Transcript Meg Fencil
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: – – – – – – 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?