Morphology and Aging Precision of Statoliths from Larvae of Columbia River Basin Lampreys

Abstract

The general morphology and precision associated with age determination of statoliths from larval Pacific lampreys Lampetra tridentata and western brook lampreys L. richardsoni found within the Columbia River basin were examined. Significant positive correlations were observed between the size of left and right statoliths from individuals. Principal components analysis indicated an allometric relationship between lamprey length and statolith size as well as a potential species grouping based on these measurements. Discriminant analysis was able to correctly classify more than 94% of Pacific lampreys and 92% of western brook lampreys based on lamprey length and statolith size, and Pacific lamprey statoliths tended to be larger than western brook lamprey statoliths for lampreys of a given size. Reader bias in age estimates of statoliths was greater for older lampreys. Multiple independent age readings of both statoliths from individual lampreys indicated that the overall average percent error was 16.7% for Pacific lampreys and 33.0% for western brook lampreys. Within‐individual average percent error ranged from 5.1% to 20.1% among species and readers. Within‐reader average percent error ranged from 6.4% to 17.8% among species and readers. The average percent error observed in this study was greater than that observed in studies of other species of lampreys; however, statoliths that were ambiguous or difficult to read were not excluded from this study. In general, the modal separation of age‐groups observed in length‐frequency distributions for lampreys is poor, as seen in this study; therefore, statolith‐based ages may verify or provide better estimates of population age structure. These data demonstrate that estimates of precision are necessary before management actions founded on statolith‐based age structure determination are implemented.

Capture and collection of lampreys: the state of the science

“…Distinguishing ammocoetes of closely related species can be extremely difficult (Heard 1966;Brown and Moyle 1993;Gardiner 2003;Maitland 2003;Filcek et al 2005;Meeuwig and Bayer 2005; Fig. 2).…”

“…Often, members of paired and satellite species are not even genetically distinguishable (Docker et al 1999). Due to unreliable species identification techniques, researchers have resorted to holding specimens until metamorphosis (Heard 1966;Beamish 1980), conducting post-hoc genetic or morphological identification (Filcek et al 2005;Meeuwig and Bayer 2005), or sampling only above impassable obstacles, where anadromous parasitic forms do not occur (Maitland 2003).…”

Reconnaissance of contaminants in larval Pacific lamprey (Entosphenus tridentatus) tissues and habitats in the Columbia River Basin, Oregon and Washington, USA

“…They are thought to be sedentary once they have settled, but they can be dislodged from their burrows during scouring events. The probable age range of larvae analyzed for this study is approximately 1e6 years based on available size and age data (Meeuwig and Bayer, 2005). After the sedentary stage, Pacific lampreys undergo metamorphosis to prepare for parasitizing fish and mammals in salt water.…”

Pacific lamprey (Entosphenus tridentatus) ammocoetes exposed to contaminated Portland Harbor sediments: Method development and effects on survival, growth, and behavior

“…The variability in lipid content could be attributed to the multiple age classes likely present, and lipids have been shown to accumulate over the course of their larval period prior to metamorphosis . We could not verify the age of the ammocoetes used in the present study, however, because the use of statoliths for aging larval lampreys can be problematic, according to Meeuwig and Bayer .…”