Growth rate of certain killies

[erikthur]

I have been hatching some eggs lately and noticed that the growth rate differs among these killies.
Situation after close to 3 weeks old:

Fastest growing -> slowest growing (number of fry in parenthesis):
Simp whitei (ab 70)
Notho foerschi (ab 20)
Fp walkeri (ab 20)
Fp gardneri (ab 20)
Simp suzarti (2)
Notho rachovii (2)

What suprises me most is the difference between foerschi and rachovii.
Can I assume I end up with female rachoviis (again) and predominantly male foerschis (again) or is this obvious difference in growth rate expected?

[RonWill]

...or is this obvious difference in growth rate expected?

Erik, sorry but I don't quite understand the numbers you quoted, eg. Simp suzati (2)... what does this mean? Is that 2 slow growing fry or 2 that are much larger than the rest?

I've been raising a bunch of Simp sp. aff. stellatus 'Urucuia' and yes, there are very obvious fry sizes, that I suspect the larger will predate on their much smaller siblings. From the same brood/hatch/wetting, my largest is 2cm and a few smaller at 1cm (maybe 8mm or so). There were much smaller ones but I think these became lunch

If you have sufficient grow-out containers, sort and separate the smaller ones (these could be females!).

This size difference is observed more in annuals than non-annuals. Fp gardneri fry all grow out about the same rate, if they're fed enough small food like daphnia, during the early stage.

[erikthur]

The number in parenthesis is the number of fry I got .
Thus, the slow growing fish are not crowded - no food shortage.

About the walkeri and gardneri - they are of practically the same size.

What suprises me most is the difference between foerschi and rachovii.

[RonWill]

aahhh.... now I understand. You're listing the species in order of growth rate

Erik, my observation with rachovii* disagrees with yours. I gave a RAC male to Kho and that bugger grew very fast, like the suzarti and stellatus.

I grow-out my fry in clear containers, so I can observe them closely and sort them if size difference is too obvious.

* Kho has a nice pic of the RAC but I can't find the image in the gallery

[shortman]

aahhh.... now I understand. You're listing the species in order of growth rate

Erik, my observation with rachovii* disagrees with yours. I gave a RAC male to Kho and that bugger grew very fast, like the suzarti and stellatus.

I grow-out my fry in clear containers, so I can observe them closely and sort them if size difference is too obvious.

* Kho has a nice pic of the RAC but I can't find the image in the gallery

I forgotten what size it was when I get it from Ronnie. :P
But it sure grow very fast to 1 inch in 2 x weeks time, here is the image of the lonely fat fellow

[erikthur]

To be more exact.
My 15 days old foerschi are about 2 cm long.
My 17 days old rachovii are about 1 cm long.

[erikthur]

Late report on this matter about some observations made.
Later the gardneri outgrow the walkeri. Today the gardneris are approaching twice of the size of the walkeris.
N. foerschi - male heavy distribution as suspected.
And here is the surprise - after two months time one of the slow growing rachovii actually got male coloration (the strain is Beira 98 ).

[stormhawk]

Observations of my fish:

Fastest to Slowest Growth

Simp. sp. "Urucuia"
Rivulus cylindraceus "Al Castro strain"
Simp. hellneri
Simp. notatus "Alvorada do Norte"
Simp. fulminantis "Guanambi" BHS 95/12

Of course if you segregate the fry by sizes you end up with an equivalent rate of growth. Some species have faster-growing fry by means of natural evolution whereas others take a longer time to grow since their habitat is existent all year round.

I get a proper sex ratio when I segregate the fry for the Urucuia. Majority male for this round but I managed to get some young females from the smaller juveniles that were growing out separately.

Simp. fulminantis also show differing growth rates with some fry growing triple as fast as others. I believe the smaller fry are meant to grow slowly and become food for their siblings in nature.

Got 3 surviving fry from a hatch of 7 fry. Largest fry is about 2+ weeks old and its 1.1cm now. Smaller fry is same age but around 7-8mm in size.

The key is to getting adequate food to all the fry and segregating the fry as they grow otherwise the smaller ones may become stunted.

[stormhawk]

I believe the slowest growing species in SG to attain sexual maturity must have been Rivulus xiphidius. Apart from that, Ronnie's got a slow growing Simp. species but I'll let him explain more on that bit.