Linking freshwater habitat to salmonid productivity

1
Linking freshwater habitat to salmonid
productivity
Watershed Program1
1. NW Fisheries Science Center 2725 Montlake
Blvd. East, Seattle, WA 98112-2097
2
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

3
Spawner recruit relations and the effect of
altered capacity or survival
Number of recruits
Number of spawners
4
Spawner recruit relations and the effect of
altered capacity or survival
Change in capacity
Number of recruits
Number of spawners
5
Spawner recruit relations and the effect of
altered capacity or survival
Change in survival
Number of recruits
Number of spawners
6
Carrying capacity life stage distinctions for
fall spring chinook
7
Total habitat area Spawning capacity example -
North Fork Stillaguamish
8
Total habitat areaNorth Fork Stillaguamish
chinook spawning capacity
9
Total habitat areaNorth Fork Stillaguamish
chinook spawning capacity
10
How do we compare capacities among life stages
and habitat types ?

• habitat area average fish density

• ?Aij is the sum of areas of all habitat units
  (j 1 through n) of type I.
• di density of fish in habitat type i.

11
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)

12
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.

13
Change in historic v. current coho smolt
potential production
14
Range of current estimated v. measured coho
smolt potential production
15
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
16
Expected change in juvenile salmonid abundance
normalized to abundance in riprap (always 1.0)
Beamer et. al., 1998
17
From Beamer, unpublished data
18
Habitat preference Chinook spawning
19
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

20
Survival life stage distinctions for fall
spring chinook
21
Peak flows and egg to migrant fry survival
estimates - Skagit Chinook (1989-1996)(Seiler
others 1998).
22
Peak flow recurrence interval and egg to migrant
fry survival estimates - Skagit Chinook
(1989-1996)
23
Chinook recruits/spawner v. flood recurrence
interval
24
A change in peak flows in the North Fork
Stillaguamish
25
A change in peak flows in the North Fork
Stillaguamish
26
Sensitivity of regression to changes in peak
flows in the North Fork Stillaguamish
27
Survival Scour? Entombment? Oxygenation?
Downstream displacement?
28
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

29
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

30

• 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