During summer sympatric steelhead trout and summer chinook salmon segregated in Crooked Fork and Johnson creeks. In short-term allopatry, each species occupied the same types of habitat as in sympatry. Most age 0 steelhead lived over rubble substrate in water velocities and depths of less than 0.15 m/sec and 0.15 m, respectively; most age 0 chinook lived over silt substrate in water velocities of less than 0.15 m/sec and depths of 0.15–0.3 m; most age I steelhead resided over large rubble substrate in water velocities of 0.15–0.3 m/sec (near bottom) and 0.75–0.9 m/sec (near surface), and in depths of 0.6–0.75 m. As fish of each species became larger they moved into faster, deeper water. Juvenile chinook and steelhead of the same size used the same physical space. But steelhead spawn in spring and chinook spawn in early fall, and disparate times of spawning create discrete intra- and inter-specific size groups of pre-smolts. The size differences minimize potential for social interaction, both intra- and inter-specific.
Fishery managers are currently spending millions of dollars per year on habitat enhancement for anadromous salmonids but often do not have the tools needed to ensure success. An analysis of factors limiting production of salmonids in streams must be completed before any habitat-enhancement program is begun. This paper outlines the first formal procedure for identifying physical habitats limiting production of coho salmon.
A new method has been developed for collecting, sorting, and interpreting gravel quality. Samples are collected with a tri-tube freeze-core device and dry-sorted using sieves based on the Wentworth scale. An index to the quality of gravel is obtained by dividing geometric mean particle size by the sorting coefficient (a measure of the distribution of grain sizes) of a sample. The resulting number is called the "fredle index" and is proposed as a standard for evaluating the reproductive potential of spawning gravel.
Chronic turbidity in streams during emergence and rearing of young anadromous salmonids could affect the numbers and quality of fish produced. We conducted laboratory tests to determine the effect of chronic turbidity on feeding of 30-65 mm long steelheads Salmo gairdneri and coho salmon Oncorhynchus kisutch in straight and oval channels. Fish subjected to continuous clay turbidities grew less well than those living in clear water, and more of them emigrated from channels during the experiments. Yearling and older salmonids can survive high concentrations of suspended sediment for considerable periods, and acute lethal effects generally occur only if concentrations exceed 20,000 mg/liter (see reviews by Cordone and Kelly 1961; Sorenson et al. 1977), but little is knownabout the effects of turbidity on newly emerged young. Many streams used by salmonids for spawning in disturbed watersheds are subject to chronic turbidity. Fish reared in such streams might not grow as rapidly, or be as socially fit, as those produced in clear streams. In our paper, we evaluated the effects of chronic turbidity on growth and densities of young steelheads Salmo gairdneri and coho salmon Oncorhynchus kisutch. Methods Physical FacilitiesWe used two types of laboratory streams to insure that results were not artifacts of a single apparatus. We conducted replicate pairs of tests in 1978 and 1979 in (1) a pair of indoor oval • Based on a dissertation submitted by John W. Siglet as partial fulfillment of the requirements for the Doctor of Philosophy in Fisheries Management. channels, 3.7 m wide x 4.9 m long, located at the University of Idaho, and (2) two pairs of linear raceways, 1.2 m wide x 21 m long, on a translucent plastic-covered area at the Hayden Creek Research Station. The four raceway channels at Hayden Creek Research Station had substrate arranged in riffle-pool configurations with large (10-15-cm) cobble distributed in a set pattern throughout each channel unit. A trap was attached to the downstream ends of each section (Fig. 1). Each pair of upper and lower channels was operated as a test unit. The oval channels consisted of two essentially identical units, one above the other (Hahn 1977) (Fig. 1). Rearing space in each channel was about 10 m long and 60 cm wide (usable space, 6 m2); pools were 30 cm deep and riffles 7-15 cm deep. Substrate was arranged in riffle-pool configuration with cobble placed in a set pattern throughout the substrate. A paddlewheel was used to maintain water velocities. Fine-mesh screen separated the paddlewheel from the rearing section. Free egress from the channels was provided by downstream and upstream traps.We regulated turbidity, water velocity, temperature, and photoperiod in the oval channels. Carrying capacity of each was about 30 young fish, 30-55 mm long, in clear water. The Hayden Creek raceways were larger, enabling us to use larger numbers of fish, and we controlled turbidity, flow rate (velocity), and, to some extent, temperature. Photoperiod was natural.
Hall. 1987. lnteractions between the redside shiner (Richardsonius balteatus) and the steeihead trout (Salrno gairdneri) i n western Oregon: the influence of water temperature. Can. J. Fish. Aquat. Sci. 44: 1603-1613. Water temperature i n hluenced interactions between redside shiner (Richardsonius balteatus) and juvenile steelhead trout (Salmo gairdneri) ( 2 1 +) i n the field and laboratory. Trout in cool water when shines were absent and at intermediate water temperatures with shiner present occupied a similar range of habitats. Shiner alone i n warm water occupied habitats similar to trout, but i n the presence of trout occupied slower, deeper areas than when alone. In laboratory streams, production by trout was the same in the presence and absence of shiner i n cool water (12-15°C). In warm water (1%22"C), production by trout decreased by 9% in the presence of shiner compared with when shiner were absent. Production of shiner i n cool water decreased i n the presence of trout, -0.3 g-m-2-d-' together compared with 0.5 g.m-2-d-1 alone, but was not affected by the presence of trout i n warm water. Trout distribution was not influenced by shiner in coo! waters, but was influenced at warm temperatures. Shiner occupied all areas of the laboratory channels i n the absence of trout i n coo! waters but were restricted t o a few pools i n the presence of trout. Distribution of shiner was not influenced by trout at warm temperatures.La temperature de l'eau influe sur les interactions entre le m$ne rose (Wichardsonius balteatus) et la truite arc-en-ciel (Salms gairdneri) juvknile ( 2 1 +) en milieu waturel et experimental. Les truites gardees en eau fsaiche en I'absence de menes et 21 des temperatures intermediaires de I'eau en presence de menes ont frequent6 la meme gamme d'habitats. Les menes 6leves seuls en eau chaude ont frequente des habitats semblables B ceux utilises par la truite, mais en presence de ceile-ci, ils se sont deplaces vers des zones plus profondes oh le courant etait plus faible. Dans les cours d'eau experimentaux a eau fraiche (12-15°C)' la production de la truite etait la m&me en prksence et en absence d u mene. Par contre, elle a baisse de 54 % en presence d u mene dans u n milieu a eau chaude (I%Zl5C). En eau fraiche, la production dam mene a baisse en presence de la truite pour atteindre -0,3 g.m-2=j-' par rapport 2 0,s g.m-2-j-' en I'absence de celle-ci, mais en eau chaude la production n'a pas ete aouchee par la presence de la truite. En eau fraiche, le m6n$ n'influait pas sur la repartition de la truite, mais c'etait le cas A des tempkratures plus elevc5es. En $'absence de la truite, le mene frkquentait tsutes les parties des chenalax expesimentaux a eau fraiche mais il ktait restreint a queiques trous d'eau en presence de la truite. Celle-ci n'influait pas sus la repartition du mene en eau chaude. (J8395) everal researchers have examined interspecific interactions between freshwater fish by comparing populations in sympatry and allopatry (e.g. Everest and Chapman 1972; Nilsssn and Nort...
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