The Grand can produce a mixed bag of fish, and can be productive. But the dam is not the only place you can wet a line, there are thousands of shore / wader spots to fish between the dam and York..
One word of caution though... it is Ontario's third most polluted river according to government studies and only gets worse as it heads towards Dunnville and empties into Lake Erie. Sewage, farm runoff and fertilizers appear to be the main culprits. It is only superseded by two Toronto rivers...
Keeping fish from the river for consumption is definably not advisable knowing this information and would be foolhardy.
Gerritt.