Stock Management Issues Michael B. Timmons Ph.D. J.Thomas Clark Professor of Entrepreneurship &...

Stock Management Stock Management IssuesIssues

Michael B. Timmons Ph.D.J.Thomas Clark Professor of

Entrepreneurship & Personal Enterprise

Cornell University

Recirculating Aquaculture Systems Short Course

Production StrategiesProduction Strategies

• Continuous production strategies • can double total system production

• compared to batch strategies

• rely on year round stocking and harvesting• maintains the system near its carrying capacity

• ideal situation• not always attainable


Stock Management IssuesStock Management Issues• Batch strategy

• P/B = 1.74/yr,

• ts = th = 224 days N0 = 1965

0200400600800

1,0001,200

0 56 112 168 224 280 336 392 448

Bio

mas

s, k

g

Time, days


Stock Management IssuesStock Management Issues• Concurrent batch stocking and harvesting

• P/B = 3.14/yr• ts = th = 56 days N0 = 1125

0200400600800

1,0001,200

0 56 112 168 224 280 336 392 448

Bio

mas

s, k

g

Time, days


Stock Management IssuesStock Management Issues• Concurrent mixed-stocking and graded harvesting

• P/B = 3.48/yr

• ts = 56 days th = 14 days N0 = 1438

.

Time, days

0200400600800

1,0001,200

0 56 112 168 224 280 336 392 448

Bio

mas

s, k

g


Stock Management IssuesStock Management Issues

• For > 5 years, Freshwater Institute produced rainbow trout:• 4.6 MTON annual production• 1.0 MTON maximum biomass

• stocked every 8 weeks at 30 to 40 g• harvested weekly at 340 g • 1 mm/day growth

• vs. 2:1 to 4:1 annually for many commercial farms


Stock Management IssuesStock Management Issues

• Harvesting and grading:• IMPORTANT!• can add considerably to labor cost!• mechanism/strategy must be incorporated with

culture tank design.

• Automated fish grading/pumping equipment:• reduces labor costs• can reduce fish stress and damage


Harvesting and GradingHarvesting and Grading

Small box graders work well at small scale.



Clam-shell graders reduce labor and are easy on fish!



Belt graders and roller graders handle large numbers.



Counting channels track fish numbers after grading.



• Moving fish is hard work!• Fish moving equipment:

• fork lift a palletized tank• fish pumps

• heli-arc• vacuum• pescalator

• swim fish through channels and raceways


Tank Access & Tank EnclosuresTank Access & Tank EnclosuresWas tank access designed into the tank layout?

Stock Management Issues Michael B. Timmons Ph.D. J.Thomas Clark Professor of Entrepreneurship &...

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