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SH 155
.R7
Copy 1

A DEVICE FOR COUNTING YOUNG FISH

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By Robert K. Robinson

Superintendent U.S. Fisheries Station, White Sulphur Springs, W. Va.

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Paper presented before the Fourth International Fishery Congress
held at Washington, U. S. A., September 22 to 26, 1908

BULLETIN OF THE BUREAU OF FISHERIES : : : : : : VOL. XXVIII, P. 1001-1004
Bscuments NomsOlmercmes! srk utieare he SUS AS enn, ok Rae ke ened ApnlaI9i10,

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APR 15 1910
, OF B.

A DEVICE FOR COUNTING YOUNG FISH.

a
By ROBERT K. ROBINSON,

Superintendent U. S. Fisheries Station, White Sulphur Springs,

&

W. Va.

This device is intended as a means of measuring or counting young fish of a
size from the fry stage up to the length of 114 inches. The instrument is made

of thin brass, nickel plated, and weighs about 1 pound. ‘The
cylindrical base is 4 inches in diameter and 4 inches high,
with a top or neck which tapers to a diameter of 114 inches,
at which point is joined an upright tube of this diameter and
15 inches long. The tube is enlarged at its upper end to
form a funnel mouth. Immediately above the base, upon
the sloping neck, is fastened a small metal tube, and to this
is attached, by means of a short piece of small rubber tubing,
a glass tube 3 inch in diameter which extends up to the base
of the funnel at the top and is held in place by wire clamps.
Behind the glass tube, on the main tube of the apparatus, is
engraved a 10-inch scale, graduated r1o points to the inch,
beginning at zero at the bottom, and each fifth point above
numbered consecutively to the top, or to 100 points. The
lower end of the small metal tube is set in a shield-of metal,
which is soldered to the sloping neck of the base of the vessel,
this covered area of the latter being perforated to pérmit the
entrance of water into the small tube while screening out the
fish. Immediately below the zero point, and to the side of
the scale, there is a small vent or valve, which is controlled
by a spring lever and serves conveniently to adjust the water
level in the apparatus to the zero point on the scale. The
mode of using the apparatus may be understood by the fol-
lowing directions:

Fill the measure with water until the latter appears in
the glass tube slightly above the zero point on the scale. By
pressing the upper end of the valve lever the water may be
allowed to escape and thus be easily adjusted to the zero
point.

Count out from any given lot of fish to be measured 300
to 500 of average size. Put the counted fish into the measure
as free of water as possible; this may be done by putting
them into a quart graduate and, holding a small hand net

Measure by means of which
to count young fish.

tightly over the top of the graduate, draining the water off quickly by in-
verting the graduate. A perforated dipper may serve in place of the hand net.

1003

1004 BULLETIN OF THE BUREAU OF FISHERIES

The displacement made by the counted fish will be shown by a rise of
water in the glass tube above the zero point; then by reading the number of
points to which the water rises the average number of fish per point may be
easily ascertained. To find the number of fish in an entire given lot, empty the
measure, replace the water to the zero point, put the fish in by the operation
above described, again read the number of points above zero, then multiply the
latter by the number of fish per point, previously ascertained.

The measure should be held perpendicular, which may be accomplished by
suspending it between the thumb and index finger placed at the base of the
funnel.

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