Growth of juvenile chinook salmon (Oncorhynchus tshawytscha) as an indicator of density-dependence in the Chena River Item Type Thesis Authors Perry, Megan T. Download date 02/10/2021 14:37:11 Link to Item http://hdl.handle.net/11122/10938 GROWTH OF JUVENILE CHINOOK SALMON (ONCORHYNCHIJS TSHA WYTSCHA ) AS AN INDICATOR OF DENSITY-DEPENDENCE IN THE CHENA RIVER By Megan T. Perry RECOMMENDED: Advisory Committee Chair Chair, l^jrortiiipikof Biology and Wildlife APPROVED: Dean. College of Natural Science and Mathematics Dean of the Graduate School Date GROWTH OF JUVENILE CHINOOK SALMON (ONCORHYNCHUS TSHA WYTSCHA) AS AN INDICATOR OF DENSITY-DEPENDENCE IN THE CHENA RIVER A THESIS Presented to the Faculty of the University of Alaska Fairbanks in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE By Megan T. Perry, B.A. Fairbanks, Alaska August 2012 Abstract In management of Pacific salmon, it is often assumed that density-dependent factors, mediated by the physical environment during freshwater residency, regulate population size prior to smolting and outmigration. However, in years following low escapement, temperature may be setting the upper limit on growth of juvenile Chinook salmon Oncorhynchus tshawytscha during the summer rearing period. Given the importance of juvenile salmon survival for the eventual adult population size, we require a greater understanding of how density-dependent and independent factors affect juvenile demography through time. In this study we tested the hypotheses that (1) juvenile Chinook salmon in the Chena River are food limited, and (2) that freshwater growth of juvenile Chinook salmon is positively related with marine survival. We tested the first hypotheses using an in-situ supplemental feeding experiment, and the second hypothesis by conducting a retrospective analysis on juvenile growth estimated using a bioenergetics model related to return per spawner estimates from a stock-recruit analysis. We did not find evidence of food limitation, nor evidence that marine survival is correlated with freshwater growth. However, we did find some evidence suggesting that growth during the freshwater rearing period may be limited by food availability following years when adult escapement is high. Table of Contents Page Signature Page ..........................................................................................................................i Title Page .................................................................................................................................. ii A bstract................................................................................................................................... iii Table of Contents ....................................................................................................................iv List of Figures ........................................................................................................................vii List of Tables .........................................................................................................................viii Acknowledgements .................................................................................................................ix General Introduction ...............................................................................................................1 References ..................................................................................................................................5 Chapter 1. Responses to in-situ supplemental feeding of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Chena River, Alaska...................................................10 Abstract..................................................................................................................................... 10 Introduction ..............................................................................................................................11 Methods .................................................................................................................................... 13 Study A rea................................................................................................................... 13 Supplemental Feeding................................................................................................ 15 Mark-Recapture, Fish Condition, and Mass Frequency Distribution................... 16 Data Analysis ............................................................................................................................17 Fish Condition.............................................................................................................17 Indices of Competition................................................................................................ 17 V Abundance Estimates................................................................................................. 18 Results......................................................................................................................................20 Discussion ................................................................................................................................ 21 References ............................................................................................................................... 26 Figures ......................................................................................................................................31 Tables.......................................................................................................................................36 Chapter 2. Retrospective analysis of juvenile Chinook salmon growth in an Interior Alaska River: Insight into marine survival and density dependence .................................. 38 Abstract.....................................................................................................................................38 Introduction ............................................................................................................................. 39 Methods ....................................................................................................................................40 Study Area...................................................................................................................40 Length Data.................................................................................................................41 Temperature Data......................................................................................................45 Growth Modeling........................................................................................................ 47 Bioenergetics...............................................................................................................47 Survival........................................................................................................................ 49 Results......................................................................................................................................50 Discussion .................................................................................................................................51 References ................................................................................................................................55 Figures ......................................................................................................................................60 Tables.......................................................................................................................................62 vi General Conclusion.........................................................................................................64 References ............................................................................................................................... 66 Appendix.......................................................................................................................... 67 v ii List of Figures Page Chapter 1 Figure 1. Map of the Chena River demarcating upper and lower study reaches and control and supplemented sites within each reach (modified from: Brase and Doxey 2006) ........31 Figure 2. Regression of log-transformed mass and length for all juvenile Chinook salmon collected from upstream and downstream reaches in both control and supplemented food sites of the Chena River, Alaska.............................................................................................32 Figure 3. Mass frequency distributions of juvenile Chinook salmon at upstream sites of the Chena River, AK, 2009. In the upper right hand of each plot is the sample size used to make the plot, as well as the Gini coefficient (Gc) for the sampling event ....................33 Figure 4. Mass frequency distributions of Chinook salmon at downstream sites of the Chena River, AK, 2009. In the upper right hand of each plot is the sample size used to make the plot, as well as the Gini coefficient (Gc) for the sampling event ........................34 Figure 5. Abundance estimates (± standard error) of juvenile Chinook salmon at three sites in the downstream reach of the Chena River, AK, 2009............................................. 35 Chapter 2 Figure 1. Mean observed length for fish in upstream and downstream reaches of the Chena River, Interior