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 Sockeye salmon in Bear Creek, Tustumena Lake drainage, Alaska
Alaska Science Center - Biological Science Office                  Fisheries Projects
Tustumena Lake Sockeye Salmon Investigations


Sockeye salmon run time differences
coordinate fry emigration time
Carol Ann Woody, Ph.D.

Carol Woody holding a sockeye salmon in Tustumena Lake, Alaska Fall at Glacier Flats Creek, Tustumena Lake, Alaska

Introduction

  • High mortality (>90%) during early life in sockeye salmon indicates strong selection for traits that increase survival at this stage.  Two key traits, adult spawn time and fry emigration time, can affect early survival and are influenced by stream incubation regime.

  • Heritable traits of adult spawn time and fry hatch rates are positively correlated with temperature.

  • It is hypothesized that differences in adult spawn time among tributaries with different thermal regimes will coordinate spring fry emigration.  Further, this coordination should coincide with optimal lake rearing conditions (e.g. after ice off).

  • Tustumena Lake is a relatively unproductive glacial Alaskan lake.  Primary production is limited to the short summer so the system provides an extreme test of these hypotheses.  Populations in two tributaries with different thermal regimes were compared to examine the degree of coordination between adult spawn time and fry emigration time.

Methods

  • Stream thermal regimes were monitored by probes buried about 15 cm in stream gravels.
  • Adult return was monitored with picket weirs, spawn time estimated by mark-recapture.

Weir on Nikolai Creek

  • Fry emigration time was monitored with fyke nets and a simple stratified design for mark-recapture.

Sampling sockeye salmon fry in the spring on Nikolai Creek

Study Site

Study sites for Tustumena Lake sockeye salmon investigations

Featured Results

Stream thermal regimes for Nikolai and Glacier Flats creeks
Nikolai Creek has a cooler incubation regime (mean = 0.3oC; SD = 0.88) than Glacier Flats (mean = 2.2oC; SD = 1.65).
(click on images for larger view)
Adult sockeye salmon spawn timing in Nikolai and Glacier Flats creeks Fry emigration timing in Nikolai and Glacier Flats creeks
Adults spawn earlier in systems with cooler incubation regimes (Nikolai) and later in warmer systems in a geographic area. Compared to adult spawn time differences, fry emigration time coincided with >75% of emigration occurring between 29 April and 29 May.

Emigration time coincided with lake break up.  Nikolai break up occurred on 27 April, while Glacier Flats break up was 10 days earlier, 17 April.

 

Sockeye salmon in Bear Creek, Tustumena Lake drainage Tustumena Lake in the winter near Glacier Flats Creek

Results or So What?

  • Results agree with past research indicating both spawn time and fry development rates are positively correlated with incubation regimes.

  • This is the first empirical study indicating that adult run time differences coordinate fry emigration time in spring.

  • Future changes in stream thermal regimes may shift optimal adult spawn and fry emigration times.

  • Managers need information regarding adaptive implications of spawn time, since differential harvest of specific spawn time components can diminish population productivity.

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Last Reviewed: 06/03/02