Algal supplements in formulated feeds: Effects on sea urchin gonad quality

In the effort to increase the commercial value of urchin gonads produced via roe enhancement aquaculture, a variety of formulated feeds have been tested to increase gonad production and improve colour and taste. The addition of dried algal supplements to formulated feeds can further enhance gonad quality, but the level of improvement is highly variable and algae or urchin species dependent. Here we test whether the inclusion of three types of dried algal supplements (Sargassum fallax, Ecklonia radiata, and Durvillea potatorum) added to a pellet-based formulated aquaculture feed could further enhance the colour, taste and gonad quality in the temperate urchin Heliocidaris erythrogramma during two 12 wk. gonad enhancement periods, April to June, and July to September. All feed types resulted in urchins with gonad indices (GIs) of commercially acceptable quantities (Apr-Jun: GI = 14.6%, Jul-Sep: GI = 14.9%). The proportion of marketable gonads (A + B grades) was significantly higher during the Jul-Sep (87.9 ± 3%, mean ± SE) compared to the Apr-Jun (76.6 ± 3%, mean ± SE) enhancement period, however, algal supplement type did not improve gonad colour, taste, or the proportion of marketable gonads when compared to the control feed. We conclude that additional algal supplements may fail to further improve roe quality if the base formulated feed used to roe enhance is already of a standard that produces a sufficient proportion (>70%) of marketable roe.