Intensive Culture of Larval Walleyes with Dry or Formulated Feed: Note on Swim Bladder Inflation

Abstract

Abstract Two experiments were conducted to test the effects of modified feeding techniques and three dry or formulated diets on the survival, growth, and swim bladder inflation of larval walleyes (Stizostedion vitreum). In experiment 1, duplicate lots of 3,000 fish/tank were fed either a gelatin–casein diet (Gel), a semimoist extruded diet (Biotrainer), or dehydrated, decapsulated brine shrimp (Artemia sp.) cysts (Decaps). Mean survival to 21 d was greater for fish consuming Biotrainer (12.3%) than for fish fed Decaps (1.6%) or Gel (0.5%). Fish consuming Decaps were longer at the end of the trial (P < 0.01) than either Biotrainer- or Gel-fed groups (18.2 mm versus 16.7 and 13.1 mm total length, respectively), but the proportion with inflated swim bladders was less (44% Decaps versus 83% Biotrainer and 94% Gel; P < 0.01). In experiment 2, Biotrainer and Decaps were fed to triplicate lots of 2,000 fish/tank. Mean total length at 28 d was greater (P < 0.01) for fish consuming Decaps (21.3 versus 17.3 mm), but survival (Decaps, 6.1 %; Biotrainer, 5.3%) and swim bladder inflation (Decaps, 57%, Biotrainer, 60%) did not differ between the two treatments. The percentage of fish with inflated swim bladders, which had been low in earlier trials, seemed to increase with the use of feeding rings; the rings restricted the area of surface film caused by the feeds. The Decaps and Biotrainer were both consumed well and supported adequate growth rates.