Kim K. Jones

Species composition, distribution, and invertebrate prey of fish assemblages in the Columbia River Estuary

Abstract The fish community of the Columbia River Estuary was sampled with trawl, beach seine, and purse seine over an 18 month period during 1980–1981. Seasonality of abundance and species richness in the estuary reflect the timing of migrations and the reproductive cycles of marine and anadromous species. Composition of the fish community and dominant species in the Columbia River estuary are similar to many smaller estuaries in the Pacific Northwest. These similarities reflect the influence of the nearshore marine environment on fish community structure throughout the West Coast as well as the wide geographic distribution and considerable physiological tolerance of many dominant euryhaline species. The distribution of fish assemblages within the Columbia River estuary is influenced by large seasonal variation in river discharge and salinity. Within large areas or salinity zones, species assemblages use different habitats and invertebrate prey. The distribution of abundance and the stomach fullness of fishes vary directly with the density of potential prey. We hypothesize that fish production may be limited by dynamic physical processes that control prey availability or the feeding efficiencies of predators in the highly turbid estuary.

Reconstructing Juvenile Chinook Salmon Life History in the Salmon River Estuary, Oregon, Using Otolith Microchemistry and Microstructure

Abstract We quantified the juvenile rearing and migratory patterns of individuals from a population of fall-spawning Chinook salmon Oncorhynchus tshawytscha in Oregons Salmon River estuary using otolith microchemistry and microstructure. The study confirmed the daily periodicity of otolith growth increments in a natural fish population under field conditions and validated fundamental assumptions about increased otolith strontium: calcium values during entry into saline waters. The otolith results indicated that more than 75% of the subyearling Chinook salmon captured near the mouth of the Salmon River had entered the estuary during the summer and that two-thirds of these fish had spent more than a month in the estuary before capture. Unlike in other Oregon coastal estuaries, in which the fingerling-migrant portion of their life histories is dominant, approximately two-thirds of Salmon River Chinook salmon in upper-estuary marshes were early fry (<50-mm) migrants. A much smaller proportion at the river mo...

Community structure, distribution, and standing stock of benthos, epibenthos, and plankton in the Columbia River Estuary

Abstract Secondary producers were sampled in the Columbia River estuary during the 1980–81 Columbia River Data Development Program (CREDDP) studies. Benthic infaunal macroinvertebrates were sampled in all estuarine zones and habitats with a grab sampler during a single estuary-wide survey. Epibenthic macro- and meiofauna were sampled monthly with epibenthic pump and sled, beach seine, and trawl in tidal flat, slope, and channel bottom habitats throughout the estuary. Zooplankton and larval fish were sampled monthly with oblique zooplankton net tows in the main channel. The distribution of secondary consumers coincided with division of the estuary into three salinity zones and siz habitat types, where the principal physical and biological processes that influenced the distribution and assemblage structure of secondary consumers were: (1) river discharge; (2) river discharge and tidal flow interaction which created circulation and salinity patterns and turbidity maximum characteristics; and (3) benthic processes, such as sediment type and transport and geomorphology. Standing stocks of benthic infauna were highest in protected tidal flat habitats and were comparatively depressed in the Estuarine Mixing Zone of the estuary. Standing stocks of epibenthic and zooplanktonic organisms, in contrast, were concentrated within the Estuarine Mixing Zone.

The contribution of estuary-resident life histories to the return of adult Oncorhynchus kisutch

This study evaluated estuarine habitat use, life-history composition, growth and survival of four successive broods of coho salmon Oncoryhnchus kisutch in Salmon River, Oregon, U.S.A. Subyearling and yearling O. kisutch used restored and natural estuarine wetlands, particularly in the spring and winter. Stream-reared yearling smolts spent an average of 2 weeks in the estuary growing rapidly before entering the ocean. Emergent fry also entered the estuary in the spring, and some resided in a tidal marsh throughout the summer, even as salinities increased to >20. A significant portion of the summer stream-resident population of juvenile O. kisutch migrated out of the catchment in the autumn and winter and used estuary wetlands and adjacent streams as alternative winter-rearing habitats until the spring when they entered the ocean as yearling smolts. Passive integrated transponder (PIT) tag returns and juvenile life-history reconstructions from otoliths of returning adults revealed that four juvenile life-history types contributed to the adult population. Estuarine-associated life-history strategies accounted for 20-35% of the adults returning to spawn in the four brood years, indicating that a sizable proportion of the total O. kisutch production is ignored by conventional estimates based on stream habitat capacity. Juvenile O. kisutch responses to the reconnection of previously unavailable estuarine habitats have led to greater life-history diversity in the population and reflect greater phenotypic plasticity of the species in the U.S. Pacific Northwest than previously recognized.

A Comparison of the Performance and Compatibility of Protocols Used by Seven Monitoring Groups to Measure Stream Habitat in the Pacific Northwest

Abstract To comply with legal mandates, meet local management objectives, or both, many federal, state, and tribal organizations have monitoring groups that assess stream habitat at different scales. This myriad of groups has difficulty sharing data and scaling up stream habitat assessments to regional or national levels because of differences in their goals and data collection methods. To assess the performance of and potential for data sharing among monitoring groups, we compared measurements made by seven monitoring groups in 12 stream reaches in northeastern Oregon. We evaluated (1) the consistency (repeatability) of the measurements within each group, (2) the ability of the measurements to reveal environmental heterogeneity, (3) the compatibility of the measurements among monitoring groups, and (4) the relationships of the measurements to values determined from more intensive sampling (detailed measurements used as a standard for accuracy and precision in this study). Overall, we found that some stre...

Tidal movements and residency of subyearling Chinook salmon (Oncorhynchus tshawytscha) in an Oregon salt marsh channel.

A novel application of full-duplex passive integrated transponder (PIT) tag technology was used to investigate movements of individual subyearling Chinook salmon (Oncorhynchus tshawytscha; fork length ‡ 60 mm) into and out of tidally flooded salt marsh habitat in the Salmon River estuary, Oregon, USA. PIT interrogation was effective, with mean tag detection ‡ 92%. Salmon movement peaked late during both flood and ebb tide periods, indicating that salmon did not drift passively. Most movements were in the direction of tidal currents, but 20% of individuals entered the channel against the ebbing tide. Individuals occupied the intertidal channel for a median 4.9 h and as long as 8.9 h per tidal cycle, and few were detected moving when water depth was <0.4 m. Some individuals used the channel on multiple successive tidal cycles, and others entered intermittently over periods of up to 109 days. Using an individual-based approach, we character- ized diversity of juvenile Chinook salmon behavior within a marsh channel, providing insight into the value of such habi- tats for conservation and restoration of salmon populations. Resume´ : Une utilisation inedite de la technologie des transpondeurs passifs integresatransmission bidirectionnelle simul- tanee( etiquettes PIT) a servi a etudier les deplacements de saumons chinook (Oncorhynchus tshawytscha; longueur a la

Detection of Regional Trends in Salmonid Habitat in Coastal Streams, Oregon

Abstract Freshwater habitat quality is broadly recognized as fundamental to the viability of salmonid populations. Temporal trends in freshwater habitat have rarely been quantified, however, perhaps owing to a lack of methodical and rigorous time series data sets. We present an approach for evaluating change in freshwater habitat using data from a long-term program to monitor salmonid populations and their habitats in coastal drainages of Oregon. Our goals were to (1) evaluate the presence and magnitude of an underlying linear trend in freshwater habitat condition across coastal watersheds in Oregon and (2) determine the effectiveness of the current sampling design for meeting the monitoring objectives. Four features were selected to characterize freshwater habitat: percent of pool area, large wood volume, quantity of fine sediment, and stream size. We developed a statistical model to describe the trend in these features that incorporated an error structure to account for site, year, and site-by-year vari...

Status of Lahontan Cutthroat Trout in the Coyote Lake Basin, Southeast Oregon

Abstract Lahontan cutthroat trout Oncorhynchus clarki henshawi occur in streams flowing north through the Trout Creek and Oregon Canyon mountains into pluvial Coyote Lake in southeast Oregon. The Coyote Lake basin has the only native population of Lahontan cutthroat trout in Oregon that is without threat of hybridization and is broadly distributed throughout a drainage. In October 1994, the number of Lahontan cutthroat trout in the basin was estimated at 39,500 fish, and fish were limited to 56 km of the potential 114 km of stream habitat available. Distribution was limited by dry channels and thermal and physical barriers to movement, which created two disconnected populations in the Willow Creek and Whitehorse Creek drainages and influenced population density, structure, and life history. Lahontan cutthroat trout in the Coyote Lake basin would be more secure if aquatic habitat were improved to allow the two populations to expand their current distributions and become more connected.

Landscape-Level Sampling for Status Review of Great Basin Redband Trout

Abstract In response to a petition to list Great Basin redband trout (subspecies of rainbow trout Oncorhynchus mykiss) as threatened or endangered, the U.S. Fish and Wildlife Service conducted a status review in 1998. To support that review, we conducted a survey of the abundances of redband trout in each of six subbasins of the Great Basin that included the states of Oregon, California, and Nevada. We used a generalized random-tessellation stratified algorithm to select a target sample size of 35 sites/subbasin. Out of a target number of 210 sites, 185 were visited by three-person crews that surveyed stream habitat and estimated the abundance of fish populations in sample reaches with lengths that were nearly 20 times the respective channel widths. A minimal sampling intensity was based on previously encountered levels of between-site variance in estimates of redband trout abundance. The total population estimate of age-1 and older (age-1+) redband trout in the Great Basin was 971,313 fish, with a 95% co...