The objectives of these cruises of the research vessel Musky II in 1965 and 1966 were: To determine changes in the fish population and environmental conditions in recent years; to determine if the geographic and depth distributions of certain species of fish in the summer differed from that in the autumn; and, to obtain much-needed information on the selectivity of experimental gill nets, particularly for the fresh-water drum (sheepshead) and the walleye. In general, the kinds of fishes, and the geographic and depth distribution of the catches in the eastern basin in June, 1966 did not differ greatly from those in September of the preceding year. The numbers of some fishes, however, had changed- the so-called trash fish were more abundant and the more desirable commercial species were less numerous than in 1965. Yellow perch was by far the most abundant species in the catches. Other fishes taken frequently included white suckers, stonecats, white bass, smelt, and walleyes. Sizeable populations of small-mouth bass and fresh-water drum were also found.