We were asked to highlight advances made since Larvi '91 and to identify, where appropriate, perceived deficiencies in our coverage of the subject area. With regard to advances, I think it has to be said that at this stage in the development of the field of aquaculture quantum leaps forward can not be expected, rather we are seeking a steady step-wise erosion of the problems that confront us.
The first two days of the meeting were dedicated to the subjects which most concern culturists, namely egg quality and the availability and quality of food. With regard to the former we learned there has been some progress in relation to our ability to identify practical criteria for recognising poor quality eggs as well as in understanding the importance of hormones in controlling over-ripening and subsequent embryonic and larval development. Evidence was presented that mollusc investigators are ahead of the rest of us in understanding parental influences on egg and larval development. We also heard that cryopreservation techniques for fish and mollusc gametes are at or near the point of commercial exploitation.
With regard to nutrition studies it is clear that our thoughts are still dominated by lipids. The HUFA story does seem to have become the soap opera of larvae culture - a never-ending tale with a plot that thickens only very slowly! Much of current work is repititious or, to put it more kindly, confirmatory, though some increase in our understanding of requirements was evident. Since Larvi '91 the focus of attention has moved from a consideration of total or individual HUFAs to a greater appreciation of the importance of ratios, not only between DHA and EPA but also with arachadonic acid and possibly with saturates. In addition, the protective role of phospholipids has also been appreciated. It does seem we are moving towards a better understanding of how respective pathways may be interlinked, but in general the physiological and biochemical mechanisms are still unclear and important fundamental questions remain unanswered. These include:
The session on the availability of food stressed the importance of reducing our dependence on Artemia in the light of the current world shortage of cysts, and in this respect it was encouraging to hear that some progress toward the development of microdiets both as a partial or total replacement for live foods has been made. It would, however, be premature to throw out our Artemia hatching apparatus!
Subsequent sessions on culture techniques and new species gave us some encouraging snapshots of impressive commercial developments and new species that will be coming on line, some sooner and others clearly later. The scale and diversity of recent developments in Taiwan was particularly impressive. Perhaps our enthusiasm for new species was a little dampened by the view expressed by Prof Anderson (University of Rhode Island) at an Economics Workshop that ultimately product diversity will be accomplished not by increasing the number of species but by devising a variety of ways of presenting a relatively small number of species to the market.
It was perhaps appropriate that microbiology and disease was left to the final session since disease is the last thing that a culturist wants to be reminded about! The importance of the subject, however, is clearly evident as was the various contibutions that probionts can make through competitive exclusion of pathogens, stimulation of the immune system and the provision of nutrients as part of the intestinal flora. Subsequent contributions elaborated on alternative ways of stimulating the non-specific immune system using substances such as glucans and mannuronic acid. This is clearly a most important research field that will undoubtedly contribute much in the future.
Finally, an appeal not to neglect other areas of importance to the development of culture techniques which have not been prominent at this meeting. These would include studies of the behaviour and environmental requirements of target species as well as perhaps the greater use of genetic and microbiological techniques.
In summary, given that communication is the essence of science, I would say that this has been a most successful conference. We should all be grateful to Patrick Sorgeloos, his organising committee and all those who have provided us with this opportunity to exchange our information and views in such pleasant surroundings. The organisation has been impeccable and I do thank and congratulate you for your efforts on our behalf.
