What is causing declines in the annual returns of Fraser River sockeye salmon?

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1 What is causing declines in the annual returns of Fraser River sockeye salmon? Mike Lapointe, Catherine Michielsens; Pacific Salmon Commission Secretariat Sue Grant, Bronwyn MacDonald; Fisheries and Oceans Canada

2 We are here! 2

3 Long-term History of Returns Total Return (millions of fish) Hells Gate Slide Fishways operational Period of increase Mike Starts his career at PSC! Period of decline 2018 median forecast Year (of return) 3

4 Recent Status assessments Run timing or Wild Salmon COSEWIC Stock group Policy (DFO 2017) (2018) Early Stuart Early Summer run Summer run NAR NAR NAR NAR NAR NAR Legend Wild Salmon Policy Lower Benchmark Upper Benchmark Low Spawning abundance High and/or distribution NAR COSEWIC Late run NAR EN Endangered THR Threatened NAR Not At Risk SC Special Concern 4

5 Management response to declining returns Exploitation rates have decreased Total Return millions of fish) avg. 76% Year (of return) avg. 36% 100% 80% 60% 40% 20% 0% Fraction of Return Harvested 5

6 Declining exploitation rates have increased spawning abundance Spawning abundance (millions of fish) avg. 1.8M avg. 3.2M Year (of return) 6

7 Fraser sockeye productivity has declined! Index of Total productivity Mature offspring produced per female spawner Log e (Return per EFS) Modified from Grant et al Year of return 7

8 Productivity varies among stocks 2009 return Index of Total productivity (deviations from Ricker or Larkin (L) Stock-Recruit models) L L Below average productivity Above average productivity L Updated from Grant et al Year of parental spawning (brood year) 8

9 Productivity varies among stocks and life stage Index of productivity (deviations from Ricker Stock-Recruit model) Below average productivity Above average productivity C. Michielsens pers comm. S S Freshwater (fry or smolt(s) per female spawner) Marine (survival post-fry or smolt;return per fry or smolt (S)) Year of parental spawning (brood year) 9

10 10 Two factors are adding to productivity declines 1. Early Upstream migration of one Fraser sockeye stock group (Late run) 2. Impacts of warming Fraser River

11 Historical normal migration behavior of Late-run sockeye Marine Area Peak August 17 Late-run sockeye migration Peak arrival Aug 24 followed by 3-6 weeks delay in Georgia Strait Mission Marine area Peak August 17 11

12 Historical normal upstream migration of Late-run sockeye Cultus Sockeye Fraction of Total Abundance 15% 10% 5% No migration in August Very little migration in September % 01/Aug 15/Aug 29/Aug 12/Sep 26/Sep 10/Oct 24/Oct 07/Nov 21/Nov 05/Dec Sweltzer Creek Fence Date 12

13 Early upstream migration of Late-run sockeye Cultus Sockeye Fraction of Total Abundance 5% 4% 3% 2% 1% No migration in August Very little migration in September % 01/Aug 15/Aug 29/Aug 12/Sep 26/Sep 10/Oct 24/Oct 07/Nov 21/Nov 05/Dec Sweltzer Creek Fence Date 13

14 Recent abnormal upstream migration pattern is consistent among stocks 29/Nov Up-river migration date (median date) 09/Nov 20/Oct 30/Sep 10/Sep Cultus Weaver 21/Aug Adams Harrison 01/Aug Year Updated from Lapointe

15 Early migration correlated with extremely high migration mortality Index of Migration Mortality 1 (% of the run) early migrants are dead fish swimming Hinch et al Discrepancy between lower and upper river estimates Up-river migration date (Median date passing Mission hydroacoustic facility near river mouth) 15

16 The Fraser River is getting warmer Maximum Annual Fraser River Temperatures have increased by about 2 C! Maximum Annual Fraser River Temperature ( C) r² = Updated from Eliason et al Year 16

17 Consequences of warming Fraser River Migration Mortality during thermally stressful years for Early summer and Summer runs ( ) 80% Index of Migration Mortality 1 (% of the run) 60% 40% 20% r 2 = % Fraser River Temperature (31-day mean ºC) 1 Discrepancy between lower and upper river estimates Hinch and Martins 2011

18 18 Conclusions 1. Fraser River sockeye returns have declined since 1993 as a consequence of decreased productivity (across the total life cycle). 2. Decreased total productivity cannot be attributed to any single causal factor; productivity has varied at both freshwater and marine stages.

19 19 Conclusions 3. Abnormal migration behavior and a warming Fraser River are leading to migration mortality; thus despite decreased harvests, fewer fish are reaching spawning areas.

20 Acknowledgements Co-Authors Sue Grant and Bronwyn MacDonald Fisheries and Oceans Canada Catherine Michielsens Pacific Salmon Commission staff Some slides provided by: Scott Hinch University of British Columbia, Vancouver Dan Selbie Fisheries and Oceans Canada 20

21 End