Here is my report on Davis

[1flyfisher]

I put in quite a few dozen days last fall and a couple dozen so far this spring/summer.
I began noticing the sores already last fall and the fish were jumping out of the water quite often with unusual frequency like I had not seen before. I believe they may have been trying to shake off the parasites. Some kids I know from reno showed up to fish with me (last july 200 having never fished the lake they just wore shorts in their float tubes and t shirts as it was mid july and HOT. They got bit up real bad by something but were unable to see what it was (perhaps something microsized?). Mosquito bite size welts all over their legs and stomachs (dozens) and they were very itchy they said. They launched from cow and tried to catch up to me as I was already at first point fugawee and they could see my kayak from cow. They kicked straight through all the weeds. So be careful wetwading starting about now. I did swim in the lake last week with no bites.
Last summer the lake level was quite low and was a swamp of weeds from north point fugawee all the way over to freeman. One big giant weed bed. Lake levels are the same this year as the lake didn't come up much from last season. The parasites are ergasilus or commonly known as gill maggots and also anchor worms. I have never seen this in the decades I have been fishing Davis. Parasites do not kill the fish outright but do stress the fish and open them up to infection, Sores result in a loss of body fluids and increases the risk of summer or winter kill and that is just not good. Ergasilus Gill maggots also do damage to the gills. The energy levels of the fish do not seem to be effected as I had some very hot fish this spring/summer and only one that I had to nurse for a half hour as it kept rolling over. That fish had massive amounts of gill maggots and was in really bad shape. There have been fewer of the holdover 20"+ fish porpoising around the shoreline as in years past. I do not know if that is due to fisherman yanking out limits or due to winter kill stress from parasites. Trollers do pound the lake hard and davis has been receiving alot of pressure since the re-stocking post treatment and the trollers seem to like taking limits of 10.

I don't often eat these fish as they have poor taste to me but DFG says you can eat them if you want to. I'll pass as they look pretty damn unappetizing with all the sores and holes in their skin and parasites in their gills. Nasty.
Last week I landed quite a few that were clean and in pristine condition. I think they may have been recent planters as I heard DFG threw in some larger fish recently. There have been alot of dinker size fish this year in the 8-12" range. They are covered with sores and parasites also. You could have caught 20-30 of these planters. I tried to avoid them as much as possible and target bigger fish in the skinny water. It was a tough spring though.
DFG says the outburst of parasites is cyclical and occurs from warmer water levels (last summer). Perhaps this year with the cold june and cooler water temps they will go away.
The lake needs a good fill with a wet winter to raise water levels and improve water conditions.
One positive note. I have been seeing some improvement in the number of snails in the LightningTree to Mosquito Slough area. Hopefully they can spread back through the entire lake again as they have been few and far between the last few years. I have logged a couple dozen days this season so far and have seen 2 blood midges. Damsels were very light but they are there and next spring should be a great hatch weather permitting. This june we had rain for 6 weeks straight in reno and some days didn't even make it out of the 50's. It really shut down the damsels compared to average numbers we should normally see. Last year being a mega size hatch. Another positive. Callibaetis were out in big numbers and fishing the nymph was a good choice. Not so much fish keying in on the duns though. I would see hundreds of duns on the water with only the occasional sporadic riser which made the fish hard to target with a dryfly.
Compared to what I have experienced in years past I would rate this season pretty low. It is a bit disappointing as I was expecting this spring/summer to have had some really nice quality fat 20-22+" rainbows porpoising around and the lake to really shine as we are a few years post treatment and this season should have been a good one. The sores are a real bummer to me. It is tough seeing those feisty davis bullets all covered with holes.
Maybe this fall things will turn around and all the 8-12" dinks add some size.
We shall see......

......I may go up this coming week. If I do I will report back.

Paul B.

[Dabalone]

Thanks for the report. Are they having the same parasite problem at Frenchmans? Same area and similar water I believe.

[Hairstacker]

Paul, welcome aboard and thank you for the detailed report!

[1flyfisher]

So far Frenchmans is ok. Frenchmans is close to davis several miles apart. I don't know what you mean by similar water. It has similar aquatic insects.

As far as the current parasite problem.....Davis has always had water quality problems and low survivability high mortality rates for the trout, especially the fingerlings. But this is the first time anything like this parasitic explosion has occurred since the lake was formed in 1967. Low Oxygen levels in the deeper depths, high ammonia levels, dangerous thermal and toxic levels and stressful conditions resulting in big winter and summer kills is the norm at davis. The highest mortality for trout in davis generally comes in low water years such as last year and this year. The parasites aren't helping matters and only time will tell what effect they will have. I think things will be fine once water levels rise.
The lakes biomass of fish has always been very low for trout with other populations of illegally introduced fish taking over the lake, such as the golden shiners which had over run the lake in the late 70's early 80's. The results of the recent treatment indicated that some 90%+ of the fish biomass was bullheads. The final summer I was seeing them by the thousands. It is my belief that they damaged the snail populations as opposed to a cyclical reason in the decline or some other biological reason. The lake was over run by the bullheads and the snails were their easy food source. They were mopping the bottom in huge schools off the points the last summer. Hundreds/thousands in the shallows on the points in the spring when snails cover the points. They were pounding them from my observations. I am just guessing here that the bullheads were the reason for the snail decline and I have no biological reason other than observations and a strong hunch. DFG believes all the illegally introduced species(Largemouths, Bluegills, black bullheads, Pumpkin Seeds, Golden Shiners, Fathead Minnows, Lahontan Redsides, speckled dace, Sacremento suckers, sac perch etc, and of course pike) have been eradicated except for the brown bullheads. I hope that population doesn't explode to pre-treatment levels again. Davis despite all its problems and its high dfg cost to maintain a trout fishery has had some great fishing over the years and I am sure it will come back strong despite likely future ups and downs. I am hoping the snails and blood midges come back strong. When Frenchmans was treat with rotenone for pike the blood midges dropped off but did come back. But after the 1997 davis treatment I saw huge blood midge hatches covering the lake from Fugawee to Lightningtree so that rotenone treatment didn't seem to affect them. Insects are highly cyclical so that likely explains it. Snails are once again starting to show up a bit more this summer. They were in decline prior to the treatment so you can't really blame that, and they were pretty think after the 1997 treatment. The lake really fishes much better with high water, the water quality is better with high water and the weed channels are much more defined with defined edges and deeper fishable holes, Right now the weed beds are turning into one big mat from fugawee to freeman (like last year) with no channels like we had in the past years.....Keep your fingers crossed and pray for rain and high water levels

Thanks for the report. Are they having the same parasite problem at Frenchmans? Same area and similar water I believe.

[Troutstalker55B]

Hey Paul,

Good to see you on here, been a year since I've seen you last. The decline of the snail population happened when the DWR and the Forest Service dropped the level of the lake to fix the boat ramps. They did it too quickly leaving millions of snails high and dry on the bank. This was recorded with a formal complaint by my dad to both agencies.

Yeah, things are not what they use to be, but it's still a beautiful lake. See ya out there.

JB

[FRSam]

Hey Paul it's good to hear from you. I haven't seen you out on the lake but with that kayak of yours you get into some pretty skinny water where I can't with that whaler of mine. That rash your buddies picked up sounds like "swimmers itch" a parasite that is transferred from snails to ducks and sometimes people. Here's the skinny: The larval parasite called a "cercaria" is released by aquatic or amphibious (moves both on land and water) snails and causes dermatitis when it mistakenly penetrates a person's skin rather than its rightful host, usually a duck. Swimmer's itch occurs in both freshwater and in the marine coastal environments. It only lasts seven to ten day and usually clears up completely after this period. It can be avoided for the most part by toweling off after exiting the water.

Now I'm not completely convinced this is the culprit for the rashes people have been reporting and I did sent a letter off to Fish and Game specifically asking whether or not the copepod parasite was able to infect or penetrate human skin if it was exposed in the water. This was sent out last week and I haven't heard back from them yet....I'll post the results when I get them.

Was the West side road open when you put in or did you have to drive all the way around the lake? Last time I was out it was closed to the Camp Five turn off.

I'll keep an eye out for you on the lake,

Pete

[markem8]

I fished Davis a few years ago from my pontoon boat and did not wear waders. I ended up with several bites as well. I mentioned this to a couple of folks and someone told me the bites were from Daphnia. They said it that daphia are water fleas that are in the lake. I have also read that the are good trout food. The bites cleared up quickly.

I am not certain that is where the bites came from, but it sounded good to me. All I know is that I always wear waders at Davis now.

[1flyfisher]

Hey Jon, Hey Pete.
How's it going?

[Kevin Goding]

Not sure if a Daphnia would bite a person, as the name "water flea" just pertains to their small size, not their fondness for blood. Pretty sure they just eat algae and bacteria predominantly by filtering it out of the water. I think the prior explanation above about swimmers itch is more plausible. However, you never know since a lot of organisms blood sucking/carnivorous or not will take a taste test just to see.

[1flyfisher]

Originally I thought it may have been the backswimmers as they are abundant in the lake and inflict a painful bite that welts up.

After seeing all the sores and bites on the fish I saw last fall I then wondered IF the parasites I found on the fish Ergasilus/Gill Maggots and anchor worms had something to do with the mosquito type bites my friends experienced.

Pete posed the theory that it was swimmers itch. I did some reading on swimmers itch and that seems the plausible answer.