When the trout have reached the desired size for planting, the U. S. park rangers take over the fish planting, or the final phase of fish culture, from the California Division of Fish and Game hatcherymen who have fostered the fingerlings from the eggs.

Assistant Chief Ranger Duane Jacobs reports that 490 miles of stream waters and 150 lakes in Yosemite National Park have been stocked with trout prior to March 17, 1949. Some of these waters are now able to provide sufficient natural reproduction to more than care for the demands but others must be planted annually, biennially or triennially to supplement the natural spawn and take care of the anglers’ demands upon them.

Some of the waters are easily accessible and can be reached by truck. This entails the loading of cans into the truck and hooking up an aerating device, which keeps the air circulating throughout the water of each can. Sufficient oxygen and constant, though moderate, water temperature (40°-50°F.) are the main factors considered in transporting trout. To stock the lakes and streams of the back country accessible only by trail, the cans are loaded onto pack animals.

Modern planting of trout by approved methods is far different from that of two decades ago. Formerly the planter’s worries were over as soon as the cans of fingerlings were literally dumped anywhere in the lakes and streams that happened to be convenient. Large losses resulted, as naturally many trout in a small area created definite food competition and provided many easy meals for fish predators.

Nowadays fish planting is done

[click to enlarge]
Tenaya Lake

—Photo by Anderson

more scientifically and requires a great deal more time and effort. Such factors as temperature equalization of the water in the can with that in the stt eam, food supply, predators and spawning conditions are given considerable attention. The fish are spread widely to avoid overcrowding and excessive loss to natural enemies. Young fingerlings are released a few at a place, along the margins of the lake or stream over long distances. Quiet water provided with sufficient food and shelter can be found with a bit of patience. This practice at least gives the small trout a fair start in life.

In Yosemite National Park about a million trout are planted in this manner each season by especially trained and skilled rangers. In spite of this vast number planted, many fishermen are disappointed with their small catches (small in both size and numbers), especially in heavily fished areas such as the Merced River in Yosemite Valley. As Dr. J. O. Snyder states it, “Depletion of the trout has lately attracted attention to almost every possible cause except the increased activities of anglers.”⁸ The answer is simply that fishing intensity often badly overbalances the natural increase of trout. For instance, a rainbow trout does not spawn until it is two or three years old and around ten inches in length. Consequently, the majority of fish planted in the Merced River never mature before being captured. No heavily fished stream can long depend on light artificial stocking alone, but must be backed by natural reproduction, which is more effective than most people realize.

It would be beneficial if stream and lake surveys of all potential waters important to fishing could be made before plantings are undertaken. This would alleviate much waste of time and money by seeing that fish are stocked in waters providing a biologically sound environment for that particular species or strain. Many such survey programs are being conducted by fish biologists in various parts of the country today and their value has been amply demonstrated.

Research along such lines, plus creel censuses and fishermen questionaires, have greatly increased our working knowledge of the game fish of inland waters. Only through public cooperation in promoting proper legislation, submitting accurate information, and abiding by legal restrictions can our fisheries resources be restored to the high level that once existed.

8. Snyder, J. O. 1940. The trouts of California, California Fish and Game. Vol. 26: No. 2 pp. 96-138. figs. 1-58.

Next: Enemies of Trout • Contents • Previous: Hatchery Operations