The reproductive biology of pipi, Paphies australis (Gmelin, 1790) (Bivalvia: Mesodesmatidae). II. Spatial patterns of the reproductive cycle

A population of adult pipi, Paphies australis, was sampled monthly from February 1992 to January 1993 at three subtidal sites within a small harbour in northeastern New Zealand. Analysis of the reproductive cycle used standard histological techniques and all specimens were assigned to one of six categories: early active, late active, mature, partially spawned, empty and parasitized. The reproductive cycle was similar between sites, with an extended spawning period of late winter to summer. It was concluded that the reproductive cycle of pipi in the Whangateau Harbour was synchronized at all three sites sampled. A visual maturity index gave the same overall pattern of reproductive cycle as the histologist analysis, but was found to be inaccurate mainly due to a poor recognition of the mature stages. It was concluded that the visual index was of limited value in accurately assessing the maturity of an individual. The sex ratio of adult pipi was not significantly different from 1:1. A small percentage (0.87%) of pipi were infected by a digenetic trematode fluke that, in most cases, totally castrated the individual.