Lake whitefish and walleye population responses to dreissenid mussel invasion in eastern Lake Ontario

Abstract

We reviewed responses associated with the invasion of dreissenid mussels by two eastern Lake Ontario fish populations and the fisheries they support. Resurging lake whitefish and walleye populations declined following dreissenid mussel invasion in the early 1990s. Impacts on whitefish were associated with the loss of a key diet item, Diporeia, and its replacement with diet items of lower energy value. Impacts featured a die-off, dispersal, declines in juvenile and adult condition and growth rates, delayed age-at-maturity, and several years of reproductive failure. Impacts on walleye were consistent with dreissenid driven ecosystem change, particularly, clearer water. The key response by the walleye population was a downward shift in recruitment levels. This shift appears to be due to a change in the stock-recruitment relationship caused by decreased survival during early life (i.e. egg to 4-months), and suggests that the carrying capacity for these early life stages has diminished. Currently, whitefish reproduction has resumed and walleye reproduction appears stabilized at a lower level. Recent (i.e. 2003 and 2005) whitefish year-classes were relatively large but the fish are growing slowly and annual survival rate is not yet known. The whitefish commercial harvest continues to decline in synchrony with the declining adult whitefish population. The walleye recreational fishery (i.e. effort and harvest) has stabilized at a smaller size consistent with lower walleye year-class strength.

Reproductive allocation in exploited lake whitefish (Coregonus clupeaformis) and walleye (Sander vitreus) populations

“…In contrast, in eastern Lake Ontario a rapid increase in abundance of invasive dreissenid mussels in the early 1990s was followed by declines in both walleye and lake whitefish abundance (Hoyle et al, 2008). The dreissenid invasion had the greatest impact on lake whitefish; alterations in their benthic prey community led to reduced growth and condition and later age at maturity (Hoyle et al, 2008). Though it is not clear how these environmental changes may have influenced the observed relationships between our dependent variables and age, it seems plausible that they could have influenced the overall differences between species and lakes.…”

“…In Lake Winnipeg, productivity was probably increasing in response to increasing nutrient inputs (Mayer et al, 2006), and the walleye population appears to have responded through increased abundance and growth and decreased age at maturity (Johnston et al, in press). In contrast, in eastern Lake Ontario a rapid increase in abundance of invasive dreissenid mussels in the early 1990s was followed by declines in both walleye and lake whitefish abundance (Hoyle et al, 2008). The dreissenid invasion had the greatest impact on lake whitefish; alterations in their benthic prey community led to reduced growth and condition and later age at maturity (Hoyle et al, 2008).…”

“…Changes in food availability due to changes in population abundance, ecosystem productivity, or prey community composition are often accompanied by a response in growth rates or energetic status for many fish species, including both lake whitefish (Healey, 1980;Mills, 1985;Pothoven et al, 2001;Lumb et al, 2007;Hoyle et al, 2008;Rennie et al, 2009) and walleye (Chevalier, 1977;Jones et al, 1994;Craig et al, 1995;Colby and Baccante, 1996). In the current study, we used somatic lipid content as an index of energy storage, a variable that correlates well with morphometric condition in both species (Kaufman et al, 2007;Rennie and Verdon, 2008).…”

Fish community structure in the Bay of Quinte, Lake Ontario: The influence of nutrient levels and invasive species

“…Our analysis only included summer (June-September) data, and therefore makes no attempt to address seasonal variation in species abundance. Detailed sampling methods have been reported elsewhere (Hurley, 1986a(Hurley, , 1992Bowlby et al, 1991;Casselman and Scott, 2003;Hoyle et al, 2008) but brief summaries are provided here.…”

Metrics of ecosystem status for large aquatic systems – A global comparison

“…3B). Declining commercial catches have been attributed to poor water quality, loss of habitat, overexploitation, and negative impacts of invasive species (Hoyle, 2005;Hoyle et al, 2008;Lauer et al, 2008;Lumb et al, 2007) all of which can directly impact stocks but have also likely affected market demand because of the negative perception of the health of the lakes and historic contamination of their fish.…”