State of the Lake Huron Prey Fish Community in 1999:
Progress toward Fish Community Objectives
Jeff Schaeffer, Gary Curtis, Ray Argyle
USGS Great Lakes Science Center,
Ann Arbor, MI.
Is the Prey Base Matched to Primary Production?
Is the Prey Base Matched to Predatory Demand?
• What prey species are present?
• What species are eaten?
Can we see effects of predation?
The Prey Community is Diverse: 32 species
Planktivore Biomass Dominated by Three Species
Prey Base dominated by two species!
Sculpins, Sticklebacks, Troutperch
Bloater Biomass is Cyclic
Rainbow Smelt Biomass
Alewife Biomass: 5 Year Intervals
Rainbow Smelt Biomass: 5 year intervals
Rainbow Smelt Abundance
Alewife as Prey
Prey availability may depend on age-0 fish
Year class strength
Good year: small prey
Poor year: few prey
Growth may be important
Affects prey biomass
Rainbow Smelt as Prey
May no longer be a resource for large predators
Very few large fish
Scarcity may increase pressure on alewife
Major changes in the food web
Total planktivore biomass decreasing
Decline in bloater not due to predation
Declines in R. smelt and alewife consistent
with predation, but growth may be important
Prey size structure declining
Few large alewife or rainbow smelt
Trends are consistent with predation
Prey Fish Objectives
May be difficult to attain (numbers)
Food Web changes
Predator demand high
Pelagic planktivores declining
Other 0bjectives may be enhanced
Greater proportion of native species in biomass
Reduced interactions with exotics
New approaches now possible