The trawl index numbers are based on data from hundreds of trawls conducted by fisheries staff at dozens of locations on Lake Erie by the ODW in Ohio and the Ontario Ministry of Natural Resources and Forestry in Canadian waters, plus some additional fisheries data. The final numbers, derived from combined information from Ohio and Ontario, are intended to give fisheries managers a glimpse into the future and help them guide current decision-making with knowledge about how many young fish will become part of the catchable population.