FEED RATE PREDICTION FOR larvaE TO ADVANCED FINGERLING Walleye Sander vitreus.

The intensive larvae culture, pond fingerling habituation, and ongrowing techniques for walleye developed in the 1990's used with contemporary diets result in good growth and survival rates.  Appropriate feeding rates that meet the growth demands for fast-growing larvae and early juvenile life stages and are critical to prevent cannibalism in this piscivorous species. Feed rate tables for larvaculture, habituation feeding rates, and ongrowing growth predictions and feeding calculations are presented here.

Currently, three-day post hatch (dph) fry are cultured intensively in tanks using turbid water on an experimental basis at Rathbun Fish Culture Research Facility.  The specialized tank culture method also requires specific diets to achieve high survival rates.  Fry are fed an imported microparticulate larval feed with 54% protein and 16% fat at an initial rate of 4 g/1,000 fry/d.  The intensive larval culture system produced good growth and high survival rates (e.g., 75% in 2010, 71% in 2012). Daily weight gain exceeds 15% bodyweight per day, thus feeding rates must increase on a daily basis to meet the requirements for growth and prevent morbidity and mortality due to cannibalism.

Pond-reared fingerlings are fed 8 to 12% bodyweight per day during habituation to prepared feeds.  A highly palatable diet is fed during the first 10 days of habituation before gradual transition to the Walleye Grower 9206 formulation with 49% protein and 17% fat. Daily weight gain during the 30 to 60 day post hatch period can exceed 7.8% as fish grow to 4.0 g before transfer to ongrowing tanks.

Feed offered during ongrowing is calculated based on measured growth rates (mm/d) and length-weight relationship or relative weight using an assumed 1.2 kg of feed required to produce 1.0 kg of gain. Using this method of feed rate calculation the observed feed conversion ratios vary from 1.3 to 1.7 in walleye production at Rathbun Fish Hatchery.