Adjust feeding when growth, appetite or water quality changes.

Plan aeration capacity and monitor pond carrying capacity.

Identify possible growth problems early.

Improve farm records and production planning.

Important Terms Used in Shrimp Biomass Calculation

Before calculating biomass, understand these five terms.

Term: Stocked PLs

Meaning: Total post-larvae released into the pond

Term: Survival rate (%)

Meaning: Estimated percentage of stocked shrimp still alive

Term: ABW (g)

Meaning: Average body weight of sampled shrimp in grams

Term: Population

Meaning: Estimated number of live shrimp in the pond

Term: Standing biomass (kg)

Meaning: Total estimated live weight of shrimp in the pond

Shrimp Biomass Calculation Formula

The basic formula is:

Biomass (kg)=Live shrimp count×ABW (g)​​/1000​

To estimate the live shrimp count:

Live shrimp count= Stocked PLs × Survival rate (%)/100

Combining both formulas:

Biomass (kg)= Stocked PLs × Survival (%)×ABW (g)/100, 000

This combined formula uses survival rate as a percentage, such as 75 rather than 0.75.

Important: Survival rate during culture is generally an estimate unless the population has been measured reliably. The formula is only as accurate as the survival estimate and the body-weight sample.

Step-by-Step Example: Calculate Biomass in a Vannamei Shrimp Pond

Consider a hypothetical shrimp farm with the following details.

Sample pond data

Initial stocking - 100,000 PLs

Estimated survival rate - 75%

Average body weight - 18 g

Step 1 — Estimate the live population

100,000×75/100 =75,000

Step 2 — Calculate total weight in grams

75,000×18=1,350,000 g

Step 3 — Convert grams to kilograms

1,350,000÷1,000=1,350 kg

​

Estimated standing biomass

1,350 kg

Equivalent to 1.35 tonnes of live shrimp.

How to Calculate Average Body Weight (ABW)

Average body weight is a key input in biomass calculation.

Use the following formula:

ABW (g)= Total sample weight (g)/Number of shrimp sampled

Example

Suppose you collect 100 shrimp from representative areas of the pond.

Total weight of 100 shrimp: 1,800 g

Number of shrimp sampled: 100

Therefore:

ABW=1800/100=18 g

The average body weight is 18 grams per shrimp.

Best practices for ABW sampling

Collect shrimp using a suitable cast net or other consistent sampling method.

Sample several areas of the pond rather than relying only on feeding points.

Avoid selecting only large, active shrimp.

Count the shrimp and weigh the entire sample using a calibrated weighing scale.

Repeat sampling when results differ substantially between locations.

Record the sampling date, culture day, sample count and ABW.

Return healthy sampled shrimp to the pond carefully, following farm biosecurity practices.

How to Estimate Shrimp Survival Rate During Culture

Survival rate is the estimated percentage of shrimp that remain alive compared with the number initially stocked.

The formula is:

Survival rate (%)= Estimated live shrimp count/Initial stocked PLs×100​

For example, if 100,000 PLs were stocked and the estimated live population is 75,000:

75,000/100,000×100=75%

​

The estimated survival rate is 75%.

How can farmers estimate survival during culture?

Review stocking records and confirm the number of PLs actually released.

Track known mortality events and any shrimp removed from the pond.

Use consistent sampling and population-estimation methods where feasible.

Compare estimated biomass with average body weight and feeding trends.

At harvest, compare the actual harvested count (estimated from harvested weight and harvest ABW) with the original stocked count.

Important: Do not automatically assume that survival is 80% or 90% simply because the crop looks healthy. Unverified survival assumptions can produce significant biomass and feed-calculation errors.

How to Calculate Daily Shrimp Feed Based on Biomass

Once you estimate standing biomass, you can calculate an initial feed allowance using an appropriate feeding rate.

The basic formula is:

Daily feed (kg)=Biomass (kg)×Feeding rate (%)/100

Example

Suppose:

Estimated biomass = 1,350 kg

Feeding rate selected for this example = 2.5% of biomass per day

Then:

1,350×2.5/100=33.75 kg/day

The calculated starting feed allowance is 33.75 kg per day.

How to adjust feeding after tray observations

If feed is consumed well and shrimp show normal activity, continue evaluating the current ration against the farm feeding plan.

If significant feed remains, investigate appetite, water quality, disease, moulting and feed distribution before increasing the ration.

If shrimp show reduced feeding activity, check dissolved oxygen and other water-quality parameters promptly.

Avoid increasing feed automatically just because the calculated biomass has increased.

Alternative Biomass Estimation Using Feed Consumption

Where survival is difficult to estimate, recent feed consumption can provide a useful cross-check on the biomass estimate. However, this method relies on knowing a realistic feeding rate and assumes the feed-consumption records are reliable.​

The approximate formula is:

Estimated biomass (kg)=Daily feed (kg)/Feeding rate as a decimal

For example, if the recent daily feed consumption is 30 kg and the assumed feeding rate is 0.025:

30÷0.025=1,200 kg

Complete Shrimp Biomass Calculation Checklist

Use this checklist during routine pond management.

Farm technician's checklist

Confirm the pond area and initial PL stocking count.

Record the date and days of culture (DOC).

Collect a representative shrimp sample from several pond locations.

Count all shrimp in the sample and weigh them accurately.

Calculate the current average body weight (ABW).

Review mortality, health observations and any shrimp removals.

Estimate the current live population and survival rate.

Calculate biomass in kilograms using consistent units.

Compare the result with recent biomass and growth records.

Calculate the initial daily feed allowance using an appropriate feeding rate.

Review feeding trays, appetite and water-quality conditions.

Record the calculation and schedule the next sampling

Simple Biomass Record Format for Shrimp Farmers

Maintain a record for every pond so that biomass estimates can be compared over time.

Date DOC ABW (g) Estimated survival (%) Biomass (kg) Feed (kg/day)

Day 30 30 5 85 425

Day 45 45 9 80 720

Day 60 60 14 76 1,064

Conclusion

Accurate shrimp biomass calculation is essential for effective feed management, growth monitoring and production planning. By measuring average body weight, estimating survival and using the correct formula, shrimp farmers can make more informed management decisions.

For better results, combine regular sampling with mortality records, feeding-tray observations and water-quality monitoring. Review estimates regularly instead of relying on the initial stocking count or a fixed survival assumption.

Remember: Biomass calculation is an estimation tool. The best results come from consistent sampling, reliable farm records and feeding adjustments based on actual shrimp performance.