dead gammerus pulex?

[lipase]

hello,
I've just been down to a nearby stream and it looks like all the gammerus pulex are dying!? I collected 8 of them, two of them are still waggling their legs but the other six are just lying there motionless. It's a bit bizarre because for starters the 'dead' ones haven't changed colour; they're still the same colour as the live ones plus I went down only a week and a half ago and they were all flourishing in that stream. A couple of the 'dead' ones I've collected seem a bit contorted; instead of them being curled up kinda like a banana they are extended with a small kink in the spine.

I collected about a dozen a week and a half ago to breed in a tank. But I must not have provided them the right conditions since they died within about 6 hours in the tank last week which I was very surprised about. I suspected the reason they died in my tank was since I hadn't provided them enough food. I'd left the tank to stand for over 12 hours but I didn't put any food in the tank appart from a small amount of tiny soil particles left from the tank that previously had a lot of 'pond sludge' at the bottom along with a few gammerus and newts.

In both instances (the tank and the stream just now) I don't fully understand why they are dead?!

Can anyone shed any light on the situation??

Jack

[Dogghound]

Did you have high oxygen levels in the tank? this species is highly susceptible to chemicals such as chlorine, and oxygen. The numbers in the stream could be indicative of chemical run-off from farmland.

Perhaps the temperature is slowing their decomposition.

[lipase]

Originally Posted by Dogghound

Did you have high oxygen levels in the tank? this species is highly susceptible to chemicals such as chlorine, and oxygen. The numbers in the stream dont sound large enough to worry about, although it could be indicative of chemical run-off from farmland.

You could well be right in terms of the chlorine content of the water in the tank, I would have thought it would take longer than 6 hours for them to die due to chlorine however. Oxygen shouldn't have been a problem since the water was aerated as I put it in the tank.

The stream is a very small stream and it appears literally all the population of gammerus is dying off. It's the major contributing stream to a small lake/pond in which probably over 10 species of fish and a number of other species live. You could well be right about the chemical run-off. Although it would be from gardens and houses since the stream doesn't drain from any nearby farmland

[lipase]

oh yeah very good thinking wih the temperature thing. I missed that on my first read through

[Dogghound]

These live in fast streams and rivers as you know so you would need a powerful pump for them to survive in a tank, they require a large amount of dissolved oxygen. Was the water tap water? It will kill them quickly if chlorine is present they are very intelerant of any chemical, usually if something is not right they are the first thing to be affected in a river. Has there been any changes to the stream any where local or up stream?

[tom00_uk]

breed them in still jam jars with no issues in the lab,

you need to not use tap water, spring water, stream or collected rain/snow will be required as the range of chemicals in tap water will see them off

[lipase]

You must be right about the chlorine in the tank then; I had left the tap water for probably between 12 and 16 hours but apparently that wasn't long enough. In terms of oxygen I've kept them in that tank before without any aeration or oxygen producing plants aswell as also keeping some in a glass with no aeration for a few weeks so I'm fairly certain oxygen wasn't too much of a problem.

Unfortunately I don't know if anything's happened 'upstream' in the surrounding area since it's privite land (just houses and gardens). There's been no building work or anything like that as far as I'm aware. Do you think it could have been someone fertilising their grass and/or garden?

Come to think of it, nearby farms have limed their fields recently although I can't imagine the fields I've seen limed being in the catchment area of this stream. They are about a mile off with a couple of other streams between the fields and this stream. Plus gammerus prefer slightly alkaline conditions I'd imagine?

[tom00_uk]

Originally Posted by lipase

You must be right about the chlorine in the tank then; I had left the tap water for probably between 12 and 16 hours but apparently that wasn't long enough. In terms of oxygen I've kept them in that tank before without any aeration or oxygen producing plants aswell as also keeping some in a glass with no aeration for a few weeks so I'm fairly certain oxygen wasn't too much of a problem.

Unfortunately I don't know if anything's happened 'upstream' in the surrounding area since it's privite land (just houses and gardens). There's been no building work or anything like that as far as I'm aware. Do you think it could have been someone fertilising their grass and/or garden?

Come to think of it, nearby farms have limed their fields recently although I can't imagine the fields I've seen limed being in the catchment area of this stream. They are about a mile off with a couple of other streams between the fields and this stream. Plus gammerus prefer slightly alkaline conditions I'd imagine?

12 hours will not solve the problems tap water creates

aside from all the additives like chlorine and chloramine, fluride etc you will have copper pipes and this will also affect the life expectancy of any inverts you force these conditions on

[Fauna]

Just a note of interest...

We are using Gammerus in tubed cages to monitor polution incidents on our clubs local stretch. Gammerus acting i suppose as the rivers canary, the cages are checked daily, if they are found to be dead then there a chance theres been an incident. This along with the riverfly monitoring is helping to curb polution incidents. If anyone is interested heres a link Riverfly - Monitoring

[lipase]

These 'canaries' have worked very well I suspect, compared to other wildlife in the stream; the stream has suddenly become completely 'infested' by stonefly nymphs. Or atleast that's what I thought they were.

Could it be that the gammerus were outcompeting the stonefly nymphs before the stream was polluted? Even a week ago I found no stonefly nymphs (whilst finding lots in a nearby river) and now they are all over the place. It's not as if there's not enough dead leaves in there for them to co-exist without running out of food.

Maybe the gammerus were eating the stonefly eggs or small nymphs?

I'll try and get a photo of the nymphs