Morone americana has a high environmental impact in the Great Lakes. Realized:
Fish eggs are an important component of the diet of White Perch, especially in the spring months. White Perch generally preys on eggs of Walleye, White Bass, other species, and can cannibalize 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 feeds heavily on Minnows (Notropis spp.) (Schaeffer and Margraf 1987). Madenjian et al. (2000) hypothesized that egg predation by White Perch was the most significant contributor to the large decline in white bass recruitment in Lake Erie in the 1980s.
White Perch were dominant in the open water habitat of Lake Erie relative to areas with submerged aquatic vegetation (Miller et al. 2018). Bur and Klarer (1991) found that a large portion of the White Perch diet in the central basin of Lake Erie consisted of zooplankton. It has been speculated that a White Perch diet of Daphnia in Lake Champlain contributed to the decline of the species in this locality since White Perch became established (Couture and Watzin 2008). Parrish and Margraf (1990) hypothesized that White Perch compete with native Yellow Perch (Perca flavescens) for zooplankton. They determined that growth rates of Yellow Perch had declined since the invasion of White Perch 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 White Perch consumed 27% more food than Yellow Perch. In contrast, a recent study in Lake Erie found that the below-average population levels of White Perch and Yellow Perch allowed them to coexist under a wide range of trophic conditions (Kraus et al. 2021). Similarly, Pothoven and Höök (2015) found overlap in standard diet assemblages of age-0 White Perch and White Bass in Saginaw Bay, Lake Huron, indicating that complete trophic separation was not a requirement for long-term stable coexistence.
It has been speculated that competition between White Perch and forage fishes, such as Emerald Shiner (Notropis atherinoides) and Spottail Shiner (N. hudsonius), as well as Freshwater Drum (Aplodinotus grunniens), is complex and may be responsible for the declines of the latter species (Parrish and Margraf 1994; Stapanian et al. 2007). Decline of these species could also affect Walleye, the top predator in Lake Erie (Parrish and Margraf 1994).
Invasion of the Great Lakes brought White Perch into sympatric distribution with a closely related but previously allopatric species, native White Bass, allowing hybridization to occur (Todd 1986). White Perch are known to hybridize with M. chrysops in western Lake Erie and in Ohio and Michigan waters (Todd 1986). Hybrids 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 in all of the 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, personal communication). Todd (1986) provided photographs of both parent species and the hybrid and gave characteristics of each. Because these hybrids are capable of backcrossing with the parental species, and possibly producing F2 hybrids by crossing amongst themselves (Todd 1986), they dilute the gene pool of each parent species. The White Perch/White Bass hybrid is the first naturally occurring Morone hybrid known (Todd 1986).
Potential:
Hybrids of White Perch and Yellow Bass (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 that region.
Within three years of being introduced into a Nebraska reservoir, White Perch had completely replaced the previously dominant Black Bullhead (Ameiurus melas). Species composition changed from 74% Black Bullhead to 70% White Perch over that timeframe (Hergenrader and Bliss 1971). In North Carolina reservoirs, introduced White Perch have a high diet and trophic niche overlap with Black Crappie (Pomoxis nigromaculatus) and are significant competition for invertebrate resources and could reduce growth rates and survival of young Black Crappie (Feiner et al. 2019). Black Crappie are also native in the Great Lakes, but similar impacts have yet to be studied.
White Perch may pose a health threat to animals that consume it. It can accumulate the cyanotoxin microcystin in concentrations exceeding the WHO guidelines for human consumption (Wituszynski et al. 2017). In the Chesapeake Bay, White Perch is host to the novel coccidia parasite Goussia bayae (Matsche et al. 2019).
Morone americana has a moderate socio-economic impact in the Great Lakes.
Realized:
The collapse of the Walleye fishery in the Bay of Quinte (on the north shore of Lake Ontario) coincided with an increase in the White Perch population and may have been a result of egg predation and lack of recruitment (Schaeffer and Margraf 1987). Other recreationally/commercially important species, such as White Bass, Yellow Perch (Perca flavescens), and species of forage fish are likely negatively affected by White Perch through competition, egg predation, or hybridization (see above).
Potential:
White Perch may pose a health threat to humans that consume it. It can accumulate the cyanotoxin microcystin in concentrations exceeding the WHO guidelines for human consumption (Wituszynski et al. 2017). Of fish tested for microcystin, White Perch accumulated the second highest concentration (37 ng MC/g wet weight) relative to Walleye (71 ng MC/g) and Yellow Perch (8.1 ng MC/g). Resource competition from invasive White Perch reduced the abundance of stocked Hybrid Striped Bass in the recreational fishery located in Branched Oak Reservoir, Nebraska (Perrion et al. 2020).
Morone americana has a high beneficial effect in the Great Lakes.
Realized:
As of 2003, it was estimated that over 500,000 lbs. of White Perch are caught commercially in the U.S. and Canada each year (188,000+ lbs. in the U.S. alone), particularly in lakes Erie and Ontario (Brown et al. 1999; Dann and Schroeder 2003). This provides an estimated value of approximately $107,000 yr-1 in the U.S. and $260,000 yr-1 overall (Dann and Schroeder 2003).
White Perch is one of the most frequently found prey items in the diet of the Double-Crested Cormorant in the southern basin of Lake Michigan (Madura and Jones 2016).
Potential:
While White Perch is a good food fish and could potentially be pursued recreationally, it is not as commonly exploited as a game fish (Scott and Crossman 1973). In some Great Lakes states, White Perch is allowed to be caught but is largely prohibited otherwise.
One study found that relative to available zooplankton, a disproportionately large amount of White Perch diet consisted of the invasive Bythotrephes cederstroemi (Bur and Klarer 1991). White Perch may play a role in the life cycle of some mussels species. White Perch is a host for the freshwater mussel Roanoke Slabshell (Elliptio roanokensis) in South Carolina (Eads et al. 2015). This species is not native to the Great Lakes, but the congenerics E. complanata and E. dilatata are native and present in the region. However, it is unknown whether White Perch will play a similar role in the life cycle of these two species.