1 Nechako River white sturgeon: biological links with physical habitat and recruitment restoration Steve McAdam, BC MOE Cory Williamson, BC MFLNRO NWSRI – TWG and CWG Acipenser transmontanus (Nechako)

2 Talk outline 1)Life cycle 2)Recruitment failure 1)Spawning & site selection 2)Substrate condition – effects on larvae 3)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 Egg Days 1-12 Egg Days 1-12 Larvae Hiding Days Larvae Hiding Days Larvae Feeding Days Larvae Feeding Days Sub-Adults 1-m to maturity Sub-Adults 1-m to maturity Mature Adult Population Juveniles Less than 1-m Juveniles Less than 1-m Sturgeon Life Cycle ~25 yrs. ~1.5 m ~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 Egg Days 1-12 Egg Days 1-12 Larvae Hiding Days Larvae Hiding Days 13-26

6 Hydrograph: Then and now Current spawning ‘window’

7 Spawn monitoring on the Nechako since Staged approach to detection: Radio telemetry → Egg mats → D-ring nets Spawning Behaviour → Eggs → Larvae Physical: Depth & surface velocity, and temperature Results: Population Vanderhoof annually Spawn at ~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

8 Spawning Cues Photoperiod and temperature drive maturation of eggs 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

9 Spawning locations may be determined by: Proximate Factors. Hydraulic conditions & turbulent flow high velocity areas (relative) ~1 m/s ( m/s) higher relative depth substrate type? (not likely- Nechako and Kootenay spawn on fines) Recruitment Failure: Spawning Site Selection

10 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

11 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

12 What is the link between substrate change and recruitment failure? 230 cm 120 cm 30 cm15 cm 40 cm collection area pump output test section pump input horizontal weir screen X  Substrates tested:  Sand  Embbeded cobble (50%)  Small gravel  Medium gravel  Cobble  Responses:  Hide  Drift

13 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 Percent Drift vs. hiding – substrate and age effects

14 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 Spawning Incubation/ Hiding Early Rearing/Feeding Recruitment 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

18 ALH spawning site and Waneta spawning site (Columbia River) Restoration simplified due to: a)Fixed spawning location b)Input of fines is limited by upstream dam Restoration approaches

19 Spawning locations are dispersed Restoration 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 m 3 gravel-cobble added at two spawning sites

300,000 Eggs Placed High flows ~450 cms Spawn distribution altered Zero larvae captured 2011 Several 1-5 day old larvae 2012! Possible to detect juveniles > age-3 Results to date:

23 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 spawning 2) Maintaining a suitable substrate quality