Embryonic and Larval Development of Sacramento Splittail Pogonichthys macrolepidotus

Embryonic and larval development of Sacramento splittail (Pogonichthys macrolepidotus) was characterized from zygote to metamorphosis in laboratory conditions. Fertilized eggs were obtained from induced and natural tank spawning of adults caught in the Yolo Bypass of the Sacramento River. Splittail produced transparent adhesive eggs with a moderate perivitelline space. Duration of embryonic development from fertilization to hatching was 100 h at 18 ± 0.5 °C. Newly hatched larvae were 5.2 to 6.0 mm total length with no mouth opening. Yolk-sac larvae were demersal and absorbed the yolk within 10 days post-hatch. Exogenous feeding started at 6 days post-hatch, concomitant with swim bladder inflation and swim-up movement. Fin differentiation began at approximately 10 d post-hatch (ca. 8.3 to 8.85 mm total length) and was completed at 50 d post-hatch (ca. 19.6 to 20.85 mm total length) when larval finfold was fully resorbed and the adult complement of fin rays was present in all fins, but scales were still lacking.

Temperature stress induces notochord abnormalities and heat shock proteins expression in larval green sturgeon (Acipenser medirostris Ayres 1854)

The effects of thermal stress on survival, development and heat shock protein (hsp) expression of green sturgeon (GS) yolk-sac larvae, from hatching through yolk depletion were investigated to provide insight into effects of highly altered natural river hydrographs. Hatched GS larvae were reared at constant water temperatures 18°C (control) through 28°C at 2°C increments. Larval survival significantly decreased at 26-28°C, with 28°C being lethal. Significant proportions of deformed larvae were found at sub-lethal (20-26°C) and lethal 28°C rearing temperatures, with kyphosis (i.e. backward flexion of notochord) accounting for >99% of morphological deformities. Histological analysis of larvae preparations indicate that elevated water temperature affects notochord cell function and physiology. At rearing temperatures 20-28°C, thermal stress elicited a quick (24 h) and long lasting (yolk-sac absorption) significant over-expression of measured heat shock proteins (hsps), all of which are known components of intracellular protein repair and stabilization mechanism. Thermal sensitivity, as indicated by the incidence of abnormalities and expression of different hsps, varied significantly between crosses. Thermally tolerant progeny exhibited a short but rapid hsp72 (size in kDa) over-expression, and more pronounced hsp60 and hsp90 over-expression, than less tolerant progeny which exhibited a prolonged hsp72 and hsp78 over-expression. At environmentally relevant water temperatures bent larvae exhibited spiral swimming, which in the wild would compromise the ability of emerging larvae to forage, avoid predators, and migrate downstream, ultimately compromising survival and recruitment. Before larvae hsp content can be used as a thermal-stress biomarker for GS, field validation studies are needed. © 2013 Blackwell Verlag GmbH

The effect of white sturgeon (Acipenser transmontanus) ovarian fat deposition on caviar yield and nutritional quality: introducing image processing method for sturgeon ovary fat determination

Image analysis can predict the fat content of sturgeon ovaries that had been categorized as having a low, medium, and high fat content based upon the caviar yield expressed as a percent of the total ovary weight, and were correlated with the chemical measurement of total fat (R 2 = 0.83). The fatty acid composition of eggs was not influenced by ovary fat content. Palmitic acid (16:00) was the most abundant saturated fatty acid and oleic acid (18:1n-9) the most predominant monounsaturated fatty acids in sturgeon eggs regardless of the ovary fat content. No significant differences (P > 0.05) were observed in docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in eggs from fish with different fat ovaries. Fourier transform infrared spectroscopy (FT-IR) coupled with principal component analysis indicated no significant difference in chemical compositions in sturgeon eggs separated from ovaries of different fat contents confirming the fatty acid composition results