observation will suffice, would, of course, be available for the same 

 years. With ten seasons and the loss of six degrees of freedom there 

 would be left four degrees of freedom on which to base judgment as to 

 significance of results. This nvunber is perhaps too low to do nore than 

 indicate whether the general hypothesis is on the right track, 'Certainly 

 it will not be enough to conclude that the hypothesis is disproved. 

 (Of course, correlation analysis can only disprove: it can never prove 

 by hypothesis.) ~~~~' 



SUMMARY 



As the pilchard program now stands, tv/o lines of evidence when the 

 work on them is completed, will give the rates of catch and natural mor- 

 tality, and the rates of recruitment over an 8-season period, 1932-3 

 to 1939-40, with the prospect of adding two subsequent seasons. By ap- 

 propriate computat' on, estimates of the total size of the population 

 and its size-composition will be available on an annual basis from the 

 "vital statistics** approach, and also available as a mean for a group 

 of seasons through tagging studies. This will afford estimates of the 

 effects of fishing at different levels of intensity on the quantity and 

 quality of the catch. The estimates will be true only for the seasons 

 covered by the analysis. To extrapolate them so as to predict what con- 

 sequences will follow any particular level of fishing intensity, a third 

 line of evidence is needed for determining v.'hether the recruitment has 

 been conditioned by the size of the stock itself (and hence predictable 

 from the "vital statistics" evidence) or v/hether it was affected to an 

 important degree by oceanographic conditions (and therefore unpredictable 

 except in teni;s of range of variations about a certain mean condition). 

 This matter is being investigated. Great difficulties have been met 

 and still others may be anticipated, but in spite of these possibilities 

 of solution exist. 



An important phase of the entire problem is whether the range of 

 intensities of fishing, which happened to have been included in the 8 

 or 10 seasons under study, is sufficient to cover reasonably well the 

 range to be anticipated in the future. The range could be extended to 

 lower intensities by going back to the records of still earlier periods 

 of fishing. To extend it to higher ranges would depend on developments 

 in the fishery. To permit development to higher ranges of intensity 

 could involve the risk of reducing the stock so far below a desirable 

 level that recovery might be slow. Appraisal of the degree of risk in- 

 volved and of the desirability of undergoing that risk will depend on 

 the nature of the results that flow from the current program, and may 

 well be deferred until they become known. 



LITERATURE CITED 



Baranov, F. I. 1918, Nauchnyi issledovatelskii iktiologisheskii 

 institut. On the question of the biological basis 

 of fisheries, Izvestia I (l), pp. 81-128, 12 figs, 



