Fisheries Investigations in Crater Lake, Oregon, 1937-1940 by Arthur D. Hasler and D. S. Farner
A summary of the creel censuses (Table 5) shows that more fishes were caught per hour of angling during July than in August in all years. In 1938 a study was made to compare day fishing and evening fishing by a group of rangers who kept separate records of their angling before and after 3: 00 p.m. During July and August they fished 26 hours between 8 : 00 a.m. and 3 : 00 p.m. and caught an average of 0.17 fish per hour per angler. The same men, using identical tackle and in the same months, also fished between 3:00 p.m. and dusk and then averaged 0.86 fish per hour per angler. Boats are not available to the public for early morning or evening fishing, because of local conditions; otherwise anglers would obtain greater yields.