These ditches have been dug at the end of Wairewa (Lake Forsyth) to catch eels as they migrate to the sea. Teone (Hōne) Taare Tīkao, an elder of the Ngāi Tahu tribe, described how this method was used in the South Island:

‘When the great eel migrations (heke-tuna) were on you could catch them in surprising numbers by two or three ways. One way was to make canals or drains from the waterways for a chain or two through the sand or shingle with a hole (parua) at the end, and sometimes the eels could be scooped out in thousands.’

Teone Taare Tīkao. Tikao talks: ka taoka tapu o te ao kohatu: treasures from the ancient world of the Maori. Auckland: Penguin, 1990 (originally published 1939).