Life history, growth and demographic variation in a highly invasive fish species during its range expansion in the Trent River, Ontario: The round goby (Neogobius melanostomus)

In 2007 and 2008, I studied the invasive population of round goby ( Neogobius melanostomus) in the Trent River, southeastern Ontario Canada to show that phenotypic plasticity in fish can result in variation of life history traits and demographic structure at different stages of invasion. I found that compared to the area of first introduction, round gobies at the edges of their range had higher reproductive energy allocation, lower age at maturity, and greater growth rates. I also showed that in 2008 the life history traits of gobies at the upstream edge and the area of first introduction had become more similar than in the previous year. Using angling I found that the edges were characterized by relatively few round gobies and that the average body size was larger when compared to gobies in the area of first introduction. The highest male to female ratio was found at the upstream edge of their range (2.2:1), followed by the downstream edge (1.5:1) and the area of first introduction (1.4:1). The results of my thesis indicated the dynamic nature of a successfully invasive population and suggest that invasive equilibrium life history strategists can utilize phenotypic plasticity to alter life history traits to suit population growth for a given stage of an invasion.;Keywords: phenotypic plasticity, colonization, non-native, angling...