Feeding ecology of invasive age-0 white perch and native white bass after two decades of co-existence in Saginaw Bay, Lake Huron

Steven Pothoven,Tomas Höök

doi:10.3391/ai.2015.10.3.10

Abstract

The diets and energy content of sympatric populations of invasive age-0 white perch Morone americana and native age-0 white bass Morone chrysops were evaluated in Saginaw Bay, Lake Huron following >20 years of coexistence. Fish were collected during July-November in 2009 and 2010 to assess seasonal and interannual patterns of diet composition, diet similarity, feeding strategy and energy density for the two species. The diet composition by weight of age-0 white bass was dominated by various zooplankton taxa, fish, or emergent insects, depending on the month and year. Although fish occasionally comprised a large fraction of the diet biomass, they were eaten by <24% of white bass each month. The diet composition of age-0 white perch shifted from one dominated by chironomids and other benthic macroinvertebrates in 2009 to one largely consisting of Daphnia spp. in 2010. There was more overlap in standardized diet assemblages in 2010 than in 2009 due to the increased importance of Daphnia spp. in white perch diets in 2010. Contrary to expectations, complete separation of diets was not a requirement that enabled the long-term coexistence of invasive white perch and native white bass in Saginaw Bay. Both age-0 white bass and white perch had a mixed feeding strategy with varying degrees of specialization and generalization on different prey. The inter-annual variation in prey, i.e., higher densities of zooplankton in 2009 and chironomids in 2010, is directly opposite of the pattern observed in white perch diets, i.e., diets dominated by chironomids in 2009 and zooplankton in 2010. Energy density increased from July into autumn/fall for both species suggesting that food limitation was not severe.

Highlights

The introduction of invasive species into aquatic systems is known to cause profound ecological changes
One example is the invasion of white perch Morone americana (Gmelin, 1789) into the Laurentian Great Lakes where white bass Morone chrysops (Rafinesque, 1820) are native
We evaluated the diet composition, diet overlap, feeding strategy and condition of sympatric populations of age-0 invasive white perch and age-0 native white bass in Saginaw Bay, Lake Huron following >20 years of coexistence

Summary

Introduction

The introduction of invasive species into aquatic systems is known to cause profound ecological changes. One example is the invasion of white perch Morone americana (Gmelin, 1789) into the Laurentian Great Lakes where white bass Morone chrysops (Rafinesque, 1820) are native. White bass are a freshwater fish native to the St. LawrenceGreat Lakes, Hudson Bay (Red River), and Mississippi River basins, whereas white perch is a euryhaline species native to the Atlantic coast region (Page and Burr 1991). Both species have been introduced outside their native range either through intentional or accidental stockings resulting in situations where these two congeners, once formerly isolated from each, other overlap (Irons et al 2002; Kuklinski 2007; Feiner et al 2013a). In the Laurentian Great Lakes region, white perch were found in lakes Ontario and Erie in the 1950s and spread to Lake Huron by the early 1980s (Boileau 1985; Johnson and Evans 1990)

Methods

Results

Conclusion