TWEXTY-SEVEXTII BIENNIAL REPORT. 75 



from this procedure confirmed the determination of ago and rate of 

 growth as determined from the scales. A great amount of work had to 

 be done in developing new principles, for the science of fisheries conser- 

 vation is a young one as yet and this work, as well as much of the work 

 done in the sardine investigation, will l)e distinct contributions to the 

 methods employed in this science. After developing methods of finding 

 the age of the fish it is an easy step to working out the comparative 

 abundance of the year classes, which will enable one to say quite posi- 

 tively which is a natural variation in abundance as distinguished from 

 actual depletion from over-fishing. 



This question of depletion is the all-important one lint it is necessary 

 to observe the relation of the several year classes through several sea- 

 sons before depletion is positively proven. 



The average j^early catch of a boat fishing for albacore has decreased 

 rather steadily over a period of years. This does not necessarily mean 

 depletion but it is enough to cause anxiety. Last season tliere was a fall- 

 ing oif in the proportion of older fish which, if it continues in subse- 

 quent seasons, is the best of evidence that depletion is occurring. The 

 problem is more difficult than it appears at first sight for the methods of 

 the fisheries are undergoing change. During the past two seasons one- 

 man or "jig" boats, which catch the albacore by trolling, have increased 

 rapidly in number and the hook and line boats, which catch the albacore 

 by short lines on poles or by hand after they are attracted around the 

 boat by live .sardine baif, complain that these ".jig" boats scatter tlie 

 schools and are the cause of the reduced catches of tlie boats fishing with 

 the old Japanese method. These are questions which wo are now confi- 

 dent are subject of solution with the methods being pursued in tho 

 investigation. 



SARDINE INVESTIGATIONS. 



The sardine investigation has continued along the line of tho pro- 

 gram laid down in 1920 and published in this Commission's quarterly 

 magazine, (Vol. 6, No. 1, pp. 10-12.) 



The objects of the investigation are stated by Mr. Thompson ir. an 

 article on the progress of the work, in Californi.v Fish and Camk. 

 Vol. 6, No. 4, page 180, as follows: 



"The program under which the work has been done (•()ntciii|)late.s 

 (1) the discovery of depletion if it should occur; (2) tho di.scovcry of 

 any great natural fluctuations in abundance or quality other Hum 

 those due to over-fishing; (3) the foretelling of those Huoluations, \vlii<-li 

 in other fisheries have at times caused groat danuige; (4) tho dcciplior- 

 ing of those habits of the species which are of importance to th.- raum r 

 and fisherman, such as migration, and (5) a knowledge of such facts as 

 will aid the legislator. The absolute completion of tliis prou'ram is 

 without doubt well removed, but contributions to it of great value 

 will be made in the very near future, enal)ling us to nuiko at least 

 provisional answers, a thing impossil)le now. .\inong those wo ni.iy list 

 the age and rate of growth, the brooding season. ;ind the degree of iiuie- 

 pendence of the sardines in ditferent regions. That the foretelling 

 of fluctuations is not visionary may be seen from the work of the 

 Norwegian fisherv authorities on the herring. The other elements of 



'O' 



