The population dynamics and reproductive cycle of Septifer virgatus (Bivalvia: Mytilidae) on an exposed rocky shore in Hong Kong
Article first published online: 23 MAR 2009
Journal of Zoology
Volume 235, Issue 3, pages 485–500, March 1995
How to Cite
Morton, B. (1995), The population dynamics and reproductive cycle of Septifer virgatus (Bivalvia: Mytilidae) on an exposed rocky shore in Hong Kong. Journal of Zoology, 235: 485–500. doi: 10.1111/j.1469-7998.1995.tb01764.x
- Issue published online: 23 MAR 2009
- Article first published online: 23 MAR 2009
- Accepted 8 February 1994
Exposed rocky shores in Hong Kong are dominated at mid-tidal levels by a broad band of the mytilid Septifer virgatus. A 48-month study of a population inhabiting the shores at Cape d'Aguilar has been undertaken. The species matures at a shell length of ≅ 15 mm, about one year after recruitment. Septifer virgatus is dioecious with a slight, but insignificant, female bias overall. There is, however, a significant juvenile male bias. Generally, most adult individuals remain mature year round, although spawning is limited to two periods in spring (February to March) and autumn (September to December) with subsequent recruitment into the adult population. The species lives for ≅ 4–5 years, although older individuals, possibly up to 12 years of age and with a maximum recorded shell length of 65 mm, occur as solitary individuals lower down the shore. Mortality in winter mainly affects newly recruited juveniles. A heavy mortality of adults in summer is thought to be related to high rock temperatures at midday (≅ 50°C), concurrent with low spring tides.
The life-history tactics and sexual strategy of Septifer virgatus can be correlated with seasonal changes in hydrography. There are a number of similarities with other local mytilids, notably the dioecious condition and the bimodal pattern of spawning and recruitment. Such similarities are discussed in relation to the habitats occupied by these species.