Determining sexual maturity in white sturgeon (Acipenser transmontanus) to maximize yield and quality of caviar

Xiaonan Lu

Knowing more about the reproductive status of female sturgeon and being able to predict the proper time to harvest fish roe for caviar is an important factor for producing high yield and consistently uniform caviars. Current techniques for predicting sexual maturity of white sturgeon involves the measurement of oocyte polarization index (PI) that requires an invasive surgical biopsy. Surgical biopsy is stressful to fish and time consuming. New methods would be helpful which are less stressful to fish and also provide additional information about biochemical changes that occur during gonadal maturation and how these changes correlate with roe quality, and to the oocyte PI. This research examined the feasibility of using Fourier transform infrared (FT-IR) spectroscopy (in the mid-IR range, 4000-400 cm-1 ) to predict biochemical and potentially morphological changes occurring during vitellogenesis through atresia. Studies were conducted on fish held for a nine month period. Changes were observed in the FT-IR spectra of sturgeon plasma at selected maturity levels. Differences in plasma biochemical compositions in the steroid region of FT-IR (around 3000 cm-1 ) were detected along with changes in the concentration of vitellogenin in plasma (around 1080 cm-1 ). Clear segregation of plasma according to maturity stage was evident using Principal Component Analysis (PCA). It was possible to predict stage of maturity (late vitellogenesis vs. early atresia) about 70% of the time using Soft Independent Modeling of Class Analogy (SIMCA) models. Combination of second derivative transformation, PCA cluster model and SIMCA pass test together precisely predicted maturity stage of sturgeon. A rigorous Partial Least Squares (PLS) model was established to predict PI values between 0.1 and 0.3 (R=0.98, SEP=1.01%) based upon differences observed in spectral features. However, few changes were observed in spectral features of the roe recovered at selected maturity stages indicating that the composition of fish roe is relatively static from vitellogenesis through atresia. FT-IR spectroscopy combined with various multivariate analyses may provide a useful tool for a more rapid and less invasive assessment of white sturgeon maturity and timing harvest, reducing the need for traditional invasive and stressful surgical biopsy methods for PI determination.

Determining sexual maturity in white sturgeon (Acipenser transmontanus) to maximize yield and quality of caviar

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