Project title: Lake trout otoliths as indicators of past climate patterns and growth in Arctic lakes
Personnel Eric Torvinen (MS 2017) Funding source(s): Natural Institutes for Water Resources Alaska Climate Science Center Project description: The effects of climate change on freshwater ecosystems are amplified in high-latitude regions, however, due to the remote location of Arctic Alaska climate data are limited. Predictions have indicated that warming temperatures owing to climate change could increase fish growth, but the magnitude and factors influencing these changes remain uncertain. Here I investigated the relationship between Lake Trout Salvelinus namaycush growth and physical and biological characteristics, fish community structure and climate patterns. I applied biochronology techniques to predict recent climate patterns from annual growth increments recorded on Lake Trout otoliths. Growth increments were also used to perform length-at-age back-calculations and to estimate the growth coefficient K, as described by a von Bertalanffy growth model. Lake Trout were captured from 13 climate-sensitive lakes in the Fish Creek watershed in Arctic Alaska during 2014 and 2015. Individual Lake Trout (N = 53) ranged from 471–903 mm fork length (FL; mean = 589.3 mm) and their readable annuli, representative of age, ranged from 9-55 annual growth increments. I constructed a growth chronology for the period 1977–2014 and used model selection to identify the best predictive model of relative Lake Trout growth (ring width index; RWI) as a function of climate descriptors. A single covariate model was the best predictor and indicated that RWI tracked mean August air temperature recorded at a local weather station from 1998–2013 (P < 0.001; R2adj = 0.55; RMSE = 0.048). Lake Trout growth (K) was subsequently modeled as a function of physical and biological characteristics, and fish community structure, using multiple linear regression. The highest ranked model included physical (i.e., depth, distance to river and coast, connectivity class, and number of stream intersections) and biological (sex) covariates. Model averaging indicated K was higher in deeper, well connected lakes, located further from the coast and was lower with increasing distance from a large river, though relationship with depth was found to be the single significant covariate. This study demonstrated the utility of biochronology techniques to estimate past climate patterns in remote regions, as well as provided valuable knowledge regarding growth-environment relationships for Lake Trout. In turn, this information can be used to better understand the effects of a changing environment in sensitive Arctic lake ecosystems. Co-Investigators: Chris Arp - UAF Ben Jones - UAF Chris Zimmerman - USGS Trent Sutton - UAF Matthew Whitman - BLM |
Outreach:
Products: Peer-reviewed publications: Torvinen, E.S., Falke, J.A., Arp, C.D., Jones, B.M., Whitman, M.S., and C.E. Zimmerman. In review. Lake trout (Salvelinus namaycush) otoliths as indicators of past climate patterns and growth in Arctic lakes. Thesis: Torvinen, E. S. 2017. Lake trout (Salvelinus namaycush) otoliths as indicators of past climate patterns and growth in Arctic lakes. Unpublished Master's thesis. College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, Alaska. 97 pp. Oral and poster presentations: Falke, J., Sparks, M., Torvinen, E., and P. Westley. 2017. Climate vulnerability and salmonids in Alaska: hind- and forecasting freshwater growth and phenology across species and habitats. Western Division American Fisheries Society Annual Meeting, Missoula, Montana, 23-25 May, 2017. Torvinen, E., Falke, J., Arp, C., Sutton, T., and C. Zimmerman. 2017. Using lake trout (Salvelinus namaycush) otoliths to recreate past patterns of recent climate and growth in Arctic lakes. Alaska Chapter American Fisheries Society Annual Meeting, Fairbanks, Alaska, 19-23 March, 2017. Torvinen, E., Falke, J., Arp, C., Whitman, M., Adams, J. and C. Zimmerman. 2015. Lake Trout (Salvelinus namaycush) otoliths as biochronological indicators of recent climate patterns in Arctic lakes. Alaska Chapter American Fisheries Society Annual Meeting, Homer, Alaska, 4-6 November, 2015. |