The effect of substrate rearing on the growth, development, and survival of larval white sturgeon (Acipenser transmontanus) during early ontogeny.

White sturgeon, Acipenser transmontanus, were reared in the presence (gravel) or absence (bare) of substrate at either 13.5 or 17.5°C during the yolk sac phase. Fish reared in gravel were transferred to bare tanks at emergence from substrate and reared to 46 days post hatch (dph). At any given dph or Accumulated Thermal Unit (ATU), the fish reared in gravel were significantly larger and survival was higher than those reared without substrate at both temperatures (T). Cumulative survival was lower at high T and was 20% greater in gravel-reared larvae in both T. Yolk absorption rate did not vary between bare and gravel, but was significantly greater at high T. Yolk absorption efficiency was greatest in gravel-reared fish, but did not vary with T. Liver histology indicated that fish reared in gravel had significantly greater quantity of lipid during the yolk sac phase. In a second experiment, yolk sac larvae were reared in the presence (gravel or bio-spheres) or absence (bare) of substrate at 13.5°C and respirometry used to measure both routine and maximum metabolic rate for assessing metabolic scope. Larvae reared in gravel had significantly greater metabolic scope, and whole body glycogen was significantly greater in larvae reared in both substrates at 8 dph indicating that substrate rearing may provide a greater capacity of growth and development at a time of intense organogenesis. Histological analysis of the liver showed greater lipid and glycogen in larvae reared in substrate. These findings suggest that larvae reared without substrate may divert more of their energy to non-growth related processes, such as swimming activity, which was observed but not quantified. Thus, larvae reared without substrate may be at a significant physiological disadvantage, leaving less energy for growth and development. --P. i.