Affect of grading frequency on production of alligator gar fingerlings in tanks

Alligator gar fingerling production may be influenced by cannibalism.  Grading is time consuming, and the benefits have not been quantified.  Our objective was to quantify the relation between grading frequency and survival or growth.  Eight day post hatch larvae were stocked into 75-L tanks at 2 larvae/L.  Grading occurred at four frequencies.  During each grading effort, larvae were redistributed among three or four 75-L tanks to minimize within tank size variability.  Larvae were initially offered Artemia at 5 nauplii^.mL^.-1d^-1.  Larvae were also fed combinations of moist starter and extruded floating pellets, at 10% of body weight/d.  Tank bottoms were siphoned twice daily, and water quality was monitored daily.  At 50 days post hatch, alligator gar from each grading frequency and tank were individually counted, weighed, and measured.  Average (SD) weight of fingerlings was 2.7 (0.9) g. Survival ranged from 53% to 65%.  Growth rates ranged from 1.5 to 1.8 mm/d.  There was no relation between grading frequency and survival or growth.  There was a significant difference in size frequency distributions among the grading frequencies (Chi² = 138.25, df = 24, P < 0.001), with smaller larvae present when grading occurred every day, and larger larvae without grading.