Standard Presentation (12 minutes) Australian Marine Sciences Association 2025 Conference

Uni-fied, or are we? Testing the effects of sea urchin removal on kelp (119654)

Chanelle Webster 1 , Adriana Verges 1 , Cayne Layton 2 , Peter Steinberg 1 , Dane Wilmott 3 , Rob Chewying 4 , Simon Rowe 5 , Maria Byrne 6
  1. School of Biological, Earth & Environmental Sciences, University of New South Wales, MAROUBRA, NEW SOUTH WALES, Australia
  2. Institute for Marine and Antarctic Studies & Centre for Marine Socioecology, University of Tasmania, Hobart, Tasmania, Australia
  3. Nature Coast Marine Group, Sydney, New South Wales, Australia
  4. NSW Aboriginal Land Council, Sydney, New South Wales, Australia
  5. Ocean Watch, Sydney, New South Wales, Australia
  6. School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia

Degradation of kelp under intense herbivory by sea urchins presents an opportunity to identify quadruple–bottom-line solutions that provide cultural, economic, environmental and social benefits. We set up a collaboration amongst Traditional Owners, fishers, government agencies, and conservationists to test the effects of removing sea urchins on kelp and roe quality. After obtaining support from the South Coast People, approximately 11 tonnes of longspined sea urchin Centrostephanus rodgersii were harvested by local fishers within three rectangular stripes (70 x 20 m) along a depth gradient (6-12 m). Before and after the harvest, in situ surveys were conducted to quantify the abundance of kelp, crayfish and abalone and fish diversity. Urchin gonad quality was also assessed. Three kelp reference and three urchin barren sites were included for comparison. Adults and recruits of kelp (Ecklonia radiata and Phyllospora comosa) were observed 18 months after the first harvest but only in the shallower depths and in low densities. Urchin roe was of sufficient quality to be marketable but not yet premium. Combined, these results are indicative of early-stage recovery. Our preliminary results suggest that active actions like sea urchin removal can support the return of our underwater forests and sustain important socioeconomic values.