A sensitive analytical method for quantifying petromyzonol sulfate in water as a potential tool for population monitoring of the southern pouched lamprey, Geotria australis, in New Zealand streams.

The migratory southern pouched lamprey, Geotria australis, is a culturally important fish native to New Zealand. Anecdotal evidence suggests that populations of G. australis have declined from historic levels, and presently, this species is rare in many New Zealand rivers and streams. Migratory sea lamprey (Petromyzon marinus) use a pheromone mixture to locate suitable spawning sites. This mixture is comprised of three steroids: petromyzonol sulfate (PS), petromyzonamine disulfate (PADS), and petromyzosterol disulfate (PSDS). We examined the migratory pheromone mixture released by G. australis ammocetes and found that they excrete predominantly PS. PADS has been detected on some occasions in low concentrations, and PSDS either is not released, or is released in extremely low concentrations. By using a recently developed sensitive mass spectrometry method, we compared passive sampling techniques against more traditional active water sampling as methods for estimating lamprey populations in local streams. Passive sampling provided quantitative data for PS from all sites surveyed, with uptake rates of 0.3 to 45.7 pg/day observed. Conversely, active sampling returned only one positive result out of 19 samples, and with a method detection limit of 2.5 × 10(-14) M, this suggests that concentrations of PS in these streams are either extremely low or variable. The combination of passive sampling and triple quadrupole mass spectrometry is a promising tool for monitoring of G. australis in New Zealand streams.