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1 1 11 1 1 1 occasionally seen at the pond, but we have no data and can offer no specu- lation on the predatory impact herons might have had on the stocked squaw- fish. Cannibalism among squawfish may have been a problem because alter- native forage was limited. Personnel at Dexter NFH report severe losses of Colorado squawfish due to cannibalism in concrete raceways when food was withheld (Buddy Jensen, personal communication). Though the incidence of cannibalism is well known for squawfish held under crowded, confined conditions in aquaria or raceways, we doubt cannibalism would be equally severe under pond conditions where squawfish are more dispersed. If cannibalism occurred, it could not account for the complete elimination of the squawfish population in Fish Chalet Pond. However, some cannibalism could have occurred; by 9 July 1987 the difference in size classes in the pond may have allowed the largest squawfish to prey on many of the smaller squawfish size classes (Table 2); by 12 August, however, the difference in sizes was less and the largest squawfish would have had very few small ones to prey on. The body-depth limit, predicted by Bulkley and Berry's model (1985) should, however, be treated with caution when dealing with very fusiform prey such as Colorado squawfish. According to the model, squawfish should be able to consume other squawfish up to 67% of their own length. The maximum size of squawfish that another squawfish might actu- ally consume could be much smaller than the model predicts, because the body depth of squawfish is small relative to the fishes overall size (i.e., though the prey's body may theoretically fit between the jaws, its overall size would cause handling problems for the predator). Until controlled feeding experiments are conducted to clarify the prey size limits of Colorado squawfish, we have reservations about applying Bulkley and Berry's (1985) model in estimating the vulnerability of various sizes 17