In most places on Fishing Creek, there is not enough dissolved aluminum to be toxic, although East Branch Fishing Creek has aluminum concentrations of over 100 μg per liter, approaching a lethal level for fish. Fishing Creek itself and all its other tributaries have concentrations of less than 70 μg per liter. The concentration is seasonal: aluminum trapped in frozen ground is released into the streams when the soil thaws. As a result, aluminum levels in the creek peak in March and April and drop to almost zero in the summer.