Walleye Gender Criterior.

[Walleye Express]

Hey, Everyone.
Tried to post this twice on the Lake Erie Answer board, but it kept sending me into the Neutral Zone. You know that place where Romulins and Clingons are not allowed to kill you. Finally e-mail Fred Snyder personally to come here and answer the question when and if he could. I'd also like to here from any or all of the other knowledgeable egg heads on this board to debate or add to this subject as well.

[b] Hi, Fred.
Capt: Dan Manyen, Walleye Express Charters here. I was really sorry I forgot about your on-line chat on Walleye Central the other night. I had some real neat questions to ask you personally. It's always that 1 hour difference that gets me doing something else and by the time I remember, It's over. Anyway, heres one of the questions I was going to ask.

I know that temperature during the egg development of a lot of different species, not just and including fish, can determine what gender that particular specie will be when born. You can even sterilize or change the life cycles and inherent habits of some species, like the triploid salmon experiments by Howard Tanner of the late 70's. And if this is a vialble theory for walleyes, how is the Natural reporduction of Lake Erie walleyes effected by it from one year to the next?

And on that note. Being most of Michigan's Saginaw Bay walleye recruitment comes from rearing ponds, could incubation of the eggs at certain temperatures determine how many males versus females could/would be born? And if so, is one gender hardier in their given environments (on the average) than the other in most instances. And if so, would it be wise, or even helpful (for us in Michigan) to add more of one gender than the other to the gene pool to reinforce more natural reporoduction or simply aide in overall survival?

Now, I'll bet your glad I missed the chat huh Fred? Thanks in advance Fred, Capt: Dan.

[pb]

Hey Dan, Is that really only one question.....Did you teach Biochemisrty? Thats a heck of a question!! Take care

[Terroreyes]

I'd like to hear the answer about walleye. I was just discussing something similar, but about bass. I'm a saltwater enthusiast and have tried to breed some fish here and there down the line. I was unsucessful, but I did learn from sucessful breeders that many fish are asexual as juveniles and depending on the sex of the mate it is kept with, will determine the ultimate sex of the juvenile. Common practice is to put a known adult male in a tank with an asexual juvenile of the same species, and the juvenile will develop into a female, or vice-versa with the sexes. I don't know how it would apply to even saltwater fish out in open water, in large groups, or without being purposely paired up.
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[Walleye Express]

>Hey Dan, Is that really only one question.....Did you teach
>Biochemisrty? Thats a heck of a question!! Take care


[b] pb.

I wish I would have been that smart in my life. No, I was one of those c+ to c- kids, who always had (Can do better) and (Does not work up to his potential) attached to his report card. I always sat next to the window at school and stared out most of the day, wondering if the weather was going to be good for the weekend, so the hunting or fishing trip My Dad, Brother and myself always had planned was not spoiled.

Then in the winter, I'd be going over in my head all day just where I placed all 125 muskrat traps I ran after school. The only book I ever read from cover to cover was "April Morning", a book about the Revolutionary War. I did absorb every Field & Stream, Outdoor Life and Sports Afield magazine that Dad subscribed to though. I heard him yell plenty of times after work from the (bathroom library), "Dan!!" "Where are my magazines?" I just could not learn enough about what I truly loved doing the best back then. Would I change or apply myself more in school if I had it to do over? Well, I'd bring the grades up to maybe a B- anyway.:D

[mrbreeze]

Hi Capt:

I'd be interested in hearing an answer on this as well. But - I'll put a little of my background in biology to work here. Not saying it is right, but I'm betting that it is.

There are very, very few instances that I can think of where the gender of offspring is actually determined by incubation temperature. In fact, I can only think of one example that has been empiracly proven in laboratory studies, and that is in turtles. There is some speculation that salmon are also affected - particularly in the pacific northwest because there appears to be a growing displacement of male salmon there (a growing femininity of the species). However, most scientists believe that this is due to herbicides that tend to have components that mimic female hormones and that the change in gender actually occurs after the salmon have hatched.

Walleye, and the vast majority of fishes, are heterosexual reproducers. Not unlike humans. From a genetic perspective, a female fish hold the XX chromosome, while a male holds the XY chromosome (chromo 23 on the DNA sequence chain I think - throw that in your hat for useless trivia at your next party or when the fishing gets slow). Ultimately, it is the male that is responsible for determining the sex, as the female always has an "X", and the male can supply either an "X" or a "Y" to the equation.

In almost all cases of heterosexual reproduction, the sex of the offspring is determined at the instant that the male sperm cell enters the egg. Some commentators might argue that (and we see it on the news all of the time), but from a scientific perspective it is indeed factual. Beginning with second number "2", incubation begins and the sex has already been determined.

It is not unlike the 9 month "inubation" of the human embryo (more correctly calle the "zygote" in the earliest stages). Sex has been determined the instant before "incubation" begins.

Of course - you can throw all of this out the window if you bring genetic manipulation into play. As you might be aware, there are now medical procedures that can actually "sort" sperm cells to identify male and female producting cells in humans. This is most common in the far east, where it is often preferrable to have male children. I don't know why this or other manipulations cannot occur in fishes, and they likely can and are being used in the lab.

[Walleye Express]

[b]Breeze.
It was Dr. Howard Tanner (the man who introduced salmon to the Great Lakes in the late 60's) who discovered that in the course of incubation of the Chinnok Salmon, that by raising the water temp for a certain period of time, it changed the fishes Chromozone makeup without killing it and rendered it sterile. These Triploid salmon (as they were called because of the extra chromonzone) were planted but never showed up in anybodies catch. His hopes and assumptions were that this salmon would stay out in the lake and continue to feed, would ignore it's inherent life cycle impusles to return to spawn in the usual 3 to 5 years and grow to gigantic sizes. Just the chance to catch a salmon that was over 5 years old, would revive the fishery that was going through a very bad period in the late 70's early 80's.

I've also heard from the guy I buy Pheasants from, that incubation temperature determines the hen to rooster ratio. And Aligators are also determined in this fasion. I had the pleasure of actually taking Mr. Tanner and his son on a charter on the Bay about 5 years ago. We talked briefly about the triploid project. He thought that the altered planted salmon may have indeed succombed to it's genetic alterations at some point after it was planted. But they were as healthy as any other smolt they had ever planted prior to this experiment. I hope Fred takes this one as well.

[mrbreeze]

Capt.

I actually had Tanner for a professor at MSU for a class or two. The triploid salmon were indeed created through a "heat shock" system. Triploids are still being "created" today, and can be found mainly in fenced-in enclosures in the North Atlantic. These are raised for commercial purposes. It's worth noting that there is some concern that under some circumstances, these triploid fish can indeed reproduce. Hence a major argument on the safety of genetically engineered fish and what MIGHT happen if these were allowed to breed with a native species.

As far as determining the hen/rooster ratio based upon incubation temperature, I think that your pheasant guy may perceive a difference in this ratio based on temperature, but I doubt that is occuring.

I have never heard that about alligators, so that is news to me. I do know that in addition to turtles, that some salamanders are also affected by incubation temperature gender-wise. I am not familiar with this same effect on any warm-blooded species.

[ginamaria]

I think I heard this is true about armadillos. no really!