Hi there

I started a red cherry colony with 1 male and 4 females. I'm now the happy owner of at least 300 red cherries 

in the F1 and F2, I can see very interesting colours : deep red, orange/red, deep red with racing stripe. So, I think it should be a good idea to go select breeding and improve colours.

Though, the F1 & F2 shrimps seem to be smaller, or is it just my imagination? Does that mean I need to introduce new blood in that colony? Does that mean too that selective breeding will very quickly bring me to nicest but smaller/weaker shrimps?

In case I have to introduce new blood, what is better: new males or new females?

I think there are several factors influencing why your shrimp may be 'smaller'.

For starters, how old are your new shrimp? Younger shrimp are smaller. Many crustaceans (I can't remember whether this is true for shrimp but it is certainl;y true for lobsters) never stop growing. Eventually something will kill them off, be it a disease, predator, ect. but  they don't stop growing.

Secondly I'm assuming you have the 300+ shrimp in the tank where you used to keep the original 5? Even if this number is spread over several tanks, the relatively high density will naturally produce a much higher concentration of wastes (think hormones, pheromones in addition to nitrogenous wastes) and all of these will cause the growth of your shrimp to slow down.

It is highly unlikely that 2 generations of inbreeding are enough to begin causing genetic abnormalities that would only reduce the size of the shrimp, without any other physical abnormalities becoming apparent.  

As for selective breeding, yes you should. It is the only way to maintain or improve the colouration in your shrimp. But as pointed out by several of the best breeders on this forum, you must be specific about what you want to select for, be it colour, pattern ect. Trying to do everything at once is a recipe for disaster.

 

Thanks for clarifying Fishmosy.

The colony started with 5 in the same tank, a 140 liters. The parents have passed away, and I now have only the F1 + F2 and many other shrimplets...

The F1 are about 3 months. I carefully watched the crowd in the tank and found some of them to be from a "decent" size, so yes, I'm may be to much in a hurry to have nice big reds... What should have made me thinking the F1 are smaller is that they start breeding as they were only 2 months old and small.

I only had the experience of the parents which started to breed only after 3 months and they were bigger.

As for selective breeding, as I said, I saw 3 interesting patterns, which means 3 extra tanks... Not sure wifey will agree with that. She said the yellow + the sunkist + the blue pearls + the RCS might be enough...

But wait, I might try to explain to her that I would be more tolerant with her if she is interested in a twentieth pair of shoes , who knows?

Just kidding ...

And for the time I will have to introduce new blood, what's the best option? New males or new females? or it doesn't matter?

I dont know if there ever becomes a stage where you 'have' to introduce new blood. After all, the story goes that all the CRS we have came from three individuals. 

The problem with new blood is that you never know what genes you'll be bringing into your colony, the colony you have been selecting to limit genes to the ones that code for the characteristics you want. 

You could use either males or females as new blood, it just depends on your goal. For example, you might want stronger colour in your colony. Might be best to add better coloured males and remove your weaker coloured males. You might want to build the number of individuals in your colony, best to get more females. 

 It sounds like you need a bigger tank, or split your different varieties into more tanks (without going too small) to lower the density.

fishmosy is spot on.  High density living = smaller shrimp.   I've had several hundred juvenile DAS in a 100l tank and they grow slowly and berry up at a small size.  When I take some of those small shrimp and put them into a much larger tank (e.g. 20 shrimp in 400l ) then I see them moult more frequently and they grow quickly to the large sizes that you would normally expect.   This even occurs if I move 2 yr old (but size stunted) shrimp.  i.e.  they "catch up". 

Being pro-active in your breeding program by culling and removing the poorer quality shrimp (however you might define that) is therefore a good thing to be doing to lower the density while simultaneously improving the quality.

 

How many shrimps is it affordable to keep in a tank? Is there a "good" number of shrimps per liter?