Poster Presentation Australian Society for Fish Biology Conference 2022

Stable Isotopes: a rapid method to determine lobster diet and origin? (#222)

Jennifer E Smith 1 2 , John Keane 1 2 , Craig Mundy 1 2 , Caleb Gardner 1 2 , Michael Oellermann 1 2 3
  1. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
  2. University of Tasmania, Taroona, TAS, Australia
  3. Die Technische Universität München, Munich, Germany

While working on methods to determine lobster diet in the wild, we learnt of a need by industry to be able to identify the source location of Southern Rock Lobster (Jasus edwardsii) from post-harvest/market samples. Stable isotope analysis is one suggested method of achieving this. If location is identifiable from isotope signature it will prove a valuable tool for commercial catch control and management of fisheries; for example product recalls or resolving trade disputes. Given rock lobster stable isotope research is currently underway to investigate lobster diet in Tasmania, the research team identified scope to expand the current program from eastern Tasmania to south eastern Australia in an attempt to meet the industry’s interest. The collection of rock lobster stable isotope data across this distributional range will identify if stable isotopes can be used post-hoc to determine catch location.

Previously, application of stable isotope analysis has suggested that spatial variation in carbon and nitrogen isotope values at the base of the food chain are reflected in predator isotope signatures. If this is identifiable in lobsters, and we are able to distinguish between locations of foraging, it would be a feasible method to determine lobster catch origin.

Stable isotope analysis could be a valuable method because it: (a) Provides a long-term view of lobster diet – which is likely to differ between locations, (b) allows estimation of the proportion of prey contribution to the diet – which will allow for investigation into consumption rates and inferences about predation pressure, and (c) only requires a very small, potentially non-lethal sample of lobster tissue (0.5mg), meaning it will not affect the market value of the fishery's catch.