Abundance and Survival Rates of Juvenile Coho Salmon (Oncorhynchus Kisutch) in Prairie Creek, Redwood National Park PDF Download
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Author: Kyle E. Brakensiek
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 220
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Author: Kyle E. Brakensiek
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 220
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Author: Peter Drobny
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 136
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I evaluated the effects of fish length, habitat attributes, and densities of Coho Salmon and trout on overwinter survival of juvenile Coho Salmon in Prairie Creek, California. Survival of PIT tagged juvenile Coho Salmon was estimated using a Cormack-Jolly-Seber Model based on mark-recapture data from seine net captures, PIT tag antenna detections, and a rotary screw trap. A zero inflated Poisson binomial model, based on a 2-pass snorkeling methodology, estimated pool-specific abundance of juvenile Coho Salmon while accounting for variable snorkeler detection efficiency as well as estimating the effect of habitat attributes on density. Trout densities were obtained using raw snorkel counts. Overwinter survival of PIT tagged juvenile Coho Salmon during 2014-2015 was estimated to be 0.35 (95% CI 0.30-0.40), similar to survival estimates for Prairie Creek in previous years. Survival increased with fish length and decreased with intraspecific density. There was no evidence that density of small (150 mm) trout, large (150 mm) trout, or habitat attributes influenced survival. Estimated density of juvenile Coho Salmon in pools averaged 0.5 fish/m2 (n= 159) and ranged from 0- 2.2 fish/m2, consistent with regional density values within the Pacific Northwest. Juvenile Coho Salmon density estimates declined with cover complexity and watershed area, and increased with pool depth. Probability of detecting a fish while snorkeling varied with habitat features and among observers; estimated probability of detection averaged 0.63 (n=318) and ranged from 0.19 to 0.96 across snorkel passes.This study not only continued valuable monitoring of juvenile Coho Salmon overwinter survival in the southern portion of their range, but also determined factors that may be contributing to survival rates. In addition, this study successfully applied a relatively new hierarchical modeling technique (N-mixture model) to estimate juvenile Coho Salmon densities using non-invasive methods.
Author: Tancy R. Moore
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 120
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During the summer of 2012, juvenile coho salmon (Oncorhynchus kisutch) in Prairie Creek, California and its tributaries were marked using PIT tags to monitor winter redistribution and estimate overwinter growth and survival. Since a substantial number of juvenile coho salmon in the Prairie Creek watershed may rear in freshwater for two years, a scale sample analysis was also conducted to determine what proportion of the 2012 population was exhibiting a two-year freshwater residency. The Cormack-Jolly-Seber model and Program MARK were used to examine how rearing location, size at tagging, habitat unit depth, and volume of large woody debris affected overwinter survival. I found that 98.6% of juveniles in 2012 were age 0, and apparent overwinter survival was 39.4%. On average, juveniles experienced a 0.13% increase in length per day and 0.35% increase in weight per day, with the smallest fish experiencing the highest growth rates. Fish that were larger in fall and tagged closer to the confluence of Prairie Creek had higher apparent overwinter survival, but habitat depth and quantity of large woody debris did not appear to impact survival probability. Large juveniles appeared to have low survival near the confluence of Prairie Creek; however, the model could not distinguish deaths from emigration, meaning the high mortality rate for large juveniles near the mouth may actually reflect a pattern of early emigration from the study area. Since juveniles that migrate to sea prior to spring trapping are typically treated as mortalities, these results have important implications for the way managers estimate freshwater survival for coho salmon.
Author: Ethan Bell
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 150
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Author: Sean M. Cochran
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 110
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California coho salmon Oncorhynchus kisutch populations are at low abundance and factors governing recruitment variability remain unclear. Changes in freshwater habitat that increase juvenile growth and size of salmon outmigrating to sea (smolts) may improve ocean survival. The best data to evaluate this among wild coho salmon populations in California come from life-cycle monitoring (LCM) stations. This study investigated whether marine survival is size-dependent (larger individuals within a cohort have higher marine survival) and whether sites and years with higher growth have higher marine survival across five LCM locations. I tested for size-dependent survival using two techniques: comparing the size of outmigrating smolts and back-calculated smolt sizes from scales of adult fish that survived to return; and using information from fish that were tagged as smolts and survived to return as adults. Analyses comparing smolt sizes back-calculated from adult scales and observed lengths from smolt traps indicated that within-year size-dependent mortality at sea occurred among many outmigrant cohorts, while analyses using smolt lengths of recaptured adult fish tagged as juveniles did not indicate any within-cohort size-selective mortality at sea. Potential explanations for the conflicting results include errors in scale back-calculation; smolts growing in habitats below smolt traps prior to ocean entrance; and fish with alternative juvenile life histories that were unaccounted for in outmigrant sampling surviving and contributing to the adult populations. In regressions across sites and years, marine survival was positively associated with early marine growth measured from the scales of surviving adult salmon and in some instances marine survival was also positively associated with mean fork length of outmigrating smolts. Although size may be an important determinant of ocean survival, this study shows that comparison of back-calculated smolts sizes from scales of adult fish and observed lengths of smolts at an upstream trapping location are unreliable approaches for testing size-selective mortality. This study also provides support for expanding studies at LCM stations to determine how juvenile coho salmon use habitat downstream of migrant trapping locations.
Author: Michelle R. Krall
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 80
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Substantial investment has been directed toward construction of off-channel ponds in the middle Klamath River basin to benefit Coho Salmon populations. Previous research showed that abundance, retention, and growth of juvenile Coho Salmon varied across sites but were not consistently different between constructed ponds and natural habitats; instead, variation was attributed to individual site characteristics. However, the characteristics responsible for these differences are not clear. In this exploratory study, I investigated the effect of accessibility on juvenile Coho Salmon abundance within nine constructed ponds. I also assessed whether habitat conditions, Coho Salmon density, and food availability within the ponds could predict abundance, retention, and growth of Coho Salmon. Few strong relationships were found between characteristics of ponds and the response variables. Despite potentially stressful conditions at some sites, Coho Salmon occupied most ponds through the summer, suggesting that they provide suitable rearing habitats. Lack of accessibility throughout the year had potentially important effects on the survival and life history of individuals trapped in constructed ponds. Retention rates were strongly correlated with zooplankton availability, while Coho Salmon density and available benthic prey displayed little correlation with retention. While growth rate differed among ponds; while measures of prey availability did not explain variation in growth rate, growth rate was negatively correlated with Coho Salmon density in the ponds. Constructed off-channel ponds serve as important rearing habitat for Coho Salmon and an increased understanding of their role in Coho Salmon rearing and production is necessary.
Author: Nicholas Van Vleet
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 101
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Accounting for life history diversity and overwinter survival of juvenile Coho Salmon is important to inform restoration and recovery efforts for this threatened species. Multiple seaward migration patterns of Coho Salmon have been identified, including spring fry migrants, fall and winter parr migrants, and spring smolt migrants. Previous studies have indicated that spring smolt migrants have low overwinter survival rates while they are rearing in upstream habitats, suggesting that freshwater overwinter survival may be one factor that limits smolt production. However, previous research did not account for the early emigration of fall and winter parr migrants from the study area, which most likely negatively biased their overwinter survival estimates. Furthermore, previous mark-recapture methods aggregated continuous detection data into course seasonal scales in order to estimate movement and survival. In an effort to refine previous methodology, I developed a multi-state model that allowed for estimation of early emigration and survival rates in space and time by having weekly time-varying occasions paired with discrete spatial states.
Author: Paul M. Iwanaga
Publisher:
ISBN:
Category : Fishes
Languages : en
Pages : 56
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Author: Richard Allan Crone
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 158
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Behavior and survival in fresh water were studied for three brood years of coho salmon in Sashin Creek, Alaska, from October 1963, until September 1966. Investigations of spawning adults were conducted to determine numbers of spawners, distribution on the spawning grounds, effects on pink salmon, age composition, redd life, fecundities, and egg retention. Juvenile coho were studied to determine changes in population size, distribution in the stream, age composition of the population, food habits, and rates of mortality during fresh-water life. The number of coho spawners counted into Sashin Creek each year normally varied from 50 to 300. Weir counts and estimations of the number of spawners determined from observed spawning effort and redd life were not accurate methods of estimating the coho escapement into Sashin Creek. In 1965, a more accurate estimate was obtained by tagging a portion of the run and recording marked to unmarked ratios on the spawning grounds. I estimated that less than two percent of the viable pink salmon embryos were destroyed in 1965 by the spawning activities of coho salmon. Most coho spawners returned to Sashin Creek in 1965 and 1966 in their fourth year of life after having migrated to sea in their third year (designated 43). Smaller numbers of 32 and 54 individuals composed the remainder of the spawning population. The mean redd life of 56 females was 13 days. A small sample of coho from Sashin Creek examined for fecundity in 1966 gave a mean of 2,868 eggs per female. A weir or fyke net was fished in the spring to estimate emigration of juvenile coho. Coho smolts left Sashin Creek from April through July; peak emigration occurred in late May or early June. Coho fry left the stream in the spring and summer in widely varying numbers from year to year. I estimated from growth data, population estimates, and analysis of scale samples that most coho juveniles remained in Sashin Creek for two growing seasons before migrating to sea. Analysis of scales from juvenile coho indicated that some reabsorption of scales occurs during the winter. The possibility of reabsorption of circuli makes back-calculation of the length of younger age-groups of coho from scale measurements unreliable. Diptera were represented more often than any other order of insects in the stomachs of juvenile coho. Hemiptera were important as food items to juvenile coho in a tributary stream. The estimated survival from egg deposition to immediately prior to emergence varied between 17.5 and. 34.9 percent for the three brood years, and averaged 27. 8 percent. Early summer populations of fry were variable in size and dependent on the size of the egg deposition of the brood. Populations of fry declined rapidly during July and early August. Instantaneous mortality rates were much higher for this period than during any other time in the fresh-water life of coho salmon in Sashin Creek. Mortality dropped to a low level during the following winter period.
Author: John D. Deibner-Hanson
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 96
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Some studies suggest that Coho Salmon populations are limited by overwinter survival as a result of insufficient winter habitat. While many small-scale projects aim to define reach and basin-level habitat requirements for Coho Salmon, large-scale studies that assess multiple independent populations remain few. For my research, I quantified large woody debris (LWD) by volume and low-velocity rearing habitat (LVH) as percent area in three coastal watersheds of similar size in northern California to untangle the relationships between Coho Salmon overwinter survival, emigration timing and specific winter habitats. I used mark-recapture techniques with PIT tags to formulate Cormack-Jolly-Seber models for each of three years (2013-2015) to (1) estimate apparent overwinter survival of juvenile Coho Salmon populations, (2) determine to what extent outmigration timing varies among basins, and (3) evaluate the relationships between reach-specific survival, movement and winter habitat. LWD volume ranged from 47.8 to 109.9 cubic meters per kilometer among stream reaches while LVH area spanned from 9.3% to 23.6% of total stream area per reach. Effects of LWD on apparent overwinter survival and early emigration were absent during all three years of the study. Effects of LVH were not observed during 2013 and 2014. In 2015, LVH correlated positively with apparent overwinter survival and negatively with emigration. Larger Coho Salmon had higher apparent overwinter survival rates than small fish, whereas smaller fish had greater emigrations rates before spring. Mean apparent overwinter survival varied by basin from 0.052 to 0.567 but basins maintained consistency across years. Early emigration rates ranged even further by basin (0.023-0.773). Variation in both apparent overwinter survival and early emigration was much greater among basins than within basins. A lot remains to be learned regarding how habitat affects the migratory behavior of Coho Salmon in California and these results suggest the effects may vary significantly by stream. The drastic life history differences observed in neighboring Coho Salmon populations demonstrate the plasticity in a species once thought to be relatively inflexible. Moving forward, incorporating multi-basin approaches should be considered when evaluating freshwater survival and movement to inform large-scale restoration and conservation.
