NIWA and Auckland Council freshwater scientists have developed a pheromone sampler that detects the presence of lamprey in freshwater, an important taonga species for Māori but now believed to be in decline. The samplers, which absorb pheromones going past in the water column, were placed in 12 streams across Auckland in a project commissioned by Auckland Council, and supported with additional funding from the Ministry for Business, Innovation & Employment.
Dr Baker said the next step with the pheromone project was to better understand the concentrations of lamprey and determine whether there is a good correlation between what the pheromone samplers were indicating and the actual numbers of lamprey in the stream. They would also like to extend the samplers to include other pheromones.
The lamprey could be anywhere in the stream system when they secrete the pheromones that are then absorbed by the samplers. “Once analysed, the samplers indicate whether there are lamprey in the catchment and, to an extent, whether they are present in high or low densities.” The samplers placed in the Piha and Glen Esk streams in the Waitakere Ranges were the only two streams to return positive results. Electric fishing and a search for lamprey egg nests was then carried out along an area of about 1km in one stream and 500m in the other and the lamprey were discovered. “We found two juvenile lamprey in the Piha Stream and three in Glen Esk so they’re not present in huge densities but they are definitely there. We’d anticipate that there may be higher numbers of lamprey in the stream’s lower reaches. However, the deeper waters are difficult to survey so we specifically targeted higher stream elevations.”
Read the full story here: http://www.niwa.co.nz/news/scientists-make-rare-find-in-auckland-streams