Quality aspects of wild caught and enhanced sea urchins (Strongylocentrotus droebachiensis)

Abstract

Sea urchin roe is a culinary delicacy worldwide, but with global catches are down due to overfishing and diminishing stocks, interest in aquaculture has increased. Sea urchin aquaculture lacks consistency in the quality of the product, good quality sea urchin roe should be large with an orange or yellow colour, with a distinct sweet-salty taste and have the right firm texture. The main objective of this study has been to compare quality aspects of roe from wild and enhanced sea urchins (Strongylocentrotus droebachiensis) using the following quality parameters: gonad index (GI), water content, reproductive stages, histological examination of relative cellular area and morphology, amino and fatty acid analysis and scanning electron microscopy (SEM). Green sea urchins were collected (n=250) from a wild population. The sea urchins were then held in raceways where they were fed the Nofima manufactured diet for 14 weeks (mid-August – mid-November). The GI increased significantly in the enhanced urchins during the trial, from 6.1% to 29.65% at week 12. No significant increase was recorded in wild urchins. The amino acids glycine, leucine and lysine was different between the treatments. Wild sea urchins had 6% more unidentified fatty acids, most likely a NMID fatty acid. Histological examination showed significant progress in reproductive stages in enhanced sea urchins, none in the wild sea urchins, suggesting gametogenesis is inhibited in captivity. Enhanced sea urchins had less relative percentage reproductive cells and an overall messier and less uniform appearance mid-trial (week 8-10). SEM showed less structured and greater number of surface cells in enhanced sea urchins. The results of this study suggest that a rapid increase in GI may be too fast to preserve structural integrity. Further research suggested is long-term enhancing and gonadal wall structure analysis during enhancing.