Broodstock conditioning of the oyster Crassostrea gigas: origin and temperature effect Jorge Cha ´vez-Villalba a , Julien Pommier a , Jimmy Andriamiseza a , Ste ´phane Pouvreau b , Jean Barret b , Jean-Claude Cochard b, * , Marcel Le Pennec a a U.M.R. C.N.R.S. 6539, Institut Universitaire Europe ´en de la Mer, 29280 Plouzane ´, France b Laboratoire de Physiologie des Inverte ´bre ´s, IFREMER Centre de Brest, BP 70, 29280 Plouzane ´, France Received 27 February 2001; received in revised form 4 June 2001; accepted 4 December 2001 Abstract Broodstock conditioning of the pacific oyster Crassostrea gigas (Thunberg) was examined in the laboratory under controlled conditions. Three experiments were undertaken to determine (i) the effect of the origin on gametogenesis, (ii) the time necessary to obtain the first mature oocytes in standard conditioning procedures, and (iii) the impact of different conditioning temperatures (16, 19, 22 and 25 jC) on gametogenesis. Oocyte size was used to identify mature oocytes. Significant differences among populations were observed in the number of mature oocytes produced. Only the oysters from northern locations (Normandy and Brittany) reached the mature stage by the end of the standard conditioning. Concerning the effect of different temperatures during conditioning, the first mature oocytes were detected (absolute days) by the 27th day at 16 jC, 23rd day at 19 jC, 19th day at 22 jC and 22nd day at 25 jC. This information was applied to fit a logistic model to predict oocyte growth using temperature and time as main affecting parameters; D = D max /(1 + ae  kt ) with D—oocyte diameter at time t (Am), D max —the asymptotic oocyte diameter (Am), a—adjustment parameter, k—slope of the curve during growing stage and t—time (days). The model fit consistently with values achieved at 16, 19 and 22 jC. The results obtained during this study could be used to improve conditioning procedures for C. gigas. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Gametogenesis; Temperature; Conditioning; C. gigas 0044-8486/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0044-8486(01)00898-5 * Corresponding author. Tel.: +33-02-98-22-43-96 E-mail address: Jean.Claude.Cochard@ifremer.fr (J.-C. Cochard). www.elsevier.com/locate/aqua-online Aquaculture 214 (2002) 115 – 130