AUTHOR=Day Jeremy K. , Knott Nathan A. , Swadling Daniel S. , Huggett Megan J. , Gaston Troy F. 

TITLE=Assessing lobster and co-predator feeding rates on barrens-forming sea urchins in South East Australia

JOURNAL=Frontiers in Marine Science

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2024.1418506

DOI=10.3389/fmars.2024.1418506

ISSN=2296-7745

ABSTRACT=<p>Globally, key predators such as lobsters are thought to control urchins. In south-eastern Australia, the role of <italic>Sagmariasus verreauxi</italic> (eastern rock lobster) as a key predator of the native urchin <italic>Centrostephanus rodgersii</italic> (long-spined urchin) has been questioned while the sympatric <italic>Heliocidaris erythrogramma</italic> (short-spined urchin) may be eaten more frequently. To test this, we tethered and filmed 100 urchins (50 C<italic>. rodgersii</italic> and 50 <italic>H. erythrogramma</italic>) outside of a lobster den over 25 nights to identify predators and quantify predation rates, time to feeding onset and handling time. <italic>Sagmariasus verreauxi</italic> exhibited very low predation rates (4%), despite being filmed walking past urchins repeatedly whereas <italic>Heterodontus galeatus</italic> (crested horn shark) was the main predator (45%). Predation rates by all predators (lobsters and sharks) were influenced primarily by tethering night but not urchin size or species. Predation increased throughout the study and while <italic>H. erythrogramma</italic> and <italic>C. rodgersii</italic> were eaten at similar rates, there was a trend for lobsters to eat <italic>H. erythrogramma</italic> and sharks to eat <italic>C. rodgersii</italic>. Feeding onset had no significant predictors though large <italic>C. rodgersii</italic> took longer to handle during feeding for both predators. Importantly, sharks readily consumed 25 C<italic>. rodgersii</italic> up to 121 mm Test Diameter (TD) while lobsters only ate one <italic>C. rodgersii</italic> (58 mm TD). These findings, although from only one test location, provide important insights into the species eating urchins and highlight the potential significance of overlooked predators such as <italic>H. galeatus</italic>.</p>