Freshwater and Marine Survival of Coho Salmon (Oncorhynchus Kisutch) as a Function of Juvenile Life History PDF Download
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Author: Grace Katherine Ghrist
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 77
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Overwinter survival for all three cohorts and all life histories ranged from 25-73%. In cohort one, overwinter survival for spring migrants was greater than the early migrants: overwinter survival was between 38-53% for spring migrants (depending on analysis assumptions) compared to 26% for early migrants; overwinter survival for the two life histories was indistinguishable in the other two cohorts. Apparent marine survival, including all cohorts and life histories ranged from 1.6-4.9%. Marine survival was indistinguishable between juvenile life history strategies likely due to small sample sizes. A power analysis performed with simulated data, to estimate the sample size of fall tags necessary in order to distinguish between juvenile life histories; this ranged from 3500-6000 tags. The transition probability to the jack state ranged from 1.5-55.8% and was indistinguishable between life history strategies. Multistate models provide the opportunity to incorporate life history diversity into estimates of population demographic rates. Use of these models and ongoing monitoring effort will continue to add new insights into Coho Salmon life history variation and the consequences for populations.
Author: Grace Katherine Ghrist
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 77
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Book Description
Overwinter survival for all three cohorts and all life histories ranged from 25-73%. In cohort one, overwinter survival for spring migrants was greater than the early migrants: overwinter survival was between 38-53% for spring migrants (depending on analysis assumptions) compared to 26% for early migrants; overwinter survival for the two life histories was indistinguishable in the other two cohorts. Apparent marine survival, including all cohorts and life histories ranged from 1.6-4.9%. Marine survival was indistinguishable between juvenile life history strategies likely due to small sample sizes. A power analysis performed with simulated data, to estimate the sample size of fall tags necessary in order to distinguish between juvenile life histories; this ranged from 3500-6000 tags. The transition probability to the jack state ranged from 1.5-55.8% and was indistinguishable between life history strategies. Multistate models provide the opportunity to incorporate life history diversity into estimates of population demographic rates. Use of these models and ongoing monitoring effort will continue to add new insights into Coho Salmon life history variation and the consequences for populations.
Author: Molly Gorman
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 79
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The Scott and Shasta rivers, Klamath River tributaries, experience spatial disparity in habitat quality in spring and summer as a result of historical and current land-use. Juvenile Coho Salmon (Oncorhynchus kisutch) born in the upper tributary reaches often rear in natal streams before migrating to sea. However, those born in the lower reaches often encounter unsuitable habitat and emigrate during their first spring to seek non-natal rearing habitats. It is assumed that these early outmigrants are population losses. This study evaluated first-summer survival, and contribution to the adult population, of non-natal rearing juveniles in the Klamath River Basin. In the spring of 2014 and 2015 juveniles were tagged using Passive Integrated Transponder (PIT) tags as they were leaving the lower Scott and Shasta Rivers. Movement and survival was subsequently tracked using recapture and detection efforts in potential mainstem summer rearing locations. Strontium microchemistry from otolith samples of returning adult Coho Salmon throughout the basin was analyzed to estimate the contribution of non-natal rearing juveniles to adult returns. Few tagged individuals were detected in non-natal rearing habitats, but those detected in these habitats had survival rates comparable to natal-rearing individuals. Otolith analysis indicated that the proportion of juvenile Coho Salmon rearing in non-natal habitats varied by spawning site. In total, 53% of the 116 adults sampled reared in a natal location as juveniles, while 47% reared in a non-natal location. These results suggest that non-natal rearing can contribute to adult returns and could be a significant population segment with increased restoration.
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: 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: 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: Theodore H. Blahm
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 32
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Author: Bethany E. Craig
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 170
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Author: Adam D. Weybright
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 110
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Juvenile salmonids display highly variable spatial and temporal movement patterns that are influenced by density dependent (e.g., competition, predation) and density independent (e.g., genetics, stream discharge, physical habitat conditions) factors. The effects of these factors differ with fish life history stage, but will ultimately affect how salmonids utilize freshwater nursery habitats and influence their size at smolting. Although juvenile coho salmon (Oncorhynchus kisutch) (Walbaum 1792) movement patterns and their relationships with body mass have been previously examined, the temporal scale considered in most studies has been within individual seasonal periods. In this study, we monitored the movement of PIT tagged juvenile coho salmon throughout the period of freshwater residence in an entire southern Oregon coastal basin to identify the prevalent sedentary and mobile strategies these fish may adopt and to examine possible relationships between those strategies and fish body mass, growth and survival. Specific objectives include: 1) to describe juvenile coho salmon movement strategies and patterns during the freshwater residence period; 2) to determine the relative proportions of juvenile coho salmon that exhibit each movement strategy; 3) to establish whether juvenile coho salmon body mass and growth rates are related with a set of habitat variables recorded during this study; 4) to determine whether coho salmon body mass or growth rates are related to movement strategy; and 5) to evaluate whether winter survival of juvenile coho salmon is associated with movement strategy. Results revealed seasonally and spatially variable movement. More than half of coho salmon tracked throughout the period of freshwater residence exhibited movement behavior that differed between summer and winter seasons. Within seasonal periods, coho salmon in tidally affected reaches exhibited greater prevalence of mobile behavior relative to those in riverine reaches. Regression analysis indicated coho biomass density, habitat unit structural complexity and size at tagging were important in predicting summer growth of coho salmon. Juvenile coho salmon that were mobile during summer were either larger or no different in body mass in early summer relative to fish that exhibited sedentary behavior. Similarly, no consistent differences were observed between sedentary and mobile coho salmon in regards to summer growth. Coho salmon that were sedentary in summer and winter experienced higher apparent winter survival than mobile fish in each season, though the reach in which an individual resided at the start of winter appeared to also affect survival. Coho salmon residing in the tide gate reservoir reach and mainstem headwater reaches experienced greatest apparent winter survival. These results indicate that juvenile coho salmon movement within a stream basin is spatially and temporally variable and that mobility does not necessarily indicate inferior competitive ability. In a broader context, variable movement patterns reflect the capacity for plastic behavior in salmonids and this research demonstrates the importance of maintaining seasonally diverse freshwater and estuarine nursery habitats for juvenile fish.
Author:
Publisher:
ISBN:
Category : Chinook salmon fisheries
Languages : en
Pages : 338
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Author: Jennifer J. Hauer
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 152
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