![]() The suction dredge collected 32 lamprey in fine sediment, 21 lamprey in coarse sediment, and 28 lamprey in the control group, including 30 lamprey that were not initially stocked. The mean time to burrow was recorded for each study group (3 fine, 3 coarse, 3 controls) on the day of the field test injury was evaluated at 24 hours and survival was evaluated at 24 hours, and at 7 and 14 days after the test. The dredge was used inside each enclosure to collect lamprey and they were transported to the laboratory for evaluation and holding. For the field test, lamprey were tagged with visible elastomer implants based on small (89 millimeter or less) and large (92 mm or more) size categories and stocked into mesh enclosures over fine or coarse sediment. The system used a hydraulic eductor (also known as a Venturi valve) to create suction so that sediment and lamprey avoided passage through the pump impeller. We evaluated the injury rate, survival, and burrowing capability of lamprey following passage through the dredge system and used collection of lamprey from water without sediment as a control. Director, Western Fisheries Research CenterĪ portable suction-dredge and sluice-box system were used to collect larval lampreys ( Entosphenus tridentatus and Lampetra spp.) from fine and coarse sediment in field and laboratory tests.
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