Freshwater Jellyfish found in Loughs Derg and Erne

slowburner

Yet another alien species has arrived in Irish waterways.
The freshwater jellyfish craespedacusta sowerbii is a native species of the Yangtze river basin in China and was probably imported accidentally into Irish waters by boat. Scientists appear not to see the arrival of this species as a significant threat to the native freshwater ecosystem.
http://afloat.ie/marine-environment/marine-wildlife/item/23133-freshwater-jellyfish-discovered-in-lough-derg

OpenYourEyes

Glad to hear the they aren't expected to have a significant negative effect on the ecology of the lakes, but it really does highlight the need for the ballast water/biosecurity issue to be addressed before it's too late and the communities of our lakes are irreperably changed by invasive species.


Of course you could argue that with the amount of aquatic invasive fauna and flora we already have that our freshwater systems are already irreperably changed, but lets not let it get any worse.....

Kess73

Am wondering how they could be regarded as not being a threat to the current freshwater ecosystem.

Unless the jellyfish become part of the food chain in a significant manner, then they will prey heavily upon the various daphnia and the like, which in turn will have a big impact upon those that currently feed on them.

This in turn would have a knock on effect further along the food chain.

slowburner

If I understand it correctly, they are unlikely to become a self sustaining population. The exceptional summer has allowed this population to develop but it will not survive the winter? That's what you would hope for anyway.

mr lee

ireland has poor controls for this sort of thing,
look at border security on tv shows like nothing to declare,the aussies and new zealand dont mess around with this s#+t,
its just another thing where ireland is miles behind other country's

Kess73

slowburner wrote: »

If I understand it correctly, they are unlikely to become a self sustaining population. The exceptional summer has allowed this population to develop but it will not survive the winter? That's what you would hope for anyway.

Was just reading up on them and it would appear that summers of exceptional heat in other countries saw big increases in their numbers, but we are talking countries where the heat was in the ninties and above, so I wonder would our heat this summer really qualify as exceptional heat for the species.

What did catch my eye though was how they have survived in American states that have very cold winters by our standards and also in some parts of Canada it would seem.

As someone who uses Lough Derg a lot (fishing, boating, running, nature walks, twitching etc etc) I would really hate for it to be damaged (same goes for anywhere else in Ireland) by another invasive species to these shores and I really do think that any invasive species that has the ability/need to compete directly for the same food supply as some of our native species has to be seen as a potential threat at this point.

Will have to educate myself a lot more on these jellyfish though, as my knowledge of them is very basic to say the least.

ytpe2r5bxkn0c1

Just to be clear. The specimens found recently were in the second phase of their life cycle. If there is insufficient water temperate they remain in a polyp state - in which they reproduce. Chances are they have been here for years but the very high water temperature this year led to the jellyfish stage we are more familiar with and in which they are visible to us.

At this sage they are classified as alien rather than invasive.

recedite

I agree that they have probably been around for years as polyps.
According to the wiki page they occur in Canadian lakes and in Moscow, so surviving the winter is not a problem for them. Here's how they do it;

During the cold winter months, polyps contract and become resting bodies, called podocysts. It is believed that podocysts are transported by aquatic plants or animals to other bodies of water. Once conditions become favorable, they develop into polyps again.

Considering they have been on the loose in the UK since 1880, I think the scaremongering that they will damage the ecology of the Shannon is a bit exaggerated. They could even have come here on the feet of migrating birds. Also bear in mind they have been spotted in Lough Erne, according to the afloat magazine article, which is connected to the Shannon waterway by their favourite habitat, a warm slow moving canal, so I think we can assume they are already widespread throughout the whole navigation, but in mainly the polyp form.
I was down at Lough Derg during the warm weather looking at the breeding sea eagles introduced there, and a guy in a cabin cruiser told me the water was at 24 degrees in the lake. This was from a thermometer sensor under his boat. Seeing as the temp in a sheltered harbour or canal gets up an extra few degrees, it explains why these medusae appeared in the three harbours recently.

I don't see a problem with them eating the daphnia. The daphnia population will explode in warm weather in response to algal blooms, which in turn are dependent on eutrophication of the waterways, ie humans pouring in sewage and silage effluent. If you are worried about the ecology of the lakes, deal with that. Its well known that introduced zebra mussels have done a lot to clean up the water in the lakes, which makes them safer and healthier for fish, even if they do foul up boats and compete with native mussels. Swings and roundabouts. Anyway I for one, welcome our new jelly creature residents.

Kess73

recedite wrote: »

I agree that they have probably been around for years as polyps.
According to the wiki page they occur in Canadian lakes and in Moscow, so surviving the winter is not a problem for them. Here's how they do it;
Considering they have been on the loose in the UK since 1880, I think the scaremongering that they will damage the ecology of the Shannon is a bit exaggerated. They could even have come here on the feet of migrating birds. Also bear in mind they have been spotted in Lough Erne, according to the afloat magazine article, which is connected to the Shannon waterway by their favourite habitat, a warm slow moving canal, so I think we can assume they are already widespread throughout the whole navigation, but in mainly the polyp form.
I was down at Lough Derg during the warm weather looking at the breeding sea eagles introduced there, and a guy in a cabin cruiser told me the water was at 24 degrees in the lake. This was from a thermometer sensor under his boat. Seeing as the temp in a sheltered harbour or canal gets up an extra few degrees, it explains why these medusae appeared in the three harbours recently.

I don't see a problem with them eating the daphnia. The daphnia population will explode in warm weather in response to algal blooms, which in turn are dependent on eutrophication of the waterways, ie humans pouring in sewage and silage effluent. If you are worried about the ecology of the lakes, deal with that. Its well known that introduced zebra mussels have done a lot to clean up the water in the lakes, which makes them safer and healthier for fish, even if they do foul up boats and compete with native mussels. Swings and roundabouts. Anyway I for one, welcome our new jelly creature residents.

Actually that is a very good point to make. Remember making a very similar point (and think it was in this very forum) four or five years ago when they were getting a lot of media publicity.

I think my own fear regarding the jellyfish boils down to a lack of knowledge on them as a species and only have a very basic knowledge to try and join the dots with, whereas the zebra mussels I was quite aware of, and I knew quite a bit about them and their impact upon bodies of water.


Srameen's post last week prompted me to go and educate myself further on the jellyfish, and from what I can gather they just become part of the food chain when in polyp form, and it is only if there are a few years in a row of them reaching jellyfish form that they have an impact on things like fry or small fish numbers (and as a result on anything above fish in the food chain).

I don't think they are a risk free species when it comes to tipping the balance in Irish waterways, but thanks to getting some extra information on them I think that the likelyhood of getting that perfect storm of conditions needed for them to have a major negative impact is far less than I originally thought.