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

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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’

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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