Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

The first age data for the commercial octopus species, Octopus berrima (#133)

Erica Durante 1 , Gretchen Grammer 2 , Jasmin Martino 1 3 , Justin Payne 1 , Zoe Doubleday 1
  1. University of South Australia, Mawson Lakes, SA, Australia
  2. South Australian Research and Development Institute, West Beach, SA
  3. Australian Nuclear Science and Technology, Sydney, NSW

Determining the sustainable harvest of a fishery requires data on growth, maturation, mortality, and recruitment, all of which are underpinned by age data. Age data have been used to develop stock assessments for Octopus pallidus and Octopus cf. tetricus in the Tasmanian and Western Australian octopus fisheries respectively, but not in South Australia. The South Australian fishery is predominantly composed of Octopus berrima, or the southern keeled octopus, and this is the first study to estimate age. Growth increments were observed on the stylet, internal vestigial shell, and the beak. Increment periodicity was determined by injecting the live octopus with a fluorescent stain that would be absorbed by the stylets and beak. After a certain number of days, they were euthanised and days passed were compared to the number of increments formed since the stain. Beaks did not absorb the stain and increments varied from larger (width) to smaller (width) with no apparent pattern nor correlation with body size, therefore discarding the beak as an ageing method. The stylet proved to be the better ageing method of the two, but still had some limitations. Further results and conclusions will be discussed.