To recap: I have been spending my time on Hovedøya in my boat for over 8 weeks. During this time I have been monitoring the Pacific oysters (C gigas). Until this summer I have never observed such oysters (or any other oysters) in the six year period of living aboard a boat. My first observations of such oysters in July 2017 were scattered patches of oysters – some smallish, others looking more mature – about 25 of them on the edge of the stoney beach besides my boat. Since then the water has been clouded by sporadic bouts of rain, high winds, higher temperatures causing green sheens of algae, all of which has hidden the underwater world.
Yesterday, at 7am, I did my practice of removing mainly glass and plastic debris coming onto the shore. The temperature had dropped, the water was clear. Clinging on to rocks, about 10-30cm underwater, were a multitude of very small pacific oysters – about half the size of an infant’s little fingernail, unmistakable from other shell fish in shape and form.
Under my nose and through the green shroud of algae, the few oysters had been spawning larvae …. but how long does it take from spawning to become a ‘spat’ cemented down to rocks, glass and other shellfish?
Here comes the answer from Food and Agricultural Organization of the United Nations (FAO):
In the meantime I will watch over the little oysters to see if I can fathom out how many will survive. There are too many to count. What I really need is a visual scanning system that can show growth and mortality ranges.