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3 <br />INVERTEBRATE, PREDATORS: Trapping also revealed an alarmingly high <br />number of predaceous aquatic insect nymphs of the order Odonata (dragon <br />flies and damsel flies). Densities some times exceeding 5,000 odonate nymphs <br />per trap set. Aquarium tests were conducted by placing sucker larvae and <br />nymphs together. Results indicated the odonates did feed on sucker larvae <br />and could be effective predators. A special report, "Predation by Odonate <br />Naiad on Larval Razorback Sucker under Laboratory Condition" is provided <br />as Appendix D. <br />BEHAVIOR: Growth of juvenile razorback suckers in Yuma Cove during <br />1992 was remarkable, but the rapid growth required a suite of collecting <br />techniques be utilized. During their phototactic stage (<14 mm),the larval <br />razorback suckers were easily captured in light traps or with dip nets after <br />being attracted to white lights. However, as they grew, they became <br />increasingly more difficult to capture. Whether this was a factor of fish <br />availability or capture techniques is unknown. Large schools of suckers were <br />never observed. Fish were normally alone or seen in small groups. Fish <br />between 15 and 25 mm were best captured during the day with hand dip- <br />netting and beach seining. <br />At the same time the juvenile razorbacks were attaining 25 mm in length, the <br />algae and macrophyte growth in Yuma Cove was impeding collections. As <br />pondweed became more dense, suckers became more evasive, and the number <br />of fish collected decreased. Several attempts were made using minnow traps <br />and specially constructed fyke nets baited with dog food and crackers -hut <br />these techniques proved ineffective. As suckers attained 125 mm in length - <br />they became susceptible to % inch trammel nets. This collection technique <br />proved to be the most effect method of sampling juvenile razorback suckers <br />as they continued to grow past 150 mm. During November, when the average <br />size of the juvenile razorback suckers had exceeded 250 mm, a combination <br />of trammel netting and electrofishing was very successful in capturing the <br />young fish. <br />¦