|dc.description.abstract||Lake trout reproductive habitat was characterized in three small lakes, 250 km northwest
of Thunder Bay, Ontario, by measuring the physical characteristics of preferred spawning
habitat including 1) depth, 2) substrate size, 3) interstitial space depth, 4) organic material
abundance, 5) embeddedness, 6) particulate debris, and 7) permeability. Principal
Components Analysis indicated that periphyton, macrophyte, and particulate debris
abundance all increased with shoal depth, while substrate size decreased. Hydraulic
permeability, indexed by the erosion of gypsum cylinders, was higher in coarser substrates.
Lake trout egg deposition density in egg traps averaged 70 eggs m'2, of which 45% were
viable by late fall Lake trout embryo survival and emergence in enclosures varied with
Fredle Index, and was highest (75%) in cobble/rubble mixtures. Fine sediment which was
added to incubators in the fall was absent when the incubators were retrieved in the spring.
At the single fine sediment dosage tested in this study (equivalent to a layer approximately
2.5 cm deep across the surface of each incubator), lake trout hatching success was not
significantly affected. Although experimental nutrient enrichment CP and N) of a spawning
shoal increased periphyton biomass by 2.5 times over the summer, the effects of this on
reproductive habitat are not known at present.||