Frequently Asked Questions
About Oyster Seed
2 to 4 years – but this is very dependent on where you are and oysters of the same age and batch will not grow evenly anyway. We have had customers where it takes just over a year to reach market size but these are exceptional!
Everyone wants seed in the Spring but it is rarely available before mid April when growth starts in oyster nurseries. Providing your site is quite sheltered, consider taking between August or October when growth will continue through the Autumn and the seed will take off earlier in the Spring
Weigh up the advantages of buying larger seed (eg. seed graded on 10mm (G10 or above) against the extra initial cost. The bigger the seed the large the mesh bags you can use, the less handling and grading needed and most likely the lower losses in terms of mortality. If you are new to oyster farming we recommend starting with larger seed. However our standard size is G7 (graded on 7mm screen) when you must be prepared to grade the stock after 6-8 weeks. It is advised not to take smaller than G7 unless you have special nursery facilities.
Work backwards from the unit weight you expect them to be when next graded or split and the maximum weight per bag. For example if you expect to next grade when 5 grams and want max 5kg per bag then put 1000 /bag. A ‘rule of thumb’ would be 5000 G4 grade after 6 weeks to 4mm bags, 2000 G7 grade after 2 months to 6mm bags, or 1000 G10 or G13 grade after 6 months to 9mm bags.
This is the key question for profitability of your business! The best growers can achieve 80 % survival or 70 tonnes per million seed. Good husbandry such as extra attention to the seed in the first months after laying, clearing mesh of any fouling, and regular turning keeping the growing densities in the bags down (eg 4- 8kg/bag) are vital. see also our All about oysters FAQ about oyster diseases
The normal farming method is using mesh bags (‘poches’) strapped onto steel tressles placed in rows near the low water Spring tide line and serviced by tractor and trailer. There are also various designs of cylindical bags which are more expensive but give better results by reducing labour and providing more even growth. Some farms start off using floating systems such as rafts or long-lines which can give ideal conditions for growth but intertidal is still better to ‘harden’ the shells by wave action and build up meat quality.
Market size Oysters can be “trained” to stay out of water for up to a week as long as they are kept cool and in damp conditions. We arrange shipments so that seed do not exceed 3 days out of water.
See here for information on counting oyster seed (add link)
The simplest and safest rule is always to use a mesh size HALF the G-size so G2 onto 1mm, G10 onto 5mm. It is important to move up mesh sizes as soon as growth allows.
Stock must always be graded when moving up mesh size – not just split.
The recommended bag mesh sizes are listed on the ‘About our Oyster Seed’ page here
Grading is only necessary when more than 50% by weight (30% by number) will make the grade – otherwise it is an unnecessary stress. Take care when handling at the peak growing season and in hot dry weather
Yes! With excellent air connections from Guernsey, seed can be delivered to worldwide destinations within 48 hours