An aspect of the genetic structure of coastal Oregon steelhead was
explored and found to gradually change in a north to south pattern for the
allelic frequencies of several enzymes. Isocitrate dehydrogenase and
superoxide dehydrogenase were the clearest examples of this pattern of
variation. This pattern was most evident in...
I used program CAPTURE to analyze 1,535 data sets for 33 North American species of small mammals for sources of variation in capture probabilities and to characterize species-specific responses to markrecapture trapping. CAPTURE incorporates seven models to account for all possible combinations of heterogeneity (h), behavioral response (b), and time...
Two sets of experiments measured changes in the oxygen consumption of the euryhaline teleost Oreochromis niloticus during acclimation to progressively increased salinity. Six acrylic respirometers were constructed for this purpose. The salinities tested were 9, 18, 27 and 36 ppt, with 36 ppt considered as full strength seawater. Fish were...
The eastern margin of the Eastern North Pacific Ocean
was classified into physiographic regions based on a suite
of physical characteristics. Information on cultural and
biological characteristics of this area was meshed with this
classification. The result was a classification of the
Eastern North Pacific into natural-cultural systems whose
boundaries...
The research involved development of two ecological
simulation models to explain the complex dimensionality of
chinook salmon (Oncorhynchus tshawytscha) life history
structure (represented by the age composition of the
spawning stock) and management difficulties entailed in the
complexity.
Since different sizes of chinook salmon are thought to
adapt differently to...
Ecologists have studied the responses of pelagic ecosystems
to varying levels of nutrient loading and fish predation on many
different scales ranging from small experimental enclosures to
whole lake systems. There are recurring patterns of response to
these two variables, which are generally predictable on the basis
of biogeographic, behavioral,...
Newly emerged steelhead fry (Oncorhynchus mvkiss) of hatchery and
wild origins were studied in laboratory stream channels and natural
streams. Objectives of the study were to determine if and how earlier
emerging hatchery fry influence the emigration, realized densities,
growth, habitat use, social structure, and activity patterns of
localized populations...
Documentation of the seasonal feeding habits and ability to
assimilate algae are presented for the first time for a North American
grazing stream fish. The chiselmouth, Acrocheilus alutaceus, begins
feeding on algal matter in early spring and has deposited large fat
reserves prior to an early summer spawning season. A...
Although differences between selective pressures in hatcheries
and streams have been theorized to cause genetic divergence between
hatchery and wild salmonids, evidence of this is lacking. This study
was initiated to document the presence or absence of genetic change
in hatchery and wild stocks by characterizing genetic traits in fish...
The garibaldi, Hypsypops rubicundus, is a sexually monochromatic pomacentrid found in rocky subtidal areas of Southern and Baja California. During the spawning season, males attempt to attract females to a nest of red algae located within individually defended territories. Females were observed to enter the nests of several males before...
A hierarchical classification system of Iceland's
watersheds and rivers is presented. The classification
is based on Iceland's substrate, climate, water, biota,
and human cultural influences. The geological formations
of Iceland are very different in character depending on
their age and formation history. Three major types of
formations occur: Tertiary, Plio-Pleistocene,...
Rainbow trout were exposed to aluminum at pH 7.25 and
8.25 and four hardnesses (10, 30, 80, and 120 ppm CaCO₃)
for 96 hours in a continuous-flow system and mortality and
aluminum accumulation in the gills were determined.
Temperature, pH, and dissolved oxygen were measured
daily for each treatment. Dissolved...
The corvina reina (Cynoscion albus) is an important part of the artisanal fishery
in the Gulf of Nicoya, Costa Rica. Stock assessment on this sciaenid species has been
restricted to the use of length-based methods because of the lack of age data. Direct age
determination methodologies for tropical species often...
As part of a hierarchical approach to classifying watersheds and stream habitats based on geomorphic and geologic criteria, we defined ten classes of fluvial and lacustrine habitats at the scale of valley segments. Valley segments are landscape units which encompass surface waters and the adjacent floodplains and hillslopes with which...
Differences in primary production and periphyton and macroinvertebrate
biomass between pairs of constrained (valley floor width of less than twice the active
channel width) and unconstrained reaches were investigated in Elk River and four
tributaries in southwest Oregon. In August 1991, macroinvertebrates were sampled
from individual cobbles, and rocks were...
Experiments were carried out in fall and winter, 1990
and spring and summer, 1991 , to determine growth and
mortality of juvenile Pacific oysters {Crassostrea gigas)
in effluent from cultured coho salmon {Oncorhynchus
kisutch) , and effluent from salmon in which the red
macroalga Palmaria mollis was cultured. Ambient sea...
This investigation explored the use of microcosms as a tool for
studying the dynamics of tropical aquaculture ponds. The potential use
of rabbit excreta as a pond fertilizer in integrated farming systems was
also investigated.
Twelve insulated fiber glass tanks were utilized as microcosms to
simulate earthen ponds. Seven hand-sexed...
Sexual maturation and sex differentiation comprise facets of a
common theme: reproduction. The endocrine system regulates many
of the critical physiological processes necessary for reproduction and
offers a framework within which technologies can be developed for
controlling sexual maturation and sex differentiation. The studies
described in this thesis were undertaken...
This study was designed to provide information about the juvenile life history of coho salmon, Oncorhynchus kisutch, in the Tenmile Lakes in Oregon by 1) classifying scales of spawning fish and outgoing smolts (1+), 2) assessing the contribution of juvenile life history types to the returns of adults (3₂) and...
Microhabitat use by adult speckled dace (Rhinichthys
osculus), adult longnose dace (R. cataractae), and
juvenile dace (R. spp.) was investigated during the summer
of 1992 in an Oregon Cascades stream. Selected areas were
snorkeled day and night in order to evaluate differential
use of habitat resources both temporally and spatially....
Fishermen's and managers' perceptions of fishery issues are an
important factor to consider when studying conflicts between the
two groups. According to theories of conflict management,
differences in perceptions may cause situations to be characterized
by misunderstanding and mistrust, and may add to the difficulties in
managing the conflict.
A...
Soil, water, and climatic classification systems are reviewed as
background for the construction of a classification system for earthen
aquaculture ponds. The physical and chemical properties of important
soil types are also reviewed because of the critical role that the
soil plays in earthen pond systems. A pond classification system...
The average size and age of chinook salmon (Oncorhynchus
tshawytscha) caught in commercial fisheries along the Pacific Coast
of North America have decreased substantially in this century. These
declines might be caused in part by changes in size and age at
maturity within the stocks contributing to those fisheries. Upriver...
Visual estimation techniques were used to quantify habitat characteristics,
habitat type (pool, riffle) use and longitudinal distribution of steelhead
(Oncorhynchus mykiss), cutthroat trout (0. clarki), and coho salmon (0. kisutch)
in spring, summer and fall in 8.8 km of Cummins Creek, a basin in the central coast
of Oregon. Fish...
Detection and treatment of bacterial kidney disease (BKD)
was investigated. Experiments were conducted to evaluate the
quantitative, fluorescent antibody technique (QFAT) that is used
to detect, identify, and quantify both typical and 'bar form'
Renibacterium salmoninarum cells. Smears of kidney tissue from
naturally and artificially infected salmonids, both with and...
Various aspects of the energetic response to handling stress in juvenile
coho salmon (Oncorhynchus kisutch) were examined. Fish were subjected to
four different handling stressors in a Blazka-style respirometer. Stressed fish
had rates of oxygen consumption that were higher than controls. The
magnitude of the increase ranged from 139 to...
Habitats for juvenile chinook salmon (Oncorhynchus tshawytscha) were
observed at a high flow during the spring of 1989 and at a low flow during the
spring of 1991 in the lower American River of California. Parameters of
microhabitats in eight macrohabitats were measured. Mean column water velocity
and total water...
The early life history stages and metamorphosis in Dover
sole (Microstomus pacificus) are described from 201 larvae and
juveniles. Unlike other pleuronectids, with the possible exception
of the deep-sea sole (Embassichthvs bathvbius), initial migration of
the left eye is not associated with metamorphosis or transition from
plankton to benthos. The...
This research focused on features of a genetically
isolated population of cutthroat trout (Oncorhynchus clarki)
in the Triangle Lake basin of coastal Oregon. A falls at
the outlet of Triangle Lake has blocked upstream migration
of trout and anadromous salmonids into the basin. Cutthroat
trout were found throughout the six...
The importance of hormone reservoirs in mature teleost eggs is
unknown. To elucidate the effects of hormones on embryonic development,
steelhead trout eggs, Oncorhynchus mykiss, were immersed in either cortisol,
testosterone, or thyroxine at two different stages of development. Elevated
concentrations of cortisol were detectable in the trout eggs or...
Although nearshore macroinvertebrates are integral members of high
mountain lentic systems, knowledge of ecological factors influencing their
distributions is limited. Factors affecting distributions of nearshore
macroinvertebrates were investigated, including microhabitat use and
vertebrate predation, in the oligotrophic lakes of North Cascades National
Park Service Complex, Washington, USA, and the conformity...
An approach to understanding and managing anadromous salmon, steelhead,
and sea-run cutthroat trout (Oncorhynchus spp.) based on life history and
evolutionary adaptive capacities of species and stocks is presented. Species, stocks,
and local populations are viewed as systems that are continuously adapting to
changing environmental conditions. They have the potential...
Ten high mountain ponds in Mount Rainier National Park, Washington State, were
studied from June through September 1992 to investigate the influences of fluctuating
pond volumes on zooplankton communities. A temporary pond of short wet phase
duration was inhabited by zooplankton taxa with short generation times and a crustacean
taxa...
The groundfish trawl fishery operating off the coasts of Oregon
and Washington 1985-1987 caught six major assemblages of species
which could be treated as units in developing mixed-species
management plans. Eighty-one percent of the tows observed on
commercial vessels were consistently placed in one of the assemblage
designations using three...
A static-renewal, seven day test was developed and
utilized to study the effects of nutrition on the sensitivity
of Mysidopsis intii Holmquist to zinc. It was found that
juvenile growth was the most reliable and sensitive endpoint
that could also reflect the subtle effects of low zinc
concentrations and diet...
Despite the fact that fishing is an inherently uncertain business, risk has rarely
been formally recognized in fisheries science or management. Few fishery
management plans include any form of risk assessment and those that do focus on
minimizing risk caused by uncertainty associated with markets and environmental
conditions. Fishermen's attitudes...
The Sultanate of Oman has 1700 km of coastline extending from the Arabian Gulf
south to the Arabian Sea. The demersal fish distributions and assemblages have not previously
been well defined. In winter, variations in the oceanography of the area are minimal. In
summer, however, the Arabian Sea is strongly...
Demographic characteristics of juvenile Dover sole
(Microstomus pacificus) were examined in relation to
physical and biotic factors to develop a hypothesis
explaining annual variations in recruitment. Surveys were
conducted along the Oregon continental shelf at depths
between 50-400 m bimonthly during 1989 and annually (in
March) between 1990 and 1993....
The restoration of rivers and streams should be based on a
strong conceptual framework. Streams are developing systems. As
such, streams exhibit temporal behaviors that change with changing
stream environments. Underlying the dynamic development of streams is
potential capacity. Streams express this capacity as an array of
habitats over time...
Genetic differences between early and late forms of
Alaskan chinook salmon (Oncorhynchus tshawytscha) were
identified using two genetic approaches: mitochondrial
DNA (mtDNA) analysis and protein electrophoresis. The
study populations consisted of early- and late-run chinook
salmon in each of the Kenai and Kasilof rivers in Alaska,
and a single population...
The environment under which fish are maintained as broodstock before
reproduction is often stressful; however, the impact of stress on broodstock and gamete
quality is not well known. We investigated the effects of stress over the final stages (i.e.
the 3 months preceding ovulation) of sexual maturation of female rainbow...
Considerable controversy exists about how fish assemblages are
organized. I explicitly took fish movement into account while I
studied the effects of disturbance, habitat complexity, and predation
at different times of the summer to understand the major factors
influencing assemblage structure in a high desert Oregon stream. The
effects of...
Life-history organization of the cutthroat trout (Oncorhvnchus clarki) may be viewed at various levels, including species, subspecies, metapopulation, population, or individual. Each level varies in spatial scale and temporal persistence, and components at each level continually change with changes in environment. Cutthroat trout are widely distributed throughout the western USA,...
Sampling error associated with estimates of species composition and age composition
of commercial groundfish landings in Oregon from 1989 to 1991 is documented to evaluate
the impact of variable landing data on fisheries management and monitoring programs. The
statistical reliability and bias associated with two multistage sampling designs are
investigated...
Of 109 aquatic birnaviruses (AB) belonging to 9 serogroup A, all replicated and produced rapid and extensive cytopathology in CHSE-214 and RTG-2 cells, whereas only half produced significant levels of cytopathological effect (CPE) in two nonsalmonid cell lines tested (EPC and FHM). In many instances it was found that although...
The relationship of coastal cutthroat trout (Oncorhynchus clarki clarki) populations in the Muck Creek basin, a 238 km² southern Puget Sound stream basin in western Washington, was examined using starch gel electrophoresis and meristic analysis. Coastal cutthroat trout were collected from six sites throughout the basin including tributaries, portions of...
Redband trout density was examined in three forested streams in central
Oregon at two scales, pool channel unit and microhabitat. Two streams were in
roadless areas and one was in a "highly managed" watershed. At the larger
spatial scale, trout displayed a seasonal shift in habitat use from early to...
Twenty-three bottom-trawl fish assemblages were identified from the relative biomass of
33 dominant species that occurred in the National Marine Fisheries Services' triennial
trawl surveys over the continental shelf and upper slope off California, Oregon, and
Washington from 1977 to 1992. The assemblages accounted for about 70% of the total...
Temperature influences the incidence of chemically induced cancer in fish,
with warmer temperatures being associated with higher cancer incidence. The
mechanisms of temperature-modulated chemical carcinogenesis in fish, however,
have not been described in detail. Therefore, one primary objective of this study
was increased understanding of how temperature-modulated genotoxicity of 7,12-...
Responses of juvenile steelhead trout to changes in stream habitat resulting from an instream habitat rehabilitation project in Meadow Creek, Oregon were measured from 1991 through 1992 and compared to pre-treatment data from 1987 through 1990. Sixty nine pool-forming, and 59 channel-stabilizing log structures were constructed by the U.S. Forest...
This study examined the distribution and behavior of adult spring chinook salmon
(Oncorhynchus tshawytscha) related to patterns of stream temperature and physical
habitat at channel unit, reach, and basin-wide spatial scales in both a wilderness stream
and a disturbed stream in the John Day River basin in northeastern Oregon. Thermal...
Initially, components of an aquatic food web were examined to study impacts of recreational use on the aquatic ecology of Quartzville Creek, Oregon in 1995 and 1996. Measurements of the food web components consisted of observations of harlequin ducks (Histrionicus histrionicus), visual counts of the larval caddisfly Dicosmoecus gilvipes, benthic...
Waldo Lake, located in the Oregon Cascades, is
considered to be one of the most dilute lakes in the
world. Even with very low nutrient concentrations and
sparse populations of zooplankton, introduced fish in the
lake are large in size and in good condition when compared
to fish from other...
The long-toed salamander (Ambystoma macrodactylum)
is the top vertebrate predator in fishless high-elevation
lakes in North Cascades National Park Service Complex
(NOCA), Washington. The purpose of this research was to
determine the effects of physico-chemical factors and
introduced trout on abundance and behavior of A.
macrodactylum larvae. Although high-elevation lakes...
The distribution of herring (Clupea harengus pallasi) in
the Northeast Pacific extends from southern California to
northern Alaska. Studies on variation in herring life-history
are limited to local
characteristics and recruitment
populations or relatively restricted regions of the Northeast
Pacific. In this study I assessed herring life-history
patterns and recruitment...
Stocks of salmon are declining in the Pacific Northwest. Based on region-wide studies that list and categorize the status of salmon stocks (Nehlsen et al., 1991; Huntington et al., 1994; and Nawa, 1995), I analyze the watersheds where stocks of salmon spawn for several anthropogenic variables, most of which are...
Relations between the diversity of juvenile anadromous salmonids and pool features
were examined in a managed and a pristine watershed in Oregon during the summer of
1990. There were no differences (p>0.05) in pool depth, velocity or pool wood volumes
between streams. However, the pristine system had twice the number...
Three experiments were designed to determine if and how steelhead trout,
Oncorhynchus mykiss, may affect chinook salmon, O. tshawytscha, when they are
confined together as in a raceway or on a barge. We observed groups of chinook and
steelhead together and groups of only chinook in a behavioral experiment to...
Field collections in the Southern Gulf of Oman and the Northwestern Arabian Sea, and
examination of museum collections from this study area, yielded 7 genera and 33 species
of apogonid fishes. Twenty one species of Apogon, one Archamia, four Cheilodipterus,
three Fowleria, one Rhabdamia, two Siphamia, and one Holapogon are...
I studied the occurrence of two sympatric morphs of arctic charr, Salvelinus
alpinus (L.) in Vatnshlidarvatn, a small shallow lake in NW Iceland. The arctic charr
were subjectively distinguished by colour and appearance as brown morph or silver
morph, and measured for morphological and life history characters. The study
revealed...
Species associations of fifteen major commercial groundfish species in the
northeastern Pacific ocean and their spatial and temporal characteristics were studied
using Oregon bottom trawl logbook data, 1987 to 1993. Screening procedures were used
to remove questionable data from the original logbook files, which resulted in the
exclusion of information...
Distribution and life history characteristics of lacustrine-adfluvial bull trout (Salvelinus
confluentus) were described in the North Fork Skokomish River Basin (including Lake
Cushman, a reservoir) from 1994 to 1996. Day snorkeling was conducted in the river to
determine initiation of the bull trout spawning migration, abundance of spawners, and
duration...
Because riparian canopy controls most energy inputs to stream
ecosystems, it directly affects the structure of aquatic food webs and the
ecological processes that govern interactions among trophic levels. This
study addresses the interdependence among riparian canopy, benthic
community structure, and the carrying capacity of high desert streams for
salmonid...
Nest sites of reticulate sculpin (Cottus perplexus) were located in two stream reaches, one from a basalt basin and one from a sandstone basin. Stream reaches were similar in gradient, basin area, elevation, climate, and riparian vegetation but differed in biologic community structure and substrate characteristics. An electivity index was...
Statistical modeling has evolved around building increasingly more complex models, even though it is common knowledge among statisticians that an optimal model size usually exists for any given data set. Having overly complex models leads to imprecise parameter estimates and tends to increase the subjective role of the modeler, which...
The species compositions and densities of the littoral and pelagic zooplankton
assemblages in Crater Lake were compared. The littoral and pelagic zooplankton
assemblages of most lakes are typically different due to different habitat conditions in the
two zones. The littoral zone of Crater Lake lacks many of the habitat characteristics,...