ORCID Profile
0000-0002-6004-4780
Current Organisations
NSW DPI
,
The University of Newcastle
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Publisher: CSIRO Publishing
Date: 23-03-2021
DOI: 10.1071/MF20287
Abstract: Worldwide, lobsters are considered important predators of macroalgae-consuming urchin species, but this has not been tested for Australia’s common lobster, the eastern rock lobster (Sagmariasus verreauxi). We predicted that the abundant urchins, the long-spined urchin (Centrostephanus rodgersii) and the short-spined urchin (Heliocidaris erythrogramma), would form substantial components of lobster diets. To test this hypothesis, we examined 115 lobster stomachs from 9 locations and conducted 14 feeding trials, in which lobsters were offered either urchin species. Dissections revealed various stomach items, with detritus (51%), bivalves (34%), gastropods (28%) and algae (26%) occurring more frequently than urchins (19%). Urchin spines were found in 22 lobsters that ranged in size from 91- to 124-mm carapace length, with all in iduals containing H. erythrogramma spines and C. rodgersii spines observed only once. During feeding trials, seven urchins were consumed. Four H. erythrogramma were eaten on Day 1, whereas one was not eaten until Day 11. Two C. rodgersii were eaten on Days 2 and 10. Only three of the six lobsters observed to eat urchins ingested spines. Together, these data show that S. verreauxi is a generalist predator that consumes urchins, although, because urchins could be eaten without ingesting spines, future studies are needed to assess the importance of urchins as dietary items for S. verreauxi.
Publisher: Wiley
Date: 18-12-2023
DOI: 10.1002/RCM.9435
Abstract: Isotope analysis can be used to investigate the diets of predators based on assimilation of nitrogen and carbon isotopes from prey. Recent work has shown that tissues taken from legs, antennae or abdomen of lobsters can give different indications of diet, but this has never been evaluated for Sagmariasus verreauxi (eastern rock lobster). Work is now needed to prevent erroneous conclusions being drawn about lobster food webs, and undertaking this work could lead to developing non‐lethal s ling methodologies. Non‐lethal s ling for lobsters is valuable both ethically and for areas of conservation significance such as marine reserves. We evaluated this by dissecting 76 lobsters and comparing δ 13 C and δ 15 N isotope values in antennae, leg and abdomen tissue from the same in iduals ranging from 104 to 137 mm carapace length. Stable isotope values were determined using a Europa EA GSL elemental analyser coupled with Hydra 20–20 Isoprime IRMS. We found the abdomen δ 13 C values to be lower than other tissues by 0.3 ± 0.2‰ for antennae tissue and 0.1 ± 0.2‰ δ 13 C for leg tissues, whereas for δ 15 N, no significant difference between tissues was observed. There was no significant effect of lobster size or sex, though we did observe interactions between month and tissue type, indicating that differences may be seasonal. Importantly, the detected range of isotopic variability between tissues is within the range of uncertainty used for discrimination factors in isotopic Bayesian modelling of 0‰–1.0‰ for δ 13 C and 3.0‰–4.0‰ for δ 15 N. We show that S. verreauxi can be s led non‐lethally with mathematical corrections applied for δ 13 C, whereas any tissue is suitable for δ 15 N. Our results indicate that a walking leg is most favourable and would also be the least intrusive for the lobster. The application of non‐lethal s ling provides avenues for the contribution of citizen science to understanding lobster food webs and to undertake fieldwork in ecologically sensitive areas such as marine reserves.
No related grants have been discovered for Jeremy Day.