Food Webs information and PDF Files

2. Carcass Food Web Nutrients
Nutrient Input to Watersheds from Anadromous Fish Returns

• Oligotrophic rivers like the Skagit River receive valuable Nitrogen and Phosphorus from salmon carcasses in coastal rivers.
• Marine derived nutrients (pathways).
• Important for biological productivity and biological diversity within the watershed.
• Carcasses affect all trophic layers in the food web.

Body biomass and nitrogen and phosphorus imports in metric tons to selected freshwater catchments within the Puget Sound Basin from recent peak wild spawning salmon escapements.

In an undisturbed stream the majority of the energy input is allochthonous (CPOM). Shredders and collectors around the CPOM/FPOM processing dominate the food web. Light is a minor energy input from gaps in the canopy.

When the riparian zone is removed the food web is reduced to a simple producer/grazer system. If eutrophication is added the food web is further simplified.

Macroinvertebrates Tolerance Groups to Eutrophication

Group I; Pollution Intolerant, Sensitive to Pollution

• Trichoptera (caddis fly)
• Megaloptera, Corydalus (hellgrammites)
• Ephemeoptera (mayfly)
• Gastropoda (gilled snails)
• Coleoptera, Elmidae (riffle beetles)
• Plecoptera (stonefly)

Group II; Somewhat Pollution Tolerant

• Coleoptera (other beetles)
• Pelecypoda (clams and mussels)
• Pisididae (fingernail clams)
• Turbillaria (flatworms or planaria)
• Diptera, Tupulidae (Cranefly)
• Crustacea (crayfish, scud, sowbug)
• Hemiptera (water boatman, backswimmer, toe biter, water strider)
• Odonata (dragonfly, damselfly)
• Megaloptera, Chauliodes & Sialidae (fishfly, alderfly)

Group III; Pollution Tolerance High

• Oligocheta (worms)
• Diptera, Simulidae (blackfly)
• Hirudinea (leech)
• Diptera, Chironomide (midge, bloodworm)
• Gastropoda (other snails)