Effect of prepared and macroalgal diets and seed-stock supply on somatic growth rate of juvenile green sea urchin, Strongylocentrotus droebachiensis

Sea urchin populations, harvested for their gonads, are in decline worldwide so research now focuses on full life cycle grow-out. Three experiments were conducted to compare the growth rates of juvenile green sea urchins, Strongylocentrotus droebachiensis, fed a variety of foods. The first experiment compared juvenile growth on seven different diets; feed type significantly affected growth rate, the best growth being supported by the red alga Porphyra purpurea and prepared feed. A second experiment showed that macroalgal storage method affected juvenile growth of S. droebachiensis, with long-term frozen L. saccharina supporting significantly slower growth than other storage methods. The third experiment compared the growth rates of wild-caught and hatchery-reared S. droebachiensis. Seed-stock supply affected growth rates with hatchery-reared individuals displaying greater growth than wild-caught individuals. Identifying which diets and sources of juvenile sea urchins optimize growth may help aquaculture operations produce market-size sea urchins in a minimum amount of time.