Riverkeeper Report: Fish kill not as bad as after Hurricane Isabel
Published 11:20 am Saturday, September 17, 2011
I always hate when I start getting phone calls about dead fish on the river.
However it has become a pretty much guaranteed final slap in the face after we have storms that dump more than 6 inches of rain. Irene was no exception.
I watched river dissolved oxygen levels drop last week to 1.12, and they most likely went lower than that. Under 1 ppm is pretty much assured a kill.
When all the debris, dead and already decaying vegetative matter gets washed out of the swamps and into the river, it causes a high biological oxygen demand for that stuff to decay. That uses up dissolved oxygen and causes a fish kill.
I toured the rivers Monday. I first put in at Hercules. Dissolved oxygen levels were about 2.60 there, and I saw no dead fish until I got to Monroe Bridge. Dissolved oxygen levels there were 1.80.
The further downriver I got, the more dead fish I saw. However, you got to remember that the river flows that way, downriver, so dead fish end up there. So I really don’t know if the fish kill was worse downriver, or not for sure, but I would have to still say I believe it was worse downriver.
I halted my progression downriver at the Highway 258 Virginia Department of Inland Fisheries and Game ramp where the dissolved oxygen was 1.60. I saw nearly every species dead except for gar and bowfin. They have a primitive lung they can use to gulp air when they break the surface and can therefore survive extremely low dissolved oxygen levels.
I saw a carp that would have weighed 30 pounds. Unfortunately I also saw about 50 largemouth. Many of those were 3 to 4 pounds, and I saw a few that were in the 6- to 7-pound range and that’s taking into account the bloat factor.
The lowest dissolved oxygen reading I took was in the back end of Sims Gut. There I got a .50 ppm reading, which is the lowest reading I have ever seen in the river.
The strange thing was I saw no dead fish in there. The Blackwater seemed to fare better.
I put in at Franklin where I got a 1.80 dissolved oxygen reading. I traveled to Old South Quay before I saw a dead fish. The readings on the lower Blackwater averaged about 1.60 ppm.
I saw a few largemouth, but most were small carp and a lot of bream. In all, I saw about 200 dead fish combined on both rivers. This is fewer than what I saw after the 1999 flood, Isabel or the North Easter we had in 2006.
All the dead fish I saw today were more than three days old. I saw no fresh dead fish so I’m hoping for the most part the kill is over. In the main run of the river, I saw no dissolved oxygen levels lower than 1.60 ppm, and that is enough to sustain the fish.
Hopefully the worse is over and soon the stench of rotting fish will clear the river.
Both rivers will as always recover pretty quickly. Unfortunately I could not pick up the piles of trash I saw on the Nottoway like I did on the Blackwater. The trash and dead fish occupy the logjams, and on the Nottoway, the smell was just too much.
I guess I’m going to have to let the Riverkeeper turtles do their job and clean up first.