Synopsis of Biological Data on the Chum Salmon, Oncorhynchus keta

are used by the species. Churn salmon pass
over fishways at three major darns on the
Columbia River (Bonneville, The Dalles, and
McNary Darns) . In Hokkaido, over 100 manmade
darns or other facilities either totally
or partially obstruct the migration <strong>of</strong> adult
and young fish (Japan Fisheries Rf'source
Conservation Association, 1966).
6.25 Fish screens
Because <strong>of</strong> the short distances to their
spawning grounds, churn salmon seldom encounter
fish screens, but Weber (1965) listed
six such installations that confront churn
salmon in Washington.
6.26 Improvement <strong>of</strong> spawning
grounds
Some experiments on improvement <strong>of</strong> spa wning
areas have been carried out in the United
States and Canada, based on research which
has shown that flooding , gravel erosion, silting,
and predation cause serious losses. These
detrimental characteris tic s <strong>of</strong> na tural s tr earns
have been partially eliminated by regulating
flow, improving spawning gravel, and excluding
predators. Improved spawning areas for churn
salmon are <strong>of</strong> two types: One consists <strong>of</strong> a
completely artificial streambed, excavated and
supplied with clean gravel, an example <strong>of</strong>
which is the Jones Creek channel in British
Columbia (Woodland, 1961); a second is a
natural stream in which a storage darn regulates
flow and where the natural streambed
has been improved by loos ening and clearung
<strong>of</strong> the gravel. This type <strong>of</strong> improvement was
recently undertaken on the Big Qualicum River
in British Columbia (Lister and Walker, 1966).
Egg-to-fry survival has been increased in
these controlled-flow spawning areas over that
in uncontrolled streams (see section 4.31).
Other stream improvements on spawning
areas <strong>of</strong> churn salmon include the removal <strong>of</strong>
rock slides, logjams, beaver darns, debris,
and gravel deposits and the channelization <strong>of</strong>
streambeds.
6.27 Habitat improvement
Measures to improve natural habitat have
not been reported except for those listed in
section 6.26.
6.3 Control or alteration<strong>of</strong>chemical
features <strong>of</strong> the environment
6.31 Water pollution control
Waste products from mining and the production
<strong>of</strong> wood pulp, dairy products, alcohol,
gas, sugar, and starch were detrimental to
churn salmon in Hokkaido (Japan Fisheries
74
Resource Conservation Association, 1966).
Similar kinds <strong>of</strong> pollution occur in other
countries and undoubtedly affect chum salmon.
6.32 Salinity control
No information.
6.33 Artihcial fertilization <strong>of</strong> waters
No information.
6.4 Control or alteration <strong>of</strong> the biological
features <strong>of</strong> the environment
6.41 Control <strong>of</strong> aquatic vegetation
No information.
6.42 Introduction <strong>of</strong> fish foods
'0 information.
6.43 Control <strong>of</strong> parasites and disease
See section 4.43.
6.44 Control <strong>of</strong> predation and competition
Populations <strong>of</strong> predators and competitors
have been reduced in artificial spawning channels
and in some rearing areas <strong>of</strong> churn salmor.
in North America .
6.45 Population manipulation
o information.
6.5 Artificial stocking
6.51 Stockmg to maintain runs
Hatchery operations for churn salmon are
much more extensive 1n Asia , particularly in
Japan, than in North America (table 51). From
10 to 12 hatcheries produce less than 10
million fry annually in North America, whereas
in Hokkaido alone, 49 hatcheries have produced
from 200 million to over 400 million fry.
Japanese scientists consider artiiicial propagation
as the only practical method to maintain
runs <strong>of</strong> salmon in Japan, which are faced with
deterioration <strong>of</strong> spawning streams from industrial
growth (Japan Fisheries Resource
Conservation Association, 1966). In Hokkaido,
where churn salmon enter 160 streams, from
300,000 to 500,000 adults (57 percent <strong>of</strong> the
escapement) are taken annually from 52 to 64
<strong>of</strong> the streams for artificial propagation; from
150,000 to 200,000 fish inHonshu are also taken
each year for artiiicial propagation.
The Japanes e have estimated maximum sustainable
yields and economic returns for their