The average lengths of lake trout (Cristivomer namaycush) captured in the various Algonquin Park lakes during the decade varied from 13.3 to 24.8 inches and the number captured per 100 boat-hours from 39 to 154. When the average length of fish captured is plotted against number captured per unit effort, all the points fall below a line which begins at a length of 13.3 inches with an availability of 220, rises to an availability of 355 at 15.5 inches, and drops lower as the size increases until at 24 inches the line falls below 100 fish per hour. This line has been taken as the standard for availability of lake trout in Algonquin Park and a fishing index has been proposed which compares each fishery with this standard curve. Certain lakes have shown marked annual fluctuations in size and abundance of lake trout that suggest the progression of major year classes through the fisheries. More detailed examination of the catch statistics indicates that an extremely uneven success of year classes of lake trout appears to be universal in the Algonquin Park lakes.