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[Rodney]

I would have to disagree, even if there is no evedence.  Look at the Thompson.  I have fished it and big fish produce big fish.  Been there since the eighties.  Big wilds produce big wilds.  Jacks cannot be a good thing gauranteed.  Something went wrong otherwise they would be coming back a year later.  I bet they dont use them as brood stock.  Even when they are tubing Steel on the vedder, they take all of the fish they can get for brood just to be sure they get the numbers they need.  Can you say that they they should take all of the first wild fish they get?  They do because they have to.  If they knew they could wait and get all 12 to 18 lb fish and meet the quota they would.  But they do the best they can, and do a great job, cause who knows?  So they take what they can get and that is it.
That is why some of the untouched wild rivers have the monster Steel that people travel the world to catch here in BC.  Make no mistake that big broods poduce big fish on the returns.  just look at the egg size and numbers when you clean a big doe.

That's not what I was trying to suggest in the last post. Big fish definitely will produce offsprings that have a tendency to be big, there's no doubt about that. I'm suggesting that it's unlikely jacks have a tendency to produce offsprings which will become jacks. The occurrence of jacks cannot be simply explained as big produces big, small produces small. If it is as straight forward as that, then we'd see female offsprings of jacks returning as small 2 year olds as well. Also, I don't think the size of eggs and fecundity have any direct relationship to the size of the matured offsprings.

Also, when you are suggesting big fish in the Thompson River, are you referring to steelhead or salmon? If steelhead, then it does not really apply as the occurrence of jacks is very minimal for steelhead in general, for all populations. Chinook and coho salmon runs of the Thompson River also have a pretty visible abundance of jacks, just look at the summer chinook jack fishery as an example. The percentage of jacks in those runs is most likely similar to what you would see in other hatchery supplemented systems.

It'd be interesting to see and understand the genetic mechanism of this natural occurrence. Is it as simple as a dominant-recessive relationship? Maybe there already are studies that touch on the subject.

BTW, in several salmonid species, males do have a tendency to be significantly smaller than females, and males also have a tendency to stay in or close to their natal streams. Brown/sea trout is a good example of this.

[BCfisherman97]

Question, why do only certain species "jack" while others don't?

[Sterling C]

Coho grow an average of a pound a week in their last few months before spawning. They are a super fast growing fish (but it is based on food), and all coho returning in a given year are the same age (with exception to jacks). If I remember correctly, all coho are 28 months old (or somewhere around that) from egg to adult spawning stage (Over winter in FW after hatching and spend a year and a half in SW).

Adult fish and juvenile fish don't eat the same thing, so I highly doubt we would see a diminished run due to this.
The part about smaller sizes is possible, but as Rodney stated, there is always variation in ocean conditions.

If most of the coho put on all of their weight in their last few months and as they are returning to the rivers, this doesn't even necessarily mean there is a food shortage up where they develop over the main course of their life.

A few points.

I'm not sure I understand how you can have a 28 month cradle to grave life cycle. I would have thought it should go in yearly increments or else the run times would vary from cycle to cycle.

Furthermore, I agree that juvenile and mature adults would have different feed sources. I would argue that if ocean productivity is trending downwards then it would be across the board, not just the bait that adult coho feed on. My point was that after 2 straight years of banner runs of average to slightly above average sized coho, this years large yet smaller run of coho could be a sign of things to come.

[Rodney]

28 months sounds about right, maybe a bit longer. I think it's 28 months from the time of hatch until adult spawning, not from the time when eggs are fertilized.

Question, why do only certain species "jack" while others don't?

My guess (only a guess ) is differences in the life history of the juvenile stage (the amount of time spent in freshwater before migrating into the ocean).

[Dryfly22]

why are you blocking my posts?

[Rodney]

why are you blocking my posts?

Dryfly22, I'm not blocking your posts (we don't even have the ability to do that unless the account is banned). Be aware that the thread is gaining quite a few posts in a short time so it's possible that someone else has replied to the thread while you were constructing your post. If that's the case, the forum will tell you that when you hit the post button, just to make sure you may want to modify your post before posting. If you didn't hit the post button again when that reminder shows up, then it doesn't get posted up. Hit the back button on your browser a few times, it's possible that the post you constructed is still available for reposting.

[Brian the fisherman]

the avg size of the fish i kept was between 7 and 13 lbs.
retained 18 fish this season from the vedder and the smallest one was 7 lbs.. largest was just under 14. and there were 4 more fish in the 10-12 lb range.
you guys must have taken all the small ones and left me the biggies.
Thank you fellas.
I did fish from a boat chucking spinners though so maybe I was pickin off the big ones before you had a chance  
The 4 fish I retained from the harrison were runts though. 5-8 lb range. but very tasty

[adriaticum]

Ah yes, the purpose of jacks.

They are mature fish and have milt and they die after they spawn just like all other pacific salmon.
Nature has it that that when male and female spawn not all the eggs are fertilized. Some go to waste.
Eggs can only live for a few seconds in the water and become fetilized. After about 5 seconds they are duds.
The purpose of jacks is to fertilize eggs that would not otherwise be fertilized.
Becase jacks are small and look like females, big males won't fight and possibly injure them.
So when the female releases eggs the big males will fertilize a majority of the eggs and jacks will fertilize a bit more.
That way a higher percentage of eggs are fertilized.
So they do get their "squirt" in without a problem
This is just nature's way of increasing the reproduction of these fish.

This all comes from the bible for those who study pacific salmon.

[Every Day]

I'm not sure I understand how you can have a 28 month cradle to grave life cycle. I would have thought it should go in yearly increments or else the run times would vary from cycle to cycle.

The 28 month cycle is from hatch to spawning like Rodney said. Coho spend the first few months (6 or so months) in the river and/or off channel habitat, sloughs, swamps, lakes, etc and then head to the ocean. Adult coho only spend 24 months or less in salt water with no variation (ever discovered any ways). Jacks only spend 4-6 months in salt water.

It'd be interesting to see and understand the genetic mechanism of this natural occurrence. Is it as simple as a dominant-recessive relationship? Maybe there already are studies that touch on the subject.

Rodney, from what I learned at VIU the mechanism for jacking is somewhat genetics but also food availability, etc. As I said before, jacks are the FASTEST growing fish of that year or age class. This means that they grew faster and more efficiently than other fish in their year class, and were at a larger size heading to freshwater. This is why hatchery raised fish tend to have a higher % of jacking than wilds, due to their larger size going out to the salt. That is why hatcheries use jacks in spawning. Not only because it is a natural occurrence, but also because these were the fastest growing fish in their age class (also allows for genetic variation since they are a different age class/year than returning adults - nature's backup plan).

It would be interesting to hear from anyone that really knows if the oportunistic jack spawners(as they must be) create more runts/jacks in the following cycle of spawning fish.  When you clean a jack the milt looks mature so I guess the question is does it create more fish likely to come back a year early and mess up the future stocks. 

In short, no they do not create more jacks. The fastest growing individuals of that jacks offspring may jack, but its (the jacks) offspring would have the same jacking ratio as an adult + adult spawning pair.

All of these males are coming back a year early but they are sexually mature.  Small fish, no such thing as a female jack in all my years fishing.  My thinking with the jacks is that they beak in on the big mature bucks and Does when they are spawning and do there thing as well. 

Correct, ALL jacks are males. Egg fecundity is based purely on size, therefore it is not beneficial for a female fish to come back a year early as a smaller fish. Males however can produce the same amount of milt if they are small or large. That is why males are the only jacking fish in a population.

You are correct in your second statement as well. Jacks do indeed sit behind spawning pairs of fish and rush in when the female lays eggs, fertilizes what he can and gets out of there fast. The big males don't like it and you'll see big males chasing around small fish all the time.

Eggs can only live for a few seconds in the water and become fetilized. After about 5 seconds they are duds.

One last point I thought I'd chip in on... definitely not only 5 seconds. Average is about 40 seconds before the egg swells too much from water and the micropyle gets blocked (meaning they can no longer be fertilized).

The purpose of jacks is to fertilize eggs that would not otherwise be fertilized.

Ok maybe one more last point.
Jacks fertilize a lot of eggs that would have otherwise been fertilized by other males.
They use the "sneak" method and wait till a female releases her eggs, rush in, fertilize and get out.
It's a way of spreading around genetics, as jacks will also move from female to female and not stick with one mate like larger males will.
Should also mention, a large female fish will have sometimes 3 or 4 jacks sneaking in while spawning, therefore there is a lot of genetic diversity.

Cheers,
Dan

[chris gadsden]

Good info Dan.

[bederko]

Good stuff Dan I might just add a few points on steelhead. When the hatchery program started on the the Vedder steelhead, larger 3 year ocean adults were selected as brood stock. The returns were divided  into 2 and 3 ocean adults not just 3 ocean fish. Fish size is controlled not just genetically but mostly environmentally. For example a half pound mature pennask rainbow trout may have offspring that are 10 pounds when released into a more productive lake. Being cold blooded fish don't have a predetermined size like a mammal does. That is why all sizes of the population of steelhead are used as brood.
Steelhead jacks {one year ocean growth} are really not needed as a survival mechanism although they apparently do exist. The so called resident rainbow within the system provide the sperm for any forgotten females.

[Every Day]

Steelhead jacks {one year ocean growth} are really not needed as a survival mechanism although they apparently do exist.

They definitely do exist.
The one river I fish out here on the island has quite a few (not sure if this is due to a once depleted and now rebuilding run?)

This little guy had sea lice on him (not on the picture side). No doubt in my mind he was a little steely jack.
 


Only place I have ever caught these "half pounders" is out on the island though, never seen one on the mainland (but maybe that is because I am catching these near to the salt and they have sea lice, where a fish this size in the river would be instantly called a rainbow). When I showed some pics to my fisheries prof, he said they may not even be full out jack steelhead. They may just be the juvenile smolts that go out to the ocean at 1 or 2 weeks at a time, feed on needlefish, etc and then come back without doing the long journeys.

[bederko]

I would think that fish is more likely a smolt feeding in the estuary  (richer food source) before going totally to the ocean. The jack steelhead that I have heard about in the Vedder caught in the 60's were about 18 inches (about right for 1 yr. ocean). However without scale readings they could have been small 2 ocean or even "resident rainbow". The lower and mid river were still excellent habitat at that time with lots of perminent logjams etc. I do believe there are jack steelhead it's just that I have never verified it.
My point was that the "resident rainbow" in the system will spawn and do spawn with adult steelhead if needed.

[bkk]

Wow! Lot's of info on Jacks. Some of it is even correct Lot's of misconceptions and half truths. Some basic facts about Jacks. All of the salmon except Pinks have a Jack component to some degree. Chum very few too chinook and coho which have more with some populations having lots (south Thompson chinook). Jacks were present long before hatcheries showed up so they are just not a component of hatchery production. Hatcheries can produce more jacks in proportion to the total adult returns due to a couple of factors, these being size of fish at release and sheer numbers released. Those are the main factors but there are other reasons as well. Jacks are used in broodstock programs in proportion to there presence in the return. If 5% of the returning fish are Jacks, then 5% of the spawning population should be Jacks. That is the DFO genetic policy that is used. Jacks are Mother Natures way of passing genetics between brood years. That is the reason to use Jacks, not that they grow faster but mature earlier. Coho are primarily 3 year old fish on the south coast and the juveniles spend about 12 - 13 months in freshwater before they smolt and go to the ocean. They also spend about 16 - 18 months in the ocean before returning to their natal streams between June and January depending on the stock. Jacks are fully viable and they do spawn. Very opportunistic spawners as I have observed this many, many times over the years. Big adult males will get too fighting and the Jack will just zip in and have a very short quicky and then the big boys see him and the chase is on. And yes they do catch them some times and the Jack ends up much worse for the ware and some times and even lethally crippled. Kind of like the little guy in high school who snagged the girl at the party when the big "studs' got to scrapping. Jacks do not produce any more Jacks than "normal fish". A good example was the Babine Lake sockeye channels back in the late 70's early 80's ( can't remember exactly as the mind is the 2nd thing that go's). For what ever reason the adult male sockeye return was a bust and the Jacks out numbered the males by a 5:1 ratio ( as I was told by a friend of mine who was working there at the time). Most females were serviced by Jacks. So 4 years later when those offspring returned the sex ratio was back to the normal amount.

 The other thing that has not been suggested as to why it appears that there are more Jacks this year could be as simple as that brood year just got better survival. Would not take much of a upward swing in survival per centages to make a significant increase in the amount of fish seen. Survivals can still be low but if they changed from 1% to 2% then you effectively doubled your population. If it went to 4% or higher everone would be ex-static. Hard to imangine what it would be like if we actually went back to the 80's when survivals were routinely between 10 and 15% .

[EZ_Rolling]

The good old days before FF