The Willamette River flows north between the Cascade Mountains and Coast Range of western Oregon within a 29,728-km² basin. The fish community in the geologically young basin consists of 36 native species, but introductions of non-native fishes have added 33 additional species for a total of 69 fish species. During...
To begin to understand freshwater seasonal floodplain fish communities in the context of human alteration of the physical system, species introductions and wetland restoration efforts, I studied fish assemblages in fifteen seasonal floodplain wetlands within four geographic regions (coastal, upper Columbia River estuary, Puget Sound and eastern Oregon/Washington) in the...
The conservation of declining desert fish species requires the identification of relations between fish population dynamics and their environments. Dynamic occupancy modeling, an approach that requires less information than traditional mark-recapture studies, may help identify important factors affecting population processes and aid desert fish conservation and restoration efforts. I used...
Seasonally, in 1998 and 1999, I examined spatial and temporal variation in fish assemblages of agricultural, forested, and acid mine drainage tributaries within the Wayne National Forest (WNF) in southern Ohio. Land use and natural disturbance explained patterns in stream fish assemblages. Creek chub and green sunfish were present in...
In the fall through spring of 2002/03 and 2003/04, the composition of fish and amphibian communities were examined in intermittent streams in the upper Willamette river basin in western Oregon. I recorded standard aquatic habitat variables and water nutrient concentrations (nitrate and phosphate) and correlated them with fish and amphibian...
To best manage Eagle Creek National Fish Hatchery and minimize any negative impacts that the current hatchery program may be having on Endangered Species Act-listed salmonids in the Eagle Creek Basin, I determined if wild fish are being displaced from preferred habitats by hatchery salmonids Oncorhynchus spp. This thesis had...
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,...
Pacific lamprey, Entosphenus tridentatus, have shown recent and rapid declines in abundance. These anadromous fish return to streams where they mature, spawn and die. It has been inferred that Pacific lamprey enter freshwater and reside for ~ 1 year before spawning. This long exposure to the freshwater environment may affect...
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...
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...
Biological invasions are the second largest threat to biodiversity following habitat loss, and studying invasions has been a focus of ecological the past two decades. Despite the intense research, many basic questions remain empirically unanswered, particularly in the realm of behavior. The purpose of this research was to explore the...
The composition and distribution of fish assemblages was examined in a
floodplain lake system in the Amazon basin. Quantitative samples were
collected during the 1992-1993 flooding season at Marchantaria Island, Solimoes
River. A total of 25,819 specimens representing 8 orders, 30 families, 101
genera and 139 species of fish were...
The work presented in this dissertation examines possible
modes of action for growth inhibition by anthropogenic endocrine
disrupting chemicals (EDCs) as well as endogenous hormones
associated with growth in fish. Using the sheepshead minnow (SHM)
(Cyprinodon variegatus) as a model, I developed methods to examine
perturbations in the endocrine axis...
Ecological resources available to freshwater fish shift spatially, temporally and across life stages. To better understand how spatial-temporal availability of resources influence fish, I examined the phenologies of hatching and emergence of Coho Salmon (Oncorhynchus kisutch) in streams with contrasting and strongly defined seasonal thermal variability. The study streams included...
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...
Large dams and their respective reservoirs can provide renewable energy and water security, but also profoundly alter riverine ecosystems. In the Pacific Northwest, dams and reservoirs cause discontinuities in river networks that have been particularly problematic for anadromous fishes. As barriers to the upstream and downstream migration of anadromous fishes,...