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<br />.., <br />; <br /> <br />. ~ <br /> <br />"'"j <br /> <br />C'.::) <br />c') <br />1'-' <br />, <br />>~, <br />1-- <br />W <br /> <br />development and devoid of any visible abnormalities, All eggs were examined under a <br /> <br />stereoscope at 30X magnification prior to stocking, The egg incubation cups were 220-ml glass <br /> <br />jars with the bottoms cut off and replaced with 0.285-mm mesh polypropylene screen. The cups <br /> <br />were suspended in glass aquaria (described above) from a rocker arm apparatus connected to a <br /> <br />0.3 amp motor, which continuously oscillated the cups in the water column and was positioned <br /> <br />so that the eggs were completely submerged at all times. The aquaria were divided into three <br /> <br />chambers, one large chamber (37-cm long, 30-cm wide, 30-cm deep) where the four egg cups <br /> <br />were suspended and two smaller growth chambers (36-cm long, 15-cm wide, and 30-cm deep) <br /> <br />where the resulting larvae were tested. Air stones supplied with compressed air were placed in <br /> <br />each chamber. The aquaria were placed in a water bath maintained at 21 x 1 DC and received test <br /> <br />water from an intermittent flow-through diluter at a rate of I L every 15 minutes. The fish were <br /> <br />tested under a photoperiod of 14 hours light: 1 0 hours dark. <br /> <br />The number of live and dead eggs were recorded daily and all dead eggs were removed <br /> <br />with a glass pipet. When hatching commenced, the number of eggs hatched and the number of <br /> <br />live, deformed, and dead larvae were recorded daily and all dead larvae removed. The criteria <br /> <br />for death were whitening of the embryo or yolk in the eggs and absence of a heart beat (under <br /> <br />30X magnification) in the larvae. The types of deformities recorded followed the descriptions <br /> <br />given in Scudder et al. (1988) and Bantle et al. (1990). For each spawn, the time to onset and <br /> <br />completion of hatch was recorded to the nearest day and the average day to hatch was calculated <br /> <br />using the formula of Scudder et al. (1988) as follows: <br /> <br />n <br />Average day to hatch = L E; X; <br />i= I <br />M <br /> <br />17 <br />