Online

Harrington, Michael R.

Natural Resource Planning Program

2008

MS

Female sea lamprey (Petromyzon marinus) seek males through chemical cues of a sex pheromone. Female choice experiments in the Great Lakes indicated females were responsive to sex pheromone in half of the trials and could differentiate among concentrations of sex pheromones emitted from traps; i.e., females entered traps with higher concentrations. Those results were corroborated in experiments with Lake Champlain sea lamprey. However, none of these studies conducted experiments in the presence of background pheromone, which would be present under natural conditions. We conducted female choice experiments in which we stocked mature males (n = 3-9) for the purpose of providing competing pheromone in a 50-m stream enclosure in Malletts Creek, a tributary to Lake Champlain. The equivalent of pheromone released by 0, 1,3, 9, or 27 males was pumped through a lamprey pot 35 m upstream of a release cage containing a female.
In each trial, lasting a maximum of 1 hour, a female was released and her behavior and movements were recorded through visual observations and antenna readings. Females swam to a pheromone source or swam upstream moving rocks in 17 of the 38 trials. Six of those females approached ambient males, six approached the lamprey pot, and four entered the lamprey pot. The greatest proportion of females approached the lamprey pot when the pheromone we applied was greater than that produced by ambient males. Although females were attracted to male pheromone in 17 trials, the positive response rates in these trials were lower (< 50%) than in previous experiments without ambient males. We conclude that a portion of females could be attracted to traps in an effort to provide some reduction in population sizes of sea lamprey. However, the ability to adequately capture the majority of females in this manner remains elusive.