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The Effects of a Parasitic Copepod ( Achtheres ) on Striped Bass Populations

The Effects of a Parasitic Copepod ( Achtheres ) on Striped Bass Populations. Presented by: Douglas Thomasey. Tom Shahady and Joe Ashwell. Parasitic Copepod ( Achtheres ) Parasite becomes attached to the host Dies with the host Larva is free-swimming

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The Effects of a Parasitic Copepod ( Achtheres ) on Striped Bass Populations

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  1. The Effects of a Parasitic Copepod (Achtheres) on Striped Bass Populations Presented by: Douglas Thomasey Tom Shahady and Joe Ashwell

  2. Parasitic Copepod (Achtheres) Parasite becomes attached to the host Dies with the host Larva is free-swimming First outbreak occurred in 1981 in the Tellico Reservoir “Gill Maggot” Background Information

  3. Mathematical Modeling • Lokta-Volterra • Describes a Predator vs. Prey relationship • x represents the Prey • y represents the Predator • a, b, c, d,are known as parameters • xy is the likelihood of an encounter

  4. Smith Mountain Lake Model • Assumptions • Closed system – no reproduction • Introduce one infected fish into the population • Once infected always infected • Loss of parasite only through the death of a fish

  5. Probability Fraction • Is a built-in probability that an encounter with another fish would result in the transmitting of the parasite • The chance of actually contracting the parasite is dependent on the ratio of infected fish to the entire population

  6. Parameters • b : Encounter rate • 0.9 • v : Death rate of the infected • 0.25/12 • d : Death rate of the susceptible • 0.1/12

  7. Sensitivity • Sensitivity of parameters • Drastic changing the values of our parameters will not influence the outcome • These values do not have to be correct to gain correct assumption about our model Keeping parameters d, v, constant, while changing the values of b, gives us an idea its sensitivity d = 0.1 v = 0.25 b = 1 b = 0.5 b=0.1

  8. Questions be answered to • If one infected fish becomes infected, how long until the entire population is infected? • How does the interaction rate impact transmission in this model? • How do the mortality rates and initial conditions impact the model? • How much to stock?

  9. Question 1: • Time it would take to infect the entire population, with certain stocking rates. Stocking Rates: 21 fish per acre 7 fish per acre no stock

  10. The effects of the interaction rate. Schooling fish vs. territorial fish Question 2: Interaction Rate: 90% 10%

  11. Question 3: • How the initial conditions and morality rates impact the model. Initial Population: 10 fish per acre 100 fish per acre 200 per acre

  12. Question 3: (con’t) • How the initial conditions and morality rates impact the model. Mortality Rates: (Changing the death rate of the infected population) 0.25/12 0.5/12 0.75/12

  13. Question 4: • How much to stock? Stocking Rates: 21 fish per acre 7 fish per acre no stock

  14. Question 4: (con’t) • Alternating years of stocking rates Stocking Rates: (21 fish per acre for the first 2 years and the last 3 years) 7 fish per acre years 3-9 No stock years 3-9

  15. Conclusions • Spread into other states?

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