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These observations and philosophies were, therefore, incorporated into this preliminary investigation to eValuate the relative importance of manner of feeding and diet preferences of the brown trout. PROCEDURES The fish source for the experiment was eggs hatched at the Fish Research Hatchery, Bellvue, Colorado, which had been taken from wild spawners in Delaney Buttes Lake, near Walden, Colorado. The experiment was started 17 December 1981 when 12,000 brown trout swim-up fry were divided into six lots of 2,000 fish each. Lots one and two were fed by hand as controls. Lots three and four were fed by automatic feeders hung above the troughs which simply dropped the feed onto the water surface. With this manner of feeding, human inter- ference was removed during feeding. Lots five and six were fed by automatic feeders with submerged feed delivery systems, which were designed to cater to the brown trout's bottom-feeding tendencies in addition to removing human interference. The automatic feeders and submerged feed delivery systems (Fig. 1) were designed by Tom Mandis, Superintendent of the Fish Research Hatchery. The feeders and delivery systems were constructed of readily available materials to be economical in cost ($15/feeder) and simple in operation. The automatic feeders were connected to a common 24-hr timer which turned on an hourly timer to activate the feeders eight times a day. The hand-fed lots were also fed eight times a day. All lots were trained to feed with BioDieti however, since this was a preliminary investigation, another variable, diet preference, was introduced into the experiment (Table 1). When the fish size reached approximately 1,500/lb, lots one, three and five were switched to a dry commercial diet. Lots two, four and six remained on BioDiet for the duration of the experiment. Table 1. Manner and diet fed for six lots of brown trout. Lot Manner fed 1 Hand fed 2 Hand fed 3 Automatic feeder, surface deli very 4 Automatic feeder, surface delivery 5 Automatic feeder, submerged delivery 6 Automatic feeder, submerged delivery Diet fed d' a Dry let BioDiet . a Dry dlet BioDiet ,a Dry diet BioDiet aTrained on BioDiet but switched to a dry diet as fish size reached approx- imately 1,500 fish/lb. Such a feed switch is a factor of economics and with cutthroat trout (Salmo clarkii), the feed switch increased growth rates over fish fed strictly BioDiet (Harris et al. 1980). 49