Box-type grader for catfish fingerlings.


are first graded into uniform size classes. At least three
samples with a minimum of 200 fish each are counted
and weighed before, midway, and at the end of loading.
The weight per thousand fingerlings is estimated from the
samples. All of the fingerlings are then weighed as they
are loaded into the transport tank, and the total number
of fish is estimated from the average weight of the in-
dividual samples. For example, three samples of 200 fish
each might weigh 10, 11, and 12 ounces, or a total of 33
ounces (2.06 pounds) for 600 fish. If a total of 500 pounds
of fish is loaded into the tank, then the number can be
estimated as follows:



 Sample Number = 600 fish
 Sample Weight = 2.06 pounds
 Total Weight = 500 pounds


 The sharp pectoral and dorsal spines of fingerlings can
become tangled in nets and cause undue stress. Entangle-
ment can be reduced by dipping nylon seines and nets
in an asphalt-base net coat prior to harvesting, or by us-
ing polyethylene nets. Partial grading of different-sized
fingerlings can be done in the pond by using seines with
different mesh sizes (Table 6).
 Some producers use traps to successfully harvest
fingerlings from ponds. Harvesting fish from raceways,
troughs, cages, and other facilities can be conveniently
accomplished using catchment basins, dip nets, and other
equipment.

Table 6. Seine mesh sizes and grader bar widths used
 for separating size classes of fingerlings.
 Smallest Fish Seine Mesh Grader Bar Spacing
 Length (inches) (inches) inches millimeters
 3 1/4 27/64 10.7
 4 3/8 32/64 12.7
 5 1/2 40/64 15.9
 6-7 3/4 48/64 19.1
 8-10 1 1 25.4

Grading
 Fingerlings must be graded and counted into different
sizes before shipment. Grading is most easily done in
holding tanks or vats by using specially constructed boxes.
Box-type graders usually have aluminum or stainless steel
rods that are spaced at appropriate widths and retain cer-
tain size fish but allow smaller ones to pass through.
Recommended bar widths for grading fingerlings are
given in Table 6.

Counting
 Fingerlings may be sold by weight, length, or a com-
bination of both. Counting them is more accurate if they


Total Number
 of Fish


 Number of fish in samples
 X total weight of all fish
 Weight of fish in samples
 600 fish X 500 pounds
 2.06 pounds
= 145,631 fish


The average weight in pounds of each 1,000 fish can then
be calculated:
 Total Weight = 500 pounds
 Total Number = 145,631


Pounds/1,000
 fish


 Total weight (pounds) X 1,000
 Total number of fish
 500 pounds X 1,000
 145,631
= 3.4 pounds/1,000 fish


Tank with aerator for hauling fingerlings.