74 FISH AND GAME COMMISSION. 



above the low tide line. As the Pismo clam inhabits only such beaches 

 as are the most frequented by people for surf bathing, they are, during 

 these years, exposed to the illicit digging not only of the visitors but 

 of local people as well, for one of the attractions of the beaches is the 

 serving of clams in the restaurants and chop houses. It is clear that 

 even if the commercial digging of the larger legal-sized clams is entirely 

 stopped, the continued taking of these small clams will result in the 

 practical extermination of the beds in San Luis Obispo County as 

 they have been exterminated in the past in the southern part of the state. 



ALBACORE INVESTIGATIONS. 



Publication of the results of the albacore investigations has been 

 delayed partly because of the necessity of economy, the personnel of the 

 State Fisheries Laboratory has been cut down and much of Mr. Thomp- 

 son's time has been taken up with directing the sardine and other inves- 

 tigations ; and partly because of the fact that with the continued analysis 

 of each season's albacore catch, new problems have presented themselves 

 which have necessitated the reworking of much of the earlier data. 



On account of evidence that the albacore may now be undergoing 

 depletion it is probably best to delay publication of the results of the 

 investigation until the data collected during the present season can be 

 worked over. In the case of the albacore it has been extremely difficult 

 to determine whether evidences of decreasing abundance of albacore 

 were caused by actual depletion of the fish from over-fishing or only a 

 fluctuation due to natural causes. To determine this point it will prob- 

 ably be necessary to wait until the comparative abundance of the older 

 year classes can be determined in future seasons, although it is possible 

 this can be determined from the data of the present season. 



If we are to conserve these fish in an intelligent manner we must 

 learn, from the comercial catch, what is their actual abundance from 

 year to year. To determine this and to be able to distinguish depletion 

 caused by over-fishing from natural fluctuation in abundance, it is nec- 

 essary to determine the relative abundance of the year classes from 

 year to year. This can only be done by determining the age and rate 

 of growth of the species. This has been a difficult task as the age can be 

 determined from the structure of the scales only with the greatest diffi- 

 culty. To decipher the age from the scales it was uecessary to develop 

 a special technique for the purpose which would not be sub.ject to the 

 criticism that the age determination was largely the individual opinion or 

 guess of the observer. It was necessary to supplement this by determin- 

 ing the age from the length frequency. That is by measuring great 

 numbers of individuals and flnding the size groups into whicli they fall. 

 Theoretically there is a different size group into which they fall. 



After the first three j^ears the albacore grows so slowly and irregu- 

 larly that the .size groups overlap so that it is not possible to determine 

 age beyond the second or third group by this method. Nothing which 

 has been done by the countries most advanced in fisheries conservation 

 work gave any knowledge of how to proceed under these circumstances. 

 It was necessary to work out an entirely new principle and after a great 

 deal of work it was discovered that the age groups are indicated by a 

 sex ratio aruilysis in comparison with the size of the fish. The results 



