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A FIELD INVESTIGATION OF THE POTENTIAL TO CONTROL SEA LAMPREY THROUGH
PHEROMONE-MEDIATED REDISTRIBUTION OF MIGRANTS IN THE GREAT LAKES
C.M. Wagner¹, T.D. Meckley¹
¹Michigan State University
Department of Fisheries and Wildlife
13 Natural Resources Building
East Lansing, MI, 48824
1. Two novel control approaches have been proposed for the use of the sea lamprey migratory pheromone: 1) redistribution of migrants into areas where they are increasingly vulnerable to capture or destruction; 2) baiting traps to increase the efficiency of trapping operations.
2. These strategies are based on two hypothesized functions for three putative migratory pheromone compounds (PADS, PSDS, PZS): 1) they attract/retain migrating lampreys near river mouths; and/or, 2) once in rivers they guide migrants to areas with suitable larval rearing habitat. Although whole larval odor does induce tributary selection in the field (Wagner et al. 2006), PADS, PSDS, and PZS are not responsible for this phenomenon in the river, but could be important at the river mouth.
3. We carried out three years of field study to determine how sea lamprey would return to the coast, encounter rivers in the Great Lakes and to ascertain the functional role of the full larval odor, as well as to specifically test three larval odor compounds in attracting and retaining migratory lampreys at river mouths, to develop a full-scale control strategy for the migratory pheromone at the lake-river interface.
4. The movements of sea lamprey were captured with fixed acoustic telemetry both on the coast in front of a river, and offshore, over 3 km from the coast. Before the telemetry data could be used we had to develop a framework for describing animal behavior from telemetered observations (Gurarie et al. 2015) and develop a standardized approach for assessing and filtering the fixed acoustic telemetry known as the VEMCO Positioning System (VPS) (Meckley et. al. 2014).
5. In 2010, we initiated a two-year major field experiment designed to record sea lamprey behavior in and near the Ocqueoc River plume with the VPS system, under both a low natural larval odor condition (2010), following larval removal via pesticide (TFM; treated below dam in 2008 and above dam in 2009) and a high larval odor condition (2011), created from natural larval recruitment and the addition of PADS, PSDS and PZS daily to bring the concentration of each synthetic component of larval odor to a 1 x 10 -12 molar concentration in the Ocqueoc River. We monitored the lake conditions adjacent the river mouth with both an autonomous underwater vehicle (YSI, EcoMapper) and an upward facing aquatic Doppler current profiler
(ADCP) to monitor a suite of water quality, bathymetric, and hydrologic parameters necessary to evaluate the shifting position of the river plume, which was used to develop a dynamic model of river plume structure. Together these datasets allow for the recreation of the hydrological experience of individual sea lamprey. Upon reaching a coastline, sea lampreys move parallel to shore. Encounter with river water appears to trigger localized search, regardless of larval odor content. However, when larval odor was abundant, the migrant was more likely to enter the river. Whether a migrant enters a river, is modulated by the presence of detectable larval odor, manipulation of river selection by invasive sea lamprey for management is viable in rivers with high encounter rates.
6. In 2013, three-dimensional (3-D) paths of migrating female sea lamprey were obtained by an acoustic array with 3 km² of coverage, centered 3.3 km from the coast in Lake Huron. The findings indicated that sea lamprey sampled an area of lake-bottom to assess absolute hydrostatic pressure and to select a heading towards reducing pressure (shallower water).The dataset allowed us to describe how sea lamprey orient to a coast when in a lake and we hypothesized that sea lamprey navigate to the nearest coast by (1) orienting to the local bathymetric gradient and (2) maintaining straight movements counter to the local slope to move towards shallow water. Together our findings suggest that sea lamprey will only be biased to return to a particular region if they are attached to a host that gathers in a particular region of the lake.
7. An annular tank was insufficient to determine the minimum effective combination of known synthetic components of larval odor, potentially because larval odor influences habitat selection, and does not influence movement rate. We have been unable to determine any effective lab assay to reveal any effect of these compounds on sea lamprey behavior and field assays have not revealed a definitive effect of the currently known synthetic replicates of larval odor on habitat selection in the river or lake.
8. If a sea lamprey encounters a river plume it becomes eligible for behavioral manipulation by an odor. The addition of the full larval odor would concentrate sea lamprey in rivers that are regularly treated or possess poor larval rearing habitat, but a sufficient imitation of the odor has not yet been identified and synthesized.