ALASKA SALMON INVESTIGATIONS IN 1900. 
337 
water of very line particles. With the more than usually excellent quality of water 
here, and its lack of foreign material, the above arrangement is found to meet the 
requirements of filtering. Where a refinement of this feature is necessary, however, 
it will readily be seen that there is no limit to the extension of the number or fineness 
of the screens. 
The burlap used is of a slightly superior quality to the ordinary bagging, and in 
addition to its efficiency has its cheapness to recommend it. When stretched on 
frames it should be evenly secured, as its shrinking tendencies cause it to tear where 
the strains are unequal. The frames should be small and in sufficient number to 
allow of at least two changes in addition to the set in the filter trough. This is neces- 
sary, as the burlap will rot if left continuously in water, but if removed and thor- 
oughly dried every ten days or two weeks the screens will last a long time. Four 
or 5 feet is a good length for the frames. When using more than one set of bur- 
lap or cloth screens care should lie observed that the joints between the ends of the 
frames do not occur directly below each other; they should be staggered — that is, 
designed to occur at different intervals— the reason for which is plain. 
While there is as yet but one filter trough in the hatchery at Karluk, the super- 
intendent, Mr. James A. Richardson, is a strong advocate of three, arranged some- 
what as shown in the sketch. This will allow one to be in use, one in reserve, and 
the third under whatever repairs it may require. With a long hatching season and a 
long nursing period little opportunity is offered to overhaul so important an adjunct 
as the filter if to do so requires that it be placed temporarily out of commission. As 
the expense is slight, such an arrangement has much to recommend it. 
It is stated that fungus has never caused trouble at the Karluk hatchery under 
the present management; at the old station, less than a mile westward on the same 
side of the lagoon, much difficulty was experienced from this cause. It is due to 
dirty water, unclean troughs and baskets, and careless and insufficient picking of the 
F. C. B. 1901—22 
