Estimating age and growth rate in Architeuthis dux

A guide for marine biologists studying giant squid

By Dr. Steve O'Shea

Auckland University of Technology, Earth and Oceanic Sciences Research Institute, Private Bag 92 006, Auckland, New Zealand.

Note: Steve welcomes discussion in TONMO's Architeuthidae forum.

Architeuthis is a leviathan amongst cephalopods, with mantle lengths reputed to, but in reality unlikely to ever approach 4−6 metres (Clarke 1966, Roper & Boss 1982). We stress the unlikely nature of such exaggerated mantle lengths because a marked contrast exists between ‘4−6 metres’ and measurements based on numerous stranded specimens, sperm whale gut contents, and fisheries bycatch, where mantle length characteristically ranges ~ 0.5−2.4 m (Aldrich 1991, Roeleveld & Lipiński 1991, Jackson et al. 1991, Gauldie et al. 1994, Fernandéz-Nunez & Hernandez-Gonzàléz 1995, Norman & Lu 1997, Lordan et al. 1998, Förch 1998, and personal observation).

As nobody has been able to rear deep-sea species of squid in captivity (yet), especially Architeuthis, we really have no idea how old this species is, and how fast it grows. Published estimates for growth rate in Architeuthis vary from 5.06−2.62 mm mantle length (ML)/day (d-1), with larger individuals appearing to grow faster than smaller individuals (Tables 1−3). These estimates are based on examination of two tiny bones (statoliths; Figs 1, 2) removed from the ventral surface of the squid’s head, that in cross-section reveal numerous rings, much like those in sectioned tree trunks; by counting the rings and comparing this to the mantle length of...
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About the Author
Steve O'Shea
Steve is an expert in the systematics and biogeography of cephalopods, and joined the staff in June 2002. He can be seen on the Discovery Channel documentary, Chasing Giants: On the Trail of the Giant Squid. For more information, see his Autobiography and Select Bibliography (2003). Dr. O'Shea lives in New Zealand.


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