Perhaps the most important outcome of this further examination of the results of the survey has been the light it has thrown on the numerous technical and methodological problems of this kind of work. Even if the estimates here of biomass and yield potentials are no great improvement on the estimates in the Final Report, their presentation with upper and lower values derived from ah estimate of confidence limits (even if admittedly the calculation of those limits is not very satisfactory) suggests the bounds within which planning decisions ought, at present, to be set. Moreover, the structure of the argument leading to these estimates is described so that as new information becomes available the estimates can be adjusted with respect to particular components of the system; which means that adjustment of the estimates need not await some repetition of work such as was done on this survey but should be achieved by systematic testing of the assumptions described in this report and by intensive work designed expressly to measure the effects of the causes discussed in Section 3.3 and to obtain a better measure of the conversion factor C.
Given the magnitude of the task undertaken for the survey -- to traverse some 44,000 nm2 of continental shelf five times in less than two years, given also the large number of species and the relative scarcity of information with regard to the display of almost all of these, allowing for weather conditions which made work impossible in at least one month and brought some difficulties at other times, and recognising the inevitability of contingencies and of human error, it is obvious that the results would be marked by a number of important uncertainties. In particular it could be expected that the results would have to be with regard to aggregates of species and could not provide a precise and detailed account of any one species.
On these terms, however, the survey was a successful exploration which has characterised the distribution and main compositional features of the fish stocks and has provided fair approximations to the annual mean biomass and yield potential of those stocks. Admittedly those estimates are low in comparison with others which have been made; indeed, we are convinced that significant upward revision of them will be made when the stocks in very shallow waters and in the 1-2 m bottom stratum can be assessed. The degree to which the estimates might be increased after such a revision, or might have to be increased for other reasons, is a matter on which nothing can be said at this stage. However we believe that industrial development based on the present estimates could be planned safely and would soon yield information from which to improve the estimates.
