Smell Sex & Death
Updated: Jun 29, 2020
(steelhead trout dead after 2 attacks by lampreys)
We recently explained the anatomy of the lamprey and many interesting facts about these proto-vertebrates in our lamprey dissection video (which you can check out here). Although these creatures are surely fascinating, they are actually huge trouble makers in many bodies of waters worldwide, ruthlessly predating on keystone species and destroying entire ecosystems.
One method scientists commonly used to control lamprey populations in the past was through sex pheromones. Male lampreys release pheromones during mating season, which lures and guides the females to possible nesting sites. Scientists took advantage of this, and mixed in chemicals mimicking lamprey pheromones into streams that lead to ecosystems where lampreys would not pose a significant threat. However, one downside of this process was that the lab-produced pheromones were often not strong enough of a scent to lure females, especially when mixed in with all the other scents of a running stream.
Luckily, scientists have recently discovered a new technique that can be used in conjunction with the pheromones. Lampreys have been shown to have great aversion to the smell of decaying lampreys– lampreys went into panic when a chemical mimicking the smell of decaying lampreys was introduced to a laboratory tank. If you haven’t figured it out by now, this technique does the exact opposite of what the sex pheromones do: the smell of sex attracts, while the smell of death repels. Although the chemical mimicking the smell of death (unlike the chemical mimicking the pheromones) is strong enough to completely deter lampreys from entering a certain stream, using such strong doses could habituate lampreys to the smell. Therefore, scientists believe the ideal solution would be to use a combination of mild doses of both the pheromone-mimicking chemical and the decay-mimicking chemical. If the stream that leads to a lake with endangered species lampreys prey on is ladened with a mild dose of the decay-mimicking chemical while the alternative stream leading to a relatively empty lake is ladened with a mild dose of the pheromone mimicking chemical, the lampreys would successfully be steered away from threatened fish species without any risk of habituation.