The significance of man-made structures for lake trout spawning in the Great Lakes: are they a viable alternative to natural reefs?

Abstract

High lake trout (Salvelinus namaycush) egg abundance reported at some man-made structures, including artificial reefs in Lakes Michigan and Ontario, indicates that construction of artificial reefs may be one means of enhancing reproduction for this species in the Great Lakes. A review of spawning at man-made and natural spawning areas indicated consistently higher abundance of eggs, fry, and young-of-the-year lake trout associated with man-made structures. Hence, artificial reefs could make a significant contribution to restoration of lake trout stocks in the Great Lakes. It was not clear, however, why some man-made structures were used by lake trout and some were not. It is recommended, therefore, that construction of artificial reefs be approached on an experimental basis and that reef construction be part of an overall strategy to increase availability of spawning habitat. Also included in this strategy is stocking lake trout closer to areas of natural spawning substrate and resolving potential resource user conflicts. Studies should also be conducted to evaluate how life stage at stocking (e.g., egg, fry, yearling) affects subsequent use of spawning habitat and to determine if genetic factors are involved.

Artificial reefs and reef restoration in the Laurentian Great Lakes

“…More recently, the focus of artificial spawning habitat construction shifted to restoring and increasing functional spawning habitat in order to enhance fish populations (e.g., Dumont et al, 2011;Fitzsimons, 1996;Manny et al, 2010;Roseman et al, 2011) (Fig. 3).…”

“…3). Emphasis of these projects was on spawning habitat for imperiled or important species, such as lake sturgeon (e.g., Dumont et al, 2011;Roseman et al, 2011), lake trout (Fitzsimons, 1996), and walleye (Geiling et al, 1996), or improving diversity of benthic-spawning fishes (Manny et al, 2010). Material used to construct fish spawning reefs has most frequently been broken limestone (Roseman et al, 2011) but has also included igneous rocks (Geiling et al, 1996) (Table 1).…”

“…Many monitoring studies lack biological or physical assessment before reef construction to compare to post-construction conditions. Adult fish variables have included the abundance of target species, such as lake trout (Fitzsimons, 1996), total fish abundance (Kelch et al, 1999), or species richness (Kelch et al, 1999). Sampling gears and methods for adult fish have varied across reef monitoring projects and have included underwater observation (Environment Illimité Inc., 2009, 2010Kelch et al, 1999), gill nets (Creque et al, 2006;Dumont et al, 2011), and trap nets (Geiling et al, 1996).…”

“…For example, egg deposition has been used to assess spawning activity of lake trout on reefs in Lake Michigan and Lake Ontario (Fitzsimons, 1996) and lake sturgeon in the Detroit River (Roseman et al, 2011). Lake trout spawning activity has also been measured in Lake Michigan by the emergence of larvae from spawning substrates (Marsden and Chotkowski, 2001) and lake sturgeon spawning success has been assessed with larval fish densities in the proximity of artificial reef structures (Bouckaert et al, 2014;Roseman et al, 2011).…”

“…In large aquatic systems such as the Laurentian Great Lakes, artificial reefs are often created to provide spawning and nursery habitat to benthic-spawning fishes (e.g., Fitzsimons, 1996;Gannon, 1990;NOAA, 2007). Artificial reefs have been used as a fishery management tool for over 40 years in the Laurentian Great Lakes and have often been championed as a successful means for improving recreational fisheries (Kelch, 2012).…”