Increased Predation by the Torrent Sculpin, Cottus rhotheus, on Coho Salmon Fry, Oncorhynchus kisutch, During Moonlight Nights

1971 ◽  
Vol 28 (9) ◽  
pp. 1352-1354 ◽  
Author(s):  
Benjamin G. Patten
Keyword(s):  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Salmon Fry

In stream aquaria, the percentages of coho salmon fry removed by the torrent sculpin averaged 70 in four tests on moonlight nights and 24 in seven tests on dark nights.

Emigration and Production of Hatchery Coho Salmon (Oncorhynchus kisutch) Stocked in Streams Draining an Old-growth and a Clear-cut Watershed

1987 ◽  
Vol 44 (8) ◽  
pp. 1397-1407 ◽  
Author(s):  
Robert E. Bilby ◽  
Peter A. Bisson
Keyword(s):  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Old Growth ◽  
Trophic Conditions ◽  
Temperature Changes ◽  
Gross Photosynthesis ◽  
Clear Cut ◽  
Salmon Fry ◽  
Streamflow Change ◽  
Downstream Movement

Downstream movement of coho salmon fry (Oncorhynchus kisutch) stocked in old-growth and clear-cut watersheds occurred in three phases: (1) a brief period of heavy emigration immediately after stocking, (2) relatively little movement throughout most of the summer, and (3) intermittent heavy emigration during early autumn freshets. Coho emigrated whenever a streamflow change ≥ 3%∙d−1 occurred, but movement nearly ceased at flows above a certain level. Temperature changes were less important than discharge in triggering movement. When high densities were stocked, emigrant fry were smaller than residents. When low densities were stocked, emigration after the initial pulse of downstream movement was generally lower and there were no size differences between emigrants and residents. Production in the clear-cut was greater than in the old-growth watershed. Proportionately fewer fish emigrated from the old-growth stream, but when population densities were high, mortality in the old-growth exceeded the clear-cut. Greater emigration from the clear-cut site was possibly related to a scarcity of pools. Although the old-growth stream possessed better rearing habitat, less food may have been available, as suggested by gross photosynthesis rates 50% lower than in the clear-cut stream. Coho production therefore appeared to be most strongly influenced by trophic conditions, while volitional residency was most strongly influenced by habitat quality.

Seasonal Changes in Habitat Use by Juvenile Coho Salmon (Oncorhynchus kisutch) in Oregon Coastal Streams

1992 ◽  
Vol 49 (4) ◽  
pp. 783-789 ◽  
Author(s):  
Thomas E. Nickelson ◽  
Jeffrey D. Rodgers ◽  
Steven L. Johnson ◽  
Mario F. Solazzi
Keyword(s):  
Habitat Use ◽  
Seasonal Changes ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Beaver Pond ◽  
Winter Habitat ◽  
Oregon Coast ◽  
Beaver Ponds ◽  
Salmon Fry ◽  
Coastal Streams

Habitat use by juvenile coho salmon (Oncorhynchus kisutch) during spring, summer, and winter was examined in Oregon coastal streams. Coho salmon fry were most abundant in backwater pools during spring. During summer, juvenile coho salmon were more abundant in pools of all types than they were in glides or riffles. During winter, juvenile coho salmon were most abundant in alcoves and beaver ponds. Because of the apparent strong preference for alcove and beaver pond habitat during winter and the rarity of that habitat in coastal streams, we concluded that if spawning escapement is adequate, the production of wild coho salmon smolts in most coho salmon spawning streams on the Oregon Coast is probably limited by the availability of adequate winter habitat.

Absence of Acute Effects on Threespine Sticklebacks (Gasterosteus aculeatus) and Coho Salmon (Oncorhynchus kisutch) Exposed to Resuspended Harbor Sediment Contaminants

1973 ◽  
Vol 30 (8) ◽  
pp. 1240-1242 ◽  
Author(s):  
Richard S. LeGore ◽  
David M. DesVoigne
Keyword(s):  
Gasterosteus Aculeatus ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Dry Weight ◽  
Oil And Grease ◽  
Volatile Solids ◽  
Salmon Fry ◽  
Threespine Sticklebacks ◽  
Sediment Contaminants ◽  
Wet Weight

Threespine sticklebacks (Gasterosteus aculeatus) and coho salmon fry (Oncorhynchus kisutch) were challenged in static 96-hr bioassays with suspensions of sediment from the Duwamish Waterway, Seattle, Wash. Doses of up to 5% wet weight (28.8 g/liter dry weight basis) were used. No observable effect on the fish of contaminants released from the sediment was elicited, although high levels of these contaminants, such as volatile solids, COD, organic nitrogen, oil and grease, zinc, and lead, were present.

Logging Impacts and Some Mechanisms that Determine the Size of Spring and Summer Populations of Coho Salmon Fry (Oncorhynchus kisutch) in Carnation Creek, British Columbia

1984 ◽  
Vol 41 (7) ◽  
pp. 1097-1105 ◽  
Author(s):  
J. C. Scrivener ◽  
B. C. Andersen
Keyword(s):  
Growth Rate ◽  
British Columbia ◽  
Growth Rates ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Growing Season ◽  
Channel Morphology ◽  
Creek Watershed ◽  
Salmon Fry ◽  
Logging Impacts

Natural patterns in emergence times, seaward movements, instream distributions, densities, and growth of coho salmon fry (Oncorhynchus kisutch) between March and September are contrasted with patterns observed during and after logging in the Carnation Creek watershed. After streamside logging in 1976–77, fry emerged up to 6 wk earlier and moved seaward more quickly than during years before logging. These observations are attributed to higher water temperatures during the winter and to emergence during a period of more frequent freshets. Increased fry movement from the stream could result in habitat being underutilized. In sections affected by intense streamside logging, the deposition of "fine" logging debris led to increased fry densities during the summers of 1977 and 1978. After major freshets in November 1978, which removed this fine debris and affected channel morphology in these sections, fry densities declined below those observed prior to logging. Growth rate of fry was inversely correlated with density in all stream sections. Growth rates, after correction for density, tended to be greater in all sections after the adjacent streamside was logged. Larger fry and more variable numbers of fry remained in the stream in September after logging than before logging. Their increased size is attributed to the longer growing season afforded by earlier emergence. This complex of interacting factors determines the number and size of fry in autumn and it can influence the production of smolts the following spring.

Role of Instream Rootwads as Juvenile Coho Salmon (Oncorhynchus kisutch) and Steelhead Trout (O. mykiss) Cover Habitat Under Varying Streamflows

1990 ◽  
Vol 47 (5) ◽  
pp. 852-861 ◽  
Author(s):  
C. S. Shirvell
Keyword(s):  
British Columbia ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Physical Structure ◽  
Steelhead Trout ◽  
Young Fish ◽  
Light Intensities ◽  
Salmon Fry ◽  
Reduced Light

Coho salmon fry (Oncorhynchus kisutch) and steelhead parr (O. mykiss) occupied previously infrequently-used mid-channel areas of Kloiya Creek, British Columbia, Canada, once artificial rootwads were placed there. Ninetynine percent of all coho salmon fry and 83% of steelhead parr occupied positions downstream of natural or artificial rootwads during artificially created drought, normal, and flood streamflows. Fish associated with rootwads regardless of distance from shore, but steelhead parr preferred rootwads away from shore while coho salmon fry preferred rootwads next to shore. Coho salmon fry increased their use of natural rootwads where currents were slow during floods, while steelhead parr increased their use of artificial and natural rootwads where light remained low during droughts. Young fish apparently selected areas having slower water 80% of the time because they provided shelter from adverse current, and areas having reduced light intensities 20% of the time because they provided protection from predators, juvenile coho salmon and steelhead in Kloiya Creek selected locations with slower water velocities and reduced light intensities irrespective of the physical structure that caused them.

THE DIEL DRIFT OF CHIRONOMIDAE IN AN ARTIFICIAL STREAM AND ITS RELATION TO THE DIET OF COHO SALMON FRY, ONCORHYNCHUS KISUTCH (WAULBAUM)

1971 ◽  
Vol 103 (3) ◽  
pp. 289-297 ◽  
Author(s):  
J. H. Mundie
Keyword(s):  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Common Species ◽  
Diel Pattern ◽  
Pupal Exuviae ◽  
Food Items ◽  
Larval Drift ◽  
Salmon Fry ◽  
The Common ◽  
High Degree

AbstractThe diel pattern of drifting adults, pupae, pupal exuviae, and larvae of Chironomidae in a stream was established. Emergence was trimodal for the common species (Cricotopus sp. and Psectrocladius sp.), and larval drift-rates increased almost two-fold in darkness. The concurrent diel consumption of Chironomidae by coho fry was examined. The fish appeared not to make use of the peak drift-rates of larvae. Closest temporal correspondence between drift and diet was shown by adults. Forage ratios demonstrated greater consumption of chironomids than would be expected from their proportions in the drift. The order of acceptance was pupae, adults, larvae, and exuviae. High degree of utilization of an item is attributed to flotation and visibility. The major determinants of how much food is taken from the stream are identified as: marginal residence of the fish, the occupation by the fish of slow-water feeding stations, and the visibility of food items.

Effect of Thermal Stress on Predator Avoidance in Sockeye Salmon

1972 ◽  
Vol 29 (5) ◽  
pp. 601-603 ◽  
Author(s):  
J. R. Sylvester
Keyword(s):  
Thermal Stress ◽  
Predator Avoidance ◽  
Sockeye Salmon ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Acclimation Temperature ◽  
Natural Conditions ◽  
Predator Prey ◽  
Salmon Fry ◽  
Predation Rates

Under laboratory conditions, predation rates of yearling coho salmon (Oncorhynchus kisutch) on sockeye salmon fry (Oncorhynchus nerka) increased with increasing acclimation temperature. Elevated temperature doses significantly decreased survival of sockeye salmon fry. The results suggest that under natural conditions, sudden increases in water temperature could alter predator–prey interactions of some fish by increasing predation mortalities.

Stream Temperatures and Inter-Annual Variability in the Emigration Timing of Coho Salmon (Oncorhynchus kisutch) Smolts and fry and Chum Salmon (O. Keta) Fry from Carnation Creek, British Columbia

1989 ◽  
Vol 46 (8) ◽  
pp. 1396-1405 ◽  
Author(s):  
L. Blair Holtby ◽  
Thomas E. McMahon ◽  
J. Charles Scrivener
Keyword(s):  
British Columbia ◽  
Chum Salmon ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Oncorhynchus Keta ◽  
Windows Of Opportunity ◽  
Salmon Fry ◽  
Median Date ◽  
Wet Weight ◽  
Laboratory Models

Variability in average stream temperatures between peak spawning and fry emergence accounted for 82 and 77% of the variance in the median emigration date of fry of chum (Oncorhynchus keta) and coho salmon (O. kisutch) respectively over a 9 to 10-yr period. The modeled relationships were indistinguishable from laboratory models that predicted time to maximum alevin wet weight. Variability in stream temperatures during the spring accounted for 60% of the variability in the median date of coho smolt emigration. As stream temperatures increased, the predicted thermal summations required for emigration were nearly constant for coho salmon fry, increased moderately for chum salmon fry and increased strongly for coho salmon smolts The duration of the emigration period also differed between the groups: 50% of the chum salmon fry emigrated over a 1-wk period compared with a 2- to 3-wk period for coho salmon fry and smolts. We speculate that the emigration timing —temperature relationships and timing of adult spawning represent adaptations for synchronizing emigration with "windows of opportunity" in the ocean or stream. The windows are of different widths and levels of predictability for coho and chum salmon fry and coho salmon smolts.

UV-Absorbing and UV-Fluorescing Substances in the Belly Skin of Fry of Coho Salmon (Oncorhynchus kisutch)

1969 ◽  
Vol 26 (5) ◽  
pp. 1185-1198 ◽  
Author(s):  
Agnes S. K. Lee ◽  
William E. Vanstone ◽  
John R. Markert ◽  
Naval J. Antia
Keyword(s):  
Carboxylic Acid ◽  
Absorption Spectra ◽  
Chemical Reactions ◽  
Paper Chromatography ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Uv Absorption ◽  
Inosine Monophosphate ◽  
Uv Absorption Spectra ◽  
Salmon Fry

The belly skin of 4-month-old coho salmon fry was extracted with 0.5 M NH4OH, and the extract was analyzed by paper chromatography for UV-absorbing and UV-fluorescing substances. Six fluorescing and three absorbing substances were isolated and characterized by Rf values, UV-absorption spectra, and chemical reactions, and were identified with known compounds where possible. The three UV-absorbing substances were identified as guanine, hypoxanthine, and inosine monophosphate. Three of the UV-fluorescing substances were identified as ichthyopterin, pterin 6-carboxylic acid, and 7,8-dihydroxanthopterin. A fourth fluorescing substance appeared to be an artefact produced by the action of NH4OH on ichthyopterin. The remaining two fluorescing substances appeared to be unknown glycosides, presumably isomers, both containing glucose, xylose, and mannose.

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