Performance of Lake Trout (Salvelinus namaycush) Backcrosses, F1 Splake (S. fontinalis × S. namaycush), and Lake Trout in Lake Huron

This paper presents the results of plantings in Lake Huron waters of lake trout (Salvelinus namaycush), F1 splake (S. fontinalis × S. namaycush), and the progeny of the backcross between splake males and lake trout females.The planted fish were piscivorous throughout age-groups II – V with rainbow smelt (Osmerus mordax), sticklebacks (Pungitius [?]), and alewives (Alosa pseudoharengus) the dominant food organisms. Hybrid stocks grew more rapidly but attained a somewhat smaller asymptotic length than did lake trout. The F1 hybrids were the earliest to mature with 34% of the males and 4% of the females spawning at age II. Earliest maturity occurred in the backcrosses at age III, in contrast to lake trout which matured predominantly at ages VI and VII. The backcrosses demonstrated a slightly broader thermal and bathymetric distribution during summer than did lake trout, while the F1 hybrids tended to concentrate in the thermocline. Total annual mortality rates (attributed mostly to predation by sea lampreys,...