The Effects of a Parasitic Copepod (Achtheres) on Smith Mountain Lake Presented by: Douglas Thomasey Tom Shahady and Joe Ashwell

Background Information Striped Bass (Morone saxatilis) Striped Bass (Morone saxatilis) Travel in schools Travel in schools Localize in cooler, oxygenated areas Localize in cooler, oxygenated areas Reproduction is prevented in Smith Mountain Lake Reproduction is prevented in Smith Mountain Lake Have made Smith Mountain Lake nationally known Have made Smith Mountain Lake nationally known 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”

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

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

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

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

Sensitivity Sensitivity of parameters Sensitivity of parameters Drastic changing the values of our parameters will not influence the outcome 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 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 =.1 d =.1 v =.25 v =.25 b = 1 b =.5 b=.1

Results What can be done to solve this problem? What can be done to solve this problem? Stocking rates Stocking rates Introduce a new fish with a lower interaction Introduce a new fish with a lower interaction Stocking Rates: 21 fish per acre 7 fish per acre no stock

Stock a different type of fish? Interaction rates: Interaction rates: 90% 10% 90% 10% The effects of stocking a type of fish with a low interaction rate Schooling fish vs. territorial fish

Conclusions Under all conditions about 18 months until appearance in the population no matter the size of the initial population Under all conditions about 18 months until appearance in the population no matter the size of the initial population Fish behavior (contact) most significant parameter for spread of parasite Fish behavior (contact) most significant parameter for spread of parasite Low stocking rates may be the best management strategy to minimize spread of parasite and fish contact Low stocking rates may be the best management strategy to minimize spread of parasite and fish contact

¿Questions?

> restart: > with(plots): > b:=.9; d:=.25/12; v:=.5/12; IntS:= ; IntI:=100000; New:=145000; years:=12; j=0; > plot1:=array(0..years); Years2:=(years-1); stock:=array(0..Years2,[145000, ,145000,145000,145000,145000, ,145000,145000,145000,145000,145000]); season:=array(0..Years2,[.9,.9,.9,.9,.1,.1,.1,.1,.9,.9,.9,.9]); Graphing Conclusions territorial fish Interaction rates: Stocking Rates