Growth of the Mountain Brook Lamprey Ichthyomyzon greeleyi Hubbs and Trautman

Larvae, metamorphosing stages and adults of Ichthyomyzon greeleyi, a nonparasitic lamprey, were collected from four streams tributary to the French Broad River in western North Carolina to provide information on seasonal rates of growth, duration of the larval period, timing of metamorphosis and changes in body proportions. Metamorphosis is initiated in mid-Aug. and completed by mid-Dec. The larval period ranges between 5.2-6.2 yr with the oldest individuals being predominately female. Larval growth was most rapid during the spring and summer. Negative growth occurred during the winter among the older age groups. Annual growth increased asymptotically and was similar among three of the four populations. Differences in growth were not demonstrable between male and female larvae. A preponderance of females occurred among larvae with males being the more abundant among metamorphosing animals and adults. The change in sex ratio is attributable to the longer larval life of females. The proportional length of the prebranchial, branchial, trunk and tail regions changed throughout larval life in a pattern similar to that for other lampreys. Oral disc, dorsal-fin height and eye diameter increased through all or most of metamorphosis and the adult period.