Download Zebra mussel (Dreissena polymorpha)

Predation Impacts of Round
Goby on Zebra Mussels in
the Great Lakes
Megan Fencil
Static vs. Dynamic modeling
In fisheries ecology, GIS is mainly used for descriptive
mapping.
Increased need for visualization of ecological models
- spatially and temporally dynamic factors
- interaction of species when they meet
I’ll focus on predator-prey interaction of round gobies
and zebra mussels
Difficulties:
– Large number of assumptions
– Too many interaction effects to model
– Lack of data
Zebra mussel
(Dreissena polymorpha)
• Native to Russia
• Introduced to U.S. in ballast water
• Negative impacts: clog pipes, foul ships, litter beaches, sink
buoys, colonize native animals
• $5 billion cost in 10 years (U.S. Fish and Wildlife Service)
• Positive impact: improved water clarity from 6 inches to 30
feet!
Zebra mussels spread very rapidly!
1st U.S. appearance in 1988: Lake St. Clair
< 10 years: all Great Lakes, Mississippi, Tennessee,
Hudson, and Ohio River basins
Round goby
(Neogobius melanostomus)
Native to Black & Caspian Seas
Introduced to U.S. in ballast water
Negative impacts:
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Aggressively eat eggs & fry of native fishes
Outcompete native species for nest sites
Excellent sensory system gives an advantage (night)
Very robust
Spawn over long time period in summer
Rapid population growth (20/m3 in Calumet Harbor = 20 fish
in a bathtub)
Round gobies competitively displace native species
Is there room for one
more?
The spread of round gobies
Ohio State University
1990: St. Clair River
(channel between Lake
Huron and Lake St. Clair)
1994: well-established in
Lake Erie
1995: Lake Superior and
Lake Michigan
Preventing the spread: electric goby
barrier
Map modified from USGS website,2001
Interaction of gobies and zebra mussels
Gobies eat up to 78 zebra mussels/day
Gobies prefer small mussels near the substrate
Mussels in goby-free waters are larger
Gobies are main predators of mussels
BUT, zebra mussels will not disappear due to gobies
Negative effect of predation: mussels filter-feed and
bioaccumulate toxins
Sport fish (bass, walleyes, perch, trout) may be
affected
Work in Progress: Clarifying the problem
with ArcGIS
Apply a population growth model to overlaid distribution
maps of mussels and gobies
- Where do they interact?
- What will be the effect on mussel population size?
Population growth for prey (zebra mussels) population
(Lotka-Volterra):
dH / dt = r H - b1 H P
H = number of prey
P = number of predators
r = rate of growth for prey population
b1 = predation rate (coefficient expressing the efficiency of
predation)
Predicting the potential spread of invasives
“Hitchhikers” are carried on/in recreational boats
If they arrive at an new site, can they survive?
Potential for invasion requires proper conditions:
– Light
– Depth
– pH
– Temperature
– Food supply
Overlay of layers can predict invasion success
- Several currently uncolonized sites will be studied
- Can they support zebra mussels and/or round gobies?