Fish egg viability?

While reading the comments on the giant (38#) Brown Trout caught in Arkansas,. To counter those who were saying "what a shame to kill it", someone  wrote "funny thing about biology, in all creatures, the ability to reproduce effectively diminishes with age, bet that fish is near 18-19 years old (think 65-70 years old in human terms) hence its egg viability may approach 15%.....whereas a 5lb female egg viability is near 90% and produces more and healthier ".
On this site we talk about leaving the big ones because they produce the most eggs. We don't talk about viability. What do our experts say? Does this apply to some fish not others?

I don't believe that to the case in fish.  Their biology is just too different in many ways.  For example, fish have indeterminate growth (i.e. they never stop growing) where as I bet your grandmother is shorter now than she was when she was 25.   

Bigger fish = more eggs and bigger eggs = more fecundity and more viability

In the end a 38# pound fish will produce many more viable offspring than eight 5# fish.  It  might actually take as many as ten to fifteen 5# fish to produce as many viable offspring.

Brian

The Yahoo article doesn't mention the sex of that monster.  Rather than thinking about it's ability to reproduce, I'd think of it's ability to deplete juvenile and smaller fish of all species.

Most egg-laying fish will produce more eggs as they grow larger, but the eggs will usually be the same size.  For example, the eggs of a 2 pound largemouth bass will be the same size as those of a 10 pound bass.  But salmonids are an exception: not only will larger salmonids produce more eggs, but the eggs also increase in size.  Larger eggs mean larger alevins, and therefore larger fry when they emerge from the redds.  Being larger when you're born gives you advantages over the other, smaller fry.  In that respect, leaving the larger fish to spawn could result in larger fry that have a higher chance of survival to adulthood than smaller fry.

As for the guy saying that that large brown trout's eggs are less viable?  I haven't heard of such a thing in salmonids, though I have heard of what you could call "fish menopause" in livebearing fish like surfperch and guppies.  So I don't think it's out of the question that an old trout would experience a similar phenomenon.

I wouldn't have been disappointed in removing that fish's gene pool from the environment.  You gotta figure she (if it's a she) spawned many, many times over her lifetime already.  She probably has hundreds of progeny swimming around out there.  Personally, I would've had gripes with the fact that such a large, old fish that's gone through decades of survival meets her end with a bonk on the head by an angler.  Keeping large trout doesn't make sense to me since the smaller ones taste better anyway.  But, that's just me  .  The guy can do whatever he wants with his fish.