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Figure 12. Common prey (feeder fish) and bonytail that had previously experienced predator aggression would often take a defensive stance of swimming at the upper sides of the tank. This position minimized the possible angle of attack and denied predators a backstop to trap prey. Razorback Sucker During the flow chamber tests, we often heard fish splashing in tank no. four (control). This lank had a very active aerator that caused the water to up-well violently. On closer examination, we fOtlnd that suckers were swimming vertically through the bubble plume dm! kdpi ng lltll ollhe \\ <11\.'1 1'111' behavior was not seen in the other three tanks but was a common occurrence in lank rom Thc na(ur\.' (II reason for this behavior is not known. Initially we attempted to expose fish to predation by pl~ICin!2 Idr~l' illilll',ld "II!:, [I' I., . I, holding several hundred razorback suckers. Mo\ing prcdilIllr, "lllI\,'\\ Ill,'iI' 'i' days. Both catfish went to the far end of each lank wherc IlK) rel1\dlll\.'d 1\llill"I:ic'" I,ll I \ II razorback suckers crowded around them in mass, possibly CUriOus. Their allril\.'IIOIl III 111l' f)r,'d,lllll' gradually decreased but the razorback suckers certainly did not exhibi l predalor a \OIJaml\.' Ih\.' I I' na 1\ " curiosity would put them at greater risk in the wild. We modified our study design to move the prey to the predator; thIS j, al'll more r\.'I)ll'\l'lll ,II 1\,' of stocking practices. The handling ordeal caused the juvenile razorbal'K 'Ul'K\.'r\ III llL'l', ,111,'11 'l'l'~ \ I \~ refuge in shelters whether they contained a predator or not. With lime lhc) cdlmcd dt \\\ 11. ;III.! (ill,l! schooled in and around the shelters. Some fish remained inside the shellers Razorback suckers at night were found randomly distributed along 1!1\.' hOIlOlll ,llld I"l'lllll" 1'1: the tank's sides. We did not observe any type of schooling behavior after Jar" Ilalhl'.Id l,IIII,1I 1\ ,'I' generally active, slowly swimming around the tank. These observations were brief anJ IlInlled -"Jill'\, using an artificial light often startled the fish. The following morning, razorback suckers were generally found inside the lO-cm-diameter inflow pipe or in shelters not occupied by a predator. They became highly skittish, avoided the catfish. and darted around the tank. In the pre-exposure tank, there was only one shelter that was always occupied by "Oscar," the pre-exposure predator. Survivors from that harrowing night always avoided going into that shelter. 18