Department of Zoology, Field Museum of Natural History, Roosevelt Road at Lake Shore Drive, Chicago, I1. 60605, USA
Movement, injuries and growth of members of a natural population of the Pacific pygmy octopus, Octopus digueti
Article first published online: 13 JUL 2009
1992 The Zoological Society of London
Journal of Zoology
Volume 228, Issue 2, pages 247–264, October 1992
How to Cite
Voight, J. R. (1992), Movement, injuries and growth of members of a natural population of the Pacific pygmy octopus, Octopus digueti. Journal of Zoology, 228: 247–264. doi: 10.1111/j.1469-7998.1992.tb04606.x
- Issue published online: 13 JUL 2009
- Article first published online: 13 JUL 2009
- (Accepted 14 August 1991)
Sampling inadequacies and an inability to distinguish age classes have limited our knowledge of octopus biology in nature. Using an artificial shelter sampling technique (Voight, 1988a), and defining mature males by the presence of enlarged suckers (Voight, In press), an intertidal population of Octopus digueti was monitored for one year.
In total, 803 octopuses were narcotized; the mass, sex, arm injuries and reproductive condition of each octopus were recorded. Captures were more frequent in lower intertidal areas offering higher shelter availability and a more moderate environment. Capture rates, assumed to indicate octopus movement, correlated with sea temperature except during full moon periods when they were reduced. Over 26%, of the octopuses handled had damaged arms or arm tips, with dorsal arm pairs more often injured. The overall sex ratio was significantly male biased, probably due to maturity-linked mobility differences between the sexes.
Reproduction occurred throughout the year; reproductively competent adults, brooding females and juveniles were present every month. However, annual temperature oscillations synchronize spring hatching of eggs spawned from winter to early spring, creating a clear spring cohort. Growth and age at maturity of males in the spring and autumn cohorts were estimated. Variance was too high for these parameters to be estimated in the winter cohort. Growth rates of males over 12 weeks of age did not differ from those reported in laboratory rearing studies. Estimated average age at maturity ranged from 20 to 32 weeks, depending on temperature.