For those who dont know John Pitlo he is a Fisheries Research Bioligist working for the Iowa DNR out of Belvue on pool 13. He is renown for his walleye tracking using radio telemetry particularly in reference to spawning movements….
John was one of my teachers at Iowa State where I graduated with a degree in Fisheries and Wildlife biology… and though like many FWB people I did not end up working in that field I still retain a keen interest in whats going on there… so I have been corresponding with John and other fisheries people to try and learn whats going on in Fisheries these days… particularly in reference to the Mississippi fishery…..
OK.. enough of that!….
for those who are interested I will try and pass on (with Johns permission) what was given me…..
a little while ago Hougie sent me an article about what might happen with the walleye spawn and this strange spring…. some of the things they said seemed wrong to me….
I asked John how this late spring might impact the spawn…..
Johns response…..
As far as spawning is concerned – the cold weather has slowed it somewhat – but all of our radio tagged fish have left the wintering areas and have headed upstream. Some are located in the tailwaters, just below the L & D’s, and others are just scattered downstream. There are none in backwaters right now – all in main channel borders (between the channel markers and the shore or bank).
I don’t think late springs are necessarily bad. When we have late spring, generally the warm-up in water temperatures is fairly rapid and uniform. When the daily increase in water temperature is .5 degree a day or better, we generally have great walleye reproduction. On the other hand, an early spring and water warming early usually results in a late season snow or cold rain or cold fronts which cool the water and keep the average daily increase in water temp. below 0.4 degree/day during the spawning and incubation period which results in poor reproduction. The colder temperatures slow the incubation period and eggs are subject to longer periods of predation, disease, and landing on unsuitable substrate.
Then I was following the Spring Valley tourney on the Illinois River and I was interested in the process where the DNR strips the fish caught during the tourney and stocks them… they have attributed this stocking to greatly helping the IR fishery…..
I asked John if something similar might not work on the Mississippi……
Johns Response….Yes – I know about the sauger stocking program on the ILL River- they had very poor natural reproduction as I understand it – therefore the stocking. In the Miss. the only stocking program I’m aware of is in Pool 14 by the Cordova Power Plant. They stock (their quota is 150,000 fingerlings/yr) in Pool 14 to offset anything detrimental they might do with respect to taking water from the river for cooling purposes and putting warmer water back. They collect fish from the Miss. and actually spawn them onsite and then raise the fish in a cooling canal that surrounds the facility. If they have excess fish, they stock some in Pool 13.
Stocking is a way of improving fish populations if there is a problem with natural reproduction. I would favor ways to improve natural reproduction through protections of spawning habitat, improving nursery habitat, protecting spawning fish so that more eggs are produced, etc over stocking. Stocking is a huge effort in time and money for an agency. In the Miss., where natural reproduction still maintains the populations, I thing we need to do our utmost to protect the spawning stocks. I could go on and on, but you get my drift.
I then commented that I thought that general belief indicates that spawning stocks are not the key ingrediant and that environmental factors are the key factor……
Johns Response……
We were always taught in school that the size of the spawning stock generally made little difference, that it was conditions during the spawning period that dictates the success of the spawn. However, there have been several recent studies that indicate that size of the spawning stock, the rate of water warming in the spring, and the condition of the female the previous fall explained nearly 70% of the variation in year class strengths. So it appears that in some popualtions, the size of the spawning stock does make a difference – we just have to find out if that is the case on the UMR.
anyway… very interesting stuff…..
so every year we have discussions on the board about the value of releasing spawning stock…. well.. it would appear that it just might make a difference… so it just might pay for us to consider releasing those spawn filled females……
and further.. its interesting the information on the Cordova power plant….. I did not pursue this with John… but we have more than one power plant on the UMR.. why is that the only one that is stocking fish to compensate for losses caused by the plant?
I guess I still have more questions to ask…..
I just wanted to pass this on so that we all may understand these fisheries issues a little better……
