North Pacific Anadromous Fish Commission

Technical Report 23

Table of Contents

Is Early Marine Growth Related to Salmon Survival? Two Decades of Data from Juvenile Coho Salmon in the Northern California Current

Authors:
Brian Beckman, Meredith Journey, Cheryl Morgan, and Brian Burke

Abstract:
Early summer growth for juvenile coho salmon (Oncorhynchus kisutch) has been assessed in the Northern California Current (NCC) since 2000. Mean insulin-like growth factor 1 (IGF1) levels (an indicator of growth) differed significantly over succeeding decadal intervals (2000–2009 vs. 2011–2022) with IGF1 levels since 2010 being consistently higher than found before 2010. Across the time series, IGF1 levels were correlated with a prey index for juvenile salmon derived from plankton samples collected in the upper water column during juvenile salmon surveys. There are no apparent correlations between juvenile salmon growth and basin-scale oceanographic indictors including the Pacific Decadal Oscillation (PDO), Northern Pacific Gyre Oscillation (NPGO) or Oceanic Niño Index (ONI). Neither is there a correlation between juvenile salmon growth and upper water column temperatures concurrent with the survey. From 2000–2009 early marine growth was correlated with an index of coho salmon survival (OPIH), there was no correlation of growth with survival in the subsequent decade (2011–2022). These data don’t easily fit with current paradigms suggesting that variation in juvenile salmon growth and survival is correlated with California Current ecosystem productivity driven by variation in basin-scale ocean processes indexed as by the PDO or NPGO. Indeed, the highest IGF1 level measured in the time series were unexpectedly found during the 2016 El Niño. Together, these data suggest that there isn’t a simple relationship between early marine growth and survival for coho salmon in the NCC. Moreover, any relationship that does exist changed over a decadal time scale (2000–2009 vs. 2011–2022). Finally, it may be difficult to establish mechanistic insights into growth and survival within the framework of current environmental variation in the NE Pacific Ocean.

DOI:
https://doi.org/10.23849/npafctr23/qkl92-s

Citation

Beckman, B., M. Journey, C. Morgan, and B. Burke.  2024. Is early marine growth related to salmon survival? Two decades of data from juvenile coho salmon in the Northern California Current.  N. Pac. Anadr. Fish Comm. Tech. Rep. 23: 40.  https://doi.org/10.23849/npafctr23/qkl92-s