Pipi shell survey

The Pipis of Venus Bay are back making news in the local papers. The community has concerns regarding the impacts caused by people collecting Pipi on the surf beaches of Venus Bay. While the political debates are discussed elsewhere, the food web continues down on the beach. In our time of randomly sampling empty Pipi shells for signs of how/why they died we seldom see many examples of predation by predatory snails. The Naticidae leave a distinctive drill-hole mark on their victims, below top is a close-up of the hole a Naticid made in a Surf Clam shell. Nicely bevelled work!

In the shell survey I did on the beach Northwest of Beach Five on the 9Th Jan 2011 the chipped/non-chipped ratio was 9/10 in favour of chipped shells below bottom. The one exception was a Pipi shell with a Naticid hole.

We do this survey to gain information over time on the causal factors of Pipi mortality, but it also gives us some idea of the sizes of the Pipis present and how the Natacids (& others) are faring.

Does anyone know if Oystercatchers leave tell-tale marks on shells when they predate them?