DNR Answers

I posed a question to the new DNR Fish Biologist for Adams, Juneau, Wood Counties about a rumor of new rule changes for the Wisconsin River System and related my views on specific species. Her reply answered a lot of questions mant anglers have on Castle Rock and Petenwell Lakes.
I would like to thank Justine for her indepth response.

Good Morning Mr. Tipping.

I have had a chance now to look through the files for both Petenwell and Castle Rock Lakes as you can imagine they are rather large files as there has been a lot of work done on these two systems over the past 30 years. I was also able to have a good conversation with Dale the technician here in Rapids who was in the office yesterday about the two systems to get a good back ground on the two lakes. Dale has worked in this area in fisheries for over 25 years so has a lot of good historical knowledge not found in the files. I recently took over the position as the Fisheries Biologist for Adams, Juneau and Wood Counties. I had previously been the biologist for the Bay of Green Bay and inland for Marinette and Oconto Counties. I am just learning all my waters under my new jurisdiction so it takes a little longer for a response as I have to take some time to review our files and database for information.

I thank you for you interest in the two lakes and find your comments on the two waters very interesting. It is nice to have someone that has had a long history fishing these waters being able to let us know their observations that we can add to the information we collect though our survey work.

The answer to you question regarding any new regulations for either water bodies, the answer is no we the DNR do not plan on any changes to the current season or slot limit for walleye. We feel that the current regulation is being effective and providing for a healthy walleye population as well as providing excellent angler opportunity.

I will now address each of the species you had comments / questions/ and or concerns about below:

Yellow Perch: The yellow perch is a short lived species that has highly cyclical recruitment into a system and spring water temperatures and habitat are critical factors that can lead to complete loss of year classes of these species. Also if there are high numbers of predators and or competitors in the system then the yellow perch will be negatively impacted. The high numbers of white bass and crappies in these systems as well as the high number of predator fish is probably leading to the low numbers of perch you observed this year. The yellow perch however, does have the ability to rebound very strongly when conditions are favorable and so I would expect to see in a few years higher numbers of yellow perch return naturally.

Crappies: Again as with yellow perch these fish can be very cyclical in their reproductive success and it is common that when yellow perch populations are low then the crappie population is better and the reverse when crappie numbers are low that yellow perch numbers are high.

Musky: It is good to hear that anglers are catching the musky in these waters. Stocking of Muskellunge into these waters is still occurring with the cooperation of private clubs providing the fish. We did some late fall sturgeon netting on Petenwell and caught a few larger nice sized musky; they were all very healthy looking with good girth. The 45 inch size limit will allow for the potential in these systems to produce some trophy size musky over 50 inches in the near future.

White Bass: Looking through the files from the last survey on Castle Rock in 2006 indicated as you had suggested that there was a very strong year class of white bass in the system hatched in 2004. Although you mentioned catching some smaller ones the larger year class from 2004 should have been 8 inches and larger this past summer. So there is the possibility that there was another large year class from 2006 or 2007 coming into the system also. The white bass at smaller sizes (under 5 inches) make excellent forage for the larger predators in the system such as the walleye, northern pike and muskellunge. White bass are similar to yellow perch and crappies in their boom and bust reproductive success so it likely that you will see a cycle with the white bass also and there current high numbers will likely drop over time and rebound again at a later date.

Walleye: From the last surveys on both Petenwell and Castle Rock the numbers of walleye in the systems are very healthy. I had hoped to include some graphical data for you on the numbers and length of walleye from the previous surveys however; the database where I obtain this data is down until next week getting some technical work done so I will forward you this information next week I can access the information. As you mentioned the catch rates of the walleye in Castle Rock had appeared to be reduced over the past couple of years. This could be a combination of factors one of which is the number of forage fish available for them in the system. If there are still very high numbers of smaller young white bass in the lake then the walleye have plenty of food and are less likely to want to take your bait. According to our current lake survey schedule we are due to survey the Castle Rock Fishery in 2009 so will be able to observe if the numbers of walleye have declined or if it is just a matter of having a lot of available food.

Sturgeon: I know you did not mention sturgeon; however, I wanted to let you know that we had set three gill nets into Petenwell Lake in the fall this year for three fishing days and caught a total of 52 sturgeon ranging in size from 33 to 42.5 inches. Although we have not directly stocked sturgeon into Petenwell we have stocked in waters further up river and believe that these fish have passed through the dams. We are hoping to look more into the population in Petenwell and also determine if they have passed through into Castle Rock. If you happen to catch a sturgeon in Castle Rock I would really appreciate you letting me know.

I hope that the information I have given you above has answered some of the questions and concerns you have over these fisheries. I look forward to from hearing from you again and how fishing is going. I will forward on the information about the walleye numbers and size from our last surveys next week when I can obtain the data out of the database.

Justine

Summary of Castle Rock Lake walleye fyke netting catch from spring 2007

Seven fyke nets were set for seven days on Castle Rock flowage from March 30 to April 5, 2007. The following is a summary of the walleye catch.

A total of 339 walleye were captured (not including the recaptured walleye =6) ranging in size from 7inches to 30.4 inches (see attached figure). Male walleye average length was 13.5 inches and females were 19.2 inches. The catch per effort of 8.1 walleye per net night is one of the best captures rates recorded when compared to previous netting surveys on the lake.

The percent of walleye captured over 20 inches (8%) had increased significantly from the previous survey in 2003 (0.8%). This included 4 fish over 28 inches (or 1.2% of the catch), in the 2003 survey no fish over 28 inches were captured. The number of fish under the minimum size limit of 15 inches was 61% and the number of fish captured in the no harvest slot limit of 20 to 28 inches was 6.8%. The number of fish ranging in size from 15 to 20 inches was 31%.

Justine Hasz
Fisheries Biologist
December 2008