Hi Alexandra To answer your questions: · No, the management of larger ponds is easier than that of small water bodies such as tanks, that depend on filtration and energy. Water volume implies a certain resilience against water quality change…be that temperature or chemical changes…that would adversely affect breeding performance. I know we would all like to see our fish in carefully controlled, scientifically designed, sterile re-circulating systems…but did we ever ask the fish what they prefer? Green water ponds produce the best fish, be that for eating …or for breeding purposes…the jury is not out on that. · The catching of mouth-brooding female tilapia in round tanks can be an issue. Screens that divide the tanks have to be used, and this is often a harsh and stressful experience for the fish. In hapas, a pole under the net is slowly moved to one end to crowd the fish into one corner (as in the photo). Females are then netted out and the eggs gently flushed out using a pipette bottle (not the fish shaken violently head-down into a bucket!). Use of the pipette-bottle flushes out 100% of the eggs that the older method often does not, resulting in a few eggs still in the mouth and reduced spawning thereafter by that female fish. Once stripped of eggs, the female is then dropped into the other side of the hapa, so is only out the water for about 30 seconds. The hapa netting holds any eggs that may be spat out, and can be collected at the end of the process. Since all the water is common, no temperature changes result. Eggs collecting bowls can be floated in the tank, before removal to the hatchery. In Thailand, I have seen a mobile hatchery on a trailer, where the collected bowls are in shade, and the eggs temporarily housed in a small 12v recycling system that keeps them well-oxygenated, cool and moving. · Sure, larger tanks implies you need more space, something that many hatcheries may not have. But new systems that don’t use the concrete and plastic systems much beloved by RAS have evolved in the Far East and are now used in Africa. Rectangular ponds comprising the entire footprint of a greenhouse tunnel (50x10m or 30x 10m), lined with a liner, work well as breeding ponds where warmer water than ambient is required. This can be connected to filtration if required, but the loading on a breeding system is far less than on a grow out system. Tilapia seem to breed better if kept slightly hungry…something to do with evolution: environmental stresses causing a turn to reproduction rather than growth. A lined earth pond is certainly not more expensive than an equal sized tank system. Regards Nick *From:* Alexandra Pounds [mailto:alexandrapounds@gmail.com] *Sent:* 30 April 2018 10:22 AM *To:* Nick James <nickjames(a)intekom.co.za> *Cc:* sarnissa-french-aquaculture(a)lists.stir.ac.uk *Subject:* Re: Calling all Tilapia Hatchery Experts / Demande pour Les Experts d'éclosion de tilapia Excellent photo Nick - thanks for sharing. It makes sense that conditions closer to those in the wild would improve success rates. Some questions: - Is the management of larger ponds is more difficult? - Are there different management techniques for catching brooders in larger tanks? - Does anyone encounter space, water, energy, or financial limitations for larger tanks? Merci å Nick pour le photo excellent. C'est logique que des conditions qui resemble celle-lui de la sauvage voudraient ameliorer des taux de succes. Quelques questions: - La gestion, est-il plus difficil pour des bacs qui sont plus grandes? - Il y a des techniques differents de la gestion pour attraper des geniteurs dans les bacs plus grandes? - Il y a personnes qui rencontré des limitations de space, d'eau, d'énergie, ou de finance pour des bacs plus grandes? Alexandra On Mon, Apr 30, 2018 at 10:57 AM, Nick James <nickjames(a)intekom.co.za> wrote: 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 -- --- Alexandra Pounds MSc Sustainable Aquaculture, University of Stirling BSc Earth Systems, Stanford University (+1) 650.336.4554 (+44) 757.283.9224