Predation by the endemic whelk Tenguella marginalba (Blainville, 1832) on the invasive Pacific oyster Crassostrea gigas (Thunberg, 1793)

ABSTRACT

The endemic mulberry whelk (Tenguella marginalba) is a common predator on Australian intertidal rocky shores. The introduced Pacific oyster (Crassostrea gigas), found within the natural range of T. marginalba, is potential prey for the whelk. In experiments designed to increase our understanding of predatory behaviour by the whelk on oysters, we found that adult T. marginalba detected C. gigas and increased movement in the presence of oyster prey. Tenguella marginalba showed a preference for smaller C. gigas, but consumed oysters up to 60 mm in shell height. To access oyster flesh, whelks used their radula to drill holes in the oyster’s shell. These holes were on average 0.68 ± 0.09 mm in diameter, most frequently located central to the pericardial cavity on the right (upper) valve. Predation was greatest when predator and prey were both submerged, but was unaffected by a diurnal light cycle. When offered a choice among the native Sydney rock oysters (Saccostrea glomerata), mussels (Trichomya hirsuta) or the invasive C. gigas, whelks displayed no preference among prey. We conclude that the invasive oyster C. gigas represents a viable food source for T. marginalba, which may help to slow the spread of this invasive oyster throughout eastern Australia.

KEYWORDS:

• Predation
• Oysters
• Sydney rock oyster
• bivalve
• gastropod

Acknowledgements

We wish to acknowledge the support of the New South Wales Department of Primary Industries and Sydney Institute of Marine Science. J.M. Wright was supported by an Australian Postgraduate Award and the School of Life and Environmental Sciences at the University of Sydney. The authors declare they have no competing interests. All animals have been sampled and treated according to the national legislation and all required permissions have been obtained. We thank an anonymous reviewer for comments on an earlier version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.