Periodical growth rings in cephalopod statoliths [age determination, Gonatus fabricii, Rossia glaucopis, Alloteuthis subulata]

A direct age determination method for squid is introduced. Periodical growth rings in statoliths of the squid Gonatus fabricii are described. By comparison with the previously determined growth rate of juvenile specimens and a bimodal monthly size distribution, growth rings, called first-order bands, are for the first time shown to be daily whereas bands of second and third order are fortnightly and monthly, respectively. The relationship between the pen length and both statolith length and the number of growth rings are shown. Periodical growth rings are also shown in statoliths of Rossia glaucopis and Alloteuthis subulata .