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The Settling and Growth of Wharf-pile Fauna in Port Nicholson, Wellington, New Zealand



The most prominent polyzoan on both series was a species of Bugula. Bugula sp. was present on all the long-term Mocks except in April of both 1949 and 1950. It reached maturity and maximum growth and density in the spring months of August to November, and together with Cryptosula pallasiana (Moll.) and Bugula neritina (Linnaeus), attached in spring and early summer. C. pallasiana paralleled Bugula sp. for time range on the long-term blocks, but reached its peak for growth and development in the summer (December to February). Other species showing erratic appearance only on the long-term blocks were Beania bilaminata (Hincks) page 12 in May, Tubulipora sp. (June), and Idmonea sp. (June). Quantitatively, the polyzoan species, particularly Bugula sp. and Cryptosula pallasiana, formed a large proportion of the settling organisms. This was also the situation obtaining in Queensland and New South Wales (Allen and Ferguson Wood, 1950). In Australia, Bugula neritina was very prominent, with peaks in November and December. During maximum growth and development, Bugula showed a few colonies 9·8 cm. in height, and similarly the flat calcareous C. pallasiana reached an area 18·0 cm. by 13·0 cm.

From the evidence of the long-term blocks, it would seem that these species take more than a month to reach identifiable size. The main spawning period for Cryptosula and Bugula, as indicated from sets on the short-term blocks, was late spring and summer. These blocks were probably principally seeded from animals on the long-term blocks, where they were at maturity and maximum growth at that period. Cryptosula and Bugula sp. have a life span of approximately nine months. Bcania, Tubulipora, and Idmonea appear on the long-term blocks for a month only. Either these species have a short life span or else for some reason failed to survive.