L.O.W. Slot

[lichen fox]

Questions for any fish biologists out there....

In a given year class of walleyes on Lake of the Woods:

What percentage of male fish reach the protected, do-not-harvest slot? (I really doubt if any males ever grow out of the protected slot). And....What percetage of the female fish in that year class make it to the 19.5 inch slot and what percentage of those females ever grow out?? (over 28 inches).

[walleyenerd]

Hi Fox,

I'm trying to figure out exactly what it is you want to know. Regarding your reference to a "given year class", to answer your question you would have to tell me what the starting point is. DNR data on Lake of the Woods shows that between age-3 and age-9, 63% of the walleye in a year class survive to the next year. In other words, if I have 100 walleye in September, I will have 63 the following September.

Just to make it easy on myself, I will define the starting point in my example as age-3 walleye. In the fall, age-3 walleye are about 14 inches long. They would not reach the protected length of 19.5 inches until they are about six years old. If I start out with 10,000 age-3 walleye, there will be 2,500 left by the time they reach 19.5 inches. Walleye growth slows down quite a bit after they are 20 inches long, especially males. Since females are the only sex that could realistically grow out of the slot, I'll only refer to them for now.

A typical walleye that enters the protected slot at age-6 would not grow out of the slot until about age-16 to 20. Just for this example I will use age-18 as a typical 28 inch long walleye. At age-18, from the original 10,000 age-3 walleye, you will have...(drum roll)...10 left. It is a rare fish that gets to be, what I consider, of trophy size.

However, and this is why I wanted to know exactly what your post was getting at, there is value in having these large fish in the population, beyond anglers getting to catch and appreciate them. A recent study (on ocean fish with similar reproductive habits to walleye) was released that looked at the contribution spawning fish of various sizes made to a succeeding year class. What this study found was that large fish tended to have greater spawning success in years where weather conditions were not ideal, while smaller spawners were only successful when everything "clicked". What this suggests to me is that if you have a walleye population with more large individuals you can count on more consistent spawning success then a population without those large individuals.

There is plenty of evidence that shows what this study found is true for walleye. Some of the earliest evidence that a walleye population is being over fished is that you loose the large fish. A later warning is that you start to get into a severe "boom and bust" cycle. This type of cycle is typified by years of no or poor recruitment, and then a huge year class comes along. Not good for anglers. Not good for businesses. Not good for the fish.

I hope that helped.

[CatManLee]

Fox,

With your "EXTREME KNOWLEDGE" of Walleye, I would have thought you knew that!

Looking forward ice fishing, can't wait to sit in my shack and catch some fish.

[curt quesnell]

Since the male grows at slower rate it will take them longer

to get to that 19.5 home free size so more of them will

be harvested while females from the same year class will

hit the "safe zone" sooner to spawn through their most

productive years.

End result, more prime spawners surviving while the biggest harvest hit will be taken by the males.

Now that the deal is done it's time to let the situation

play out.

Good luck to all, especially my resort owner friends on Lake of the Woods. We do this for fun, they do it for

their lively hood so I can understand why they are at least

a bit anxious about the upcoming season. I hope in the

spring we can look back and say "that went pretty well".

First things first, let's get some ice!

[lichen fox]

Thanks nerd!!

The information you gave me was just what I was looking for....I wasn't trying to "get at" anything in particular. Your explanation at the end also helped...ie: when you loose the large fish...25-28 inches and a few "rare" fish over 28"...the lake is begining to be overharvested...then, if you get boom and bust hatches one good year out of 5 as an example the lake is in serious trouble....That's why the slot and limit reduction on lake of the woods was so important...the lake was in an extreme "boom" cycle....4 huge hatches in the last 6 years!!

Thanks again!