The estimation of live fish size from archaeological cranial bones of the New Zealand Greenbone Odax pullus

A species of fish, Odax pullus , predominantly vegetarian, common in weedy marine zones in New Zealand, is the subject of this paper. The species is primarily caught by setting gill nets today, and seldom takes a baited hook. It has variable abundance in archaeological sites, more commonly in higher latitudes. It is very rich in iodine, and is useful in preventing goitre, since the element is low in New Zealand soils. It has very low levels of unsaturated fatty acids and low levels of omega 3 lipids. Modern specimens were collected and cranial bones extracted and measured to establish equations to back-calculate fork length (FL) and ungutted weight (BWT). Power curves were fitted, and constants provided to enable live characteristics to be estimated from archaeological bones. Bones from nine archaeological sites were studied and FL and BWT estimated. Length-frequency distributions were mostly non-normal, suggesting more than one method of capture, possibly set nets or hoop nets with different mesh size. The modern practice of only eating the fillet harvests only 34% of nutrients, with a MNR of 89:10:1. Ethnohistorical observations suggest more than the fillet was formerly eaten, especially fat-rich components. We estimate a MNR of 78:21:1 was more likely if some of the head, viscera and skin was eaten. In southern latitudes, where carbohydrate-rich foods were in shorter supply, harvesting these fat-rich parts was a sensible survival strategy. The archaeological catches show 20–45% were fecund individuals, below modern legal size. This is consistent with other marine species from archaeological sites.