Íslenskar landbúnaðarrannsóknir - 01.09.1978, Side 169

SALMON MANAGEMENT AND OCEAN RANCHING 167
TABLE 4. Flood years in Ellidaár.
Year Month Total m3-106 Maximum (m3/s) m3/s (monthly)
19271 February 60
1930 February 25 31.70
1931 March 31 46.22
1935 March 12 40.86
1938 February 17 30.02
19421 February 16 40.8 39.84
1944 March 24 39.56
19461 January 58.9 39.17
19472 January 24 41.5 46.0 15.5
19482 February 18 22.8 47.5
March 55.8 43.0
1953 February 21.3 41.8 8.8
December 6 37.14
1956 February 2 32.64
19602 Apríl 8 23.0 58.0 8.57
1961 January 15 31.70
19623 Apríl 31.10
19683 February 27 162.54
19693 p ?
197l2 February 17.6 80.8 7.27
1) Saga Rafmagnsveitu Reykjavíkur (1961) Jónsson, S.
2) Rennslisskýrsiur Orkustofnunar íslands.
3) G. Eiríksdóttir (1974) The Ellidaár.
4) 4.0 before flood.
where p is the probability of an event and
w is the associated component utility or
value (Walters 1977).
The events are biological, economic,
and sociological in nature. One might, for
example, inquire about the probability of
a flood during egg incubation from Oc-
tober to February. The egg losses arising
from scouring must be substantial in
many Icelandic salmon streams, which
limit the spawning capacity. As seen from
Table 4. the probability ofsuch an event is
high in Ellidaár, and with serious con-
sequences, although these have not yet
been measured. Were a year with a low
return to coincide with flood and egg loss
during the incubation, serious repercus-
sions would ensue for future progeny.
Since fishing effort is fixed in advance, the
removals do not fall in proportion to a
decline in the run. According to Table 2
the rate of exploitation increases in years
with small runs. As a result the escape-
ment or the spawning population is depre-
ssed and an egg loss due to scouring may
result in small returns 4,5, or 6 years later.
It is granted that the damage could be
ameliorated by release ofsmolts, provided
that such smolts were available from other
sources.
Generally the angler’s catchability
coefflcient decreases with the total catch