7911 - Laserfiche WebLink

Home Browse Search

282 masses of multiple variable data were gathered, completely reliable informa- tion was lacking. The study demonstrated that there are presently unused descriptive variables in need of quantification that existing methodologies have not considered. Available methods failed to describe adequately pool quality, streambank environment, and aquatic vegetation. In turn, the rela- tionships between streambank environments and aquatic vegetation and fishery values were poorly defined. These variables need intensive research because they relate directly to the manipulation of vegetation by land- and water-managing agencies. This study demonstrates that it is the proper combination of aquatic conditions, not just one variable, that is significant in producing a fishery resource. In the natural environment, one variable alone usually cannot cause increasing or decreasing population densities. What is important is the envi- ronmental mix and how dominant variables relate to the environmental mix. Thus, the development of a valid methodology becomes more complex and the degree of validity more important. Results of the Idaho study did demonstrate that, with adequate sampling (200 samples or more), the methods used to determine mean depth, mean width, composition of stream channel substrate, percent of pool, percent of riffle, and channel elevation were reliable, and confidence intervals at the 95 per- cent level were acceptable. However, to relate this confidence to fish popu- lations will require refinement of existing methodology and the addition of more variables to more adequately quantify and describe the total environmental mix. Only with continual testing, refining, and development of new variables will the needed validity in aquatic methodology be gained. LITERATURE CITED Berg, Leo S. 1947. Classification of fishes, both recent and fossil. Edwards Brothers Inc. 517 p. Burns, James W. 1971. The carrying capacity for juvenile salmonids in some northern California streams. Calif. Fish and Game Dep. 57(1):44-57. Chapman, D. W. 1966. The relative contributions of aquatic and terrestrial primary producers to the trophic relations of stream organisms. In: K. W. Cummins, C. A. Tryon, Jr., and R. T. Hartman, ed.:Organism- substrate relationships in streams. Spec. Publ., Pymatuning Lab. Ecol. Univ. Pittsburgh 4:116-130.