Trace elements in beaks of greater hooked squid Onykia ingens: opportunities for environmental tracing

ABSTRACTUnmineralised squid beaks formed from α-chitin and protein are resistant to digestion in stomach acids and are thus useful in diet analysis. Using inductively coupled plasma mass spectrometry to determine trace metals in beaks of greater hooked squid Onykia ingens collected from east and southeast of New Zealand, we found 23 trace metal elements making up 3.7% by mass, on average, of the beaks, ranging from fairly high concentrations of Na ( = 1637 ppm) to very low concentrations of Co (  = 0.01 ppm). Na, K, P, Ca, Mn, B and Zn (all of which are major elements in sea water) accounted for over 99% of the trace element content. Variation among and within beaks suggests that the sea water of origin may be identifiable from trace elements in squid beaks and that further investigation may allow trace element profiles to become useful geographic indicators for both squid and their predators.