Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

11.  EFFECT OF DIETARY ENERGY CONTENT ON GROWTH AND LIVER CONDITION OF SHOVELNOSE STURTGEON (SCAPHIRHYNCHUS PLATORYNCHUS)

Rick Barrows, USDA-ARS, 3059-F National Fish Hatchery Rd, Hagerman, ID 83332; (208) 837-9096; rbarrows@mcn.net

Matt Toner, U.S. Fish and Wildlife Service, 4050 Bridger Canyon Rd, Bozeman, MT 59715; (406) 587-9265; matt_toner@fws.gov

Beth MacConnell, U.S. Fish and Wildlife Service, 920 Technology Blvd S, Bozeman, MT 59718; (406) 582-8656; beth_macconnell@fws.gov

Linda Beck, U.S. Fish and Wildlife Service, 920 Technology Blvd S, Bozeman, MT 59718; (406) 582-8656; linda_beck@fws.gov

Liver condition of hatchery-reared pallid sturgeon is sometimes compromised and seems to be associated with diet, growth rate and water temperature.  A study was conducted to determine if dietary fat affected liver condition or growth rate.  Four experimental feeds containing 8, 14, 20 or 24% fat were fed to 5 tanks of fish with 20 fish per tank.  Water temperature was held constant at 72F, and the experimental feeds were fed to satiation for 177 days.  There was a linear response of growth to increasing dietary fat.  The fish fed the 8% fat diet gained 85 g/f, compared to 160 g/f for those fed the 26% fat diet. No effect of dietary fat on liver fat content was observed.  Liver condition scores were only changed by feeding the 8% fat diet.  Liver condition score decreased from 3.34 for the fish fed the 14% fat diet to 2.74 for the fish fed the 8% fat diet.  This difference although statistically significant is not thought to indicate major biological differences.  The liver condition scores for the fish fed the 20 and 26% fat diets were 3.32 and 3.2, respectively.  There was also an effect of dietary fat on the percentage of fish with zonal fat stores in the liver.  This percentage varied from 30.4% of fish fed the 8% fat diet to 72.1% of the fish fed the 26% fat diet.  The percentage of fish with zonal liver fat stores can be considered indicative of dietary fat level.  Very poor liver conditions scores (4 and 5) observed in production hatcheries are probably not due to dietary fat level alone.  Feeding diets with high fat content will increase growth rate without increasing liver fat levels or decreasing liver condition scores, with the rearing conditions used in this trial.