No, they weren't.
Lake Erie is really considered to be physically three different lakes. The western basin is quite shallow, the central basin, deeper, and then the eastern basin, quite deep. They all behave differently in terms of the circulation patterns and so on.
The western basin is extremely vulnerable to the impact of phosphorus. Algae blooms, in addition to being toxic, eliminate oxygen within the water column and the fish move elsewhere.
It is the most productive lake. From the standpoint of commercial fisheries, more pounds of fish are harvested out of Lake Erie than out of all the other lakes put together, but the reality is, for parts of the year, there are very unfavourable conditions for fish survival, let alone fish production, in western Lake Erie.