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Tuatara: Volume 25, Issue 2, January 1982

A Checklist of Molluscs from North Otago Commercial Rock Lobster Pots

page 71

A Checklist of Molluscs from North Otago Commercial Rock Lobster Pots

The bluffs of the North Otago Heads, which shelter much of the town and harbour of Oamaru from southerly winds, are fringed by volcanic rocks which form a reef exposed at low tide. The reef and its tidal pools have a diverse mollusc fauna characteristic of the northern Forsterian zone. The intertidal reef extends outwards to a depth of about 18 metres to the south-east of Cape Wanbrow. This submerged reef is the habitat of the commercially exploited rock lobster, Jasus edwardsii, which supports a seasonal (June to December) local industry.

This checklist provides a list of 78 species of mollusc which have been taken from commercial lobster pots in this area between 1970 and 1980.

The pots, referred to locally as “craypots”, have a welded steel rod frame covered by plastic-coated netting and have an entrance on top. Some are woven from wire and cane, including the original type which used native supplejack, Ripogonum scandens, but these are seldom used now by commercial fishermen here. The pots are baited with fish or fish skeletons and are set on the grounds in 10-18m of water. They are lifted, cleared, rebaited and reset daily when weather conditions allow. Inevitably, many molluscs are captured in the pots and some unexpected species turn up from time to time. They may move in to consume the bait, be transported in as shells mobilised by hermit crabs (Eupagurus spp.) seeking the bait, or possibly be washed in by water turbulence (e.g. bivalves).

Some of the unexpected finds include Early Miocene fossils — ?Polinices sp., Penion sp., and Cucullaea sp.; presumably eroded from the submerged continuation of the adjacent Awamoan formation in the Old Rifle Butts locality. However, the occurrence of frequent specimens of Struthiolaria obesa, indicates an underwater Early Pliocene stratum which is not present in the terrestial Waitaki series (P. A. Maxwell, pers, comm. 1979). One valve of the brachiopod Notosaria nigricans has been recorded and the asteroids Asterodon dilatatus, Pentagonaster pulchellus, Patiriella regularis, Astrostole scabra and Coscinasterias calamaria have been taken in the pots. Notable amongst the latter were two sets of 4 to 8-armed Patiriella regularis. Many species of fishes, Crustacea, and miscellaneous invertebrates, including sea-spiders ?Achelia sp., also have been noted.

Nomenclature is based on Powell (1979). Abundance is significant and is designated after each species as follows: (P) Plentiful; (U) Uncommon; (R) Rare.



  • Amaurochiton glaucus (Gray) (R)
  • Rhyssoplax canaliculata (Quoy & Gaimard) (R)
  • Sypharochiton pelliserpentis (Quoy & Gaimard) (R)


  • Cryptoconchus porosus (Burrow) (U)



  • Haliotis v. virginea (Gmelin) (U)
page 72


  • Tugali stewartiana Powell (R)


  • Melagraphia aethiops (Gmelin) (R)
  • Diloma arida (Finlay) (R)
  • Cantharidus o. opalus (Martyn) (U)
  • Micrelenchus tenebrosus (A. Adams) (U)
  • Trochus viridus Gmelin (P)
  • Trochus tiaratus (Quoy & Gaimard) (R)
  • Maurea p.? tigris (Gmelin) (P)
  • Maurea p. ?pellucida (Valenciennes) (U)
  • Maurea punctulata (stewartiana) (Martyn) (P)
  • Umbonium zelandicum (Hombron & Jacquinot) (R)


  • Turbo smaragdus Gmelin (U)
  • Turbo granosus (Martyn) (P)
  • Astraea heliotropium (Martyn) (U)
  • Cookia sulcata (Gmelin) (R)


  • Maoricolpus r. roseus (Quoy & Gaimard) (U) Struthiolariidae.
  • Struthiolaria p. ?papulosa (Martyn) (R)
  • Struthiolaria p. gigas Powell (P)
  • Struthiolaria obesa Hutton (U)


  • Trichosirius inornatus (Hutton) (1 only)


  • Sigapatella novaezelandiae (Lesson) (U)
  • Zegalerus tenuis (Gray) (R)
  • Maoricrypta monoxyla (Lesson) (P)


  • Tanea zelandica (Quoy & Gaimard) (U)
  • ?Polinices sp. (1 only)


  • Cabestana spengleri (Perry) (R)
  • Argobuccinum tumidum (Dunker) (P)
  • Mayena a. australasia (Perry) (1 only)
  • Fusitriton retiolus(Hedley) (R)


  • Xymene ambiguus (Philippi) (P)
  • Xymene aucklandicus (E. A. Smith) (P)


  • Austrofusus glans (Roding) (U)
  • Buccinulum p. pertinax (Martens) (P)
  • Buccinulum vittatum littorinoides (Reeve) (R)
  • Penion sp. (R)


  • Alcithoe swainsoni Marwick (U)
  • Alcithoe jaculoides Powell (U)


  • Phenatoma rosea (Quoy & Gaimard) (R)


  • Amphibola crenata (Gmelin) (1 only)