SQUIRE: PELAGIC MARINE FISHES OFF SOUTHERN AND CENTRAL CALIFORNIA 



made which would provide a precise count of the~ 

 population size. 



From data for 1962 through 1966 the diurnal/ 

 nocturnal ratios in tonnage observed and in 

 sightings indicate that the northern anchovy, 

 jack mackerel, Pacific mackerel, and Pacific sar- 

 dine were observed more frequently and in great- 

 er quantities at night. Pacific bonito and yellow- 

 tail were observed more frequently and in great- 

 er quantities during the day. However, Pacific 

 barracuda were observed in greater quantity at 

 night but more frequently during the day. 



Indexes of apparent abundance for day and 

 night observations and variations in total com- 



mercial catch (Lyles, 1963, 1964, 1965, 1966; 

 Keilman and Allan, 1969) during the years 1963 

 through 1969 are shown in Figures 4 through 7. 

 The records for 1962 were incomplete (program 

 initiated in September 1962) and were not con- 

 sidered in the discussion of the index. 



In consideration of the day/night ratios, the 

 indexes reflect the following: 



Pacific sardine (Figure 4) — The Pacific sar- 

 dine is observed in greater quantity and more 

 frequently during the night; therefore,* the night 

 index should provide a better measure of the 

 sardine's apparent abundance. The night index 

 declined from 0.50 in 1963 to an index of less 



1015 



