Marine Survival of Coho Salmon (Oncorhynchus Kisutch) from Small Coastal Watersheds in Northern California PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Marine Survival of Coho Salmon (Oncorhynchus Kisutch) from Small Coastal Watersheds in Northern California PDF full book. Access full book title Marine Survival of Coho Salmon (Oncorhynchus Kisutch) from Small Coastal Watersheds in Northern California by Sean M. Cochran. Download full books in PDF and EPUB format.
Author: Sean M. Cochran
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 110
Get Book Here
Book Description
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: Sean M. Cochran
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 110
Get Book Here
Book Description
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: John D. Deibner-Hanson
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 96
Get Book Here
Book Description
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.
Author: Peter Burton Adams
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 36
Get Book Here
Book Description
"This report is a summary of the presence and absence of coho salmon, Oncorhynchus kisutch, in streams in the Central California Coast Evolutionary Significant Unit (ESU). Only streams with historical records of coho occupancy are considered. It has been prepared to assist in Endangered Species Act activities... Presence absence data used here come from surveys conducted for this study and fron data collected by other researchers. A preliminary report of this data, which included only approximately one-half of these streams, was published earlier... to meet earlier listing requirements."--p.Abstract.
Author:
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 1841
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 122
Get Book Here
Book Description
Author: Natalie B. Okun
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 64
Get Book Here
Book Description
Substantial time, money, and effort are invested in river and stream restoration projects to aid in the recovery of imperiled salmonid populations, but there is little evidence that these efforts have had lasting positive impacts on juvenile fish growth and survival. To assess the effectiveness of large woody debris (LWD) restoration, which is one of the most common restoration practices, I evaluated the growth and survival response of endangered Central California Coast coho salmon (Oncorhynchus kisutch) in a paired watershed before-after impact-control (BACI) study. To determine if LWD supplementation influenced coho salmon growth and survival, two neighboring, similar watersheds in Northern California were selected to conduct long-term monitoring of both fish and habitat metrics. Fish and habitat monitoring consisted of summer and fall electrofishing surveys, juvenile outmigrant trapping, passive integrated transponder (PIT) array detections, and summer and winter habitat surveys. After three years of pre-treatment monitoring in both watersheds, Pudding Creek (the ‘experimental’ watershed) was supplemented with 1,365 cubic meters of LWD throughout 80% of the mainstem anadromous spawning habitat in 2015. Post-treatment monitoring then continued in both watersheds until 2020. Though wood density increased more in the experimental watershed (31%) compared to the control watershed (13%) following wood treatment, there was no winter slow water habitat response, meaning the limiting factor for coho populations in these watersheds was not addressed. I used generalized linear mixed effects models with year as a random effect to evaluate summer and winter growth response to wood supplementation. I found that summer and winter growth were positively associated with wood, but the experimental watershed had consistently higher winter growth compared to the control. The wood treatment response did not align with the biological response; wood density increased more in the experimental watershed, but growth did not increase more in the experimental compared to the control watershed. To estimate winter survival rates, I used a Cormack-Jolly-Seber (CJS) model. I found that winter survival increased through time in the control while it stayed level in the experimental watershed. This thesis illuminates the utility of having a paired watershed study design with habitat and biological response analysis in tandem. The results from this experiment lead to a variety of questions and concerns relating to the treatment design and how treatment is paired with the study design. This thesis provides a foundation for long-term monitoring to understand the effects of restoration efforts for a species at the southern extent of its range. This is particularly important given the at-risk status of these salmonid populations and the additional threats these fish face from a changing climate.
Author: Thomas J. Hassler
Publisher:
ISBN:
Category :
Languages : en
Pages : 34
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 1841
Get Book Here
Book Description
Author: James Ray
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 22
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 36
Get Book Here
Book Description
A summary of the presence and absence of coho salmon, Oncorhynchus kisutch, in streams in the Central California Evolutionary Significant Unit (ESU) with historical records of this species has been prepared to assist in the Endangered Species Act listing process. Presence-absence data were used because of: 1) the short time frame indicated by the listing process, and 2) the use of presence-absence data in pre-listing documents. Presence-absence data used here come form surveys conducted for this study and from data collected by other researchers. Coho salmon were absent from 50% of the historical record streams. This figure is similar to reports by earlier researchers. The percent of historical record streams with coho salmon absent is highest in the highly urbanized San Francisco Bay and the lowest in coastal Marin County. Percent of absence was also high in Sonoma County, with other areas being roughly equal.
