Gas Bladder Inflation in Walleye Fry Cultured in Turbid Water with and without a Surface Spray

Abstract

AbstractIt has been demonstrated that a surface spray is needed to obtain a high percentage of gas bladder inflation (GBI) in intensively cultured larval walleyes Sander vitreus fed dry diets and that turbid‐water culture substantially enhances larval survival and growth. It was not previously known whether a surface spray is needed to obtain GBI when larvae are cultured in turbid water, which is produced by intermittently adding clay slurry to the culture tank. The present study was undertaken to test whether turbid water alone would enhance GBI without need for a surface spray. Larval walleyes were cultured with formulated feed from 2 to 28 d posthatch (dph) in tanks containing turbid water (∼55 nephelometric turbidity units) with surface spray (WS tanks) or without surface spray (WOS tanks). Larvae were stocked at a density of 20 fish/L and were given formulated feed every 5 min for 22 h/d. All husbandry and water quality conditions were similar between experimental treatments. Gas bladder inflation was 100% in fish surviving to 28 dph in WS tanks, but GBI was only 3.3% in WOS tanks. Fry survival (50% WS; 34% WOS), final length, and final weight were not significantly different between treatments. The results conclusively show that surface spray is essential for GBI in walleyes.