The Great Fish Depression: Exploring Three Consecutive Years of Low Catch of Fishes from U.M.R.R. Monitoring

For the 20 year period (1994 – 2013) of long-term monitoring in Pool 26 of the Mississippi River for the USACE Upper Mississippi River Restoration (UMRR), we observed the total catch of fishes had declined by 45-57% for three consecutive years (2009 – 2011), relative to the 20 year average total catch.  Conversely, total catch from 2006 to 2008, along with 2012 and 2013, ranked among our highest for the 20 year record, with 2008 being the greatest total catch across all years.  Three other LTRM field stations, Pool 13 and the Open River Reach on the Mississippi River and the La Grange Reach of the Illinois River, had similarly low catch for these years.  We explored the underlying dynamics of this pattern, identifying which species showed declines, whether catch trends were consistent across sampling gear, whether unusual environmental conditions were present that may have influenced the effectiveness of our gear or contributed to declines in fish populations.  Recent changes in flood frequency, timing, and magnitude appear to be a likely factor influencing low catch patterns.  Flooding has the capacity to affect our data by influencing sampling effectiveness and by directly influencing fish populations.