Taken from IDNR's 2008 status of Illinois walleye and sauger fishery:
FOX RIVER - In 2007, a total of 13 stations were sampled on the mainstem of the Fox
River between the McHenry Dam and the Illinois River. Catch rate of walleye was 4.6
fish per hour of boat electrofishing, compared 5.7 per hour for the period from 2000 to
2005. Although walleye were found throughout the river, higher densities (10- 15 per
hour) were found at McHenry, Geneva and, Sheridan. Most of the fish were between 9
and 14 inches (see graph below), and no fish larger than 19 inches was captured.
Young fish were present, resulting from recent spawning or downstream movement
from the Chain-O-Lakes stocking program. Walleye are also stocked each year
between Yorkville and Wedron (15,000, 2-inch).