Tributary streams in the Great Lakes and Lake Champlain basins are currently treated with lampricide every 2-4 years to reduce sea lamprey populations. Selection of streams to be treated is predicated on the assumption that all ammocoetes are the same, i.e., ammocoetes from all streams have an equal probability of survival to the parasitic stage and will do equal damage once they become parasites. A better understanding of individual stream contributions to the parasitic stage would allow targeting of streams for treatment based on their actual contribution to the parasitic population. Currently, the only method for tracking the destiny of larval lamprey is to tag transformers and recapture them as parasites.

This method, which is currently being employed in a project funded by the Great Lakes Fishery Commission, is labor-intensive and yields low returns of marked individuals. Relatively new methods available for micro-elemental analysis of statoliths offer promise for directly identifying the stream of origin of parasitic lamprey.

Micro-elemental analysis identifies the quantity and ratio of rare elements in otoliths or statoliths. These elements are acquired throughout the growth of an organism, and in stream-resident larvae they will reflect the microchemistry of the natal stream (Brothers 1998). Comparison of parasitic phase lamprey statoliths with stream 'signatures? acquired from larvae will allow identification of the stream of origin. Analysis of otolith micro-chemical composition has previously been used as a valuable tool for discriminating local spawning populations and identifying origins of recruits to the fishery in primarily marine systems. Discrimination of lamprey natal streams is a logical application of micro-elemental analysis, as sea lamprey spend the majority of their lives (4-6 years) in streams acquiring an elemental signature and only one to 1.5 years in adding to the statolith mass as parasites. Thus, the larval signature should be highly recognizable in parasitic statoliths, especially given the ability of the proposed method (laser ablation--inductively coupled plasma-mass spectrometry (LA-ICPMS)) to target the central (larval) portion of a parasite's statolith. Pilot work has demonstrated differences in four elements (i.e., strontium, rubidium, manganese and barium) among 8 Lake Champlain streams; samples of 2 to 5 ammocoetes were uniquely identifiable to their natal stream in all but one stream. Several other elements were also detectable in lamprey statoliths and will add further resolution for stream discrimination.

The goal of the Lake Champlain Fish and Wildlife Resources Office is to develop statolith elemental signatures as a natural tag for Lake Champlain tributaries. In doing so, the study would validate use of this method to identify stream-of-origin of parasitic lamprey using individuals tagged as transformers as part of the GLFC-funded study. An ability to identify natal origins of parasitic- and spawning-phase sea lamprey also would pave the way for future studies aimed at understanding attributes (e.g., stream-specific survival, growth rates, sex ratios, movement) that promote survival to adult stages and would help to better target streams for sea lamprey control measures and implement alternative sea lamprey control technologies (e.g., sterile male release, barriers, pheromones).

Progress to date: Transformer sea lamprey tagged in 2001 were collected throughout 2002 and spring 2003. They provide samples of known-origin parasites and adults that can be used to validate the microelemental identification method. Transformers tagged in 2002 are currently being collected by anglers and state agency personnel; collection of spawning adults will begin in spring 2004. A search for a graduate student to work on this project is currently underway, and two proposals have been submitted for supplemental funds for salary and supplies. Microelemental analysis of larvae can commence as soon as a graduate student has been appointed and additional funding is received. In the absence of additional funding, analytical work on this project will commence in early 2004 in conjunction with a related project in the Great Lakes.

NORTHEAST REGION, U.S. FISH AND WILDLIFE SERVICE -- Conserving the Nature of the Northeast