We compared brood sizes among adult female Euphausia pacifica Hansen, 1911 from 3
populations in the North Pacific: Puget Sound, Washington, USA; Toyama Bay, Japan; and the Oregon coast, USA. Additionally, we used multiple linear regression models to compare the interspecific brood size as a function of female length and...
Continued stock declines in marine fisheries have resulted in a search for more risk-averse management approaches. In response, the Sustainable Fisheries Act of 1996 mandates habitat protection, bs catch reduction, and stock rebuilding. These changes emphasize precaution, and imply a shift in focus from maximizing yields to minimizing ecological impacts...
Fluorescein has been used for rapid and sensitive detection of fish skin and corneal ulceration. Effective use of the fluorescein test requires knowledge of conditions that might cause misleading interpretations or otherwise interfere with test reliability. Examination of fish health and the clinical workup often require tricaine as one of...
Requirements are growing for peer review of the science used for governmental management decisions. This is particularly true for fisheries science, where management decisions are often controversial. The National Oceanic and Atmospheric Administration's National Marine Fisheries Service instituted the Center for Independent Experts (CIE) in 1998 as a national peer-review...
Tag and recovery programs can provide valuable information on population size and exploitation rates in fishes. Passive integrated transponder (PIT) tags are ideal for use in such programs because they provide identification of individual fish and are invisible to anglers, circumventing problems with nonreporting of tags. Our objective was to...
Although the adverse impact of pathogens on salmon populations in the Pacific Northwest is often discussed and recognized, little is currently known regarding the incidence and corresponding significance of delayed disease-induced mortalities. In the study reported herein, we surveyed the presence and prevalence of selected micro- and macroparasites in out-migrant...
North Atlantic right whales were instrumented with suction-cup mounted, time-depth recorders (TDR) during the summers of 2000 and 2001 to examine their diving and foraging behavior. Simultaneous observations of temperature, salinity and the vertical distribution of their principal prey, Calanus finmarchicus stage 5 copepodites (C5), were obtained alon
g each...
The extent of stress and eventual mortality in Pacific halibut Hippoglossus stenolepis that resulted from simulated capture by hooking or towing in a net, followed by abrupt exposure to warmer seawater temperature and air, were determined under laboratory conditions. Abrupt exposure to 16degreesC seawater and air after either method of...
To directly determine mortality and predation in the endangered western Steller sea lion Eumetopias jubatus, we deployed implanted, satellite-linked post-mortem data transmitters in 21 juveniles. Data recovered from 4 of 5 detected mortalities exhibited precipitous drops in ambient temperatures followed by immediate onset of transmissions (N = 3), or gradual...
Changes in the spatial distribution of U.S. west coast bottom-trawl effort in relation
to areas of prime habitat for rockfish Sebastes spp. were evaluated between 1992 and 2001. Prime trawlable rockfish habitat (PTRH) was defined based on the spatial distribution of high rockfish catches from logbook data for 1992–1995. Bottom-trawl...
Age-1 and age-2 Pacific halibut Hippoglossus stenolepis were exposed to a range of times in air (0-60 min) and air temperatures (10 degrees C or 16 degrees C) that simulated conditions on deck after capture to test for correspondence among responses in plasma constituents and mortality. Pacific halibut mortality generally...
El ano 2006 representa en dos sentidos una fecha critica para la cuenca del Rio Columbia y para los esfuerzos de recuperacion del salmon y la trucha arcoiris en la region Pacifico Noroeste: el 25 aniversario de la creacion del Consejo para la Conservacion y Poder del Noroeste y el...
If the success of the Endangered Species Act (ESA) is measured by the number of endangered species that have been recovered and delisted, then the act is not very successful. Only 15 species have been delisted because of recovery in the history of the ESA. The Borax Lake chub (Gila...
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...
During the summer of 1994, 1996, and 1997, we conducted hydrographic and plankton surveys of the upper 70 m in the nearshore, the continental shelf, and off shelf oceanic waters off Oregon, USA. Copepod densities and biomass were estimated along 4 transects from each cruise. The on shelf copepod biomass...
Describing the ocean habitats used by Chinook salmon Oncorhynchus tshawytscha is an important step towards understanding how environmental conditions influence their population dynamics. We used data from archival tags that recorded time, temperature and pressure (depth) to define the coastal habitats used by Chinook near Oregon and California during the...
Simultaneous visual and oceanographic surveys were conducted in the lower Bay of Fundy and in Roseway Basin of the SW Scotian Shelf during the summers of 1999 to 2001 to investigate the physical and biological oceanographic factors associated with North Atlantic right whale occurrence. Sightings of right whales were recorded...
Predation by piscivorous marine fishes has been hypothesized to be a primary source of marine
mortality for Pacific Northwest juvenile salmon. During the springs and summers of 1998–2004, we collected predator and prey fishes (forage and juvenile salmonids) at the surface at night off the mouth of the Columbia River....
The mortality of discarded bycatch is a critical problem in the management of fisheries worldwide. Little is known about the key principles involved in the mortality of discarded bycatch. These principles are best elaborated under controlled conditions in the laboratory where the actions and interactions of stressors found in fishing...
Efforts to restore depressed populations of Pacific salmon Oncorhynchus spp. are often hampered by the inability to assign population identity to individuals in an admixture. This knowledge is of particular concern in supportive breeding programs, in which misidentification of individuals to population may result in progeny of mixed heritage, which,...
The American Fisheries Society (AFS) recognizes the need for conservative and robust management of Pacific rockfishes because of naturally low population growth, the overfished state of many of the stocks, and complex nature of the mixed-stock fisheries (60-plus species). The AFS recommends that catch information be collected on a species-specific...
Gravid adult female Euphausia pacifica were collected off Newport, Oregon, USA and transferred to the laboratory, where females spawned eggs, eggs hatched, and larvae were reared at 10.5 degrees C. We fed 4 cohorts of larvae to excess with a combination of phytoplankton species and monitored them daily until they...
A recent trend of enhancing freshwater emergent wetlands for waterfowl and other wildlife has raised concern about the effects of such measures on juvenile salmonids. We undertook this study to quantify the degree and extent of juvenile Pacific salmon Oncorhynchus spp. utilization of enhanced and unenhanced emergent wetlands within the...
There has been a dramatic increase in jellyfish biomass over the eastern Bering Sea shelf since the early 1990s, which was previously hypothesized to have been triggered by changing climate and ocean conditions. We examine the hypothesis that the presence of these large carnivores has affected fisheries resources, either through...
Saltwater-adapted juvenile chinook salmon Oncorhynchus tshawytscha exposed to aromatic and chlorinated compounds, representative of contaminants found in urban estuaries in Puget Sound, have a higher susceptibility to vibriosis than do fish exposed only to the solvent vehicle. Susceptibility to vibriosis was assessed by examining the percent cumulative mortality of the...
After hatchery-reared salmonids are released into the wild, their survival and performance are
frequently lower than those of wild conspecifics. Additionally, negative effects of hatchery fish on wild fish are cited as factors affecting the recovery of salmonid populations. Alternative hatchery rearing environments and release practices have been proposed to...
Estimating the stock proportions of mixed-stock fishery samples by means of genetic stock identification has played an important role in the management of salmon fisheries. In addition, stock identification of individual fish has applications for population studies, forensic cases, and management issues. We examined 11 microsatellite DNA loci in 84...
Fisheries models often assume that discarded undersized fish and target species will survive and contribute to future recruitment and yield. If smaller fish are more susceptible to capture stressors than larger fish, then the assumption that smaller discards would contribute to recruitment may not be true. We tested the hypothesis...
We tested the potential of a selective flatfish trawl to reduce bycatch of slope rockfish in the upper continental slope bottom-trawl fishery (250–500 m) on the U.S. West Coast. The trawl we tested differed from typical slope trawls in that it was a low-rise, two-seam trawl with a severely cut...
We evaluated the effect of capture depth and fish size on the ability of several Pacific rockfishes Sebastes spp. to resubmerge after hook-and-line capture and surface release. We observed fish as they were released into a bottomless floating enclosure, and we recorded submergence success within a 5-min time limit. Submergence...
The Moult Rate (MR) method has been used widely to derive stage-specific growth rates in juvenile copepods. It is the most common field-based method. Unfortunately, the equation underlying the method is wrong and, consequently, large errors in juvenile growth rate estimates are widespread. The equation derives growth from the mean...
The effects of anomalous oceanographic conditions on growth, abundance, spawn-date distributions, and diet of early-juvenile Pacific hake Merluccius productus were examined in nursery grounds off the coast of central California, USA. Spring collections from 2 consecutive years of El Nino conditions, 1997 and 1998, 1 year of La Nina conditions,...
The species composition, distribution and concentration of ichthyoplankton off the central Oregon coast in the NE Pacific Ocean were examined during 2000 and 2002 to investigate annual, seasonal, vertical, and cross-shelf variability. Larval concentrations were also analyzed in relation to water temperature and salinity. The 281 samples collected from 5...
The lingcod Ophiodon elongatus is a benthic marine fish commonly caught by groundfish trawlers and discarded due to low catch limits. Managers must account for the mortality of bycatch to assess population status accurately. Our objectives were to estimate the actual mortality of trawl-discarded lingcod (50- 84 cm) and describe...
Of all Pacific salmonids, Chinook salmon Oncorhynchus tshawytscha display the greatest variability in return times to freshwater. The molecular mechanisms of these differential return times have not been well described. Current methods, such as long serial analysis of gene expression (LongSAGE) and microarrays, allow gene expression to be analyzed for...
The diel feeding periodicity of juvenile Chinook salmon Oncorhynchus tshawytscha was determined from stomachs collected in coastal waters off Oregon in 2000 and 2003. Juvenile Chinook salmon exhibited a diurnal feeding pattern with morning and evening feeding periods. There were differences in the duration and magnitude of the dawn and...
An international multi-laboratory project was conducted to develop a standardized DNA database for Chinook salmon (Oncorhynchus tshawytscha). This project was in response to the needs of the Chinook Technical Committee of the Pacific Salmon Commission to identify stock composition of Chinook salmon caught in fisheries during their oceanic migrations. Nine...
Previous studies have shown that juvenile chinook salmon Oncorhynchus tshawytscha exposed in the field or the laboratory to polychlorinated biphenyls (PCBs), an anthropogenic stressor, are immunosuppressed. It is not known whether simultaneous exposure to natural stressors can increase this immunosuppression. To examine the effects of natural and anthropogenic stressors on...
Well-defined fronts develop at the seaward edge of riverine plumes where suspended materials and planktonic organisms are concentrated by convergent water flows. Riverine plume fronts have been hypothesized to be favorable fish habitats because they can lead to localized prey
aggregations. We examined the spatial distribution of juvenile Pacific salmonids...
The sablefish Anoplopoma fimbria is a valuable North Pacific Ocean species that, when not targeted in various commercial fisheries, is often a part of discarded bycatch. Predictions of the survival of discarded fish are dependent on understanding how a fish responds to stressful conditions. Our objective was to describe the...
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....
Fishes with closed swim bladders regulate buoyancy during depth changes by secreting and
resorbing swim bladder gases. Forced ascent during fishery capture results in barotrauma caused by rapid expansion and exsolution of gases from body fluids. Pressure changes in hyperbaric chambers were used to examine changes in swim bladder integrity...
Unusual collections of several euphausiid, chaetognath, and copepod species help elucidate
the effects of the strong 1997/1998 El Niño off the central Oregon, USA, coast. Furcilia of Nyctiphanes simplex, a euphausiid typically found only as far north as central California, were collected in bi-weekly nearshore samples between December 1997 and...
Assessments for many U.S. Pacific coast groundfish stocks have been developed using the statistical catch-at-age method known as Stock Synthesis. This study used Monte Carlo simulation and a fractional factorial experiment to evaluate the effects of input data errors and stock characteristics on bias and precision in estimates of ending...
We evaluated the effect of barotrauma on the behavior of nine species of Pacific rockfish Sebastes spp. after hook-and-line capture and release using a video-equipped underwater release cage. Sampling was conducted across a range of bottom depths (12-194 m), mostly where barotrauma resulting from an expanded swim bladder and gaseous...
Seabirds have often been proposed as environmental indicators. Beached bird data may provide an additional data source and such data is efficacious because it can reliably be collected by volunteers. In addition to anthropogenic factors, such as oil spills, changes in the ocean-atmosphere can affect carcass beaching rate in 3...