RECLAMATION AND CULVERT CROSSINGS MADE OF CORRUGATED PIPES ON SPAWNING STREAMS

Recommendations are presented for solving issues that arise in the design and operation of tubular transport crossings of corrugated metal structures through spawning streams while ensuring the safety and natural reproduction of fish stocks. There are discussed the results of experimental studies of culverts made of metal corrugated pipes with a normal and spiral shape of corrugation the bottom of which is buried and filled with suitable granular material to the level of the natural channel of a small watercourse. It is established that when 10% of the area of the corrugated pipe is occupied by stone filling, its throughput is reduced by about 10-12%. Based on the review of the existing literature and the results of laboratory experiments, data is provided to estimate the values of the roughness coefficients of the composite cross-section of a single-point junction and directions for future research on culvert reclamation are outlined. Studying of the structure of the velocity distribution in culverts can lead to the improved conditions for fish passage without installing special structural elements in the transit path of the fish passage structure.

Influences of cutthroat trout (Oncorhynchus clarki) on behaviour and reproduction of Yellowstone grizzly bears (Ursus arctos), 1975 – 1989

We investigated the distribution, diet, and reproduction of grizzly bears (Ursus arctos) in the Yellowstone ecosystem that fed on cutthroat trout (Oncorhynchus clarki) spawning in streams tributary to Yellowstone Lake. We hypothesized that availability of trout influenced all of these factors for bears in a large part of the Yellowstone grizzly bear recovery area. Depending upon sex, bears that fed on trout used 30–45% of the recovery area. These bears concentrated within 12 km of spawning streams year-round and within 2 km of streams during the spawning season, 1 May – 15 July, when trout-eating bears mostly consumed trout. Despite use of this high-quality food, trout-eating females were apparently less fecund than other females and lost a larger percentage of their dependent young. We speculate that these cub losses resulted from higher rates of intraspecific predation by bears aggregated at spawning streams. These aggregated bears were also vulnerable to human-caused mortality, most likely due to concentrations of humans within 2 km of spawning streams during the spawning season.