Subject Oriented Session: Habitat Suitability/Classification

Introductions:
We began with individual introductions and our relation/interest in the topic.

Participants:
John Bauman, James Boase (facilitator), Andy Edwards, Barabara Evans, Bill Gardner, Sue Greenwood, Tim Haxton, Adrienne Kral, Bruce Manny, Ashley Moerke, Terry Perrault, Christopher Pullen, Deborah Rajchel, Paul Ripple, John Seyler.

Topics Covered:
- What HSI models are available and in use
- Are the HSI models complete/adequate
- Information needs from larval to yearling stage

Discussion Summary:
What HSI models are available and what are people using?

HSI model written by Ontario Hydro (Ron Threader) is available in draft form only and is being used. The model was written for the Fraiser River System in Northern Ontario. An outline of the model was posted showing:
1) Adult foraging requirements including; substrate preference and benthos production)
2) Juvenile habitat requirements including; substrate type, available forage, water velocity and depth < 14m
3) Spawning habitat requirements including; water temperature, depth 2-6m, substrate composition, water velocity >1m/sec.

Is the HSI complete/adequate?

HSI model is empirical and needs updating. Much has been learned since the original draft including:
1) Access to spawning habitat by adults must exist for reproduction to take place
2) Macro vs Micro habitats – over-wintering pools in river systems, staging areas pre and post spawning in connecting waterways (St. Clair River, St. Mary’s River and St. Lawrence River)
3) Flooding events may be triggering spawning in some systems
4) Spawning site fidelity/imprinting is important however, sturgeon also seem flexible in selecting suitable spawning habitat, both strategies seem to foster survival of the spp.

a) Example was presented where sturgeon having fidelity to a specific site in a tributary of the St. Lawrence River were restricted to a very small area of a preferred spawning location due to a rock slide that buried most of the site. The fish all spawned on the small area of remaining spawning substrate piling eggs which resulted in very little recruitment that year.
b) Spawning is taking place in shallow water near shore making sturgeon vulnerable (while engaged in spawning behavior fish are oblivious to predators and easily poached)
c) Spawning also taking place in deep water, greater than 15m in the St. Clair River, LaHaye documented egg deposition over a large gradient in depth in the St. Lawrence River
d) Wolf River in Wisconsin has multiple sites with a range of depths

5) Interstitial void space seems to be playing a role in spawning site selection

a) Cooler ground water may be associated with this, sturgeon have extensive sensory organs on the ventral side of the head
b) Egg release by the female may be associated with substrate roughness

What is known about the early life stages from the time larvae enter the drift until the following spring?

1) Sturgeon drift during darkness, they are difficult to catch in drift nets during this period
2) Evening drift may be timed with predator avoidance and benthic forage abundance
3) Duration of the drift is unknown, concern was expressed that an HSI model should consider duration of the drift along with current velocity to prevent larvae sturgeon drifting out of a system or past suitable habitat
4) Sturgeon seem to settle out of the drift when the reach 19mm
5) Very little is known from the time larvae reach 19mm through the following spring
6) In smaller tributaries young-of-year (yoy) sturgeon migrate to lakes by fall, while in larger systems and connecting waterways juvenile sturgeon may remain in the river until age five
7) Anecdotal evidence in the St. Lawrence suggests that yoy sturgeon drift a long distance downriver then repopulate upper reaches of the river over time as they mature
8) In the St. Lawrence sturgeon ages 2-5 occupy old river channels that are between 4-7m deep, fish move out of these refuge areas to adjacent shallow (less than 2m) to forage
9) Young sturgeon may be vulnerable to drift over dams preventing repopulation of upper reaches of rivers
10) Predation of yoy lake sturgeon (up to 30mm) by crayfish has been documented
11) Sea lamprey ammocoetes were used as bait to collect white sturgeon unknown if lake sturgeon utilize them as forage

Conclusion

1) HSI model use may be limited but does provide baseline information about sturgeon
2) The current HSI model available for lake sturgeon needs to be updated to include the current knowledge of the species
3) Information discussed seemed to demonstrate that lake sturgeon habitat requirements during all life stages occupy very dynamic environments making a “one size fits all approach” impossible
4) Lake sturgeon long term survival may be a function of the wide variation in habitat requirements/preferences during all life stages

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