Íslenskar landbúnaðarrannsóknir - 01.09.1978, Page 121

AN ANALYSIS OF KOLLAF.TORDUR HATCHERY 1 19
Date Egg House lst Stage Rearing House 2nd Stage Rearing House Outáoor Ponds Releases or Sales
1-5 6-10 11-15 16-20 21-25 26-30 31-35 36-40 1,3 4,6 7,9 10,12 2,5 8,11
Jan
Feb
Mar
Apr
May
June
July
Aug
Sep
Oct
Nov
Dec
Fig. 4. — Chart for examining management schemes.
be in the second-stage rearing house
by October 1 of their first year.1
7. a. Fish destined to be 2-year-old
smolts must weigh at least
19.1. g when placed in the
outdoor ponds;
b. such ftsh are placed in the outdoor
ponds October 1 of their sec-
ond year.
8. One-year smolts must weigh at least
19.1 g on June 1, at which time they
are released.
9. The thermal water may be used either
to heat two large ponds of the second-
stage rearing house and all 40 ponds
of the first-stage raring house, or, al-
ternatively, to heat four large ponds
of the second-stage house and none of
the ponds of the first-stage house. The
large ponds are heated to 10°C. The
temperature of the 40 small ponds
follows the graph in Fig. 2.
*) Experiments conducted in 1976 may show that
this date can be moved back to November or De-
cember.
10. Mortality rates are:
Egg mortality rate .............. 10%
Start of feeding until
May of next year ................ 25%
May of first year until
May of second year ...............20%
Eggs needed to produce 1,000
fry ................................ 1,110
1- year smolts: .................... 1,480
2- year smolts: ................... 1,850
These rules are, of course, overly
simplified and are only an approximation
of reality. Nonetheless, with careful in-
terpretation, they form a framework for
examining various alternatives. The basis
for some of the rules has already been
discussed. Comments on others follow
(the numbers refer to the rules):
1. Experience has shown that fish that do
not quickly reach a size of 1 g do not do
well.
2. It is possible to raise a 50 g fish in 11
months in heated water and one month