Report to the British Council on the third stage of the dredge oyster, Tiostrea lutaria, project / J. Illingworth and S.D. Utting.

"Not to be cited without permission of the author(s)."

5 tables.

Oysters sampled from the Menai Straits on 13th June 1995 and opened between the 14th and 23rd June yielded between 17 and 18% brooding adults carrying larvae ranging from late blastula through to pediveliger. A total of 23 broods of larvae at various stages of development were collected along with data on parent shell dimensions and numbers of larvae. Samples were preserved for the measurement of larval shell dimensions, dry weights and food reserves by biochemical analysis. Eight broods of larvae from veliger to late veliger were divided in half and grown through to pediveliger outside the parents. One batch of larvae from each parent was fed algal food and the other not. The larvae were again sampled for biochemical analysis just prior to settlement and sub-samples settled onto glass plates for spat growth and mortality measurements. Both the biochemical analyses and the spat growth and mortality results showed no apparent benefits in feeding larvae. The high success rate of rearing larvae outside the parent oysters is attributed to the very high levels of stored lipids. A visit was organised to the Seasalter Shellfish commercial oyster hatchery at South Walney Island and two days were spent with the scientific staff at MAFF, Conwy, working on flatfish culture.