To answer these questions, a concerted effort was made by the states of Indiana, Illinois, Michigan, and Wisconsin to fin clip all cohos (2. 6 million fish) planted in 1978. Different fin-clip combinations were assigned to each agency. In addition, Michigan used a maxillary clip for a special diet study promulgated by that state. There were many sources for monitoring the capture of these marked fish but the principal ones were the creel censuses in each state.

The 1978 planting contributed 197, 210 fish to the coho catches in Lake Michigan and its tributaries in 1978 and 1979, or 7.4% of the plant. The total coho catch in 1979 amounted to 212, 850 fish, of which an estimated 9. 3% were naturally spawned fish. An estimated 2, 400 cohos (2. 5% of the Michigan coho harvest in 1979) were furnished by plantings in other states to the Michigan catch whereas Michigan's contribution to the coho fisheries in the other three jurisdictions ranged between 13 and 45 thousand fish or 50 to 75% of their catches. On the average, 3.0% of the Michigan-planted cohos were caught in their respective home areas in the two years.

Highlighting the data on movements was the pronounced concentration of fish that had been planted throughout Lake Michigan in the southern end of the lake in winter and spring. Also, cohos from Lake Erie invaded Lake Michigan in 1978, but apparently not in 1979.

There were no statistical differences in adult lengths and weights among fish raised either on the Oregon Moist Pellet or the cheaper PR-9 trout formulations. Returns to the fall creel were significantly higher for the PR-9 coho but, conversely, OMP cohos arrived at the Platte River weir in significantly greater numbers.