1
Nechako River white sturgeon: biological links with physical
habitat and recruitment restoration
Steve McAdam, BC MOECory Williamson, BC MFLNRO
NWSRI – TWG and CWG
Acipenser transmontanus (Nechako)
2
Talk outline
1)Life cycle2)Recruitment failure
1)Spawning & site selection2)Substrate condition – effects on
larvae3)Restoration - two approaches
1)Restore currently used spawning habitats
2)Restore specific areas to attract spawners
Distribution
• White sturgeon found in the Fraser and Columbia watersheds, and major tributaries (Nechako, Kootenay)
• Recruitment failure present in the Nechako, Kootenay and Columbia
• Links to substrate condition likely in all three cases• Workshop focus is the Nechako
Spawning EggDays 1-12
LarvaeHiding
Days 13-26
LarvaeFeeding
Days 26-40
Sub-Adults1-m to maturity
Mature Adult
Population
JuvenilesLess than 1-m
Sturgeon Life Cycle
~25 yrs. ~1.5 m
Principle focus for restoration
5
Sturgeon: periodic spawners with extreme longevity (3-10 yrs; 100 yrs old)
• Spawn on descending limb (flood-pulse spawner) • Low parental care, no nest, eggs dispersed into
current near substrate • Require annual disturbance regime• Adapted to large stable rivers• Nechako hydrograph is truncated during spawn • Temperature and habitat effects
• Earlier spawning with warming• Spawners may spawn in wrong locations if
selecting for velocity
Spawning EggDays 1-12
LarvaeHiding
Days 13-26
6
0
200
400
600
800
Jan
Fe
b
Mar
Ap
r
Ma
y
Jun
Jul
Au
g
Sep
Oct
No
v
Dec
Date
Flo
w (m
/s)
3
1915-1952
1980-2000
0
200
400
600
800
Jan
Fe
b
Mar
Ap
r
Ma
y
Jun
Jul
Au
g
Sep
Oct
No
v
Dec
Date
Flo
w (m
/s)
3
1915-1952
1980-2000
Hydrograph: Then and now
Current spawning ‘window’
7
Spawn monitoring on the Nechako since 2003. • Staged approach to detection: • Radio telemetry → Egg mats → D-
ring nets• Spawning Behaviour → Eggs →
Larvae
• Physical: Depth & surface velocity, and temperature
Results:• Population spawns @ Vanderhoof
annually• Spawn at 10.6- ~13.5 C; apparently no
relation to discharge • No evidence of spawn concentrations
elsewhere (bio-telemetry) • Recruitment failure applies to whole
population• Bottom line: Vanderhoof reach appears
to be the place to be (and to restore).
Vanderhoof Spawning Site: Biological and Physical Monitoring
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Spawning Cues• Photoperiod and temperature
drive maturation of eggs• Migration @ ice-off from
overwinter sites in late April (10-25 km)
• Adults stage below spawning location (May)
Reach Selection• Imprinting: mechanism that
allows successful recruits to return as spawners to good spawning sites
• Lake sturgeon show “upper” and “low” site variants
• Very high site fidelity (micro-habitat)
• Kootenay and Nechako WS show high fidelity to impaired sites
Recruitment Failure: Spawning Cues and Reach Selection
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Spawning locations may be determined by:
Proximate Factors.Hydraulic conditions &
• turbulent flow• high velocity areas (relative) ~1 m/s (0.96-
1.63 m/s)• higher relative depth
•substrate type?• (not likely- Nechako and Kootenay spawn
on fines)
Recruitment Failure: Spawning Site Selection
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Install 3-d acoustic telemetry array in Vanderhoof Reach
• 24 hour (1-m) position of spawners to determine micro-site use and extent of use
• Correlation use with habitat conditions • Ex. velocity and substrate condition
• Use of known individual females and maturity • site fidelity in relation to habitat conditions
Spawning Site Selection: Next Steps
Year
Re
cru
itme
nt
Ind
ex
05
01
00
15
02
00
25
03
00
1940 1950 1960 1970 1980 1990
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Recruitment failure coincided with an influx of fine sediment
Mechanism of substrate effects verified by lab and field work
Recruitment failure: links to substrate change
Dam
Recruitment Failure
Cheslatta avulsions
Specific gauge analysis - Vanderhoof
2.72.82.9
33.13.23.33.4
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
Year
Gaug
e He
ight (
m)
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What is the link between substrate change and recruitment failure?
230 cm
120 cm30 cm15 cm
40 cm collection area
pump output
test section
pump input
horizontal weir
screen
screen
X
Substrates tested:
Sand Embbeded
cobble (50%) Small gravel Medium
gravel Cobble
Responses:
Hide Drift
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Most larvae hide interstitially immediately after hatch
Failure to hide leads to downstream displacement and increased mortality
Hiding is continuous
1 dph
9 dph
14 dph
Em
bb
ed
ed
Sa
nd
Gra
ve
l
Em
bb
ed
ed
Sa
nd
Gra
ve
l-3
-2
-1
0
1
2
3
4
5
Me
an
# o
f h
idin
g la
rva
e (
of
5)
1 day old 15 day old
drift hide0
10
20
30
40
50
60
70
80
hatch
Per
cent
Drift vs. hiding – substrate and age effects
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Substrate condition affects larval quality
GRAVEL (17 mm)
CURRENT (12 mm)
BARE – (15 mm)
Variation at 16 dph
Interstitial hiding/rearing affects:
• Growth• Survival
• Gut development• Energy availability• Swimming ability
Take home:
Both the availability and quality of interstitial habitat is important (Larvae need interstitial, not just an eddy behind a rock)
Historical flood condition: no vegetation
Historical condition -thalweg across mid channel, lower velocity water present over top of historic gravel bars
Q = 614 cms, 1951
Images from NHC- 2008
Conceptual historical spawning/larval habitat use
SpawningIncubation/Hiding
Early Rearing/FeedingRecruitment failure due to: Decoupling of spawning from freshet conditions
- incorrect timing and location- possibly results in selection for wrong velocities and location)
Incubation and rearing habitat decoupled from natural timing of processes that created it - discharge and freshet.
Spawning/larval habitat: current conditions
Low discharge- flow between vegetated islands
Spawning sites dispersed Benthic substrates provide poor hiding
habitat
Q = 175 cms, 1985
Images from NHC- 2008
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ALH spawning site and Waneta spawning site (Columbia River)
Restoration simplified due to:a)Fixed spawning locationb)Input of fines is limited by upstream
dam
Restoration approaches
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Spawning locations are dispersedRestoration must consider a) adult habitat choice (multiple locations, imprinting, hydraulics)b) Substrate quality (egg/yolksac larvae – interstitial spaces)
Restoration: Nechako
Experimental Recruitment Restoration 2011
Goals: Large River Field Experiment to produce “post-
hiding”, >12 day old larvae Increase understanding of sediment dynamics
2100 m3 gravel-cobble added at two spawning sites
300,000 Eggs Placed
High flows ~450 cmsSpawn distribution alteredZero larvae captured 2011Several 1-5 day old larvae 2012!Possible to detect juveniles > age-3
Results to date:
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Spawning habitat restoration can restore recruitment based on results for lake
sturgeon
Key challenges in the Nechako case are:
1) Matching the location of restoration with the location of spawning2) Maintaining a suitable substrate quality