COMPARISON OF GONADAL GROWTH IN PURPLE URCHINS Strongylocentrotus purpuratus USING THREE DIFFERENT DIETS

Purple sea urchins (Strongylocentrotus purpuratus) are one of the most abundant species of echinoderms that occur in the Pacific ocean. Sea urchins are a great species to raise in a mariculture setting because they are dioecious, meaning they have both male and female reproductive organs in separate individuals; Their reproductive systems are highly sought after in the restaurant industry creating a high demand for quality product. The gonads, otherwise known as ‘uni’, are a delicacy for their buttery texture and salty flavor when they are served –usually uncooked. The color of the uni usually sets the bar for how expensive the product will be since it is visually pleasing to the consumers. The California Sea Urchin Commission (CSUC) describes that the best quality will be a “California gold” color, and this was formerly known as grade A uni.

As a group, we decided to test the difference in uni growth between three feed types; Bull kelp (wild harvest), spinach from the grocery store, and Urchinomics commercial feed. Bull kelp, Nereocystis luetkeana, is the most abundant species of kelp along the California coast and an important species for many local organisms. We chose to use bull kelp as the control of our experiment because it was easily attainable and a preferred diet by sea urchins. We chose spinach because of its easy accessibility and how inexpensive this produce is. Using an agricultural feed will help us design more sustainable food resources to utilize, grocery stores and restaurants can donate their unused leafy greens for these echinoderms. From the many options of commercial feed, we chose urchinomics since the company claims that their product would grow adequate uni in less than 5 weeks. From these three feeds, we predict that Urchinomics would grow the best uni in a short amount of time.

Our conclusion was interesting, after two months we found that the spinach feed was producing grade A uni and had the “California Gold” hue that is sought after. The sea urchins receiving Urchinomics had less desired results, their uni was significantly less than spinach and had a light yellow/orange hue. The bull kelp produced barely any uni, at the two month mark they were barely starting to produce gonads.