Degree Name

Bachelor of Marine Science Honours


School of Earth, Atmospheric and Life Sciences


Professor David Ayre


It has been speculated that Sagmariasus verreauxi (Eastern Rock Lobster) is an important predator of the barrens-forming urchin species Centrostephanus rodgersii (Long-Spined Urchin) and Heliocidaris erythrogramma (Short-Spined Urchin). Both urchin species can cause extreme habitat modification when occurring at high densities and this is considered a problem within NSW marine parks. Elsewhere, lobster predation on urchin by similar species Jasus edwardsii (Southern Rock Lobster) is considered key in controlling urchin populations, but whether S. verreauxi has a similar trophic impact is unknown. In this study, I for the first time investigate the likely value of S. verreauxi as an urchin control agent. I use a holistic approach that investigates lobster diet and feeding behaviour by using dissections and feeding trials and investigate urchin predation rates inside and outside of No-Take Sanctuary Zones (SZ’s) using diver surveys and urchin tethering experiments. I also use external tagging and passive-receiver acoustic telemetry to observe whether large and small lobster use and remain resident within sanctuary zones. Additionally, I have collated 125 observations on lobster size (carapace length, mm) between all experimental locations to test whether larger S. verreauxi are associated with SZ’s. My dissections and Gut Contents Analysis (GCA) of 118 S. verreauxi freshly collected and donated frozen from areas within the Sydney, Shoalhaven, Illawarra and Central Coast regions of NSW imply that lobsters eat urchins less frequently than expected and did not support the prediction that large lobsters eat more urchins. I found urchin material in < 20% of the 118 lobsters dissected and did not find urchin in 96 individuals. I found H. erythrogramma exclusively in small-sized lobsters and C. rodgersii in lobster of various sizes, though at a lower frequency. Using open water mesocosms I presented two urchins of one species to 14 S. verreauxi during nocturnal feeding trials. Six of 14 lobsters fed on urchin (≈ 40%) and eight lobsters did not for the 14-day duration. I found that five of 16 H. erythrogramma (≈ 30%) and two of 12 C. rodgersii (≈ 17%) were eaten in total, and only the largest lobster consumed two urchins. When I performed GCA on the two lobsters that had eaten C. rodgersii I found no urchin spines in their guts, while I found H. erythrogramma spines in the guts of lobsters that had eaten H. erythrogramma. This 6 indicates that the accuracy of GCA may vary with factors such as lobster size and urchin species. Using a dataset gained through all experiments where lobsters were measured (dissections, feeding trials, acoustic tagging of lobsters) I found that S. verreauxi occurs within both SZs and surrounding fished areas and appears significantly larger on average within SZ areas. I also found that individually tagged C. rodgersii and H. erythrogramma presented on benthic urchin tethers were consumed ≈ 2-3x faster within SZs than in fished areas. I tagged and released 12 S. verreauxi across a range of sizes (105mm – 150mm CL) in Jervis Bay Marine Park (JBMP) and Bendalong, tracking them over 6 months (July – January). The largest lobsters were found in SZ’s. My acoustic receiver data download in January 2020 confirmed residency periods of S. verreauxi at SZ sites of 10 – 44 days. I found three JBMP lobsters showed residency in SZ areas while one was resident in a fished zone. Surprisingly, all lobsters showed a lag-time of 5 - 31 days between tagged-release and the first receiver detection. Lobsters were detected at times ranging from 12 - 72 days after tagging, with gaps of over one day between some detections. I could not estimate minimum distances travelled after tagging, as each lobster was only detected on a single receiver. Three lobsters tagged in JBMP were not detected at all, and no individuals were detected entering or leaving JBMP. The results of this initial study confirm that S. verreauxi consumes barrens-forming urchin species and that JBMP SZ’s are beneficial to lobster populations, though more research is needed. I indicate through urchin tethering and acoustic telemetry experiments that SZ’s could be an effective tool in controlling potential future outbreaks of barrens forming urchin-species. However, my dissections and feeding trials indicate that the contributions of S. verreauxi alone to urchin control might be less than expected. Lobster did show an apparent preference for H. erythrogramma over C. rodgersii, though this result should be treated with caution as GCA detection rates appear to differ between species. Importantly, I have shown that the medium-term tagging of lobsters using external tags and passive receiver acoustic telemetry is possible, although seemingly not overly efficient, and that lobsters can remain in SZ’s for up to 44 days. More work is needed to confirm the trends I discuss here, and these results are intended as the basis for future research.

FoR codes (2008)

060205 Marine and Estuarine Ecology (incl. Marine Ichthyology)



Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.