Caudata.org: Newts and Salamanders Portal

Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!
Did you know that registered users see fewer ads? Register today!

Asellus Invasion

neil

New member
Joined
May 7, 2007
Messages
45
Reaction score
0
Location
Huddersfield
Over the past several years all my ponds have developed a large, and apparently ever increasing, population of Asellus aquaticus. They are supposed to be 'harmless and omnivorous', but the populations of native European newts have definitely being reducing over the years. This may of course be coincidence, but I'd be suprised if some egg predation and consequently, population recruitment isn't occuring.
Under the circumstances should I try to reduce the Asellus population, and if so, how?
 

Mark

Administrator
Staff member
Joined
Oct 14, 2004
Messages
3,259
Reaction score
59
Location
Bristol
I'd be suprised if Asellus were a big risk to newt eggs. They are present in most of my aquatic tanks and I've never seen one chewing on an egg although their scavenging nature would suggest they might try. In my experience populations explode in water with a large amount of decaying organic matter and thick sludgy, anaeobic sediment. The newts themselves will predate on the Asellus, as will other aquatic invertebrates such as dragonfly larvae. What other large invertebrates inhabit the pond? A lack of mayfly or dragonfly larvae may suggest the pond is unhealthy. Asellus alway fair badly in my garden pond and yet I have a bin next to it full of stinky water which is always chock full of them.
 

neil

New member
Joined
May 7, 2007
Messages
45
Reaction score
0
Location
Huddersfield
Plenty of caddis, but little else I can see. Have had damselfly larvae in past years. Strange thing is that I used to get tons of those small flatworms but they've vanished too. Some big Ramshorns snails are appeared from nowhere (presumably on brought in plants)
 

peter5930

New member
Joined
Oct 15, 2010
Messages
184
Reaction score
19
Location
Glasgow
Try a smell test; smell the water, then scoop up some sediment from the bottom and smell that. The water quality is likely to be ok if there's just a mild earthy smell, but a sulphurous rotten egg smell could indicate that it's time to stick an airstone in there to get the water circulating, and/or clear out some of the excess decaying organic matter. The asellus are likely to be symptomatic of the problem rather than the problem itself. Also, I love asellus aquaticus.
 

neil

New member
Joined
May 7, 2007
Messages
45
Reaction score
0
Location
Huddersfield
This remains a bit of a puzzler as there appears to be very little apparent invertebrate life in the pond other than the aforementioned Asellus, ramshorn snails and caddis. The mud/debris doesn't smell suphurous but doesn't seem to contain any bloodworm etc; there isn't (or doesn't appear to be) any free swimming daphnia or cyclops. I did find a lond dead frog whilst fishing around, and the newt population is as low as I've seen for several years. The established marginal pond plants seem fine, so I'm a bit baffled as to whats going wrong. I put in a few new deep water plants last year using a bought-in aquatic compost, none have thrived and some have died. Could this be the cause of the problem?
So, do I have a fresh start? If so how do I quickly establish a florishing mixed invertebrate population as quickly as possible
 

peter5930

New member
Joined
Oct 15, 2010
Messages
184
Reaction score
19
Location
Glasgow
Maybe there was an oxygen crisis that wiped out most things that weren't tolerant of low dissolved oxygen levels, and although the water is fine now, there hasn't been enough time for the other species to recover. It could have happened while the pond was iced over in the winter, especially if there was a bacterial bloom caused by the dead plants and nutrients in the aquatic compost that used up the oxygen in the water.

Try filling a container with water from the pond, adding some daphnia to it and watching what happens to them; if they survive, the problem is probably over and it's just a matter of waiting for the invert population to recover.
 

neil

New member
Joined
May 7, 2007
Messages
45
Reaction score
0
Location
Huddersfield
Thanks for the suggestion. Althought the icing was very limited this winter compared to the previous two. Another thought has occured to me. The pond is situated on a terraced slope, and the higher side was held up with an old conifer trunk untill it rotted down. I replaced it with a reclaimed railway sleeper which historically were soaked in cresote. There is an approx gap of 12 inches between the sleeper and the water, and I suppose it's possible that rain run-off could get into the pond itself, although the surrounding terrestial plants are showing any signs of suffering
 
General chit-chat
Help Users
  • No one is chatting at the moment.
    There are no messages in the chat. Be the first one to say Hi!
    Top