Chers Veverica et Prof Lionel Je viens de lire le courrier de Veverica sur la menace des prédateurs et les options de maîtrise. Il est intéressant de réaliser combien la nécessité est mère de l'invention. Cela me donne de nombreuses perspectives car je suis confronté à un défi quotidien avec la prédation aviaire sur toutes les tailles de poisson, alors que les grenouilles ciblent les alevins. Les notonectes ne doivent pas non plus être sous-estimées, car elles s'attaquent aux jeunes poissons. Lorsque j'ai commencé à travailler au Centre d'Aquaculture de Sagana depuis le Lac Turkana en tant que chercheur, mon premier défi a été le nombre de prédateurs aviaires que j'ai vu dans et autour des étangs pendant ma visite de la ferme. J'ai immédiatement ordonné que des filets soient posés au dessus des étangs. Cela a permis de venir à bout de tous les oiseaux pendant quelques temps. Toutefois, il est intéressant de noter que les "hammer cobs" (NdT: je n'ai pas trouvé le nom français, si quelqu'un sait ?) ont réussi à s'habituer rapidement aux filets et à retrouver le chemin sur le bord des étangs, notamment ceux empoissonnés avec des Clarias de moins de 3 mois. Les cormorans ont suivi et comme ce sont de bons pêcheurs, ils ont profité des ouvertures sur les bords pour pénétrer dans les étangs. Toutefois, pour les pélicans kingfisher et pygmée, ils ont eu moins de chance à cause de leur mode de prédation. Enfin, l'Aigle pêcheur d'Afrique est mon dernier défi. Je m'en inquiète car il chasse des Clarias adultes. Comme il s'installe sur les arbres à proximité, j'ai demandé au service des pêches en charge du CAS de couper tous les arbres à proximité de la ferme. Ensuite, l'heure critique coïncide avec l'heure du nourrissage, donc j'ai des équipes de garde à ces heures là. Concernant les loutres, je n'ai pas de problème, j'aurais tendance à penser qu'une barrière écologique est ce qu'il y a de plus efficace. Merci et je vais partager avec vous des photos de Centre d'Aquaculture de Sagana, Kenya pour illustrer le défi prédateur. Paul Orina Le 23 juil. 2010 à 10:48, paul orina a écrit :

Dear Veverica and Prof Lionel

I have gone through Veverica's letter on predator menace and control options. It is very interesting to realize how necessity is the mother of invention.This gives me a lot of insight as i face a daily challenge with birds predation on all fish sizes while frogs also target fry. The backswimmers are not to be taken lightly as their target is the tender age of fish. On reporting to Sagana Aquaculture Centre from Lake Turkana as a Research scientist,my first challenge was the number of avian predators I saw in and around the ponds during my farm orientation. Immediately i ordered for nets to cover all stocked ponds. This waded off all the birds from the ponds for some time. However interesting to note the hammer cobs were quick to adjust with the netting and now found their way around the pond edges particularly those stocked with 3 months and below Clarius fingerlings. The Commorants followed in and being good fishers took advantage of opennings at the edges to get into the ponds. However, for Pelican Kinfishers and the pygmy, they were unlucky due to their mode of predation. Finally the African fisheagle is my latest challenge.It is my worry due to the fact that it goes for the adult Clarius.Since it prefers positioning itself at the nearby trees!!, I have asked the Fisheries incharge at SAC to have all trees near the farm cut down. Secondly, the timing is coinciding with feeding hours thus i have staff guarding within this periods. Concerning the Otters, though it is not my challenge, I tend to believe that an ecological barrier would serve best. Thank you and I will surely share with you some of the photos from Sagana Aquaculture Centre, Kenya on the predator challenge. Paul Orina- Research Officer KMFRI P.O.Box 30100-451 SAGANA, KENYA. 0710-774477

On Thu, 7/22/10, 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: Thursday, July 22, 2010, 6:25 PM

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/

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