120 FISH AND GAME COMMISSION 



to study all the questions in this comparatively unknown field of the 

 life history and behavior of fishes, so we attempt to confine our inquiry 

 to such questions as appear to be necessary in formulating legislation 

 to apply in each fishery. 



Of equal importance is the accumulation of information desirable 

 in heading off unnecessary or unwise legislation and the acquiring of 

 such knowledge as will be a benefit to the fisheries industries or will 

 aid in the fuller utilization of a neglected resource. 



The program briefly summarized gives first consideration to ques- 

 tions of existing supply of fishes and the detection of the first signs 

 of depletion in each fishery in the endeavor to distinguish between full 

 use and overutilization. In addition, problems in the life history and 

 behavior of fishes are studied when knowledge of such questions appears 

 to have a direct bearing on existing or proposed legislation. Along 

 with such problems information is gathered for the purpose of benefit- 

 ing the existing industries and encouraging full utilization of our 

 fisheries resources. 



TWO METHODS FOR STUDIES OF DEPLETION 



The most important question about any fishery is whether or not 

 it is being depleted. From the viewpoint of the people of the state 

 all other questions are secondary. For this reason the major part of 

 the research program of the California State Fisheries Laboratory is 

 a study of the existing supply of fishes and the possible depletion of 

 that supply. Two methods of studying the supply are now being used. 

 One method is to follow, through a series of years, the average catch 

 of fish resulting from a given unit of fishing effort since a dropping 

 off in the returns for a given amount of fishing effort would show 

 that the available supply of fish was becoming less. 



The other method is to examine from year to year possible changes 

 in the proportion of age classes of fish in the commercial catch because 

 a decrease in the proportion of older fish would indicate a depletion 

 of the fish supply. This involves a study of samples taken from the 

 commercial catch at regular intervals over a period of several years 

 and although a laborious process, it gives more complete knowledge 

 of the changes taking place in our fish supply. 



The first method is usually referred to as an analysis of boat catches 

 since the catch of a boat for one day is a convenient unit of fishing 

 effort. The daily catches of a certain group of boats are then followed 

 from year to year to determine whether or not their average daily 

 catches are being maintained. 



RECORDS OF THE CATCH OF FISH 



Records of the catch of fish, showing the amounts landed are a 

 necessity to the administration of the fisheries as well as forming the 

 basis for a study of possible changes in supply. It is a fact, frequently 

 overlooked, that we have available detailed catch records for the past 

 twelve years which show the monthly catches by species for each 

 region. Such information is continuously called upon in the routine 

 administration of commercial fisheries and whenever existing or pro- 

 posed legislation is being considered. From these records much more 

 detailed information may be compiled as required, such as the amounts 

 of fish handled by any one dealer, prices paid, the deliveries by any 



