Re: [Sarnissa-french-aquaculture] [Sarnissa-african-aquaculture] Gender control for tilapia production Mixed sex graded system
Dear Ken, It sounds cunning ! My only concern is the effect of successive stress (the successive sorting for size) on the growth rate. A long time ago (when my hair were not white...) we compare the growth rate of groups of juveniles (the size at which you should begin the sorting for size) which were manipulated 5 times (during a 3 months period) or not manipulated. The growth rate was strongly inhibited in the manipulated groups because of the successive stress. Following your sorting for size, did you also find some rare females growing very fast ? A few of them can have growth rate very similar to the males. Thank you very much for your interesting message. JF Baroiller Cher Ken,, C'est astucieux ! Ma seule inquiètude est que ces tris successifs constituent des stress successifs avec des effets négatifs sur la croissance. Il y a quelques temps (quand je n'avais pas encore de cheveux blancs...), nous avions comparé la croissance de groupes de juvéniles (à la taille où vous devez commencer à voir des dimorphismes de croissance et où vous commencez vos tris successifs) qui étaient manipulés (péchés et aussitôt remis dans leur structure d'élevage) 5 fois en 3 mois ou au contraire des groupes que l'on ne péchait jamais. Au bout de 3 mois, les groupes manipulés présentait des poids moyen beaucoup plus faibles que ceux des lots non manipulés. La seule différence entre les lots était la manipulation (même famille, même densité, même alimentation, ...). Cette moins bonne croissance était liée au stress des manipulations successives. Sinon, quand vous faites vos tris, vous arrivé-t'il de trouver des femelles dans les animaux les plus gros ? En effet, on trouve parfois des femelles qui ont des croissances très proches de celles des mâles. Merci pour votre intéressant message, JF Baroiller Quand vous faites vos tris, vous arrive-t'il de trouver At 11:54 21/11/2008, you wrote:
Content-Language: en-US Content-Type: multipart/alternative;
boundary="_000_8ED3F2CA5B78E142B8193376C57330F8E1958A45B8EXCH2007adsti_"
From: kwbetts [mailto:kwbetts@meabt.com] Sent: 21 November 2008 06:56 To: William Leschen Subject: Re: [Sarnissa-stakeholders] Gender control for tilapia production
Hi,
My situation is a bit unique since I depend on my fry. Since I have no reliable source of healthy quality male fry, I raise mixed sex. My semi-intensive green water recirculated pool produces about 30 to 40 thousand fry in a year of which I need up to 11 thousand for grow out. In the one pool, I have an area of high density cage nets and about 2/3 of the pool I intentionally keep stocked with about 100 to 200 breading tilapias. Since my breading season runs from Oct through Nov and March through April with winter between them, I catch virtually all the fry in a baited umbrella net at a rate up to 800 per day (about 30 minutes of fishing) taking me through June to catch almost all of them. Of all that I catch I keep my grow out needs plus almost 50% extra. Then, rather than sexing them all, I sort the fish for size a couple of times in a way that separates out the slow growers (most of which will be females) and discard up to 1/3 of all that I previously kept. So, by the time they reach 100 grams, they are mostly males and have the runts removed. Of the fastests growing groups of these, I restock my breading area for the next breading season.
Manged bi-sex Tilapia. Sound complex? Not really, its in getting the process right. Advantages? No need for expensive and unreliable improted fry. No need for chemicals. No need for highly reliable and labour intensive hand sexing.
Ken
On Wed, 19 Nov 2008 11:58:49 +0000, William Leschen wrote
From French forum
Dear all,
We all know the importance of sex control for tilapia production in the majority of the numerous farming conditions of this species group. It is not necessary to remind you all that numerous techniques have been used up till now (hybridisation), or is more classically used for sex control such as manual sexing, hormonal inversion and use of YY males. Each of these techniques has been often discussed showing their advantages and disadvantages. We all know farmers who use one or another approach depending on his constraints which are essentially the cost, the facility for its use and its efficiency. However, it is harder to have a relative estimation of which farmers used which approach.
Would you share this information telling us if:
you use mainly a) manual sexing, b) hormonal inversion, c) off-springs of YY males, d) hybridisation, and mentioning which rearing conditions you are using (monoculture, polyculture, extensive or semi-intensive conditions). Or do you use predators and if it is the case which species do you use (Hemichromis, Heterobranchus, Clarias, Lates)? Finally, what is the main justification of your choice?
Thank you very much,
Helena D'Cotta and JF Baroiller ___________________________________
Dr. Helena D'Cotta CIRAD-PERSYST Aquaculture Research Unit, TA B-20/A, Bur.A18 Campus International de Baillarguet 34398 Montpellier cedex 5, France Tel : 33 - (0) 467593951; Fax : /3825 <mailto:dcotta@cirad.fr>dcotta@cirad.fr http://aquatrop.cirad.fr/
PS from Will See video clip (link below) of Helena and Jean Francois at work.
Please note clip is in a section of main news report
<http://minilien.com/?aPNxm6nYpr>http://minilien.com/?aPNxm6nYpr http://jt.france3.fr/regions/popup.php?id=e31a_invite&video_number=0
No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.175 / Virus Database: 270.9.8/1801 - Release Date: 11/20/2008 9:11 AM _______________________________________________ Sarnissa-african-aquaculture mailing list Sarnissa-african-aquaculture@lists.stir.ac.uk http://lists.stir.ac.uk/cgi-bin/mailman/listinfo/sarnissa-african-aquacultur...
Dr J.F. Baroiller CIRAD-Persyst, UPR20 Aquaculture et gestion des ressources aquatiques Campus International de Baillarguet TA B-20/A, Bur.A18 34398 Montpellier cedex 5 France (: 33.(0)4.67.59.39.51 (ligne directe); 33.(0)4.67.59.39.05 (sec) Fax : 33.(0)4.67.59.38.25 * baroiller@cirad.fr http://aquatrop.cirad.fr/ -------------- section suivante -------------- Une pièce jointe HTML a été nettoyée... URL: http://lists.stir.ac.uk/pipermail/sarnissa-french-aquaculture/attachments/20...
cher ken nous avons remaqué en cote d'ivoire que lorsque que nous fesons les pêches de contôle, les deux jours qui suivent les poissons ne prennent pas correctement les aliments. Le stress a un effet négatif sur la croissance des poissons. Il nous arrive de trouver de femelles aussi grosses que les mâles. Meilleurs salutations --- En date de : Ven 21.11.08, JF Baroiller <baroiller@cirad.fr> a écrit :
De: JF Baroiller <baroiller@cirad.fr> Objet: Re: [Sarnissa-french-aquaculture] [Sarnissa-african-aquaculture] Gender control for tilapia production Mixed sex graded system À: "William Leschen" <william.leschen@stir.ac.uk>, sarnissa-french-aquaculture@lists.stir.ac.uk Date: Vendredi 21 Novembre 2008, 17h44 Dear Ken,
It sounds cunning !
My only concern is the effect of successive stress (the successive sorting for size) on the growth rate. A long time ago (when my hair were not white...) we compare the growth rate of groups of juveniles (the size at which you should begin the sorting for size) which were manipulated 5 times (during a 3 months period) or not manipulated. The growth rate was strongly inhibited in the manipulated groups because of the successive stress.
Following your sorting for size, did you also find some rare females growing very fast ? A few of them can have growth rate very similar to the males.
Thank you very much for your interesting message.
JF Baroiller
Cher Ken,,
C'est astucieux !
Ma seule inquiètude est que ces tris successifs constituent des stress successifs avec des effets négatifs sur la croissance. Il y a quelques temps (quand je n'avais pas encore de cheveux blancs...), nous avions comparé la croissance de groupes de juvéniles (à la taille où vous devez commencer à voir des dimorphismes de croissance et où vous commencez vos tris successifs) qui étaient manipulés (péchés et aussitôt remis dans leur structure d'élevage) 5 fois en 3 mois ou au contraire des groupes que l'on ne péchait jamais. Au bout de 3 mois, les groupes manipulés présentait des poids moyen beaucoup plus faibles que ceux des lots non manipulés. La seule différence entre les lots était la manipulation (même famille, même densité, même alimentation, ...). Cette moins bonne croissance était liée au stress des manipulations successives.
Sinon, quand vous faites vos tris, vous arrivé-t'il de trouver des femelles dans les animaux les plus gros ? En effet, on trouve parfois des femelles qui ont des croissances très proches de celles des mâles.
Merci pour votre intéressant message,
JF Baroiller
Quand vous faites vos tris, vous arrive-t'il de trouver
At 11:54 21/11/2008, you wrote:
Content-Language: en-US Content-Type: multipart/alternative;
boundary="_000_8ED3F2CA5B78E142B8193376C57330F8E1958A45B8EXCH2007adsti_"
From: kwbetts [mailto:kwbetts@meabt.com] Sent: 21 November 2008 06:56 To: William Leschen Subject: Re: [Sarnissa-stakeholders] Gender control for tilapia production
Hi,
My situation is a bit unique since I depend on my fry. Since I have no reliable source of healthy quality male fry, I raise mixed sex. My semi-intensive green water recirculated pool produces about 30 to 40 thousand fry in a year of which I need up to 11 thousand for grow out. In the one pool, I have an area of high density cage nets and about 2/3 of the pool I intentionally keep stocked with about 100 to 200 breading tilapias. Since my breading season runs from Oct through Nov and March through April with winter between them, I catch virtually all the fry in a baited umbrella net at a rate up to 800 per day (about 30 minutes of fishing) taking me through June to catch almost all of them. Of all that I catch I keep my grow out needs plus almost 50% extra. Then, rather than sexing them all, I sort the fish for size a couple of times in a way that separates out the slow growers (most of which will be females) and discard up to 1/3 of all that I previously kept. So, by the time they reach 100 grams, they are mostly males and have the runts removed. Of the fastests growing groups of these, I restock my breading area for the next breading season.
Manged bi-sex Tilapia. Sound complex? Not really, its in getting the process right. Advantages? No need for expensive and unreliable improted fry. No need for chemicals. No need for highly reliable and labour intensive hand sexing.
Ken
On Wed, 19 Nov 2008 11:58:49 +0000, William Leschen wrote
From French forum
Dear all,
We all know the importance of sex control for tilapia production in the majority of the numerous farming conditions of this species group. It is not necessary to remind you all that numerous techniques have been used up till now (hybridisation), or is more classically used for sex control such as manual sexing, hormonal inversion and use of YY males. Each of these techniques has been often discussed showing their advantages and disadvantages. We all know farmers who use one or another approach depending on his constraints which are essentially the cost, the facility for its use and its efficiency. However, it is harder to have a relative estimation of which farmers used which approach.
Would you share this information telling us if:
you use mainly a) manual sexing, b) hormonal inversion, c) off-springs of YY males, d) hybridisation, and mentioning which rearing conditions you are using (monoculture, polyculture, extensive or semi-intensive conditions). Or do you use predators and if it is the case which species do you use (Hemichromis, Heterobranchus, Clarias, Lates)? Finally, what is the main justification of your choice?
Thank you very much,
Helena D'Cotta and JF Baroiller ___________________________________
Dr. Helena D'Cotta CIRAD-PERSYST Aquaculture Research Unit, TA B-20/A, Bur.A18 Campus International de Baillarguet 34398 Montpellier cedex 5, France Tel : 33 - (0) 467593951; Fax : /3825 <mailto:dcotta@cirad.fr>dcotta@cirad.fr http://aquatrop.cirad.fr/
PS from Will – See video clip (link below) of Helena and Jean Francois at work.
Please note clip is in a section of main news report
<http://minilien.com/?aPNxm6nYpr>http://minilien.com/?aPNxm6nYpr
http://jt.france3.fr/regions/popup.php?id=e31a_invite&video_number=0
No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.175 / Virus Database: 270.9.8/1801 - Release Date: 11/20/2008 9:11 AM _______________________________________________ Sarnissa-african-aquaculture mailing list Sarnissa-african-aquaculture@lists.stir.ac.uk http://lists.stir.ac.uk/cgi-bin/mailman/listinfo/sarnissa-african-aquacultur...
Dr J.F. Baroiller CIRAD-Persyst, UPR20 Aquaculture et gestion des ressources aquatiques Campus International de Baillarguet TA B-20/A, Bur.A18 34398 Montpellier cedex 5 France
(: 33.(0)4.67.59.39.51 (ligne directe); 33.(0)4.67.59.39.05 (sec) Fax : 33.(0)4.67.59.38.25 * baroiller@cirad.fr http://aquatrop.cirad.fr/ -------------- section suivante -------------- Une pièce jointe HTML a été nettoyée... URL: http://lists.stir.ac.uk/pipermail/sarnissa-french-aquaculture/attachments/20...
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