Spatial and temporal structure in a sympatric steelhead and resident rainbow trout mating system - PowerPoint PPT Presentation

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Spatial and temporal structure in a sympatric steelhead and resident rainbow trout mating system

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Spatial and temporal structure in a sympatric steelhead and resident rainbow trout mating system John McMillan Oregon State University Steve Katz & George Pess – PowerPoint PPT presentation

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Title: Spatial and temporal structure in a sympatric steelhead and resident rainbow trout mating system


1
Spatial and temporal structure in a sympatric
steelhead and resident rainbow trout mating system
  • John McMillan
  • Oregon State University
  • Steve Katz George Pess
  • NWFSC

2
Objective
  1. Do anadromous and resident O. mykiss overlap
    during spawning season?
  2. Is there spatial and temporal structure to their
    spawn time and location?
  3. Do periods of overlap result in attempted
    matings?
  4. What male mating behaviors are associated with
    attempted mating events?

3
Study sites
Stream Survey location (km) Stream order Gradient ()
Calawah 14.1-17.6 5 1-1.5
NF Calawah 4.5-8.5 3 1-1.5
Lower Sol Duc 3.0-6.0 5 1-1.5
Middle Sol Duc 44.5-49.5 5 1-2
Upper Sol Duc 58.2-60.5 4 1-2
4
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5
Calawah River
6
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7
Methods (1999 2003)
  • Co-existence spatial - temporal structure
  • Arrival timing
  • Monthly snorkel survey
  • Spawn timing
  • Monthly or bi-monthly redd survey
  • Mating behavior
  • Mating event observations
  • One per redd survey
  • 30 minutes 2 hours
  • Male tactics
  • Guard or sneak

8
Surveys
Stream Stream Snorkel Snorkel Redd Redd Behavior Behavior
Stream Stream km km hours
Calawah Calawah 12 32 17 24 29 33.5
NF Calawah NF Calawah 12 48 16 32 25 29.0
Lower Sol Duc Lower Sol Duc 15 45 20 25 14 16.5
Middle Sol Duc Middle Sol Duc 17 85 22 66 35 33.0
Upper Sol Duc 14 14 33 22 37 20 25.5
9
Classification of forms
  • Anadromous
  • gt 50 cm in length
  • Sex
  • Female blunt nose, short maxillary, silvery
    coloration
  • Male long nose, long maxillary, kype, darker
    coloration
  • Resident
  • 25 50 cm in length (Pearsons et al. 1998 Narum
    et al. 2004)
  • Morphology (red stripe, dense spotting)
  • Could not determine sex during snorkel surveys

10
Female steelhead
11
Male steelhead
12
Resident rainbow
13
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14
Steelhead pair mating sneaker male
15
Median arrival time
- Denotes 50 time of arrival
16
Monthly population composition
17
Timing of redd excavation
18
Spawn timing variation
19
Spatial comp. of mating events
20
Temporal comp. of mating events by male tactic
21
Conclusions
  • Co-existence
  • Yes! Most of spawning season
  • Distribution patterns
  • Strong temporal structure
  • Male steelhead arrive earlier than females
  • Sex ratio shift across spawning season
  • Rainbow arrival skewed to end of season
  • Weaker spatial structure
  • Steelhead arrival earlier at upper-most sites
  • Greatest proportion of rainbow in upper-most sites

22
Conclusions
  • Co-existence
  • Yes! Most of spawning season
  • Distribution patterns
  • Strong temporal structure
  • Male steelhead arrive earlier than females
  • Sex ratio shift across spawning season
  • Rainbow arrival skewed to end of season
  • Weaker spatial structure
  • Steelhead arrival earlier at upper-most sites
  • Greatest proportion of rainbow in upper-most sites

23
Conclusions
  • Co-existence
  • Yes! Most of spawning season
  • Distribution patterns
  • Strong temporal structure
  • Male steelhead arrive earlier than females
  • Sex ratio shift across spawning season
  • Rainbow arrival skewed to end of season
  • Weaker spatial structure
  • Steelhead arrival earlier at upper-most sites
  • Greatest proportion of rainbow in upper-most sites

24
Conclusions
  • Mating events
  • Steelhead x rainbow trout
  • Only male trout attempting to mate with female
    steelhead
  • Most common at end of season and upper-most sites
  • Male trout sometimes lone mate source
  • What tactics did males use?
  • Male steelhead relied equally on guard and sneak
    tactics
  • Male trout relied heavily on sneak tactic, but
    also egalitarian

25
Conclusions
  • Mating events
  • Steelhead x rainbow trout
  • Only male trout attempting to mate with female
    steelhead
  • Most common at end of season and upper-most sites
  • Male trout sometimes lone mate source
  • What tactics did males use?
  • Male steelhead relied equally on guard and sneak
    tactics
  • Male trout relied heavily on sneak tactic, but
    also egalitarian

26
Next steps?
  • Research
  • What are the factors influencing the distribution
    of the different forms?
  • What is the relative success of stlhd x stlhd
    mating v. stlhd x trout mating?
  • Management and monitoring
  • More information on populations of resident O.
    mykiss

27
Next steps
  • Genetic analysis
  • Confirm parentage
  • Examine reproductive success
  • Temporal and spatial influence
  • Mating structure
  • Structure variability (e.g., male trout x female
    steelhead success vs. male steelhead vs. female
    steelhead)
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