Íslenskar landbúnaðarrannsóknir - 01.09.1978, Síða 123

AN ANALYSIS OF KOLLAFJORDUR HATCHERY 121
TABLE 1.
Maximum number of fish which can be held al various sizes.
Weight in grams Number per 5 ponds lst stage house Number per 2 large ponds, 2nd stage house Number per 2 small ponds, 2nd stage house
0.25 90.000
0.4 87.000
0.7 83.000
1.1 75.000
1.7 '55.000
2.8 22.800 144.000 58.000
4.5 16.500 106.000 44.000
7.3 13.000 83.000 35.000
11.8 8.500 54.000 23.000
19.1 6.100 39.000 16.000
30.9 4.500 29.000 12.000
50.0 3.100 20.000 8.000
TABLE 2.
Number of fish which can be reared under various
options stated in the text.
1) 2 ponds of heated water in 2nd stage rearing
house.
a. 12 cm 166.000 Ts 12 cm
24.400 2’s
b. 14 cm 104.000 Ts 14 cm
42.700 2’s
c. 16 cm 68.000 l’s 16 cm
36.000 l’s 12 cm
42.700 2’s
2) 4 ponds of heated water in 2nd stage rearing
house from Sept.-Feb.
a. 196.000 l’s 12 cm
39.000 2’s
b. 144.000 l’s 14 cm
42.700 2’s
c. 100.000 l’s 16 cm
42.700 2’s
3) 3. VVith multiple plants.
160.000 l’s 12 cm in May
11.000 l’s 14 cm in June
25.000 l’s 16 cm in July
come available for the second-stage house.
This additional hol water could be usecl to
grow 30.000-40.000 more 1-year smlts up
to a desired size. J'he number of 2-year
smolts would not be decreased, because
during the following summer they could
still pick up the additional weight needed.
In 1975 smolts were released on April
25, May 25, and June 25. Isaksson and
Bergman (1978) note that 1976 and 1977
returns showed that flsh released June 25
survived better than comparable fish re-
leased May 25, but that they weighed less
upon return. Fish released April 25 sur-
vived very poorly. Since there is a period
ofincreasing survival from at least May 25
to June 25, it may be advisable to practice
a series ofmultiple plants. The idea would
be to crop oíf fish from a pond and plant
them as they grow to exceed capacity.
Computations suggest that the number of
1-year smolts released under such a policy
would not increase, but since more could
be released in late June, the return to the
hatchery would increase.
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