The population of a certain species of fish in a lake, $P(t)$, can be modeled by the function $P(t)=500(1.06{)}^{2t}$, where $t$ is the number of years since the start of the study. This function can be rewritten in the form $P(t)=P_0(1+\frac{r}{100}{)}^t$, where $P_0$ is the initial population and $r$ is the annual percentage growth rate. What is the value of $r$?