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

Polychaeta

Polychaeta

Sixteen species of polychaetes were recorded from the test blocks. This is by far the greatest number for any one group in the present investigation, but as at least half of these were errant species, they can only be considered as casual members of the association. The most important species for the present investigation were the two serpulids, Spirorbis sp. and Galeolaria hystrix Morch., which showed clear evidence of spawning periods and were present for sufficient time to give adequate information for growth rates to be obtained. Both species were present almost constantly on the long-and short-term blocks, indicating that spawning takes place througout the year and that larval life is probably less than one month duration. Some months showed a heavier set than others. Spirorbis sp. set heavily in June and again in February, and G. hystrix in April, 1950 (Table I). Temperature does not appear to play any part in determining the density of the set, particularly in the case of Spirorbis sp., as one heavy set took place in winter and the other when temperatures were highest in the summer. In summary, it can be said of these serpulids that they were present practically throughout the year, but were never a dominant feature. The size range for G. hystrix at three-monthly intervals is as follows: one month, 3·0 mm. to 6·0 mm.; three months, 9·0 mm. to 16·0 mm.; six months, 13·0 mm. to 37·0 mm.; twelve months, 61·0 mm. to 80·0 mm.

The following species are errant and mud-dwelling species and appeared only in small numbers and for relatively short time periods on the blocks. The short-term blocks showed the errant Podarke sp. present in September and October, and Nereis kerguelensis McIntosh, Perinereis camiguinoides Augener, and Dorvillea oustraliensis (McIntosh) in January. D. australiensis appeared again in February. These four species were present on the long-term blocks earlier than on the short-term blocks—i.e., Podarke sp. in May, N. kerguelensis in June, D. australiensis in August, and P. camiguinoides in November. Next to Spirorbis sp. and G. hystrix, N. kerguelensis was the species present for the greatest length of time (seven months) on the long-term blocks. The long-term blocks also showed 10 species over and above those previously enumerated. These were present for varying periods, usually of short duration (Table II).