Re: [Sarnissa-french-aquaculture] [Sarnissa-african-aquaculture] [FRxEN Cross-post] Pourquoi le niloticus? Why niloticus?

Dear Lionel, Humans determine what species to cultivate. We do not say "What species is best for the farmer/ country", but "With O. niloticus you can make the most money". In South Africa we have the same problem with O. mossambicus, it grows too slowly. Slowly for whom? Do you compare O. mossambicus in an environment where the water temperature do not exceed 24 deg C for more than 3 months of the year, with the GIFT strain of O. niloticus, which as far as I am aware, is the fastest growing of all the Tilapias (species/ varieties/ strains within species)? And this in an environment that has a water temperature of 28 deg C for 6 or more months per year? Switching O. mossambicus with O. niloticus will not make your fish grow faster, as both have the same temperature requirement. You will just end up with fertile crosses/ hybrids, as is already happening in South Africa, with people illegally smuggling in O. niloticus (most probably from neighbouring Zimbabwe). See the (cellphone) photo attached, the mossambicus bars on the flank & the niloticus bars on the tail clearly visible. These hybrids also do not really grow any faster than their (pure) parents, as the main problem remains the low water temperature for the greater part of the year. One should rather improve the growing capability of the local species (as with the GIFT strain), or you should turn to a species that is more suitable for your own environment (Cyprinus carpio, the common European carp) in the case of South Africa. Alternatively, control the environment. This means warm water recirculating aquaculture systems, which can be done by commercial farmers, but not subsistence/ small-scale farmers. Also, why do a low cost fish like Tilapia in an expensive environment like a RAS? Anyway, these are just some of my own thoughts/ observations after 25 years. Regards, Johan Johan Theron Aquaculture Research Unit University of Limpopo Private Bag X1106 Sovenga 0727 Limpopo Province Republic of South Africa Tel +27 (0) 15 268 2295 Fax +27 (0) 86 540 4811 Mobile +27 (0) 82 200 5279 johant(a)ul.ac.za johantheron58(a)yahoo.com "To strive, to seek, to find, and not to yield" Bonjour à tous, Ce message de C. Ducarme est resté sans réponse, je me permets de le relancer et de poster une traduction sur le forum anglophone. J'essaierais de traduire en français les éventuelles réponses. Dear all, This question by C. Ducarme remained unanswered and un-commented on the French forum until now. If any comment arises from the English forum, I will try to translate it into French... Please forgive my bad English ! Thanks Lionel Dabbadie Dear all, I have a question for our scientists : Why not make more applied and applicable (...) research on species other than niloticus, which must be accounting today for 90-95% of the world tilapia production? - if we admit that optimal temperature for growth (and feed conversion) of niloticus is +/- 28°C - that below 24°C, its growth falls dramatically, - that niloticus is (theoretically) absent from many African water bodies and that introducing it is a problem. Please note that there are currently some discussion about it in South Africa - that we must not forget that in intensive farming, oxygenation efficiency is dependant on temperature, so that a lower temperature is more efficient and more profitable - that most projects I visit observe 1 to 5 months growth delay per year, with many consequences not understood by farmers Why keeping on insisting in imposing this species at the borders of its living areas, instead of valorising native fauna ? I have personally been very disappointed when work on O. aureus was stopped, because this species had many advantages, among which to be less thermophilic and to have lower level of spontaneous spawning, so that it came out more profitable to be grown in our conditions. This said, work by Maldeco was quite remarkable: adapt, on their own funds, O. shiranus and O. karongae for intensive fish farming in lake Malawi. But many stake-holder less known work in the shade on O. andersonii, mortimerii... I really hope that we will soon see "GIFT" projects developed on these species that will be very useful in limit areas of our dear niloticus Regards Ducarme Chr. Début du message réexpédié : _______________________________________________ Sarnissa-african-aquaculture mailing list Sarnissa-african-aquaculture(a)lists.stir.ac.uk http://lists.stir.ac.uk/cgi-bin/mailman/listinfo/sarnissa-african-aquacultu…