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FA153: Sturgeon Aquaculture - Specialized Techniques: Determining the Stage of Sexual Maturity in Female Sturgeon for Artificial Spawning: The Egg Polarization Index or PI

Figure 1. A photograph and drawing of a sturgeon egg (oocyte) depicting the clearly polarized nucleus or GV (off-center), and defined animal (AP) and vegetal (VP) poles. Segregation of the fine and course yolk granules helps to orientate the position of the two poles; the GV is embedded in the cortical cytoplasm of the animal pole region. The egg polarization index or PI = B/A; where A is diameter of the egg, excluding the chorion, and B is distance from the top of the GV to the plasma membrane of the egg; see diagram. For spawning, select females with egg polarization indices (PI) of less than 0.10.