Some important equation/ law of fish or shrimp farm operation

Aquaculture is the art of fish culture. To do this culture perfectly some scientific equation is important. like stocking density, survival rate, feeding rate  and actual feed demand etc..Some important equation of fish or shrimp farm operation are given below.

The pond area is calculated by the following way

Here pond depth = 6 feet

Pond length = 84+80/2=82 feet

Pond width  = 47+50=48.5 feet
Land area    =  pond length in feet (L) * pond width in feet (W)

                    = 82* 48.5 square feet
                    = 3977 square feet
If you want to convert it decimal than divided it by 435.6

Land area in decimal = 3977/435.6 = 9.19 decimal

The water volume is calculated by the following way :

Water volume = length * width* depth

                        = 82 x 48.5 x 6

                        = 23862 cubic feet

Stocking Density calculated following way:

If post larvae / fry= 10000
pond area          = 9.19 decimal

Stocking Density = Total PL / pond area
                             = 10000/ 9.19
                             = 1088 per decimal.

Average daily growth (ADG) calculated in following way:

1st  week growth= 8 gm per piece

2nd  week growth=14 gm per piece

Day difference = 7 days

ADG = 2nd  week growth  – 1st  week growth/ date deference of between 2 weight.

          = 14 – 8/7 = 6/7= 0.85 gm

Feed Conversion ratio calculation

Total feed used in kg = 12000 
Total fish biomass/Total fish weight in kg after harvest = 8000
FCR = Total feed / Total biomass
F.C.R= 12000/8000= 1.5 

Ø Total Biomass = Feed per day * 100 / % of feed.

 Bleaching rate calcouated by the following way:

Bleaching rate = Water depth * pond area * 60 / 1000.(Length, width and depth Unit must be meter)

Here,
Length = 82 m
Width= 48.5 m
Depth= 6 m

Bleaching rate            = 82 x 48.5 x 6 x 60/100
                                   = 1431 kg
 ( Bleaching rate find out unit will be kg)

Ø Check tray report = left net % * 16000 / pond area.

Survival rate calculated by the following way:
if,
Initial fry stocking= 50000
Total harvest= 40000 kg
Average wieght = 1.5 kg
Therefore, present stock=  40000/1.5= 26666 fish

Ø Survival rate = present stock * 100 / Initial stock.

                       = 26666*100/50000

                       = 53 percent.

Therefore, we can say survival rate 53% on the other hand mortality rate 47%.

  

Specific growth rate (SGR) (% bw.day-1)

If,

Initial weight Wo  = 0.31 gm

Final weight  Wt   = 58.52 gm

Date difference Dt  = 192 days 

SGR = (log Wt ‐ log Wo) × 100/ Dt  

          = (log 58.52 - log 0.31)*100/192

          = 2.27*100/192= 1.18

Return on investment:

If, net profit =  20,55,750

Total investment =  1082350

 

Return on investment =  20,55,750 / 1082350 x 100  =  189.94 %

Feed demand calculated by following way :

In our country daily feed demand of fish calculated, on the basis of fish body weight. Suppose if  per pangush body weight is 100 gm we recommended 8% body weight of feed. Thats mean for 100 gm pangush we giving 8 gm feed.  I am not saying that this is wrong technique. But we can do more calculation here, which ensure optimum growth as well as save feed.

Like, 

Base on our environmental condition of our country, average daily growth of pangush is 2.5 ( could be vary according of pond environment) gm per day and highest FCR of pangush is 2 .( otherwise it will not economically profitable)

Than feed demand= FCR* average daily growth= 2*2.5= 5 gm.

But if you see above technique giving feed demand is 8 gm. But if we calculate average daily growth we can save 8-5= 3 gm feed.

NOTE: 

• Average daily growth of fish should be know
• Single species culture

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