Mr Tyson Bessell1, Dr Sharon Appleyard2, Assoc. Prof. Rick Stuart-Smith1, Ms Olivia Johnson1, Assoc. Prof. Scott Ling1, Dr Freddie Heather1, Dr Tim Lynch2, Assoc. Prof. Neville Barrett1, Dr Jemina Stuart-Smith1
1Institute For Marine And Antarctic Studies, Hobart, Australia, 2CSIRO, Hobart, Australia
Population data in the form of species’ spatial distributions and population trends are crucial for successful conservation efforts. Obtaining sufficient population data, however, is often difficult, especially for rare marine fish and invertebrate species that are small, cryptic and thus very difficult to detect. This study sought to understand the effort required to search for undiscovered populations of small, cryptic, marine species in shallow vegetated coastal habitats, using the Critically Endangered red handfish (Thymichthys politus) as a representative species. Using a combination of environmental DNA (eDNA) and structured underwater SCUBA surveys of life-like ‘surrogate’ 3D-printed models, we designed a sampling strategy to estimate detectability. Over scales of hundreds of metres to kilometres, the eDNA assay detected red handfish presence in situ. At finer scales (< 100 m), underwater searches for independently placed surrogates by SCUBA divers found that mean detection probabilities ranged from 57 to 97%. In the most complex habitat (dense, high complex reef) each search area (a 300 m2 belt transect) must be searched in fine detail four times to be 95% confident of detecting a single individual. These findings give insight into the general effort required to detect similarly rare and cryptic species at small and large scales, and is a useful methods calibration exercise. Improving understanding of detection capabilities not only helps to refine monitoring and conservation efforts for known threatened species, but may also assist in identifying other inconspicuous species whose population declines may otherwise go unnoticed.
Presentation Slides – Tyrone Bessell
