Green Sea Urchin Ranching in the Gulf of Alaska: How do Location and Food Influence Market Readiness

Sea urchin ranching is advantageous for both coastal health and the human seafood market. In some areas, sea urchins have become hyperabundant and have overgrazed kelp forests,turning these forests into barrens devoid of most seaweeds. A solution to reduce these hyperabundant sea urchins is to harvest them for consumption; however, this is impractical because their gonads (roe, the marketable portion of the urchin) are very small due to a lack of their natural food, seaweeds, in urchin barrens. To be marketable, sea urchins from barrensmust be collected and then ranched, i.e., fed supplemental food so that their gonads can grow to a marketable size and quality. Here, we determined 1) if sea urchin ranching location influences market-readiness, 2) the time needed to grow market-ready gonads, and 3) the success of growing marketable gonads using different foods in the Gulf of Alaska. We collected green sea urchins (Strongylocentrotus droebachiensis) and then ranched them at three locations. Urchins were either starved or fed different foods: bull kelp (Nereocystis leutkeana), wrack (mixed kelp species or rockweed Fucus distichus), kelp fouling on docks/lines/buoys, and manufactured kelp pellets. It was found that ranching location had no effect on gonad marketability. Additionally, any food involving kelp resulted in marketable gonads within 6-8 weeks with equal success. Non-kelp food (F. distichus) performed as poorly as the starved controls and wild-caught sea urchins. This study demonstrates the feasibility of green sea urchin ranching in a high latitude environment.