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Geology topics

W.P. Connor

Publications and source records attributed to W.P. Connor.

17 recordsLinked to original sources
USGS2011

Distinguishing between natural and hatchery Snake River fall Chinook salmon subyearlings in the field using body morphology

We used body morphology to distinguish between natural‐ and hatchery‐origin subyearling fall Chinook salmon Oncorhynchus tshawytscha in rearing areas of the Snake River and at a downstream dam during seaward migration. Using subjective eye and body shape characteristics, field personnel correctly classified 88.9–100% of natural subyearlings ( N = 626) and 90.0–100% of hatchery subyearlings ( N = 867) in rearing areas from 2001 to 2008. The morphological characteristics used by these personnel proved to have a quantitative basis, as was shown by digital photography and principal components analysis. Natural subyearlings had smaller eyes and pupils, smaller heads, deeper bodies, and shorter caudal peduncles than their hatchery counterparts during rearing and at the dam. A discriminant function fitted from this set of morphological characteristics classified the origin of fish during rearing and at the dam with over 97% accuracy. We hypothesize that these morphological differences were primarily due to environmental influences during incubation and rearing because it is highly probable that a large portion of the natural juveniles we studied were the offspring of hatchery × hatchery mating in the wild. The findings in this paper might provide guidance for others seeking to differentiate between natural and hatchery fish.

Idaho, Oregon, Washington↗
USGS2011

Two alternative juvenile life history types for fall Chinook salmon in the Snake River basin

Fall Chinook salmon Oncorhynchus tshawytscha in the Snake River basin were listed under the Endangered Species Act in 1992. At the time of listing, it was assumed that fall Chinook salmon juveniles in the Snake River basin adhered strictly to an ocean-type life history characterized by saltwater entry at age 0 and first-year wintering in the ocean. Research showed, however, that some fall Chinook salmon juveniles in the Snake River basin spent their first winter in a reservoir and resumed seaward movement the following spring at age 1 (hereafter, reservoir-type juveniles). We collected wild and hatchery ocean-type fall Chinook salmon juveniles in 1997 and wild and hatchery reservoir-type juveniles in 1998 to assess the condition of the reservoir-type juveniles at the onset of seaward movement. The ocean-type juveniles averaged 112-139 mm fork length, and the reservoir-type juveniles averaged 222-224 mm fork length. The large size of the reservoir-type juveniles suggested a high potential for survival to salt water and subsequent return to freshwater. Scale pattern analyses of the fall Chinook salmon spawners we collected during 1998-2003 supported this point. Of the spawners sampled, an overall average of 41% of the wild fish and 51% of the hatchery fish had been reservoir-type juveniles. Males that had been reservoir-type juveniles often returned as small "minijacks" (wild, 16% of total; hatchery, 40% of total), but 84% of the wild males, 60% of the hatchery males, and 100% of the wild and hatchery females that had been reservoir-type juveniles returned at ages and fork lengths commonly observed in populations of Chinook salmon. We conclude that fall Chinook salmon in the Snake River basin exhibit two alternative juvenile life histories, namely ocean-type and reservoir-type. ?? Copyright by the American Fisheries Society 2005.

Idaho, Oregon, Washington↗
USGS2009

Behavioural thermoregulation by subyearling fall (autumn) Chinook salmon oncorhynchus tshawytscha in a reservoir

This study investigated behavioural thermoregulation by subyearling fall (autumn) Chinook salmon Oncorhynchus tshawytscha in a reservoir on the Snake River, Washington, U.S.A. During the summer, temperatures in the reservoir varied from 23?? C on the surface to 11?? C at 14 m depth. Subyearlings implanted with temperature-sensing radio transmitters were released at the surface at temperatures >20?? C during three blocks of time in summer 2004. Vertical profiles were taken to measure temperature and depth use as the fish moved downstream over an average of 5??6-7??2 h and 6??0-13??8 km. The majority of the subyearlings maintained average body temperatures that differed from average vertical profile temperatures during most of the time they were tracked. The mean proportion of the time subyearlings tracked within the 16-20?? C temperature range was larger than the proportion of time this range was available, which confirmed temperature selection opposed to random use. The subyearlings selected a depth and temperature combination that allowed them to increase their exposure to temperatures of 16-20?? C when temperatures <16 and >20?? C were available at lower and higher positions in the water column. A portion of the subyearlings that selected a temperature c. 17??0?? C during the day, moved into warmer water at night coincident with an increase in downstream movement rate. Though subyearlings used temperatures outside of the 16-20?? C range part of the time, behavioural thermoregulation probably reduced the effects of intermittent exposure to suboptimal temperatures. By doing so, it might enhance growth opportunity and life-history diversity in the population of subyearlings studied.

Journal of Fish Biology↗
USGS2003

Influence of flow and temperature on survival of wild subyearling fall chinook salmon in the Snake River

Summer flow augmentation to increase the survival of wild subyearling fall chinook salmon Oncorhynchus tshawytscha is implemented annually to mitigate for the development of the hydropower system in the Snake River basin, but the efficacy of this practice has been disputed. We studied some of the factors affecting survival of wild subyearling fall chinook salmon from capture, tagging, and release in the free-flowing Snake River to the tailrace of the first dam encountered by smolts en route to the sea. We then assessed the effects of summer flow augmentation on survival to the tailrace of this dam. We tagged and released 5,030 wild juvenile fall chinook salmon in the free-flowing Snake River from 1998 to 2000. We separated these tagged fish into four sequential within-year release groups termed cohorts (N = 12). Survival probability estimates (mean ?? SE) to the tailrace of the dam for the 12 cohorts when summer flow augmentation was implemented ranged from 36% ?? 4% to 88% ?? 5%. We fit an ordinary least-squares multiple regression model from indices of flow and temperature that explained 92% (N = 12; P < 0.0001) of the observed variability in cohort survival. Survival generally increased with increasing flow and decreased with increasing temperature. We used the regression model to predict cohort survival for flow and temperature conditions observed when summer flow augmentation was implemented and for approximated flow and temperature conditions had the summer flow augmentation not been implemented. Survival of all cohorts was predicted to be higher when flow was augmented than when flow was not augmented because summer flow augmentation increased the flow levels and decreased the temperatures fish were exposed to as they moved seaward. We conclude that summer flow augmentation increases the survival of young fall chinook salmon.

North American Journal of Fisheries Management↗
USGS2001

Early life history attributes and run composition of PIT-tagged wild subyearling Chinook salmon recaptured after migrating downstream past Lower Granite Dam

Seaward migration timing of Snake River fall chinook salmon ( Oncorhynchus tshawytscha ) smolts is indexed using subyearling chinook salmon passage data collected at Lower Granite Dam. However, not all of the subyearlings are fall chinook salmon. For six years, we recaptured wild subyearling chinook salmon smolts, which had been previously PIT tagged in the Snake River, to genetically determine if the fish were offspring of spring and summer (hereafter, spring/summer), or fall chinook salmon. Springfall chinook salmon comprised over 10% of the samples of recaptured smolts in five of six years. For these five years, we used discriminant analysis to determine run membership of PIT-tagged smolts that were not recaptured (i.e., not sampled for genetic identification). Accuracy of the discriminant analysis models, based on genetically identified smolts, varied between 75 and 85%. After using discriminant analysis to classify run membership for each PIT-tagged smolt that was not genetically identified, we compared early life history attributes between fall and spring/summer chinook salmon and calculated annual run composition. The life history attributes we studied overlapped, but spring/summer chinook salmon reared along the shoreline of the free-flowing Snake River earlier, were larger, and began seaward migration earlier than fall chinook salmon. Spring/summer chinook salmon made up from 15.1 to 44.4% of the tagged subyearling smolts that were detected passing Lower Granite Dam. As a result, the presence of spring/summer chinook salmon makes migration timing for the fall chinook salmon seem earlier and more protracted than is the case. If wild subyearling spring/summer chinook salmon smolts are not considered, fall chinook salmon abundance at Lower Granite Dam will be overestimated.

Washington↗
USGS1999

Genetic characterization of naturally spawned Snake River fall-run Chinook salmon

We sampled juvenile Snake River chinook salmon Oncorhynchus tshawytscha to genetically characterize the endangered Snake River fall-run population. Juveniles from fall and spring–summer lineages coexisted in our sampling areas but were differentiated by large allozyme allele frequency differences. We sorted juveniles by multilocus genotypes into putative fall and spring lineage subsamples and determined lineage composition using maximum likelihood estimation methods. Paired sMEP-1 * and PGK-2 * genotypes—encoding malic enzyme (NADP + ) and phosphoglycerate kinase, respectively—were very effective for sorting juveniles by lineage, and subsamples estimated to be 100% fall lineage were obtained in four annual samples. We examined genetic relationships of these fall lineage juveniles with adjacent populations from the Columbia River and from Lyons Ferry Hatchery, which was established to perpetuate the Snake River fall-run population. Our samples of naturally produced Snake River fall lineage juveniles were most closely aligned with Lyons Ferry Hatchery samples. Although fall-run strays of Columbia River hatchery origin found on spawning grounds threaten the genetic integrity of the Snake River population, juvenile samples (a) showed distinctive patterns of allelic diversity, (b) were differentiated from Columbia River populations, and (c) substantiate earlier conclusions that this population is an important genetic resource. This first characterization of naturally produced Snake River fall chinook salmon provides a baseline for monitoring and recovery planning.

Snake River↗
USGS1998

Detection of PIT-tagged subyearling Chinook salmon at a Snake River dam: Implications for summer flow augmentation

Rearing subyearling chinook salmon Oncorhynchus tshawytscha (≥60 mm in fork length) were captured in the Snake River and tagged with passive integrated transponders to provide an index of their survival to Lower Granite Dam, the first of eight dams encountered by seaward migrants. Water was released from reservoirs upstream of Lower Granite Dam to augment summer flows and thereby increase subyearling chinook salmon survival. Mean summer flow and maximum summer water temperature in Lower Granite Reservoir were highly correlated ( N = 4; r = −0.999). Acknowledging this correlation, we conducted two separate least-squares regressions using detection rate as the dependent variable. Detection rate at Lower Granite Dam was positively related to mean summer flow ( N = 4; r 2 = 0.993; P = 0.003) and negatively related to maximum summer water temperature ( N = 4; r 2 = 0.984; P = 0.008). Summer flow augmentation increased flow and decreased water temperature in Lower Granite Reservoir especially in low-flow years. Our results support summer flow augmentation as a beneficial interim recovery measure for enhancing survival of subyearling chinook salmon in the Snake River. Additional research should include replicate within-year releases of PIT-tagged subyearlings as well as studies of fish guidance efficiency.

Washington↗