Remote setting and nursing of Crassostrea virginica in bouncing buckets
In Atlantic Canada, and particularly in the province of New Brunswick, the culture of the American oyster (Crassostrea virginica) is dependent upon
- the settlement of wild larvae onto spat collectors (e.g. Chinese hats) and
- the subsequent transfer of these spats to grow out sites.
However, this seeding approach is vulnerable not only to broodstock declines, but also to regulatory transfer restrictions, which can happen unexpectedly due to health issues (e.g. MSX) or the spread of invasive species (e.g. tunicates). New transfer restrictions could have devastating effects, particularly if they apply to reliable spat collection sites such as Bouctouche Bay.
Remote setting of Pacific oysters (Crassostrea gigas) on the western coast (Canada and USA) has been researched extensively since the 1970s, and is currently applied at commercial-scales. The American oyster, on the other, has received considerably less attention (Supan, no date; Supan and Wilson 1994). To the best of our knowledge, a single investigation was conducted on the possibility of applying the remote setting technique to C. virginica in eastern Canada (Méthé, 1996). Results were encouraging and clearly demonstrated that the oyster industry in the southern Gulf of St. Lawrence could benefit from the remote setting technique. The reason is that the natural spatfall at this northernmost range of the species occurs in mid-summer, leaving little time for spat growth prior to the onset of winter. Remotely setting the larvae in early spring considerably extended the spat grow-out period and obtained large seed oysters (96 to 428% larger in size compared to naturally-set seed) by the fall of the same year.
We propose to quantify the setting rates of C. virginica pediveligers in field bouncing buckets. Méthé (1996) reported setting rates between 6% and 60% based on a controlled setting environment (tanks); an average setting rate above 20% would be considered a success for field bouncing buckets. In terms of null hypothesis testing, our proposed project essentially aims to compare an innovative remote setting approach (field bouncing bucket) with a more conventional remote setting approach (controlled environment). Regarding the nursing component, the goal is to demonstrate that the newly settled spat contained in the experimental bouncing buckets can grow into large seeds by the fall of the same year. A remote setting approach would allow the proponent to extent the summer growth period by advancing the larvae setting date from late July (typical in northern NB) to early June for instance. Research has shown that such an extended summer growth period can produce large (> 25 mm) oyster seeds by the fall of the same year.
2006 - 2007
Atlantic: Gulf of St. Lawrence, St. Lawrence Estuary
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