Ecology of New Zealand abalones,haliotisspecies (Mollusca: Gastropoda)

Abstract

The ecological distribution and commercial importance of New Zealand's three species of abalone (Haliotis iris Martyn 1784; H. australis Gmelin, 1790; and H. virginea Gmelin, 1790) are briefly discussed. Examination of gut contents of H. iris and H. australis from Kaikoura on the east coast of the South Island of New Zealand indicated that both species fed mainly on red algae at all times of the year. Feeding was greatest in the winter. H. iris from Taylors Mistake, 154 km south, fed almost exclusively on the brown alga Macrocystis pyrifera. By comparing these results with analyses of the floral composition of attached and drift algae in the two areas it was shown that food at Kaikoura was derived from drift algae washed in to shore from deeper water and at Taylors Mistake from attached seaweed. Laboratory selection experiments showed that both species preferred the red alga Hymenocladia lanceolata to either of the brown algae Lessonia variegata or Macrocystis pyrifera. H. australis was more selective than H. iris from Kaikoura. Juvenile H. iris fed in the laboratory for six months on a monospecific diet of Hymenocladia grew faster than those fed on Lessonia. It is suggested that H. iris at Kaikoura, a generally sedentary species found on flat boulder bottoms or on low rocky ridges, receives an almost continuous supply of drift seaweed and is therefore not very selective in its diet. H. australis, on the other hand, inhabits crevices but, being an active browser on attached and drift seaweed, is able to be more selective. H. iris from Taylors Mistake is an active feeder due to the limited amount of food available at this locality. Floral composition is the major factor controlling the diet of the abalones but selection has an important role for H. australis at one locality.