DENSITY-INDEPENDENT SURVIVAL OF WILD LAKE TROUT IN THE APOSTLE-ISLANDS AREA OF LAKE-SUPERIOR

The lake trout (Salvelinus namaycush) stock at Gull Island Shoal in we stern Lake Superior was one of only a few stocks of lean lake trout in the Great Lakes that survived overfishing and predation by the sea la mprey (Petromyzon marinus). Since the mid 1960s, the abundance of wild recruits measured at age 0 and the number of age-7 to -11 wild fish r ecruited to the fishable stock have increased. We used the Varley-Grad well method to test for density-dependent survival between these life stages. Survival from age-0 to ages 7-11 was not affected by increasin g density, which suggests that further increases in recruitment and st ock size are still possible. We suggest that testing for the existence of density-dependent survival can be used to indicate when lake trout populations are rehabilitated.