sexing catfish - distinguishing M vs F

wwswimming · Joined: 16 Aug 2007 Posts: 2

i have access to some healthy catfish for a reasonable price.

i researched a little and found articles saying it's not easy to tell
the difference, without dissecting them.

well, there must be indicators - size, age, color, whatever.

as far as what kind - the kind they sell in chinese butcher shops.

weight - about 2 1/2 pounds
length - almost 2 feet.

afraid to ask too many questions when busy man standing there with
sharp knife.

how do you tell the difference ?

Archived from group: alt>fishing

dc · Joined: 16 Aug 2007 Posts: 37

wwswimming@yahoo.com wrote in
@i39g2000cwa.googlegroups.com:

> as far as what kind - the kind they sell in chinese butcher shops.
....
> how do you tell the difference ?

That is not anywhere near enough information to go by. The catfish family
is huge. Some catfish are easily sexable, but most are difficult if not
completely impossible.

You can try searching for your fish here:
http://www.planetcatfish.com

There you will find info on sexing most of the more common species in their
"Cat-eLog".

wwswimming · Joined: 16 Aug 2007 Posts: 2

sounds like it's easiest to just buy 3-4 of them and hope that i get at
least one male and at least one female.

dc · Joined: 16 Aug 2007 Posts: 37

wwswimming@yahoo.com wrote in
@j33g2000cwa.googlegroups.com:

> sounds like it's easiest to just buy 3-4 of them and hope that i get at
> least one male and at least one female.

Good luck.

Keep in mind most catfish need more than just the presence of a male/female
pair to breed.

Mr. Gardener · Joined: 16 Aug 2007 Posts: 28

On 6 Mar 2006 20:56:37 -0800, wwswimming@yahoo.com wrote:

>
>sounds like it's easiest to just buy 3-4 of them and hope that i get at
>least one male and at least one female.

When buying a group in hopes of finding a pair, 6 is the magic number.
I'm no mathematician, but I read it in a book. With each increase in
the number of fish comes an increased chance of having a pair in the
mix. When you get to 6, the odds of a pair are very, very high, like
more than 96%. Or 98. I forget. But each fish added after 6, will only
increase your odds by a percentage of a percent. I'm sure somebody
else here can tell you the precise numbers.

-- Mister Gardener

Mr. Gardener · Joined: 16 Aug 2007 Posts: 28

On Tue, 7 Mar 2006 14:08:40 -0000, FishNoob
wrote:

>In article ,
>mrgardener@email.toast.net says...
>> When buying a group in hopes of finding a pair, 6 is the magic number.
>
>There isn't really a magic number; it's a sliding scale.
>
>> I'm no mathematician, but I read it in a book. With each increase in
>> the number of fish comes an increased chance of having a pair in the
>> mix.
>
>Yes, the chance of having at least one m and at least one f doubles.
>Stats lesson follows Wink

>
>> When you get to 6, the odds of a pair are very, very high, like
>> more than 96%. Or 98. I forget.
>
>96.875% Smile

>
>> But each fish added after 6, will only
>> increase your odds by a percentage of a percent.
>
>Well - almost. See that 3.125% chance of getting all fish of one
>gender above? That halves every time you add another fish. To get to
>a less than 1% chance of having all fish of one gender, you need 8
>fish - then the probability is 0.78125%
>
>> I'm sure somebody
>> else here can tell you the precise numbers.
>
>Heh... finally something I know about Wink

Anyone who isn't interested
>in how to work it out can stop reading here Smile

>
>
>Assuming that half of all fish are male and half of all fish are
>female, and assuming you were to choose fish randomly, the likelihood
>of having all the chosen fish be of the same gender is halved each
>time you add another fish. With one fish, obviously the likelihood is
>100%. With two fish, it's 50%, with three, 25%, and so on.
>
>The explanation for this is that each time you add a fish, the number
>of possible combinations of genders doubles, but the number of
>possible combinations in which all the fish are the same gender
>remains the same (there are only two genders).
>
>For example, with two fish, there are four possibilities:
>m/m
>f/f
>m/f
>f/m
>
>Each of those possibilities has the same probability - i.e. 1/4. Two
>of those possibilities give you a male and a female, thus the
>probability of getting one male and one female in any two fish
>selected at random is 1/2 (1/4 + 1/4).
>
>Adding a third fish doubles the number of possible combinations (to
> Cool

, but makes no difference to the number of combinations in which
>all fish are the same gender, so now the probability of that
>happening is 2/8.
>
>Add a fourth fish, you have 16 possible combinations - two of which
>are "all male" and "all female".
>
>Etc
>
>So the probability of getting all fish of one gender halves each time
>you add another fish (starting with one fish where the probability is
>1 - i.e. certainty of getting one gender).
>
>The probability of getting at least one m and at least one f then, is
>doubled each time you add a fish - because each time you don't get
>all fish of the same gender, you must have at least one of each
>gender.
>
>By the time you get to six fish, the probability of getting all one
>gender is at 3.125% - so the probability of getting at least one of
>each is 96.875%. To get to a less than 1% possibility of having all
>fish of one gender, you need eight fish, at which point the
>probability of them all being the same gender is 0.78125% (or 1 in
>128).

You hear that everybody? It's like Noob says.

-- Mister Gardener

FishNoob · Joined: 16 Aug 2007 Posts: 3

In article ,
mrgardener@email.toast.net says...
> When buying a group in hopes of finding a pair, 6 is the magic number.

There isn't really a magic number; it's a sliding scale.

> I'm no mathematician, but I read it in a book. With each increase in
> the number of fish comes an increased chance of having a pair in the
> mix.

Yes, the chance of having at least one m and at least one f doubles.
Stats lesson follows Wink

> When you get to 6, the odds of a pair are very, very high, like
> more than 96%. Or 98. I forget.

96.875% Smile

> But each fish added after 6, will only
> increase your odds by a percentage of a percent.

Well - almost. See that 3.125% chance of getting all fish of one
gender above? That halves every time you add another fish. To get to
a less than 1% chance of having all fish of one gender, you need 8
fish - then the probability is 0.78125%

> I'm sure somebody
> else here can tell you the precise numbers.

Heh... finally something I know about Wink

Anyone who isn't interested
in how to work it out can stop reading here Smile

Assuming that half of all fish are male and half of all fish are
female, and assuming you were to choose fish randomly, the likelihood
of having all the chosen fish be of the same gender is halved each
time you add another fish. With one fish, obviously the likelihood is
100%. With two fish, it's 50%, with three, 25%, and so on.

The explanation for this is that each time you add a fish, the number
of possible combinations of genders doubles, but the number of
possible combinations in which all the fish are the same gender
remains the same (there are only two genders).

For example, with two fish, there are four possibilities:
m/m
f/f
m/f
f/m

Each of those possibilities has the same probability - i.e. 1/4. Two
of those possibilities give you a male and a female, thus the
probability of getting one male and one female in any two fish
selected at random is 1/2 (1/4 + 1/4).

Adding a third fish doubles the number of possible combinations (to
Cool

, but makes no difference to the number of combinations in which
all fish are the same gender, so now the probability of that
happening is 2/8.

Add a fourth fish, you have 16 possible combinations - two of which
are "all male" and "all female".

Etc

So the probability of getting all fish of one gender halves each time
you add another fish (starting with one fish where the probability is
1 - i.e. certainty of getting one gender).

The probability of getting at least one m and at least one f then, is
doubled each time you add a fish - because each time you don't get
all fish of the same gender, you must have at least one of each
gender.

By the time you get to six fish, the probability of getting all one
gender is at 3.125% - so the probability of getting at least one of
each is 96.875%. To get to a less than 1% possibility of having all
fish of one gender, you need eight fish, at which point the
probability of them all being the same gender is 0.78125% (or 1 in
128).

--
FishNoob
(who should maybe be called FishNerd?)

FishNoob · Joined: 16 Aug 2007 Posts: 3

In article ,
mrgardener@email.toast.net says...
> You hear that everybody? It's like Noob says.

And don't you forget it! Wink

LOL

--
FishNoob

Catfish Crazy · Joined: 16 Aug 2007 Posts: 1

I have read about the swelling and seen it. But I cant be sure this is
a wise way to judge a purchase?

This site has some experts that can help based on what I have read.

http://catfish1.com/