Several evolutionarily significant units (ESUs) of Columbia River basin Chinook Salmon Oncorhynchus tshawytscha and Coho Salmon O. kisutch are listed as threatened or endangered under the U.S. Endangered Species Act. Yet little is known about the spatial and temporal distributions of these ESUs immediately following ocean entry, when year-class success...
One aspect of diadromy that has received little attention is buoyancy regulation in fish moving between freshwater and marine environments. Because of density differences between the two water types, fish must alter their whole-fish density (WFD) or they will become positively (float) or negatively (sink) buoyant as they change environments....
The coded wire tag (CWT) database contains detailed information on millions of Pacific salmon
Oncorhynchus spp. released from hatcheries or smolt traps and recovered in the north Pacific Ocean and its tributaries. I used this data set to examine the spatial and temporal variation in the marine distributions of 77...
The underlying causes of mortality during critical life stages of fish are not well
understood, nor is it clear if these causes are similar for naturally versus artificially propagated (i.e.
hatchery) individuals. To assess the importance of selective mortality related to production type
(hatchery vs. naturally produced) and size at...
Successfully shifting to a more piscivorous diet may be an important factor in the growth and survival of juvenile coho salmon Oncorhynchus kisutch and Chinook salmon O. tshawytscha during their first summer in the northern California Current. Nonmetric multidimensional scaling and cluster analysis of diets by size showed several distinct...
The transition between freshwater and marine environments is associated with high mortality for juvenile anadromous salmonids, yet little is known about this critical period in many large rivers. To address this deficiency, we investigated the estuarine ecology of juvenile salmonids and their associated fish assemblage in open-water habitats of the...
Relative to extensive research on the freshwater stages of steelhead Oncorhynchus mykiss life history, little is known about the species’ estuarine and early marine phases despite the decline of numerous populations, including several from the Columbia River. Comparisons of the distribution, diet, and growth of juvenile steelhead collected during surveys...
Ecological interactions between natural and
hatchery juvenile salmon during their early marine
residence, a time of high mortality, have received little
attention. These interactions may negatively influence
survival and hamper the ability of natural populations to
recover. We examined the spatial distributions and size
differences of both marked (hatchery) and...
Purple nutsedge [Cyperus rotundas L.) has been recognized as one of the
most troublesome perennial weeds of agricultural lands in tropical and some
temperate regions. This research sought to determine the effects of timing of
herbicides, shading, and soil moisture on plant population growth and tuber
production of purple nutsedge...