Gonad enhancement of green sea urchin (Strongylocentrotus droebachiensis): importance of feed and containment system

Jacques, Julie (2020) Gonad enhancement of green sea urchin (Strongylocentrotus droebachiensis): importance of feed and containment system. Masters thesis, Memorial University of Newfoundland.

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Abstract

Wild sea urchins are harvested for their gonads (roe or uni) throughout coastal areas of the world. The high value of urchin gonads on global seafood markets along with increasing popularity and demand worldwide have led to the development of formulated-feed-based gonad enhancement programs since the early 1990s. Along the coast of eastern Canada, there is an abundance of green sea urchin, Strongylocentrotus droebachiensis, representing a largely untapped resource for gonad enhancement. To gain knowledge on the conditions and systems that optimize green sea urchin gonad production, two studies were performed with Newfoundland green sea urchins fed proprietary formulated feeds. In the first study, we carried out two gonad enhancement experiments with urchins fed in conical tanks at a water temperature of 1, 3, or 6°C. The first experiment lasted 4 wk with urchins collected before the spawning period, and the second lasted 8 wk with urchins collected during the spawning period. Feed consumption, feces production, and gonadosomatic index (GSI) all nearly doubled at 6 compared to 1°C, and urchins maintained good physiological condition and high gonad production, regardless of temporal proximity to spawning. However, the feed imparted a bitter gonad taste. In the second study, we carried out a 7-wk experiment in a tiered raceway system with urchins fed at three different stocking densities (2.5, 6.5, and 10.5 kg urchins m⁻²), at a water temperature of 6°C. We also carried out concurrent trials with urchins fed kelp (Laminaria digitata), achieving a lower GSI than with the feed. Feed consumption was lowest in the most downstream raceway positions. Raceway position and urchin density influenced aggregation patterns, which reflected wild behaviours, however neither affected GSI. Regardless of different growing conditions and containment systems, in both studies urchins surpassed the GSI market target of ~10 to 15% in less than 7 wk, demonstrating the efficiency of formulated-feed-based gonad enhancement of Newfoundland green sea urchin.

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