Cherry Shrimp Dying

[Liv15]

i have had loads of cherry shrimp die the last few weeks. They are in a shrimp only tank that is established and water is fine. It has been really hot here some days and I'm thinking the heat is what has killed them? There seems to only be females left now which means they are not breeding anymore. Are the males weaker than the females?

 

[Ch4rlie]

A few questions first so I can get a picture of your tank and set up.
 
Dimension of the tank?
 
What is the temperature of your tank usually?
 
And how high did the temp go during the heat wave?
 
Exact water parameter readings?
 
Have you made any changes to the tank recently, such as new filter media, new plants, substrate, that sort of thing?
 
How long have you had these shrimps btw?

 

[Baccus]

Also on/ during the heatwave did you only have the filter running on the tank? Shrimp can be just as affected by lack of disolved oxygen in the water as fish. Did you notice if the shrimp where hanging around the surface of the water prior to them dying?

 

[Liv15]

I think it was oxygen as the air pump broke during the really hot night. I'm guessing the males are just weaker since they're smaller.

 

[Baccus]

I actually believe that its not that males are weaker its actually a survival strategy for the species, that when times are not ideal males that are not strickly necessary to be around using up limited resources die off allowing potentially pregnant females to hopefully survive the hard times and have their young in better times. This also ensure that there is less competition for available foods, when there are new shrimplets about.
Antechinus an Australian carniveriouos marsupial employs such a mode of survial of the species.
Guppies too I have noticed have a similar habit, with males dying off in winter, but females surviving through to spring/ summer when they can then drop their fry uninterrupted by males. However there is almost always one or two younger males that will survive the bad condtions and be mature enough to be the first males breeding when condtions improve.

 

[Ch4rlie]

I actually believe that its not that males are weaker its actually a survival strategy for the species, that when times are not ideal males that are not strickly necessary to be around using up limited resources die off allowing potentially pregnant females to hopefully survive the hard times and have their young in better times. This also ensure that there is less competition for available foods, when there are new shrimplets about.
Antechinus an Australian carniveriouos marsupial employs such a mode of survial of the species.
Guppies too I have noticed have a similar habit, with males dying off in winter, but females surviving through to spring/ summer when they can then drop their fry uninterrupted by males. However there is almost always one or two younger males that will survive the bad condtions and be mature enough to be the first males breeding when condtions improve.

 
I have to say I saw this occurring on one of my tanks earlier this year when I fed less food, saw the tank almost entirely of females and no males.
 
I naively thought they simply were good at hiding, but when I moved all the shrimps to the larger 3 foot tank, there was only one male, a young one, and about 25+ females. I just thought, oh thats odd but did not thought any more about it at the time.
 
That does make a lot of sense. Great to learn this kind of stuff, love it. Thanks Baccus.

 

[Baccus]

Nature has some amazing survival strategies, especially to help the species survive if not the individual.
 
I know Australian Fairy wrens employ some sneaky tricks to improve genetic survival. Males will have a mate who he woos and guards, even helps raise the chicks. But while his mate isnt looking he goes off and woos the neigboring hens, mating with them, leaving the resident male to raise at least one of his chicks. Whats funny is while he's off spreading his "wild oats" his hen at home is busy entertaining neighboring males. So each nest in any given area could have up to 4 different fathers of the chicks in the nest. The reason I bring this up, I would be interested to see / learn if any of the fish species that make pair bonds and guard territory also employ similar tricks of genetic spreading. I know some males pretend to be females in marine environments to sneak under the dominate males radar and breed with the females but its not quite the same as what the wrens do.