Physiological and biochemical parameters for egg quality determination in lake trout, Salmo trutta lacustris

The present study investigated the relationships between egg viability and ovarian fluid composition, egg physiology and egg metabolism in lake trout, Salmo trutta lacustris, to obtain biomarkers for egg quality determination . The ovarian fluid pH, protein levels and activities of aspartate aminotra nsferase and beta-D-glucuronidase were significantly correlated with egg vi ability expressed as the number of eyed stage embryos. Regression models de monstrated that an ovarian fluid pH between 8.44 and 8.57, protein levels b elow 235.56 mg 100 ml(-1) ovarian fluid, aspartate aminotransferase activit y below 31.65 mu m min(-1) l(-1) ovarian fluid and beta-D-glucuronidase act ivity below 8.62 mu m min(-1) l(-1) ovarian fluid characterized egg batches with high viability (greater than or equal to 80%). The increase in the egg wet weight during water hardening was also signific antly correlated with the number of eyed stage embryos, and egg batches wit h high egg viability (greater than or equal to 80%) increased in wet weight by greater than or equal to 13% during water hardening. From the investigated metabolic parameters the number of eyed stage embryos was significantly correlated with activities of NADP-dependent isocitrate dehydrogenase (egg viability greater than or equal to 80% at greater than o r equal to 2.07 nM min(-1) mg(-1) protein) and NAD-dependent malate dehydro genase (egg viability greater than or equal to 80% at greater than or equal to 47.25 nM min(-1) mg(-1) protein), with the respiration rate (egg viabil ity greater than or equal to 80% at greater than or equal to 8.71 nM min(-1 ) mg(-) (1) protein), with the ratio of NADH to NAD levels (egg viability g reater than or equal to 80% greater than or equal to 0.872), with the level s of free, non-esterified fatty acids (egg viability greater than or equal to 80% greater than or equal to 72.34 mu g mg(-1) protein), and the ratio o f non esterified to esterified fatty acids (egg viability greater than or e qual to 80% at greater than or equal to 0.749). Also, subjective and visual control methods were described to distinguish between batches with viable and non viable eggs.