Invertebrates are an integral part of freshwater ecosystems and provide researchers with knowledge regarding the health and productivity of streams and lakes. However, freshwater invertebrates are declining across the globe due to factors such as climate change and habitat degradation. It is pertinent to ensure that freshwater invertebrate communities are frequently sampled to monitor changes in freshwater environments, such as changes in community composition and movement of invasive species.
There are a multitude of sampling methods available for freshwater invertebrates, with methods varying in deployment time, cost, manual labour and equipment. However, most existing sampling methods for freshwater invertebrates are labour intensive or often require large amounts of equipment. This can incur additional costs to research, such as hiring of extra hands or purchasing new equipment when required.
This project saw the novel trialling of Whakaweku traps, a traditional Maori method of capturing crayfish, as an invertebrate surveying method in Tasmania. Whakaweku are constructed from ≈10 individual Pteridium esculentum fern fronds, which are shaped into a bundle and deployed individually or on a line as a group. Whakaweku have proven to be successful in monitoring populations of native New Zealand fish and crayfish, and some research suggests Whakaweku provide accurate representations of macroinvertebrate populations.
In this study we trialled Whakaweku in Tasmania, primarily to passively survey juveniles of the giant freshwater crayfish Astacopsis gouldi while simultaneously surveyed the broader instream invertebrate fauna.
Preliminary results suggest that Whakaweku can be used to collect a large diversity of species and include specimens smaller than 1 mm in size. Results also suggest that Whakaweku samples can be used to reliably compare productivity and pollution levels between different Tasmanian streams. However, no juvenile freshwater crayfish were surveyed, and possible reasons for this will be discussed. Otherwise, Whakaweku provided a low-cost, passive invertebrate surveying method without sacrificing sample quality for ease of use.