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Anita M. Martinez 8 <br />deformities were first observed on the caudal fin due to the early onset of ray formation. <br />Larvae 10-13 mm SL had no noticeable deformities, however, principal caudal fin ray <br />deformities began appearing in larvae 14 mm SL and became predominant in larvae > 15 <br />mm SL irrespective of diet or parental cross (Figure 1). A decrease in larvae observed <br />with this deformity , > 16 mm SL, does not indicate a decrease of deformity occurance but <br />rather fewer larvae had attained this size by the completion of the study. Siblings in the <br />fourth tray of each Lot were never subjected to examination during the study period. <br />These larvae were examined following the study period and displayed no fin ray <br />deformities. Deformities, therefore, could not be the result of nutritional deficiencies, <br />environmental factors or genetic predisposition. Because deformities occurred <br />immediately following the onset of fin ray formation, it appears disruption of this critical <br />developmental stage by excessive handling resulted in fin deformities. <br />Recommendations <br />Stress can result from actively handling fish during counting, weighing, moving, and <br />cleaning, or inactively by feeding, or walking by thus invoking a fright response. Reducing <br />stress during critical developmental stages is imperative for normal fin ray development <br />in razorback suckers. Hatching and rearing recommendations include: investigating the <br />benefits of hatching jars over trays; exploring the rearing of larvae in aquaria instead of <br />troughs; using automatic feeders instead of hand feeding; maintaining larvae in locations <br />away from human activity; and minimizing tray cleaning. The type and frequency of larval <br />