One of the aspects that seriously affect hatching of tilapia eggs which has not been mentioned, is the breeding set-up used. The old-fashioned rectangular concrete or (even worse) round plastic breeding tank system whereby tilapia breeders are confined to a small space goes against Nature. In the wild, tilapia nests are often 1-2m in diameter and spaced 1-5m apart, between breeding males. Once spawning is complete, mouth-brooding females leave the arena. In captivity, we try to circumvent this by cramming many males and even more females in a small space…often tanks as small as 2000-5000l. This results in much inter-male competition and aggression, interruption of the spawning process by other fish, as well as little room for mouth-brooding females to escape over-attentive or even competitive males. Modern hapa-breeding methods using long hapas (10-40m in length by 3-5m width) in tunnels or in ponds in warmer areas, get over this problem. Males have space to be territorial without interfering with each other and mouth-brooding females can find refuge. This all results in much better ‘harvests’ of more viable eggs, and is used by most commercial hatcheries these days. The main issue seems to be convincing conservative government officials who seem to be unaware of these newer and more successful methods for use in their fish stations… I attach an example (with thanks to Vedad Alavian for the use of a photo of his fish farm in Kasama, NE Zambia). Regards Nick Nicholas P E James MSc (Ichthyology) (Rhodes), BA (Hons, Geography) (Rhod.), Grad. C. E., Pr. Sci. Nat. Rivendell Hatchery PO Box 6146 Market Square Grahamstown E. Cape 6141 Cell +27-(0)82 575 9781 email nickjames(a)intekom.co.za website www.rivendellhatchery.co.za *From:* Sarnissa-african-aquaculture [mailto:sarnissa-african- aquaculture-bounces(a)lists.stir.ac.uk] *On Behalf Of *Alexandra Pounds via Sarnissa-african-aquaculture *Sent:* 29 April 2018 05:43 PM *To:* sarnissa-french-aquaculture(a)lists.stir.ac.uk; sarnissa-african-aquaculture(a)lists.stir.ac.uk *Subject:* Calling all Tilapia Hatchery Experts / Demande pour Les Experts d'éclosion de tilapia *[English] What have you found to be the key to successful hatching of tilapia eggs? Is there a magic bullet? What is your estimated survival rates for: Hatching? Swim up? First Feeding? Sex Reversal? * *Ideas presented (by Karen Veverica & Nick James): * - managers should keep the eggs moving; - eggs should not be left out in bowls for too long; - bowls should be kept clean; - eggs should be carefully ejected from the female's mouth; - temperature should stay stable; - *Oreochromis ssp.* should be kept separate to avoid hybridisation, which can result in poor fertilisation and viability. *[Français] Avez-vous rencontré la clé de l'éclosion réussi des oeufs de tilapia? Il y a un balle magique? Qu'est-ce que sont votre taux de survie pour: L'éclosion? Nager? Premiere repas? Retournement de sexe? * *Idées presenté (pour Karen Veverica et Nick James):* - les chefs doivent continuer le movement des oeufs tous les temps; - il faut que des oeufs ne sont pas délaissé pour beaucoup des temps; - il faut que des bols sont propres; - il faut que des oeufs sont s'éjectés avec prudence de la bouche de la femalle; - il faut que le temperature est stable; - il faut que *Oreochromis ssp. *sont séparé pour éviter hybridisation, dont qui pourrait provoquer mauvais fertilisation et viabilité. --- Alexandra Pounds Assistant Manager Production Hatchery - OSO Farming LGA MSc Sustainable Aquaculture, University of Stirling BSc Earth Systems, Stanford University (+44) 757.283.9224