Why do female pike grow bigger than males?

[greeny1321]

I just got asked this question at work, I assume it is just so they can produce more baby pike but in truth I dont really know?!?!

Any of you guys know anything about the reason why?

Regards, Damien.

 

[MarkTheSpark]

I did a feature years ago with a fisheries scientist who'd hatched a load of pike and watched them, in tanks, as they grew on. Straight away, some pike seemed to get a growth spurt and, while the others scoffed daphnia and the like, the bigger fry eventually became cannibalistic.

This happened especially in high stocking (of pike) densities. I don't think the scientist ever sexed the resultant giant baby pike, but I've often wondered if those were the females.

Sexual dimorphism is quite common in fish, some anglerfish males being likem larvae...

 

[woody]

It is common belief that males rarely achieve weights over 7lbs (hence, perhaps, the term 'jacks') or so and that if you catch a double figure pike she's almost certainly a female.

 

[sagalout]

It's probably because once they have snared a male they sit on their 4rse and eat cake all day :wh

 

[greeny1321]

The reading up I've already done leads me to believe that a male pike will very rarely if ever reach 11lbs and also that pike only grow for the first 12-15 years of life after which they just stay pretty much the same size and weight (other than spawning time of course) for the rest of thier days. It's fascinating stuff but nobody seems to know the reason for females growing larger.

I also read an article about some research done in sweeden that showed that only 1 female of every 200 or so would ever grow over 11lbs - makes me wonder how many "jacks" are actually jills

This time of year its easy to tell of course, for example a few weeks ago I caught a 6lb pike that was roughly 3 feet long, the following week I caught a 7lb pike that was just over 2 feet long - I wonder which was male and which was female

Is there a reliable way to sex them at any other time of year?

 

[Jeff Woodhouse]

Is there a reliable way to sex them at any other time of year?

It depends on if their mouth is still moving when you've landed her.

Or - hold a mirror to her face and move it around, see if her eyes follow it.


Ohhhh!

---------- Post added at 20:51 ---------- Previous post was at 20:50 ----------

makes me wonder how many "jacks" are actually jills

Those could be Thailand Jacks, they have a lot over there!

 

[waggy]

Sexual dimorphism is very common in fish because the females have to lay/ disperse so many eggs in those species whose eggs are almost all eaten before hatching- think millions in some species.
Males on the other hand only have to produce sperm which are thousands of times smaller than eggs, so although their bodies have to make many times more sperm, the proportion of sperm mass to adult male body weight is many times smaller than the mass of eggs per body wt that the female has to manufacture.
Put more simply: large female body produces fewer eggs than small male body produces sperm per kilo of fish weight. So a larger female is evolved to produce more eggs .

 

[greeny1321]

Sexual dimorphism is very common in fish because the females have to lay/ disperse so many eggs in those species whose eggs are almost all eaten before hatching- think millions in some species.
Males on the other hand only have to produce sperm which are thousands of times smaller than eggs, so although their bodies have to make many times more sperm, the proportion of sperm mass to adult male body weight is many times smaller than the mass of eggs per body wt that the female has to manufacture.
Put more simply: large female body produces fewer eggs than small male body produces sperm per kilo of fish weight. So a larger female is evolved to produce more eggs .

If you dont mind my asking Waggy where did you get this info? What you say is pretty much what I believe to be the reason but that is based on nothing but my own logic

---------- Post added at 21:13 ---------- Previous post was at 21:10 ----------

It depends on if their mouth is still moving when you've landed her.

Or - hold a mirror to her face and move it around, see if her eyes follow it.


Ohhhh!

:j:j I knew somebody would do it Jeff, I should have known who it would be

 

[Ray Daywalker Clarke]

I dont know a species of fish were the male grows bigger than the female

 

[Alan Tyler]

Salmon?
You'd expect the males to be bigger if they're territorial, so anything with a redd or a nest might have bigger males. Anyone know? Sticklebacks, lumpsuckers, pipefish, cichlids, seahorses?

Coelacanth, where art thou?

Otherwise, most fish play the numbers game, casting their eggs out to whatever fate awaits them and bearing the loss - that means LOTS of eggs, which means MUCH bigger females.

Another tactic, used by quite a few sharks, is live-bearing; this means big young, but fewer of them, so big females may help here...

The ultimate in sexual dimorphism is (or was, when I was a student) one of the deep-sea angler-fish. In such a food-poor environment, it is a disadvantage to waste a feeding opportunity on a mere male, when it could be put to better use making eggs - so the males have to find a female early in their lives (HOW, fergawdssake? I must have dozed off in that part of the lecture...) and hang onto her so tightly he becomes a parasite - and a dwarf, a mere sperm-factory drawing just enough from his mates blood-stream to keep body and spermatogenesis together.

Certain women would draw parallels, so careful who reads this...

---------- Post added at 23:25 ---------- Previous post was at 23:18 ----------

Salmon? You'd expect the males to be bigger if they're teritorial, so anything with a redd or a nest might have bigger males. Anyone know? Sticklebacks, lumpsuckers, pipefish, cichlids, seahorses? Coelacanth, where art thou?
Otherwise, most fish play the numbers game, casting their eggs out to whatever fate awaits them and bearing the loss - that means LOTS of eggs, which means MUCH bigger females.
Another tactic, used by quite a few sharks, is live-bearing; this means big young, but fewer of them, so big females may help here...
The ultimate insexual dimorphism is (or was, when I was a student) one of the deep-sea angler-fish. In such a food-poor environment, it is a disadvantage to waste a feeding opportunity on a mere male, when it could be put to better use making eggs - so the males have to find a female early in their lives (HOW, fergawdssake? I must havedozed off in that part of the lecture...) and hang onto her so tightly he becomes a parasite - and a dwarf, a mere sperm-factory drawing just enough from his mate's blood-stream to keep body and spermatogenesis together.

Certain women would draw parallels, so careful who reads this...

---------- Post added at 23:27 ---------- Previous post was at 23:25 ----------

Oops! Only wanted to put an apostrophe in "mate's" and it double-posted. Sorry!

 

[Ray Daywalker Clarke]

Well with all the **** thats flows in or rivers its no wonder, they change sex at times, bit like the lady boys who play football......

 

[Alan Tyler]

Ah, that's a whole nuther matter; they probably only need the tiniest of endocrine nudges to do that.
After all, some wrasses (cuckoo wrasse for sure, not sure which others) change sex as they get bigger and older. Can't for the life of me remember which way, though.
Can't comment on football, either; too tribal. 'Minds me of barbel fishing. (Inscrutible 1,000yd stare emoticon...)

 

[the indifferent crucian]

I think Alan may have it.....with predation so high amongst eggs and fry, the successful gene pool is going to be one that has the numbers to stand such losses. Big egg numbers must mean big females.

Even live-bearing fish have the female larger than the male...numbers again I'd guess. In fact my experience of live-bearers is that they are particularly cannibalistic and most breeders use a trap to keep them from eating their own new-born offspring.



Birds of prey have larger females too....more eggs again perhaps?

 

[Eric Edwards]

Having different sized sexes means the males and females don't compete with one another for preyfish as much. Males tend to eat smaller prey while females eat larger prey.
Also, when times are hard, the females can survive by eating the males. The species will thus survive so long as all the males don't succumb.
Also, as previously stated, larger females means more eggs. Predation on eggs and pike fry is massive, with less than 1% survival rate. The way pike combat this is to produce very many eggs so that a decent number survive.

 

[waggy]

If you dont mind my asking Waggy where did you get this info? What you say is pretty much what I believe to be the reason but that is based on nothing but my own logic

---------- Post added at 21:13 ---------- Previous post was at 21:10 ----------

Like Alan Tyler I read Marine Science and Zoology and it involved a lot of Fisheries stuff.
As for why some species do and some don't have such marked dimorphism: I think it depends on the amount of parental care given to eggs and hatched young. More care and better survival of individual offspring means fewer eggs need to be laid to get those critical 2 nearer to adulthood and breeding themselves. If you're going to chuck millions of eggs freely into a hungry environment however, just to get 2 to breeding-age survival, you need a hell of an egg-laying machine to do it.
It pays to remember that the female vertebrate contribution to reproduction
is the cell membrane and all the organelles contained therein. All a male contributes is a small but vital part of the nucleic genetic material. In the absence of a male, from fish up the evolved chain to reptiles, females can sometimes produce 'self-fertilising' eggs.
Sperm added = more genetic diversity, that's all.

 

[Jeff Woodhouse]

Predation on eggs and pike fry is massive, with less than 1% survival rate. The way pike combat this is to produce very many eggs so that a decent number survive.

And is it not also the case that they, along with perch, breed earlier so that the tiny recruits can also raid the eggs of other fish breeding later?

Here's another question on a bit of a tangent - what percentage are male and female at birth?

In most mammals the split is around 50/50, this is an example I sometime use on vegie warriors about drinking milk, you need a cow to have had a calf to be able to milk it and there's a 50% chance that calf will be a bullock that you can't milk, so you raise it a while, kill it and eat it. Nothing to do with fish, but a point to bear in mind later.

With fish, is there a greater percentage of males if only because they become the prey at times for bigger and older females? Also, do fish actually eat the eggs that they themselves have laid/fertilised? Just harking on to the survival of the fittest, if each fish believes that they are the fittest then why eat their own eggs, why not eat other fish's eggs that way giving their own a more fighting chance of survival?





There, a sensible post for a change.

 

[waggy]

Ah, that's a whole nuther matter; they probably only need the tiniest of endocrine nudges to do that.
After all, some wrasses (cuckoo wrasse for sure, not sure which others) change sex as they get bigger and older. Can't for the life of me remember which way, though.
Can't comment on football, either; too tribal. 'Minds me of barbel fishing. (Inscrutible 1,000yd stare emoticon...)

Senior female becomes male if anything happens to the male.

---------- Post added at 06:40 ---------- Previous post was at 06:24 ----------

And is it not also the case that they, along with perch, breed earlier so that the tiny recruits can also raid the eggs of other fish breeding later?

Here's another question on a bit of a tangent - what percentage are male and female at birth?

In most mammals the split is around 50/50, this is an example I sometime use on vegie warriors about drinking milk, you need a cow to have had a calf to be able to milk it and there's a 50% chance that calf will be a bullock that you can't milk, so you raise it a while, kill it and eat it. Nothing to do with fish, but a point to bear in mind later.

With fish, is there a greater percentage of males if only because they become the prey at times for bigger and older females? Also, do fish actually eat the eggs that they themselves have laid/fertilised? Just harking on to the survival of the fittest, if each fish believes that they are the fittest then why eat their own eggs, why not eat other fish's eggs that way giving their own a more fighting chance of survival?





There, a sensible post for a change.

Not quite.
Most of the fish I know don't have a belief system or pump Iron for that matter.
Also fish don't have an XY chromosome; they have an XXY. This makes sexual fate more labile. Eels for instance have a sex foisted on them by their environment when they're about 13" (33 cm) long. Some of the factors involved aren't too clear but it's known that stress through overcrowding causes early silvering at that size and the result is migration of small males en masse from that particular water at the next possible opportunity.

Where elver recruitment has been poor, usually a long way upstream or where a trickle outflow is not sufficient stimulus to recruit but a few elvers, these few carry on growing to enormous sized females.
So, if you want to catch big eels (can we now?) look at a map, find a likely water and check out it's outflow for constancy, volume and elver accessibility. Find one that's difficult to recruit and chuck a dead bait in.

 

[mol]

I was told that pike spawn eye to eye whilst swimming forward. The male needs to be shorter, smaller, to ensure that his milt will mix with her eggs.

As a quick aside, are male zander smaller than female zander? You'd kinda figure that as the male guards the nest a bigger fish might be a little more imposing and do a better job of defending a nest

 

[Sharky]

The only theory put forward that I have any credence in is that when a male and female are 'getting it on' and are side by side his 'bits' are beside her 'bits' allowing fertilization almost instantly on the release of the eggs. Some male pike may well in fact grow quite large but do not fertilize the females eggs through not being 'in the zone' so-to-speak, He is therefore unable to pass on his genes as easily as a smaller male so the more successful the smaller males are the more fish are likely to be smaller males.

 

[waggy]

I was told that pike spawn eye to eye whilst swimming forward. The male needs to be shorter, smaller, to ensure that his milt will mix with her eggs.

As a quick aside, are male zander smaller than female zander? You'd kinda figure that as the male guards the nest a bigger fish might be a little more imposing and do a better job of defending a nest

Sorry Mol but I don't think pike are too worried about where their eyes are when they're spawning.