Validation of an ovarian biopsy method in a sea bass, Centropomus medius Günther

In the present study, the establishment and validation of an ovarian biopsy method for in vivo assessment of oocyte maturation in the snook, Centropomus medius Günther, is described. Diameter and morphological characteristics of intra‐ovarian oocytes siphoned with a polyethylene cannula were analysed fresh, preserved with 1% formalin in 0.7% NaCl solution and also cleared with Serra solution. There were no effects detected of the preservative solution on the opaque oocytes within the 24‐h interval of the test. The clearing solution allowed excellent visibility of the membrane thickness, yolk appearance and germinal vesicle. Oocytes from each of the five ovarian sites of all examined females were in different prematuration stages and those on the tertiary yolk globule stage had a unimodal diameter frequency distribution and their diameter means were not significantly different among sites (P > 0.01) on eight females. In vivo and in vitro samples of the eight females examined were not significantly different (P > 0.05). As samples obtained with the polyethylene cannula are representative of the ovary central portion, an estimate of the coefficient of variation corrected for bias (P < 0.05) for 20 means of repeated in vivo samples was 1.4 ± 0.47. The results obtained demonstrate that for the species studied, the biopsy method is satisfactory, providing representative samples of the ovaries with the required precision.