Habitat and age of the giant squid (Architeuthis sanctipauli) inferred from isotopic analyses
The age and habitat of the giant squid, Architeuthis sanctipauli Velain, 1877, were determined based on isotopic analyses of the statoliths of three female specimens captured off Tasmania, Australia, between January and March 1996. Assuming that the aragonite of the statoliths formed in equilibrium with seawater, δ18O analyses indicated that the squid lived at temperatures of 10.5–12.9°C, corresponding to average depths of 125–250 m and maximum depths of 500 m. The capture records indicated that these squid may have occasionally ranged still deeper, to as much as 1000 m. All the statoliths were labeled with bomb 14C (Δ14C=+22.9‰ to +44.6‰), consistent with the depths inferred from δ18O. A thin section through one of the statoliths revealed 351 growth increments grouped into check-ring structures every 10–16 increments. A model for statolith growth and the pattern of temporal change in Δ14C in the water column was used to estimate the ages of the three specimens. These estimates were very sensitive to the choice of depth range over which Δ14C values were integrated. Assuming that the capture depths represented the maximum habitat depths of these individuals, the calculations suggested an age of 14 years or less. More refined age estimates require a better understanding of the variation of Δ14C and temperature with depth in the areas in which the squids live.