C'est Albert Getabu qui donne la solution à l'énigme de Karen sur les loutres ! (Thanks Albert for giving explanation about Karen's enigma on outsmarting otters !) Chers Lionel et Caren, Merci pour ce thème très intéressant que vous avez lancé. Dans notre cas, ici, les fermiers utilisent diverses méthodes qui ne sont pas toutes efficaces, mais faute de mieux, ils n'ont pas d'autres options. Cela inclue l'utilisation de méthodes d'effarouchement et la division des étangs avec des piquets en bois plantés fermement dans le sol et placés suffisamment proches pour empêcher les loutres de pénétrer. Les pieux sont assez espacés pour permettre aux poissons de circuler tout en empêchant les loutres de faire de même. Ainsi, même si une loutre rentre dans une moitié d'étang, les poissons s'en rendent compte et peuvent aller se réfugier dans la deuxième moitié. Si la loutre sort de l'eau et pénètre dans l'autre moitié de l'étang, les poissons font le chemin inverse. L'efficacité de la méthode dépend de la manière dont les piquets sont disposés dans l'étang. Si cette méthode est relativement efficace contre les loutres, en revanche, elle ne fonctionne pas contre les serpents, pas plus que les méthodes d'effarouchement; donc nous allons devoir faire avec assez longtemps en attendant que ce problème ne soit résolu. Certaines volailles peuvent se nourrir de serpents, donc s'ils sont intégrés avec les poissons, ils peuvent manger quelques serpents et grenouilles; L'intégration avec des canards fait aussi fuir les oiseaux prédateurs et aide probablement à se débarrasser des grenouilles, mais je ne sais pas s'il existe des données à ce propos ? Donc, en fonction de ce que vous avez présenté, je pense que combiner le chien avec de la volaille et de l'effarouchement pourrait constituer une bonne méthode de contrôle non-létale des prédateurs dans les structures aquacoles. Albert Le 23 juil. 2010 à 12:04, Getabu Albert a écrit :

Dear Lionel and Caren,

Thanks for the very the inresreting topic you have introduced. In our case here, farmers try various methods which are not fully effective but in absence of nothing else, they have no other option. These involve the use of scare crows and the division of the pond with wooden stakes driven firmly into the pond bottom and placed close together to rpevent otters from entering the other half of the pond. The stakes are placed at a spacing that cannot allow the otters through but can allow the fish. So if the otter enters one half of the pond and is sensed by fish, they try to run away from it and cross the wooden stakes into the other half . If the otter gets out and enters the other half of the pond, the fish again cross the stakes to the other side where they were previously. The effectivemess of the method depends on how the stakes are spaced in the pond. Whereas this method could be effective to some extent against otters, it cannot control predatory snakes, nor can they controlled by scarecrows; so still we have a long way to go to sort out this problem.

Some types of poultry can feed on snakes, so if they are integrated with fish, then they may be able to eat some snales and frogs. Integration with ducks in the ponds can also scare away predatory birds and probably help get rid of frogs, but what data is there to ascertain this?

From what you have presented, I think that combining the dog with poultry and scarecrows can be a good non harmful method of controlling predators in aquaculture facilities.

Albert

--- On Fri, 7/23/10, Karen L. Veverica <veverkl@gmail.com> wrote:

From: Karen L. Veverica <veverkl@gmail.com> Subject: [Sarnissa] non-lethal predator control To: "sarnissa-african-aquaculture Mailing List" <sarnissa-african-aquaculture@lists.stir.ac.uk> Date: Friday, July 23, 2010, 1:25 AM

Dear Prof Lionel, I see your two-part message only met with reply for the funding part. Well, I was about to write something on credit for fish farmers because we have been working on this issue for several years for Uganda and it is a major question and prospective component of some new world bank projects in the works but your non-lethal control of predator question caught my fancy.

For those of you new to this game, in short, know your predator and know how it thinks, and its biology. Also note that some predators actually render service in removing unhealthy fish. Otehrs get out of hand and remove the healthy fish and these are the ones we try to target. As for predators, I suppose you are speaking of the otters, and the worst birds which tend to be cormorants, and pelicans because they are such efficient fishers. The others pick off a few fish but rarely fish in groups. The recent advances on the big fish farms in the US, have been to purchase a very well-trained dog; most often the breed of border collie. These can be rather expensive. However, many fish farmers in Africa do train dogs to fight off birds and otters. There was a rather ingenious development of a solar-powered alligator head that would randomly re-position in a pond itself during the day, thereby making the birds think it was a real animal. This was developed by researchers at Louisianan State University. When I say alligator, it would be crocodile for Africa. There are also some inflatable 'gators that are used as children's toys in swimming pools. These work also but anything that remains stationery only scares the birds for a while. One of the most creative and clever means of controlling otters is the method that Randy Brummet explained to me that was figured out by fish farmers in Malawi. It is not really control; it is outsmarting the otters (hard to do) so they cannot eat as many fish. I will let him explain it or if others in Malawi recall it, will let them. The "bird wires" are often used across a pond as well. Some think that they should be visible to keep birds from landing and others think they should be monofilament so the birds try to land and then collide with the wires, thereby getting discouraged (and embarrassed). Hanging out one dead bird of the species that is causing the trouble is also a well-known technique but you asked for non-lethal....

The imitations of owls, hanging out old CD's as reflectors, ribbon that makes noise, air cannons that shoot off, all these are useful for about 2 weeks. After that the birds get used to them and they fly up, around in circle and then land where they were. Bird scaring devices should be changed every 2 weeks. Well , this will maybe begin the conversation, Cheers, Karen

-- Karen L. Veverica Auburn University Dept. of Fisheries and Allied Aquacultures, USA office: +1-334-844-4667 cell: +1-334-332-1560

www.ag.auburn.edu/fish/international/

_______________________________________________ Sarnissa-african-aquaculture mailing list Sarnissa-african-aquaculture@lists.stir.ac.uk http://lists.stir.ac.uk/cgi-bin/mailman/listinfo/sarnissa-african-aquacultur...

_______________________________________________ Sarnissa-african-aquaculture mailing list Sarnissa-african-aquaculture@lists.stir.ac.uk http://lists.stir.ac.uk/cgi-bin/mailman/listinfo/sarnissa-african-aquacultur...

-- Visitez mon blog / Visit my blog : http://aquaculture-notes.blogspot.com/ -------------- section suivante -------------- Une pièce jointe HTML a été nettoyée... URL: <http://lists.stir.ac.uk/pipermail/sarnissa-french-aquaculture/attachments/20100723/23d02bfc/attachment.htm>