Assessing the potential of the Cape sea urchin Parechinus angulosus as a new aquaculture species

Abstract

Sea urchin roe (uni) is a high-value seafood product. Increased demand and decreased supply present an opportunity for culturing unexploited urchin species with marketable gonad products. This gonad enhancement study used wild Cape sea urchins Parechinus angulosus (sized 30–50 mm test diameter) cultured under two temperature treatments (ambient: 15.56 ± 0.07 °C; warm: 18.94 ± 0.03 °C) and four different diets over a 6-month period. The four diets were: wild-harvested kelp Ecklonia maxima, cultured green seaweed Ulva lacinulata, a formulated feed with 16% dried Ulva, and a mixed feeding regime of the aforementioned diets. The warmer temperature condition provided no benefit to gonad growth or quality. Ecklonia maxima was shown to be an unsuitable feed for this species in aquaculture conditions based on a gonadosomatic index (GSI) of 2–3%. The formulated feed promoted high gonad yield (25–30% GSI), but the colour of the uni did not meet market standards. Ulva lacinulata promoted a favourable red–orange gonad colour and was an effective feeding stimulant, but the gonad yield was low (11–13% GSI). Finally, the mixed diet resulted in a marketable yellow gonad colour and high gonad yield (20–22% GSI). These results demonstrate that P. angulosus shows good potential to produce marketable uni, which could generate commercial interest as a new South African aquaculture species.