# Long term inbreading leading to population crash?



## RoyalFizbin (Mar 7, 2006)

Hey guys I had a colony of cherry shrimp which I stared about 10 years ago. This started with a purchase of 12 shrimp which eventually became hundreds of shrimp for many years but for the last two years the population slowly plummeted. Now I'm down to one single male left that I can find. In all that time, I never purchased new stock to mix up the genetics. Do you think this could be due to long term inbreeding? Anybody else have a similar experience?


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## ch3fb0yrdee (Oct 2, 2008)

I have a population of snowballs going for about 7years. I haven't experienced a population crash. Before accidentally gassing them, my snowball population was quite robust. I believe colony collapse has a lot more underlining issues than I just a inbreeding. 

I noticed than as mineral content inside my water depletes (from lack of waterchanges) and organics buildups, my colony would slow down. I've since meditate this with more frequent water changes rich with minerals shrimps need to grow. My shrimps will bounce back and breeding would continue. I've experience this with my blue velvets, blue pearls, and fire reds. 

How often do you do waterchanges or maintenance you tank? Are there any underlying issues you think could lead to the sudden collapse?


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## t2ak (Dec 28, 2013)

I just started a cherry colony and been wondering if this happen..

Sent using these stoopid hooves..


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## James He (Sep 17, 2009)

I have a CRS colony for more than 4 years. started from 20 shrimps.

I never have any issue, new borns all the time.

Recently I move all CRS from regular 10G to a 20L tank, a brand new setup. they thrive in the new tank.


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## Subtletanks91 (May 29, 2013)

Shrimp genetics are so diverse that with every time they breed there is always new genes to be produced. I breeding has no effect on shrimp. You can breed for years and generations and never have any problem. 

Colony collapses usually have an underlying cause, you've heard of new tank syndrome for fish tanks, but what about old tank syndrome. Where after about 5-7 years of having a tank running everything just dies for no reason whatsoever. This can happen with shrimp tanks, regular filter maintnance, gravel vaccuming every one in a while getting deep will help prevent this. 

I'm sure soothing shrimp has more to say on this though. He's the genetic master


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## Raymond S. (Dec 29, 2012)

I would check the nitrate level first. I had great breeding in my shrimp tank but then it slowed to a crawl. People are quick to tell someone about how low the bio-load is on shrimp but what is it at 150 in a 10g tank ?


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## James He (Sep 17, 2009)

Raymond S. said:


> I would check the nitrate level first. I had great breeding in my shrimp tank but then it slowed to a crawl. People are quick to tell someone about how low the bio-load is on shrimp but what is it at 150 in a 10g tank ?


No worries, I had 500+ in 10G before, NO3 < 5ppm.


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## Wasserpest (Jun 12, 2003)

I started out with 4 Cherries, of which one promptly died. It may just have been a single female. That was when Cherry shrimp came out and cost $5 a piece. Probably ~9 years ago? So offspring from that single female still cruises my tanks today.

I noticed that over time, they remain rather small and not very colored. However, every time they are introduced to a new tank, they grow large and deep red. I think once they reach a certain population density, they run short on food and don't mature really well.

In other words, I doubt that the issue is inbreeding! More likely an accumulation of nasties in the water leading to dead shrimpers.


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## RoyalFizbin (Mar 7, 2006)

Now that I think harder about it, I think I know what might have happened. About 2 years ago I changed all the plants in the tank, I got rid of Christmas moss and planted subwassertang and dwarf sage. At that time I put some osmocote root tabs in the fluorite. Everything was going well for a while but I think that perhaps the dwarf sage and its roots might have brought up some osmocote from the substrate. The dwaf sage has totally carpeted every inch of the tank. Sometimes I like to pull out a huge patch so there is a bare patch for the shrimp to feed from. 

I guess this is the right time to try crs again. I tried once before but I used tap water and eventually they all died. This time I already have an RO system, salty shrimp gh+ and a tds meter.


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## lauraleellbp (Feb 3, 2008)

From a genetic standpoint, periodic outcrossing is always a good practice just to help maintain genetic diversity and therefore statistical probability that any population will survive rather than succumb to any sort of problem; whether this be a change in environmental factors, disease/parasite, or genetic health issue.

In other words- though everyone is *probably* correct that your population dieoff was not related to a genetic issue, we *can't* know that for sure, and encouraging genetic diversity is a "best practice" for any long term breeding project.


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## Subtletanks91 (May 29, 2013)

While I agree with genetic diversity, it's not a necessity with shrimp.


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## James He (Sep 17, 2009)

wild bee shrimp comes from few creeks, it inbreeds for thousands if not millions of years.


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## Soothing Shrimp (Nov 9, 2011)

While there is an answer to this, it is not one that the scientific community has addressed. Studies have been done on clam shrimp and ocean shrimp, but ornamentals have been neglected.

While it undoubtably is true that at some point breeding depression will set in, it is not clear when that point is. Some studies on Pacific shrimp that have been done show that after 10+ generations there is still lots of genetic diversity. 

So why is this?

The way mammals are constructed, too much inbreeding is detrimental. This is given to the theory that they are able to wander away between juvie and adult age to outbreed with other mammals of the same species- so they have evolved to use outbreeding to their advantage

Shrimp are not prone to defects from inbreeding that we know of, which has give rise to the theory that they have evolved this way because of being contained within small areas for long periods of time.


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## lauraleellbp (Feb 3, 2008)

The issue here is not just one of genetic defects and recessive genes. The issue I am referring to is much larger. The resilience of any and every population to ANY type of change. The more diversity in a population, the higher statistical probability that there will be individuals who are better able to tolerate temperature changes, have a natural resistance to a disease or parasite, etc.

Can populations survive despite extreme inbreeding situations? Of course. BUT those populations are by default at much higher risk for extinction, especially when any new stressors come along, such as habitat loss, encroachment from and exposure to new species, etc.

These principles have been played out over and over in evolutionary history as well as in long-term scientifically controlled breeding projects with hundreds of different species. 

How long might it take for a completely isolated dwarf shrimp population to develop any issues? We simply have no clue. Anecdotal statements "well I've had my colony going for 10 years and haven't seen any issues" mean absolutely nothing, as that hobbyist would then need to set up a scientifically controlled research project and subject their population to different variables to measure their resilience, with a control population in place as well. Would take a LOT of shrimp to achieve any sort of results that might actually have any statistical validity and reliability. As well as the ability to autopsy deceased individuals to determine cause of death (which frankly, gives me the giggles... trying to picture instruments small enough to do that).

If it were me, I would intentionally add in new blood on a regular basis.


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## TeamKRF (Apr 30, 2013)

Iodine levels might be low or other minerals used in the process of molting. If the shrimp cant molt it cant reproduce. You can tell by observing number of molts in water.
solution;
a) dose ferts with iodine (brightwellaquatics multi W/iodine)
b) feed shrimp pellets (this is why you leave molts in the tank)


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## deanwaters (Feb 10, 2012)

RoyalFizbin said:


> Hey guys I had a colony of cherry shrimp which I stared about 10 years ago. This started with a purchase of 12 shrimp which eventually became hundreds of shrimp for many years but for the last two years the population slowly plummeted. Now I'm down to one single male left that I can find. In all that time, I never purchased new stock to mix up the genetics. Do you think this could be due to long term inbreeding? Anybody else have a similar experience?


nah, it's not imbreeding that's causing loss. I would consider every other possible reason first. You have to imagine most of the "tank-raised" fish being sold in stores and online are and have been imbred for many, many generations.


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## Briggadane (Apr 28, 2014)

Yes. A gene pool will need diversity at some point. Think about any species you wish. If you have any genetic defect, over time, that defect will be carried by all members. From all my research, one thing found across all breeds and species studied, was that natural immunity to the environment will decrease. Now, outcrossing will usually prevent this. Had you separated the tanks at some time, waited a few years and simply added 2 or so shrimp from tank to tank, this usually won't happen, or at least hold it off indefinitely. 

Bring in even one totally new member after a few years? It's a double edged sword. You get new boost to immunity, but risk bringing in new disease. You will boost your dominant traits, but if the new member has a negative recessive gene, you will see more of that trait now. 
So, it probably is environment, even a small stress could have caused the crash. Likely the shrimp could no longer fight off any changes to environment flux. 
Just my $.02


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## angelcraze (Aug 20, 2013)

lauraleellbp said:


> ....extreme inbreeding....populations are by default at much higher risk for extinction...when any new stressors come along...
> 
> _How long might it take for a completely isolated dwarf shrimp population to develop any issues? We simply have no clue........ _


Great post!!! We have no clue because the results would depend on the specific detrimental genetic defects your/*that* shrimp colony carried, and which specific environmental changes led to their demise. It's completely subjective.


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## Ghia (May 1, 2014)

Another factor could be that with most animal species the number of progeny decreases as inbreeding quotient increases. I have no idea wether this also goes for shrimp, but can't see why they would be exempt.


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## amcoffeegirl (May 26, 2009)

I have had the same line about 5 yrs and thought mine had all but stopped breeding I did separate the line now into 2 tanks and will cross back every couple years. I have about 30 new babies now and hope they will continue to increase


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