Temperature Of Water

The colder the water is, down to forty degrees, the better the trout will do. They will die in the ponds if the water rises to seventy degrees, unless there is a spring in the pond, or colder water into which they can get. We have often heard or seen the statement that fish could be kept in a frozen state a long while, and then thawed out and be as lively as ever. Our experience is against this. Fish may be frozen, so that a thin coat of ice forms over them, and so long as they can be bent they will thaw out and will recover; but if they are once frozen solid or stiff throughout, they are dead, and cannot be brought back to life. If the ponds freeze over in winter, it is no sign that the water under the ice is below thirty-two degrees. If it was, the water in the ponds would freeze solid. Unless the water is taken close to a spring and much water runs through the ponds, the surface will freeze over; but this will not injure the fish, as the water below will be much warmer than the temperature of the atmosphere; and the ice which forms over the pond serves to keep the water below from being made colder by contact with the air.

If the water is so sluggish as to be likely to rise above seventy degrees in summer, the ponds may be shaded in some way. Trees and bushes look very nicely about the borders of the ponds, and are very valuable so far as ornament is concerned. But there are certain objections to their use which will banish them pretty thoroughly from the grounds of the practical trout-raiser. One objection is that the leaves, in autumn especially, clog up the screens, and demand constant attention to prevent an overflow of the water and trout. Or the leaves fall to the bottom and decaying there, foul the pond. The roots of the trees also will force their way towards the water, and break the walls or banks of the pond. If it is necessary to shade the ponds, floats may be used, made of boards nailed together and moored in some convenient place; but the best plan of shading is by light covers placed on beams running across the pond. If the ponds are very large the floats will have to be used. But the ponds must not be made large. We have said that trout would not live in water which was raised above the temperature of seventy degrees, and would do better in water at forty degrees. This settles the question as to how far south trout will live in the ordinary rivers.

California salmon will stand a much higher temperature than trout. The McCloud river from which the eggs were obtained that have been distributed by the United States Fish Commissioner through the eastern states, often rises to 80 degrees, and occasionally as high as 83 degrees. Its temperature through a large part of the year is over 70 degrees, both at the surface and at the bottom, and yet the salmon did not seem to be injured by it. "We have kept young California salmon in a preserve when the water rose above 80 degrees in temperature, and although the inlet was open and they could have gone out, as many of them did, others remained until we thought it better to drive them out by drawing off the water. However this temperature is not safe for them unless there is a large body of water or considerable motion to it which gives it life and enables the fish to live in it longer. In an aquarium in which there were pairs of Kennebec and California salmon, brook-trout, salmon-trout and grayling, when the water rose to 74 degrees they were greatly distressed, coming to the surface and gasping. When it reached 75 degrees they all died.

It must not be forgotten that in ponds there is often a spring to which the fish can have recourse and which will save their lives. It is not always possible to judge by the temperature of the surface, for that below may be lower, but it is better to be on the safe side as far as possible. The larger the fish the more they will suffer and the sooner they will die. They exhaust the oxygen much more rapidly than the fry.

Brook trout are only suitable for clear, cold water, of which the temperature never goes above 70°. Salmon trout will live only in clear, cold, deep lakes. They need the purest water of any fish in this country. In the aquarium above referred to were put brook trout, salmon trout, greyling, California and Kennebec salmon and California brook trout, and as the water became warm the salmon trout began to suffer first, and died before the mercury went up to 74°. The brook trout went next, the greyling next, the California brook trout fourth, the Kennebec salmon fifth, and the California salmon last.

The salmon trout died twelve hours before any of the rest, and all of the others died within four hours of each other. All of the full spawning fish want clear, cold water. Whitefish will not live in water above 72° We have seen these taken in a seine, and when they got into shallow water where the temperature was 74° ten rods from the shore, the fish began to "turn up," and were all dead when they were hauled up on the shore.