hi, you possibly could use Rotenone in France, but it may be forbitten as it is in Germany. Be cautious with all the secondary effects of this pesticide. I wonder, if it could be an option for you? I know of a successful application in Norway outside the reproductive phase in order to protect a population of Triturus cristatus. However, nobody enjoys to use pesticides in this context.

Hi David, I visited Le Pinail some years ago and I remember the many small pools that characterise it, and its populations of white-clawed crayfish - I hope they are still there, without alien species. Human interference is the main reason for spread of alien species, and pesticides may be your only answer for the sunfish, but I would recommend trying a fine-meshed seine net drawn through the pond several times. Best wishes, Julian Reynolds

For effectiveness and ease of use I think rotenone or other piscicides are probably the best choice.  As your species of concern are inverts and amphibians recolonization should be relatively rapid - particularly if not all ponds are treated in the same year.  Other physical methods of removal are unlikely to be 100% effective and will result in significant habitat destruction.

conclusion: difficult...

In French we have an expression: have choice between plague or cholera....

Anyway, rotenone use is forbidden. I also considered the use of clove oil to use directly underwater similarly to Indonesian fishers.

Angling won't be 100%, but it might be the best alternative of several not ideal ones.  Depending on the terrain and access, you might also be able to create a good public outreach opportunity by opening a "pumpkinseed harvest" in the form of a youth fishing event, combined with eduction on alien invasives.  Similar public harvests are utilized on Asian carp in the US, although they are not terribly effective in reducing numbers in larger river systems. 

Hi, 

May be you can combine diverses techniques. The physical removal (like seining with a small mesh net and electrofishing), combined with drawdown (if possible) to increase predation or limit spawning habitat, might be the best option if you can't use chemicals method. If you can use chemicals methods, look into one that won't target all the species and you can think about use in a specific location like shoreline during spawning for example (some chemicals will work better at a specific water temperature, so it also need to be considerate).

We have pumpkinseed in the UK too and whilst they aren't the target of an eradication programme yet, they will be. To date, we have concentrated on extirpating topmouth gudgeon (P. parva) populations, with the aim of total eradication. Have a look at some of our publications, which detail such control measures. We have used rotenone predominantly, but also drain down & lime and some bio-control/ manipulation techniques too.

The use of physical removal techniques such as netting, electrofishing, etc., will most definitely not yield 100% effectiveness in the removal of any fish species, but they can be useful tools in beginning the process. By setting up a rigorous removal schedule using various techniques, and alternating your approach every time you will be surprised as to how many fish can be removed. Perhaps these techniques coupled with a campaign for the harvest of these fish by anglers, water drawdowns, etc., can be effective. What predator fish do you have in the water body? Is there anyway to augment there population to increase predation on pumpkinseed? Not being familiar with all the native freshwater fish in France, are there any native species that may be staunch competitors with the pumpkinseed? If so, the bolstering of those fish along with all the removal techniques expressed here and by others, may give you a boost in trying to control and potentially eradicate. Success is dependent on size of water body, ability to dedicate time and resources to the goal, angler compliance, as well as educating the public or stakeholders about the dangers these fish pose to native ecology. For example, if you are successful in the removal of these fish, it will be important to inform the stakeholders, public, anglers, etc. about the risks they pose in order to deter reintroduction.

Just my 2 cents.

I work with a researcher that has been experimenting with ammonia in pond applications. Attached is his paper. I'm not sure of your permitting requirements, but maybe this is a possibility.  

Often the best solution is to dig a new pond and just give up the old one...

regards, Menno

There is no predator in the 5000 ponds, luckily for the sunfish. We have the idea to use pike (Esox lucius) as non permanent biocontrol (easy to remove) if the side impact is not too high for other species such as amphibians.

Are the ponds being used to create nursery or rearing habitat for amphibians and invertebrates? You mention 5000 ponds with no predators. Are there other desirable  fish species present in the pond? If so, using northern pike as a bio-control might further add to your woes. If there are not other desirable fish species in the ponds, or if fish are not the main focus then northern pike might be an option to at least assist you in the active removal. 

It is not recommended the use of pesticides, I would go for a predator easy to use. The Pike is a fish with a wide range in their diet and can be a drawback for those organisms that you want to protect. You should consider another possibility, probably introduce the bass, although it would be a risk if they escape from the pond.

Hey,

I saw that some people suggested Rotenone. I just talk to a friend who used this method with a Rotenone neutralizer and were able to work on one stream reaches at the time, letting the first stream reach being recolonized with the desire fish species before moving downstream. They eradicated all the undesired species successfully. I don't know if you only have ponds but I tough I will mention this in case it could be useful.