Linking freshwater habitat to salmonid productivity Watershed Program 1 1. NW Fisheries Science Center 2725 Montlake Blvd. East, Seattle, WA

Capacity and Survival Capacity Maximum number of fish at a life stage that can be produced under average annual environmental conditions Total surface area Instream habitat Food supply Water quality Survival The number of fish that live between life stages Flows Sedimenation Pollutants Water quality

Spawner recruit relations and the effect of altered capacity or survival Number of spawners Number of recruits

Spawner recruit relations and the effect of altered capacity or survival Number of spawners Number of recruits Change in capacity

Spawner recruit relations and the effect of altered capacity or survival Number of spawners Number of recruits Change in survival

Carrying capacity – life stage distinctions for fall & spring chinook SpawningFry (<45mm) Parr (45-70mm) Smolt (freshwater) (>70mm) Smolt (estuary/ nearshore) (>70mm) Total habitat area +/-, +/-+/-+/-,+/-+/-+/-,+/- Food supply +/- +/-,+/-

Total habitat area Spawning capacity example - North Fork Stillaguamish

Total habitat area North Fork Stillaguamish chinook spawning capacity

How do we compare capacities among life stages and habitat types ? habitat area × average fish density  A ij = is the sum of areas of all habitat units (j =1 through n) of type I. d i = density of fish in habitat type i.

Habitat type preference - juvenile salmonid use Classification of habitat types allows assessment of fish use patterns and expansion to larger aggregate units (e.g., watersheds)

How do we compare capacities among life stages and habitat types ? Estimate (N) for each life stage in a given habitat Multiply by density independent survival to smolt stage habitat area × average fish density × survival to smolt Smolt production potential can then be compared in terms of number of smolts ultimately produced.

Change in historic v. current coho smolt potential production

Range of current estimated v. measured coho smolt potential production

Habitat preference – a change in freshwater rearing quality There are 5.4 times as many juvenile chinook salmon in natural wood banks as hydromodified banks Beamer et. al., 1998

Expected change in juvenile salmonid abundance normalized to abundance in riprap (always = 1.0) Beamer et. al., 1998

From Beamer, unpublished data

Habitat preference Chinook spawning

Carrying capacity – Food supply and habitat capacity Slaney and Northcote (1974) - Rainbow trout (0+) High prey density, less change in territory size Giannico (2000) – Coho (0+) Food supply high – found in pools with little wood cover Food supply low – found in pools with abundant wood A small change in food supply can effect capacity by altering territory size and density of salmonids

Survival – life stage distinctions for fall & spring chinook Egg to fryFry to parrParr to smoltFreshwater to estuarine/ nearshore Temperature +/- Sedimentation +/- Food supply +/- Flows +/- Water quality+/- (?) +/-

Peak flows and egg to migrant fry survival estimates - Skagit Chinook ( ) (Seiler & others 1998).

Peak flow recurrence interval and egg to migrant fry survival estimates - Skagit Chinook ( )

Chinook recruits/spawner v. flood recurrence interval

A change in peak flows in the North Fork Stillaguamish

Sensitivity of regression to changes in peak flows in the North Fork Stillaguamish

Survival – Scour? Entombment? Oxygenation? Downstream displacement?

Survival – peak flow caveats Cannot break down survival by mechanism Keep mechanisms lumped Egg to fry Entombment Scour Oxygenation Fry to smolt Predation Downstream displacement Different relationship in Columbia River Basin Rain-on-snow v. snow-dominated

Survival – Food supply Slaney & Ward (1993) – Steelhead (1+,2+) Increase in phosphorus & nitrogen Increase in smolt to adult survival (1+) - +62% Smolts – +30% to 130%

Being clear about assumptions and model choice Do a sensitivity analysis where possible Run multiple scenarios with different datasets Many relationships are not universal Puget Sound v. Columbia Basin flow example Keep it simple Do not assume cause and effect mechanism unless it is clear Egg to outmigrating fry example Keep numbers local where possible Check model numbers against real fish numbers