Lampreys can't stand the smell of death

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The smell of death could play an important part in controlling an invasive species in the Great Lakes in the US.

The study is researching the use of a chemical that is released by dead Sea lampreys as a repellent to migrating individuals. When the scent of dead lampreys is poured into tanks of live ones their escape reaction is quite dramatic. This research looks at how this reaction might be utilised to deter the 'invaders'.

Lead author Michael Wager, assistant professor of fisheries and wildlife at Michigan State University said: "Sea lampreys are one of the most costly and destructive Great Lakes invaders. The effectiveness of the odour combined with the ease in which it's obtained suggests that it will prove quite useful in controlling Sea lampreys in the Great Lakes."

Sea lampreys were first found in the Great Lakes in the 1800s and have decimated the fishing industry there. They attach to their hosts using their sucker mouth parts and sharp teeth and feed on the bodily fluids. It is thought that a single lamprey can kill more than 40lb of fish with only one fish in seven surviving a lamprey 'attack'.

The effect has been that prior to the arrival of lampreys, over 7 million kg of lake trout were harvested every year from Lakes Huron and Superior; by the 1960s this had decreased by over 98%.

Lampreys are very reliant on smells for their life cycle, using the odour emitted from past generations of larvae to navigate to suitable spawning grounds, and mature males emit another smell which in turn attracts females to them to complete spawning.

Previous attempts to eradicate lampreys from the Great Lakes have relied on these scents to trap the lampreys, after which they have either been eradicated or sterilised and re-released. However pheromones are subject to problems as the lampreys may use other cues to navigate by. It is hoped that by isolating the chemical from dead lampreys which deters their living counterparts that this will be far more successful.

Wagner added: "It's kind of like a stop light, a noxious odour that causes them to run away from its source. By blocking certain streams with these chemical dams, Sea lampreys can be steered away from environmentally sensitive areas and into waterways where pesticides could be used more effectively to eliminate a larger, more concentrated population of Sea lampreys."

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