A comparison of roe enhancement of the sea urchin Evechinus chloroticus in sea-based and land-based cages

A 12 week experiment was conducted to compare the efficacy of enhancing the roe of wild caught Evechinus chloroticus held in tanks on land and in sea-cages. The sea-cages were suspended from a mussel longline at depths of 3 and 6 m and identical cages were placed in land-based tanks supplied with flow-through seawater. Both land- and sea-based systems had high and low density treatments. The urchins were fed an artificial diet ad libitum throughout the experiment. An initial and a final census were conducted to measure urchin test diameter, wet weight, gonad index, and roe colour. The results showed that urchin roe quantity (GI) and quality (colour) can be enhanced in 12 weeks by feeding the NIWA artificial diet in land-based tanks or sea-cages, with high survival. There were no significant differences between the enhancement of roe quantity (GI) or quality (colour) in urchins held in land-based tanks or in sea-cages. There were also no differences between urchins held in sea-cages at 3 m and at 6 m, or between urchins held at low and high density.