While not the usual content for a coal company DVD, Solid Energy decided to document its 10-year snail program – of which it has just finished Phase 1 – at its Stockton Mine.
“The story of the snails is quite remarkable. It has received huge publicity, often generated by opponents of the initiative, which has at times overshadowed the good work by our staff and the Department [of Conservation] to enhance the prospects of this snail population,” Solid Energy CEO Don Elder said.
Solid Energy has spent the past two years relocating native land snails from the Mt Augustus ridgeline of its Stockton Mine. It is now into its third year of a 10-year program to collect and relocate the 6000-plus snails collected from the site.
Two-thirds have now been released back into the wild and the remainder are being kept in captivity at the Department of Conservation’s facility in Hokitika.
“Since the first group of snails was released in December 2006, we have tracked a selection of these which were fitted with small transponders,” Elder said.
“The snails in the wild are typically thought to live around 10 years, meaning an average survival rate in any year of around 90 percent.
“Overall survival rates of the groups of snails we are monitoring range from 97 percent (in captivity) to 90 percent for one group in the wild and 75 percent for one other site."
Along with the 6115 snails, the company recovered 1283 clusters of eggs. Of these, 168 individual eggs have hatched in captivity with a better-than-90% survival rate.
Some 484 eggs have been laid in captivity, and are expected to take up to a year to hatch. More than 1000 eggs have been returned to the wild.
“In addition, it is estimated there are another 600 snails remaining in the source location, outside the minesite,” Elder said.
“The captive population is growing, which is a very positive reinforcement for the program carried out over the past three years and gives us a high degree of confidence in our ability to establish a viable wild population.”
However, Elder noted much work remains to be done to understand the causes of the snail mortality and to confirm that the initial monitoring results are representative of all the snails released back into the wild.
“For example, we believe the weather has had an impact; a very frosty spell in the winter, and just recently the hot and dry summer,” he said.
“Solid Energy is working with the Department [of Conservation] to better understand how significant this unusual weather has been for survival rates and to assess what other factors may have come into play.
“We are also undertaking further population modelling to get better estimates of natural survival and reproductive rates.”
