Sarnissa-french-aquaculture March 2018

sarnissa-french-aquaculture@lists.stir.ac.uk

3 participants
4 discussions

Reminder for tilapia hatchery operators from Ghana Cannibalism

by William Leschen

Cher Karen Vos observations sont sur place. Même dans un système RAS soigneusement contrôlé élevant des alevins de tilapia dans des cuves en béton de 2200 litres, nous considérons le cannibalisme comme un énorme problème qui nécessite une gestion constante et prudente. Les tiges de Tilapia (celles qui poussent plus vite) de 30 mm sont tout à fait capables de se nourrir de façon vorace sur les alevins, et doubleront de taille en une semaine si elles ne sont pas étalées. C'est pourquoi la vieille pratique des années 1960 consistant à «écrémer les alevins» des étangs de reproduction est si inutile et improductive. Les grands hapas pour l'élevage (20x5m) et les petits hapas pour l'inversion sexuelle (1-2m2) fonctionnent très bien et sont faciles à gérer. Lors de l'enlèvement et du comptage des alevins, l'utilisation d'une niveleuse est essentielle pour toutes les tailles inférieures à 30 mm. Assurez-vous simplement que l'inversion sexuelle et la reproduction ne sont pas effectuées dans le même plan d'eau, en raison de l'altération hormonale. Nous constatons qu'un cycle d'enlèvement des œufs de 10 jours est plus productif que de permettre à la femelle d'achever la période d'incubation complète, ou une période de temps plus courte. Cordialement Nick Nicholas P E James MSc (Ichtyologie) (Rhodes), BA (Hons, Géographie) (Rhod.), Grad. C. E. Écloserie de Rivendell PO Box 6146 Place du marché Grahamstown E. Cape 6141 Dear Karen Your observations are spot on. Even in a carefully controlled RAS system rearing tilapia fry in 2200l concrete tanks we see cannibalism as a huge problem that needs constant and careful management to sort out. Tilapia ‘shoots’ (those that grow faster) of 30mm are quite capable of feeding voraciously on fry, and will double in size in a week if not graded out. This is why the old 1960’s practice of “skimming off fry” from breeding ponds is so wasteful and unproductive. Large hapas for breeding (20x 5m), and small hapas for sex reversal (1-2m2) work very well and are easy to manage. On removal and counting of fry, use of a fish grader is essential for all sizes below 30mm. Just ensure that sex reversal and breeding are not done in the same water body, due to the hormone impeding breeding. We find that a 10-day cycle of egg removal is more productive overall than allowing the female to complete the full incubation period, or a shorter time period. Regards Nick Nicholas P E James MSc (Ichthyology) (Rhodes), BA (Hons, Geography) (Rhod.), Grad. C. E. Rivendell Hatchery PO Box 6146 Market Square Grahamstown E. Cape 6141 Cell +27-(0)82 575 9781 email nickjames(a)intekom.co.za<mailto:nickjames@intekom.co.za> website www.rivendellhatchery.co.za<http://www.rivendellhatchery.co.za> From: Sarnissa-african-aquaculture [mailto:sarnissa-african-aquaculture-bounces@lists.stir.ac.uk] On Behalf Of William Leschen via Sarnissa-african-aquaculture Sent: 09 March 2018 03:55 AM To: sarnissa-african-aquaculture Mailing List <sarnissa-african-aquaculture(a)lists.stir.ac.uk<mailto:sarnissa-african-aquaculture@lists.stir.ac.uk>>; sarnissa-french-aquaculture Mailing List <sarnissa-french-aquaculture(a)lists.stir.ac.uk<mailto:sarnissa-french-aquaculture@lists.stir.ac.uk>> Subject: Reminder for tilapia hatchery operators from Ghana -------- Forwarded Message -------- Subject: reminder for tilapia hatchery operators Date: Sat, 3 Mar 2018 10:48:55 -0600 From: Karen L. Veverica <veverkl(a)gmail.com><mailto:veverkl@gmail.com> To: sarnissa-african-aquaculture(a)lists.stir.ac.uk<mailto:sarnissa-african-aquaculture@lists.stir.ac.uk> En francais au dessus Merci Karen I was chatting with Evans Danso in Ghana via WhatsApp recently about a problem he was having with reduced output in his tilapia fry production. Reasons can be several but the first one I mentioned was leftover fry/fingerlings that can cannibalize the new fry. Upon further discussion, he told me they harvest fry twice a day from the ponds and the photo he sent showed the long, narrow ponds. He decided to see if cannibalism was the case and drained the pond and did find a few fingerlings in there. He then dissected some and sent me a photo. One small fingerling had 28 fry in its stomach- see attachment. He sent several more photos, all of very small tilapia having very full stomachs and intestines of tilapia fry. Normally, hapa spawning can prevent this from being a problem but only if the operators are very careful not to leave any fry or fingerlings in the hapa. Draining spawning ponds after every cycle is also a means of preventing cannibalism and thus increasing fry production but it requires the operator to dry the pond between sessions and make sure no fry are left in nests. We also discussed how the females can be synchronized, which is often a practice that is beneficial but that means fry production will be high for a few days and then drop off until the females all spawn again. So somebody who collects daily would normally notice a drop in fry collections and then they would pick up again. Other reasons for a drop in fry production are: * cool temperatures- this will increase time for spawning and egg hatching; and even stop spawning * chronic low oxygen levels (those of you with hapas should be careful here, especially if you are letting the sides of the hapa foul) * low nutritional condition of the broodstock- especially the females. This is remedied by giving the females a resting time in a pond or hapa with no males present. * build up of predator insects and frogs in pond or hapa Do any of the readers have other observations to share? A big thanks to Mr. Danso for providing the photo. Karen L. Veverica Director, E.W. Shell Fisheries Research Center School of Fisheries, Aquaculture and Aquatic Sciences Auburn University, AL USA office: 1-334-844-4667 cell: +1 334-332-1560 Je discutais récemment avec Evans Danso au Ghana via WhatsApp au sujet d'un problème qu'il rencontrait avec une production réduite dans sa production d'alevins de tilapia. Les raisons peuvent être multiples, mais la première que j'ai mentionnée était des restes d'alevins / alevins qui peuvent cannibaliser les nouveaux alevins. Après d'autres discussions, il m'a dit qu'ils récoltaient des alevins deux fois par jour dans les étangs et que la photo qu'il envoyait montrait les étangs longs et étroits. Il a décidé de voir si le cannibalisme était le cas et a drainé l'étang et a trouvé quelques fingerlings là-bas. Il a ensuite disséqué certains et m'a envoyé une photo. Un petit alevin avait 28 alevins dans son estomac - voir l'attachement. Il a envoyé plusieurs autres photos, toutes de très petites tilapia ayant des estomacs très pleins et des intestins d'alevins de tilapia. Normalement, le hapa spawning peut éviter que cela ne soit un problème, mais seulement si les opérateurs font très attention à ne pas laisser d'alevins ou d'alevins dans le hapa. Le drainage des bassins de frai après chaque cycle est également un moyen de prévenir le cannibalisme et donc d'augmenter la production de frites, mais il faut que l'opérateur sèche l'étang entre les sessions et qu'il ne laisse pas d'alevins dans les nids. Nous avons également discuté de la façon dont les femelles peuvent être synchronisées, ce qui est souvent une pratique bénéfique, mais cela signifie que la production d'alevins sera élevée pendant quelques jours et qu'elle diminuera jusqu'à ce que les femelles fassent à nouveau frayer. Donc, quelqu'un qui recueille tous les jours noterait normalement une baisse dans les collections d'alevins et ensuite ils ramasseraient. Les autres raisons d'une baisse de la production d'alevins sont: • températures fraîches - cela augmentera le temps de frai et d'éclosion des œufs; et même arrêter le frai • les niveaux chroniques d'oxygène faible (ceux d'entre vous avec des hapas devraient faire attention ici, surtout si vous laissez les côtés de la hapa) • Faible état nutritionnel des géniteurs - en particulier les femelles. Ceci est résolu en donnant aux femelles un temps de repos dans un étang ou hapa sans mâles présents. • accumulation d'insectes prédateurs et de grenouilles dans un étang ou un hapa Est-ce que l'un des lecteurs a d'autres observations à partager? Un grand merci à M. Danso pour avoir fourni la photo. Karen L. Veverica Directeur, E.W. Shell Fisheries Research Centre École des pêches, de l'aquaculture et des sciences aquatiques Université d'Auburn, AL USA bureau: 1-334-844-4667 Cellule: +1 334-332-1560

6 years, 9 months

FW: reminder for tilapia hatchery operators

by William Leschen

Ce n'est normalement pas un problème lorsqu'on utilise des hapas, à moins que les opérateurs ne parviennent pas à enlever les alevins qui ont été crachés par les femelles quand ils étaient en train d'encombrer les couveuses dans le hapa. Je peux comprendre que toutes les fermes n'ont pas des travailleurs aussi prudents qui se soucient ou qui sont correctement formés et c'est donc tout à fait possible. Karen L. Veverica Directeur, E.W. Shell Fisheries Research Centre École des pêches, de l'aquaculture et des sciences aquatiques Université d'Auburn, AL USA From: Karen L. Veverica [mailto:veverkl@gmail.com] Sent: 12 March 2018 16:44 To: Gerd Teunissen <agerdteunissen(a)gmail.com>; sarnissa-french-aquaculture Mailing List <sarnissa-french-aquaculture(a)lists.stir.ac.uk>; William Leschen <william.leschen(a)stir.ac.uk>; sarnissa-african-aquaculture Mailing List Return Address <sarnissa-african-aquaculture-bounces(a)lists.stir.ac.uk> Subject: Re: [Sarnissa] reminder for tilapia hatchery operators It normally isn't a problem when using hapas unless the operators are failing to remove any fry that were spit by females when they were crowding the brooders in the hapa. I can figure that not all farms have equally careful workers who care or who are properly trained and so it is quite possible. Karen L. Veverica Director, E.W. Shell Fisheries Research Center School of Fisheries, Aquaculture and Aquatic Sciences Auburn University, AL USA office: 1-334-844-4667 cell: +1 334-332-1560 On 3/8/2018 8:43 PM, Gerd Teunissen wrote: Does this also happen when you use hapas? De: Sarnissa-french-aquaculture [mailto:sarnissa-french-aquaculture-bounces@lists.stir.ac.uk] Em nome de Randall Brummett Enviada: quinta-feira, 8 de março de 2018 16:18 Para: Karen L. Veverica; sarnissa-french-aquaculture Mailing List; William Leschen (william.leschen(a)stir.ac.uk<mailto:william.leschen@stir.ac.uk>); sarnissa-african-aquaculture-bounces(a)lists.stir.ac.uk<mailto:sarnissa-african-aquaculture-bounces@lists.stir.ac.uk> Assunto: Re: [Sarnissa] reminder for tilapia hatchery operators We had this problem all the time in Malawi with T. rendalli. After two weeks, fry production started down because we couldn't catch all the juveniles that were eating them. Had to take the pond apart and start over. From: Sarnissa-african-aquaculture [mailto:sarnissa-african-aquaculture-bounces@lists.stir.ac.uk] On Behalf Of Karen L. Veverica via Sarnissa-african-aquaculture Sent: Thursday, March 08, 2018 9:32 AM To: sarnissa-african-aquaculture(a)lists.stir.ac.uk<mailto:sarnissa-african-aquaculture@lists.stir.ac.uk> Subject: Fwd: reminder for tilapia hatchery operators here it is again, Will -------- Forwarded Message -------- Subject: reminder for tilapia hatchery operators Date: Sat, 3 Mar 2018 10:48:55 -0600 From: Karen L. Veverica <veverkl(a)gmail.com><mailto:veverkl@gmail.com> To: sarnissa-african-aquaculture(a)lists.stir.ac.uk<mailto:sarnissa-african-aquaculture@lists.stir.ac.uk> I was chatting with Evans Danso in Ghana via WhatsApp recently about a problem he was having with reduced output in his tilapia fry production. Reasons can be several but the first one I mentioned was leftover fry/fingerlings that can cannibalize the new fry. Upon further discussion, he told me they harvest fry twice a day from the ponds and the photo he sent showed the long, narrow ponds. He decided to see if cannibalism was the case and drained the pond and did find a few fingerlings in there. He then dissected some and sent me a photo. One small fingerling had 28 fry in its stomach- see attachment. He sent several more photos, all of very small tilapia having very full stomachs and intestines of tilapia fry. Normally, hapa spawning can prevent this from being a problem but only if the operators are very careful not to leave any fry or fingerlings in the hapa. Draining spawning ponds after every cycle is also a means of preventing cannibalism and thus increasing fry production but it requires the operator to dry the pond between sessions and make sure no fry are left in nests. We also discussed how the females can be synchronized, which is often a practice that is beneficial but that means fry production will be high for a few days and then drop off until the females all spawn again. So somebody who collects daily would normally notice a drop in fry collections and then they would pick up again. Other reasons for a drop in fry production are: * cool temperatures- this will increase time for spawning and egg hatching; and even stop spawning * chronic low oxygen levels (those of you with hapas should be careful here, especially if you are letting the sides of the hapa foul) * low nutritional condition of the broodstock- especially the females. This is remedied by giving the females a resting time in a pond or hapa with no males present. * build up of predator insects and frogs in pond or hapa Do any of the readers have other observations to share? A big thanks to Mr. Danso for providing the photo. Karen L. Veverica Director, E.W. Shell Fisheries Research Center School of Fisheries, Aquaculture and Aquatic Sciences Auburn University, AL USA office: 1-334-844-4667 cell: +1 334-332-1560

6 years, 9 months

Reminder for tilapia hatchery operators from Ghana

by William Leschen

-------- Forwarded Message -------- Subject: reminder for tilapia hatchery operators Date: Sat, 3 Mar 2018 10:48:55 -0600 From: Karen L. Veverica <veverkl(a)gmail.com><mailto:veverkl@gmail.com> To: sarnissa-african-aquaculture(a)lists.stir.ac.uk<mailto:sarnissa-african-aquaculture@lists.stir.ac.uk> En francais au dessus Merci Karen I was chatting with Evans Danso in Ghana via WhatsApp recently about a problem he was having with reduced output in his tilapia fry production. Reasons can be several but the first one I mentioned was leftover fry/fingerlings that can cannibalize the new fry. Upon further discussion, he told me they harvest fry twice a day from the ponds and the photo he sent showed the long, narrow ponds. He decided to see if cannibalism was the case and drained the pond and did find a few fingerlings in there. He then dissected some and sent me a photo. One small fingerling had 28 fry in its stomach- see attachment. He sent several more photos, all of very small tilapia having very full stomachs and intestines of tilapia fry. Normally, hapa spawning can prevent this from being a problem but only if the operators are very careful not to leave any fry or fingerlings in the hapa. Draining spawning ponds after every cycle is also a means of preventing cannibalism and thus increasing fry production but it requires the operator to dry the pond between sessions and make sure no fry are left in nests. We also discussed how the females can be synchronized, which is often a practice that is beneficial but that means fry production will be high for a few days and then drop off until the females all spawn again. So somebody who collects daily would normally notice a drop in fry collections and then they would pick up again. Other reasons for a drop in fry production are: * cool temperatures- this will increase time for spawning and egg hatching; and even stop spawning * chronic low oxygen levels (those of you with hapas should be careful here, especially if you are letting the sides of the hapa foul) * low nutritional condition of the broodstock- especially the females. This is remedied by giving the females a resting time in a pond or hapa with no males present. * build up of predator insects and frogs in pond or hapa Do any of the readers have other observations to share? A big thanks to Mr. Danso for providing the photo. Karen L. Veverica Director, E.W. Shell Fisheries Research Center School of Fisheries, Aquaculture and Aquatic Sciences Auburn University, AL USA office: 1-334-844-4667 cell: +1 334-332-1560 Je discutais récemment avec Evans Danso au Ghana via WhatsApp au sujet d'un problème qu'il rencontrait avec une production réduite dans sa production d'alevins de tilapia. Les raisons peuvent être multiples, mais la première que j'ai mentionnée était des restes d'alevins / alevins qui peuvent cannibaliser les nouveaux alevins. Après d'autres discussions, il m'a dit qu'ils récoltaient des alevins deux fois par jour dans les étangs et que la photo qu'il envoyait montrait les étangs longs et étroits. Il a décidé de voir si le cannibalisme était le cas et a drainé l'étang et a trouvé quelques fingerlings là-bas. Il a ensuite disséqué certains et m'a envoyé une photo. Un petit alevin avait 28 alevins dans son estomac - voir l'attachement. Il a envoyé plusieurs autres photos, toutes de très petites tilapia ayant des estomacs très pleins et des intestins d'alevins de tilapia. Normalement, le hapa spawning peut éviter que cela ne soit un problème, mais seulement si les opérateurs font très attention à ne pas laisser d'alevins ou d'alevins dans le hapa. Le drainage des bassins de frai après chaque cycle est également un moyen de prévenir le cannibalisme et donc d'augmenter la production de frites, mais il faut que l'opérateur sèche l'étang entre les sessions et qu'il ne laisse pas d'alevins dans les nids. Nous avons également discuté de la façon dont les femelles peuvent être synchronisées, ce qui est souvent une pratique bénéfique, mais cela signifie que la production d'alevins sera élevée pendant quelques jours et qu'elle diminuera jusqu'à ce que les femelles fassent à nouveau frayer. Donc, quelqu'un qui recueille tous les jours noterait normalement une baisse dans les collections d'alevins et ensuite ils ramasseraient. Les autres raisons d'une baisse de la production d'alevins sont: • températures fraîches - cela augmentera le temps de frai et d'éclosion des œufs; et même arrêter le frai • les niveaux chroniques d'oxygène faible (ceux d'entre vous avec des hapas devraient faire attention ici, surtout si vous laissez les côtés de la hapa) • Faible état nutritionnel des géniteurs - en particulier les femelles. Ceci est résolu en donnant aux femelles un temps de repos dans un étang ou hapa sans mâles présents. • accumulation d'insectes prédateurs et de grenouilles dans un étang ou un hapa Est-ce que l'un des lecteurs a d'autres observations à partager? Un grand merci à M. Danso pour avoir fourni la photo. Karen L. Veverica Directeur, E.W. Shell Fisheries Research Centre École des pêches, de l'aquaculture et des sciences aquatiques Université d'Auburn, AL USA bureau: 1-334-844-4667 Cellule: +1 334-332-1560

6 years, 9 months

Re: [Sarnissa] reminder for tilapia hatchery operators

by Randall Brummett

We had this problem all the time in Malawi with T. rendalli. After two weeks, fry production started down because we couldn't catch all the juveniles that were eating them. Had to take the pond apart and start over. From: Sarnissa-african-aquaculture [mailto:sarnissa-african-aquaculture-bounces@lists.stir.ac.uk] On Behalf Of Karen L. Veverica via Sarnissa-african-aquaculture Sent: Thursday, March 08, 2018 9:32 AM To: sarnissa-african-aquaculture(a)lists.stir.ac.uk Subject: Fwd: reminder for tilapia hatchery operators here it is again, Will -------- Forwarded Message -------- Subject: reminder for tilapia hatchery operators Date: Sat, 3 Mar 2018 10:48:55 -0600 From: Karen L. Veverica <veverkl(a)gmail.com><mailto:veverkl@gmail.com> To: sarnissa-african-aquaculture(a)lists.stir.ac.uk<mailto:sarnissa-african-aquaculture@lists.stir.ac.uk> I was chatting with Evans Danso in Ghana via WhatsApp recently about a problem he was having with reduced output in his tilapia fry production. Reasons can be several but the first one I mentioned was leftover fry/fingerlings that can cannibalize the new fry. Upon further discussion, he told me they harvest fry twice a day from the ponds and the photo he sent showed the long, narrow ponds. He decided to see if cannibalism was the case and drained the pond and did find a few fingerlings in there. He then dissected some and sent me a photo. One small fingerling had 28 fry in its stomach- see attachment. He sent several more photos, all of very small tilapia having very full stomachs and intestines of tilapia fry. Normally, hapa spawning can prevent this from being a problem but only if the operators are very careful not to leave any fry or fingerlings in the hapa. Draining spawning ponds after every cycle is also a means of preventing cannibalism and thus increasing fry production but it requires the operator to dry the pond between sessions and make sure no fry are left in nests. We also discussed how the females can be synchronized, which is often a practice that is beneficial but that means fry production will be high for a few days and then drop off until the females all spawn again. So somebody who collects daily would normally notice a drop in fry collections and then they would pick up again. Other reasons for a drop in fry production are: * cool temperatures- this will increase time for spawning and egg hatching; and even stop spawning * chronic low oxygen levels (those of you with hapas should be careful here, especially if you are letting the sides of the hapa foul) * low nutritional condition of the broodstock- especially the females. This is remedied by giving the females a resting time in a pond or hapa with no males present. * build up of predator insects and frogs in pond or hapa Do any of the readers have other observations to share? A big thanks to Mr. Danso for providing the photo. Karen L. Veverica Director, E.W. Shell Fisheries Research Center School of Fisheries, Aquaculture and Aquatic Sciences Auburn University, AL USA office: 1-334-844-4667 cell: +1 334-332-1560

6 years, 9 months

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