General Impact
Morone americana compete for food with native fish species and also eat the eggs of walleye (Stizostedion vitreum), white bass (Morone chrysops), other M. americana and possibly other species as well. They are also believed to be a potential cause of decline in S. vitreum populations. Another concern is that M. americana have hybridized with native Morone chrysops in western Lake Erie. Hybrids are capable of backcrossing with parent species as well as crossing among themselves and could dilute the gene pool of both parent species (Fuller et al. 2006). Fish eggs are an important diet component in the spring. Depending on which fish is spawning, the eggs of either walleye or white bass comprise 100% of M. americana's diet. Collapse in certain fisheries have coincided with increases in M. americana populations and are believed to be a result of egg predation and resulting lack of recruitment (Fuller et al. 2006).
Location Specific Impacts:Bay of Quinte (North America) 
Reduction in native biodiversity: The collapse of the walleye fishery in the Bay of Quinte on the north shore of Lake Ontario coincided with the increase in M. americana population and may have been a result of egg predation and the resulting lack of recruitment (Fuller et al. 2006). Great Lakes (North America)
Reduction in native biodiversity: Prolific competitors of native fish species, Morone americana are believed to have the potential to cause declines of Great Lakes walleye populations (WDNR, 2004). Lake Erie (North America)
Competition: Parrish and Margraf (1990) hypothesized that M. americana compete with native yellow perch Perca flavescens for zooplankton. They determined that growth rates of yellow perch had declined since the invasion of M. americana in Lake Erie, especially in the western basin. They also determined that the two species had considerable diet overlap and found one sample in which M. americana consumed 27 percent more food than yellow perch (Fuller et al. 2006).
Hybridisation: Invasion of the Great Lakes brought white perch into sympatric distribution with a closely related but previously allopatric species, white bass Morone chrysops, allowing hybridisation to occur (Todd, 1986). White perch hybridise with native white bass M. chrysops in western Lake Erie, in Ohio and Michigan (Todd, 1986). They have also been reported from the Detroit River and the St. Clair River in Michigan (Todd, 1986). These hybrids were first noted in western Lake Erie in the early 1980s, the same period during which white perch were increasing in this area (Todd, 1986). These hybrids probably occur in other Great Lakes because the two species are sympatric throughout the chain of lakes. However, Todd was not aware of any other locations with these hybrids, and his extensive surveys around Saginaw Bay, Lake Huron, and Lake Ontario in the mid-1980s failed to find any (Todd, pers. comm., in Fuller et al. 2006).
Interaction with other invasive species: Bur and Klarer (1991; in Fuller et al. 2006) found that a large proportion of M. americana's diet consists of zooplankton in the central basin of Lake Erie - primarily the invasive Bythotrephes cederstroemi.
Other: Parrish and Margraf (1994) speculated that competition between M. americana and forage fishes, such as emerald shiner Notropis atherinoides and spottail shiner N. hudsonius, may actually be more complex and may be responsible for the declines of the latter species. Decline of these species could also affect walleye Stizostedion vitreum, the top predator in Lake Erie (Parrish and Margraf 1994, in Fuller 2005). Lake Ontario (North America)
Predation: Fish eggs are an important component of the diet of white perch especially in the spring months. White perch generally prey on eggs of walleye Stizostedion vitreum vitreum, white bass Morone chrysops, other species, and can cannabilize its own eggs (Schaeffer and Margraf, 1987). Walleye or white bass eggs can make up 100% of white perch diet depending on which fish is spawning. During a three-year study, this diet was found to be unique in that: 1) eggs were eaten for a comparatively long time, 2) they were the only significant food item eaten by adults during two of the three years, 3) large volumes were eaten per individual, and 4) most fish were feeding. White perch also feed heavily on minnows Notropis spp. (Schaeffer and Margraf, 1987). The collapse of the walleye fishery in the Bay of Quinte (on the north shore of Lake Ontario) coincided with the increase in the white perch population and may have been a result of egg predation and lack of recruitment (Schaeffer and Margraf, 1987). St. Clair River (United States (USA))
Hybridisation: Invasion of the Great Lakes brought white perch into sympatric distribution with a closely related but previously allopatric species, white bass Morone chrysops, allowing hybridisation to occur (Todd, 1986). White perch hybridise with native white bass M. chrysops in western Lake Erie, in Ohio and Michigan (Todd, 1986). They have also been reported from the Detroit River and the St. Clair River in Michigan (Todd, 1986). These hybrids were first noted in western Lake Erie in the early 1980s, the same period during which white perch were increasing in this area (Todd, 1986). These hybrids probably occur in other Great Lakes because the two species are sympatric throughout the chain of lakes. However, Todd was not aware of any other locations with these hybrids, and his extensive surveys around Saginaw Bay, Lake Huron, and Lake Ontario in the mid-1980s failed to find any (Todd, pers. comm., in Fuller et al. 2006). Detroit River (United States (USA))
Hybridisation: Invasion of the Great Lakes brought white perch into sympatric distribution with a closely related but previously allopatric species, white bass Morone chrysops, allowing hybridisation to occur (Todd, 1986). White perch hybridise with native white bass M. chrysops in western Lake Erie, in Ohio and Michigan (Todd, 1986). They have also been reported from the Detroit River and the St. Clair River in Michigan (Todd, 1986). These hybrids were first noted in western Lake Erie in the early 1980s, the same period during which white perch were increasing in this area (Todd, 1986). These hybrids probably occur in other Great Lakes because the two species are sympatric throughout the chain of lakes. However, Todd was not aware of any other locations with these hybrids, and his extensive surveys around Saginaw Bay, Lake Huron, and Lake Ontario in the mid-1980s failed to find any (Todd, pers. comm., in Fuller et al. 2006). Illinois River (United States (USA))
Hybridisation: Hybrids of Morone americana and M. mississippiensis were first found in 2000 in the middle Illinois River (Irons et al. 2002). Hybridization and competition may represent another threat to the already dwindling yellow bass of this region. Nebraska (United States (USA))
Reduction in native biodiversity: Within three years after being introduced into a Nebraska reservoir, M. americana had completely replaced the previously dominant black bullhead Ameiurus melas. Species composition changed from 74 percent black bullhead to 70 percent M. americana in that timeframe (Hergenrader and Bliss 1971) (Fuller 2005). Ohio (United States (USA))
Hybridisation: Invasion of the Great Lakes brought white perch into sympatric distribution with a closely related but previously allopatric species, white bass Morone chrysops, allowing hybridisation to occur (Todd, 1986). White perch hybridise with native white bass M. chrysops in western Lake Erie, in Ohio and Michigan (Todd, 1986). They have also been reported from the Detroit River and the St. Clair River in Michigan (Todd, 1986). These hybrids were first noted in western Lake Erie in the early 1980s, the same period during which white perch were increasing in this area (Todd, 1986). These hybrids probably occur in other Great Lakes because the two species are sympatric throughout the chain of lakes. However, Todd was not aware of any other locations with these hybrids, and his extensive surveys around Saginaw Bay, Lake Huron, and Lake Ontario in the mid-1980s failed to find any (Todd, pers. comm., in Fuller et al. 2006).
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