Search

The timing of ocean entry by salmon smolts is presumed adaptive to maximize survival during this critical life transition. We analyzed the peak timing, duration, and interannual variation in timing of smolt migrations for 53 coho salmon ( Oncorhynchus kisutch ) populations from central California to Kodiak Island, Alaska. The objective was to examine potential influences of both local watershed characteristics and larger-scale processes in the marine environment on smolt migration patterns. Multivariate analyses demonstrated a strong latitudinal gradient in migration patterns with trends toward later, shorter, and more predictable migrations with increasing latitude. Cluster analysis performed on migration descriptors indicated three major population groupings that coincide with major coastal oceanic regions in the northeast Pacific: a northern group from Kodiak Island to the Queen Charlotte Islands, British Columbia, a central group from the Queen Charlotte Islands south to the Columbia River, and a southern group from the Columbia River southward. These regional patterns transcended local variability associated with watershed characteristics and trap location, suggesting that the patterns reflect adaptation to differences in timing and relative predictability of favorable conditions in the marine environments that smolts enter.

This study examined the influence of fall-spawning coho salmon (Oncorhynchus kisutch) on the density, growth rate, body condition, and survival to outmigration of juvenile coho salmon on the Copper River Delta, Alaska, USA. During the fall of 1999 and 2000, fish rearing in beaver ponds that received spawning salmon were compared with fish from ponds that did not receive spawners and also with fish from ponds that were artificially enriched with salmon carcasses and eggs. The response to spawning salmon was variable. In some ponds, fall-spawning salmon increased growth rates and improved the condition of juvenile coho salmon. The enrichment with salmon carcasses and eggs significantly increased growth rates of fish in nonspawning ponds. However, there was little evidence that the short-term growth benefits observed in the fall led to greater overwinter growth or survival to outmigration when compared with fish from the nonspawning ponds. One potential reason for this result may be that nutrients from spawning salmon are widely distributed across the delta because of hydrologic connectivity and hyporheic flows. The relationship among spawning salmon, overwinter growth, and smolt production on the Copper River Delta does not appear to be limited entirely to a simple positive feedback loop.

The study objective was to investigate the response of salmonid populations to disturbance in Oregon Coast Range streams in two rock types, basalt and sandstone. Salmonid abundance was estimated in a total of 30 km of channel in 10 Oregon Coast Range streams with similar basin areas (14–20 km2). These basins had a range of disturbance caused by timber harvest, fire, and salvage logging. Mean channel gradient in sandstone was 0.012 m/m, and pools were the dominant habitat type. Mean channel gradient in basalt (0.025 m/m) was twice that in sandstone, and riffles were the dominant habitat type. Mean percentages by length of pools, glides, and riffles were 47, 33, and 20%, respectively, in sandstone, compared with 24, 27, and 50% in basalt. Channel gradient and channel morphology appeared to account for the observed differences in salmonid abundance, which reflected the known preference of juvenile coho salmon Oncorhynchus kisutch for pools. Coho salmon predominated in sandstone streams, whereas stee...

Populations of coastal cutthroat trout Oncorhynchus clarki clarki were sampled in 16 Oregon headwater streams during 1991–1993. These streams were above upstream migration barriers and distributed among basins that had been logged 20–30 and 40–60 years ago and basins that had not been logged but had burned 125–150 years ago. The objective of our study was to characterize the populations and habitats of age-1 or older cutthroat trout within these three forest management types. Streams within unlogged basins had relatively low levels and a small range of trout biomass (g/m2). Streams in basins logged 40–60 years ago supported low levels but an intermediate range of trout biomass. Streams in basins logged 20–30 years ago supported the widest range of biomass, including the lowest and highest biomasses among all streams sampled. The variable that best explained the variation of trout biomass among all 16 streams was the amount of large woody debris (LWD). All streams were heavily shaded during at lea...

Continuous retrograde warm blood cardioplegia was compared with two widely used hypothermic myocardial protection techniques in a canine model of acute regional myocardial ischemia with subsequent revascularization. Animals (n = 30) underwent 45 minutes of left anterior descending coronary artery occlusion then cardioplegic arrest (60 minutes), followed by separation from cardiopulmonary bypass and data collection. The cold oxygenated crystalloid cardioplegia group (CC; n = 8) and the cold blood cardioplegia group (CC; n = 10) had cardiopulmonary bypass at 28 degrees C, antegrade arrest, and intermittent retrograde delivery. The warm blood cardioplegia group (WB; n = 12) had normothermic cardiopulmonary bypass, antegrade arrest, and continuous retrograde delivery. Overall ventricular function (preload recruitable stroke work relationship; ergs x 10(3)/mL) was significantly (p0.001) better for WB (WB, 80 +/- 11; CB, 67 +/- 13; CC, 57 +/- 12). Systolic function (maximum elastance relationship; mm Hg/mL) was also significantly (p0.001) better for WB (WB, 11.6 +/- 3.6; CB, 8.6 +/- 2.7; CC, 6.2 +/- 1.3). Diastolic function (stress-strain relationship; dynes x 10(3)/cm2) revealed significantly (p0.001) decreased compliance for CC (WB, 20 +/- 6; CB, 19 +/- 7; CC, 27 +/- 11). Left anterior descending coronary artery regional adenosine triphosphate/adenosine diphosphate ratios were significantly (p = 0.02) worse for CC (WB, 10.2 +/- 2.3; CB, 9.4 +/- 2.6; CC, 5.6 +/- 1.5). Myocardial edema significantly (p = 0.03) increased over time only in the CC animals (WB, 0.4% +/- 2.3%; CB, -0.3% +/- 3.6%; CC, 5.5% +/- 2.3%). In this model of acute regional myocardial ischemia and revascularization, continuous retrograde warm aerobic blood cardioplegia provided superior myocardial protection compared with cold oxygenated crystalloid cardioplegia with intermediate results for cold blood cardioplegia.

The objectives of this study were to examine the interactions of the riparian setting (logged vs. forested) and prey availability on the prey capture efficiency and growth of cutthroat trout, and to determine if the riparian setting influences the impact of trout predation on drift composition. Short-term relative growth rates of cutthroat trout, experimentally confined in stream pools, were greater in a logged than in a forested section of stream. Differences in growth rates were attributed to differences among pools in invertebrate drift density, and to differences in trout foraging efficiency that were related to differences between the sections in the amount of overhead shading and substrate crevices. Mean percentages of introduced prey captured by trout were greater in logged control pools and pools of both sections whose bottoms were covered with fiberglass screening to eliminate substrate crevices than in forested control pools and logged pools that were artificially shaded. A logarithmic relationship was found between trout foraging efficiency and surface light of pools. Drift density significantly increased relative to controls in pools from which trout were removed in the logged reach, but not in the forested section. This may result from .habitat features in the logged section that favor greater trout foraging success and the occurrence of behaviorally drifting prey taxa, which represent a predictable food supply for the trout.

Vertical distribution of sediment (particle diameter

Peaks in migration of wild juvenile coho salmon (Oncorhynchus kisutch) from Knowles Creek (Siuslaw River, Oregon) occurred in November and May. Condition factor of nonmigrant fish was higher than migrants or captives throughout the study. Skin guanine levels of migrant fish rose sharply during the first 2 wk of April and continued to rise through June. Gill (Na + K)-ATPase specific activity of migrants rose gradually from a low in January to a maximum in June. Gill (Na + K)-ATPase activity of migrants and nonmigrants was low and not significantly different during November to mid-March. During April, however, gill ATPase activity of migrants rose to become significantly higher than that of nonmigrants until the first 2 wk of May. Cyclic changes in gill (Na + K)-ATPase activity was not observed in these fish. Gill (Na + K)-ATPase activity of fish reared in a laboratory was similar to that of wild nonmigrants until it peaked during the last 2 wk of April, after which the specific activity was lower than either migrants or nonmigrants.

Assemblages of aquatic vertebrate and insect predators were inventoried in streams in old-growth and logged coniferous forests in the western Cascades of Oregon to assess effects of clear-cut logging on stream communities. Effects associated with logging depended on stream size, gradient, and time after harvest. Clear-cut sections where the stream was still exposed to sunlight (5–17 yr after logging) generally had greater biomass, density, and species richness of predators than old-growth (> 450-yr-old) forested sections. Increases were greatest in small (first-order), high gradient (10–16%) streams, where clear-cut sites had both greater periphyton production and coarser streambed sediment than old-growth sites of similar size and gradient. Effects on predators were mixed in larger, lower gradient streams, where clear-cut sites showed accumulation of sediment and relatively small increases in periphyton production. Second-growth logged sections (12–35 yr after logging), reshaded by deciduous forest canopy, had lower biomass of trout and fewer predator taxa than old-growth sites.Key words: trout, salamanders, insects, logging, sediment, periphyton, watershed management

The temperature and dissolved oxygen content of intragravel water were measured in three Oregon coastal streams between June 1968 and June 1969. In 1966, the watershed of one stream had been completely clearcut, and that of a second stream partially clearcut in staggered settings. A third watershed was left unlogged. Clearcut logging resulted in increased temperature of intragravel water in salmon and trout spawning beds and decreased concentrations of dissolved oxygen. The changes were related largely to reduced forest cover over the stream surface and to deposition of fine sediment in the gravel. No serious reduction in survival to emergence of coho salmon occurred along with the observed changes in temperature or dissolved oxygen. A decrease in the resident population of cutthroat trout after logging may have been related to these changes.

Spawning and emergence of coho and fall chinook salmon overlapped in timing and location in Sixes River, Oregon. In early spring both species were distributed throughout most of the river system. Underwater observations during this period indicated that both species occupied the same habitat. As temperatures increased, coho disappeared from the main river, but continued to occupy cool tributaries. Fall chinook were found primarily in the main river until early summer, when they moved to the estuary.In flowing-water observation troughs coho assumed social dominance and defended space near the source of incoming food. In allopatry in the troughs, both grew at similar rates, but coho maintained lower population densities than did chinook. In sympatry in the troughs or in cool tributary streams, coho grew faster than chinook. Coho had brighter fin and body colors, greater fin development, deeper bodies, and were heavier than fall chinook of the same length.Our study suggests that the population of fall chinook salmon in Sixes River might be adversely affected by an increase in numbers of coho. Our evidence suggests that ecology of native fishes should be examined closely before widespread manipulation of fish stocks is encouraged.