Optimizing sea urchin gonad enhancement with newly-designed formulated feeds and assessing benthic impacts of commercial-scale sea urchin farming to ensure environmental sustainability
When sea urchin population growth is uncontrolled, they can over-graze and decimate macroalgal (seaweed) beds, creating areas termed “urchin barrens”. The large numbers of sea urchins stay in these barrens with little to no food for long periods of time, not only becoming unsuitable for the sea urchin fishery due to their low roe yields, but also preventing the regrowth of macroalgae and the productive ecosystems they create. These low-roe-yield sea urchins may be captured and fed with prepared/natural diets in order to increase their roe yields and make them marketable, in a process called gonad or roe enhancement (a form of aquaculture). If enough sea urchins are removed from the barren grounds, then the macroalgal beds and their inherent ecosystem will re-establish. However, sea urchin aquaculture is a new industry that requires environmental impact studies.
This project aimed to assess the effects of two prepared diets and a natural feed (kelp) and three water temperatures on waste deposition for red and green sea urchins held under laboratory conditions so as to predict the environmental impacts of a commercial sea urchin farm. It also aimed to test the effects of these diets and temperatures on the gonad yield and quality of these sea urchins in order to determine whether the prepared diets are a viable option for a roe-enhancement operation to produce market-quality gonads.
This study examined the effect of two newly formulated prepared diets (Urchinomics V10.1.9 and V10.1.10) and bull kelp (Nereocystis luetkeana) at three temperatures (8, 12, and 16℃) on gonad enhancement and gastrointestinal parameters. Effects were studied in the green (Strongylocentrotus droebachiensis) and red (Mesocentrotus franciscanus) sea urchins.
The highest gonad yields were achieved with green sea urchins fed V10.1.9 at 8℃ and 12℃, and the best gonad colour with V10.1.10 at 16℃. Red sea urchins achieved the highest gonad yields with V10.1.10 at all temperatures and with V10.1.9 at 16℃. These same treatments achieved the best colour results. These two newly formulated prepared diets (V10.1.9 and V10.1.10) provided sufficient protein and pigment to achieve market yields and quality in both the green and red sea urchins in a land-based culture system in 12 weeks.
The data collected on faecal-pellet and gastrointestinal parameters can be used in conjunction with specific farm site parameter data in a waste deposition model to predict the potential environmental impact that a commercial sea urchin farm would have.
These results will contribute to making sea urchin aquaculture a sustainable new industry for British Columbia. If commercial-scale culture of sea urchins takes off in the province, then the industry could be worth millions of dollars.
Warren EM (in prep.) Effect of diet and temperature on gonad enhancement, ingestion rate, absorption efficiency, and faecal production in the green and red sea urchin. MSc Thesis, University of Victoria, Victoria, British Columbia.
Warren EM, CM Pearce (2020) Effect of transport method on subsequent survivorship and gonad yield/quality in the red sea urchin Mesocentrotus franciscanus. North Am J Aquacult 82: 371-376.
One year: 2019-2020
Chris Pearce, research scientist, Fisheries and Oceans Canada, Pacific Biological Station, Pacific Region
Steve Cross, Associate Professor, University of Victoria
Mark Flaherty, Professor, University of Victoria
Harm Kampen, Researcher, Urchinomics Nordics AS
Brian Takeda, CEO, Urchinomics Nordics AS
Emily Warren, MSc student, University of Victoria/Fisheries and Oceans Canada
J.P. Hastey, President, Nova Harvest Ltd.
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