I live close to the catt and fish it often, both above and below the dam. Above the dam, it is stocked with browns except for the headwaters. The headwaters have tons of wild rainbows that are more or less brook trout sized. I've caught thousands of wild rainbows in that watershed and the largest was 14 inches. I've never caught an st in the catt but some small tribe do have some. I think wild rainbows outcompete the st in the watershed. There is a decent population of wild browns in the creek, but I catch 70 percent plus rainbows.
I don't know how steelhead would affect the fishery. I'm hoping the creek will lose its resident rainbow population i.e. they all run to the lake. What would be left would be larger brown trout and some st.
To be honest, even if there were no steelhead, I'd like to see the dam removed. It would be the only undammed ny Erie trib that holds populations of wild trout. I think you have the possibility of having wild lake run brook trout, brown trout, and rainbow trout.
The only native trout (I know they are char) to lake Erie are brook trout and lake trout. Given the small st population in the watershed, I think you can argue the dam removal actually gives the opportunity to restore a native
St population in Lake Erie.