Efficacy of Using Visible Implant Alpha Tags in Pacific Lamprey Ammocoetes

Efforts to conserve declining populations of Pacific lamprey Lampetra tridentate in the Columbia River, USA are underway. In order to conserve these populations an understanding of basic life history and population attributes is essential. Juvenile Pacific lamprey growth, survival, and abundance are not well defined and methods to estimate these parameters are not fully developed. A tagging method is needed to address growth, survival, and abundance during the rearing phase. We used Visible Implant Alpha fluorescent type tags that can be visually identified to a unique alphanumeric code, thus allowing tracking of individuals. Sixty Pacific lamprey ammocoetes were tagged using Visible Implant Alpha tags and an additional 30 individuals were handled as controls. Specimens ranging in length from 120 mm to 137 mm were held in nine tubs (10 individuals per tub) that were supplied with Entiat River water. Tag readability, tag loss, specimen growth (length and weight) and mortality were recorded. Specimens were tagged July 16, 2008, handled and checked for tags once a week for the first five weeks. Specimens were then handled and checked for tags during weeks seven, 10, 15, 21 post tagging. After seven weeks readability had declined to 35%. After 21 weeks, two mortalities had occurred in the tagged groups and one in the control groups. Low tag readability was attributed to tag shedding, tag placement, and folded tags.