FISHERY BULLETIN: VOL. 70, NO. 3 



dance of these inshore younger fish, and this de- 

 cline follows the downward catch trend. 



Pacific bonito — The Pacific bonito has been 

 abundant in southern California waters since 

 the advent of the "warm years" of 1957-1958. 

 Its northward latitudinal range into southern 

 California waters is influenced by environmental 

 conditions (Radovich, 1963). Figures on total 

 abundance are not available. However, an in- 

 dex of abundance off southern California was de- 

 veloped from party boat catches by Radovich 

 (1963) . It is believed that party boat catches re- 

 flect the bonito's general abundance oflf southern 

 California within certain limits. These limits 

 were not defined and are due to the anglers pref- 

 erence for fishing more desirable species such as 

 barracuda, yellowtail, albacore, etc., when they 

 are available rather than fishing for bonito. 

 Blunt (personal communication; see footnote 3 ) 

 continued Radovich's study and calculated an in- 

 dex based on catch per angler day for the years 

 1962 through 1968. Values are as follows: 1962, 

 (1.7), 1963 (1.5), 1964 (2.4), 1965 (1.4), 1966 

 (0.9), 1967 (0.6), 1968 (1.4). The highest party 

 boat index level was in 1964, The index shows 

 an increase for 1968 and diff"ers from the index 

 of apparent abundance; however, this index has 

 shown an overall decrease since 1964. 



The day index of apparent abundance shows 

 an overall decrease from 1963 through 1969. The 

 Pacific bonito is classed as "much underutilized" 

 by Ahlstrom (1968). Due to economic factors 

 and a decline in catches of jack and Pacific mack- 

 erel, the catch of bonito increased sharply in 

 1966 and 1967 with only a slight reduction in 

 catch during 1968 and 1969. In contrast to this 

 increase in catch level, the index of apparent 

 abundance has shown a substantial decrease 

 from 1.26 in 1965 to 0.26 in 1969. A consider- 

 able reduction in catch was experienced in 1970 

 (Lester A. Keilman, personal communication) 

 as the total catch declined to 4,600 tons, about 

 one-half the 1969 catch. 



Northern anchovy — Studies by Ahlstrom 

 (1968) estimated a total population of 1.8 to 2.3 

 million tons in 1958, increasing to 4.5 to 5.6 mil- 

 lion tons in 1968. This estimate was based on 

 data from larval counts and shows a population 

 increase of approximately 8.6 times during the 



period 1951 through 1968. No total population 

 estimates for the successive years 1963 through 

 1969 are available; however, Ahlstrom does 

 state that the larval counts show that the popu- 

 lation is somewhat variable from year to year 

 and that the population reached a plateau in 

 about 1962. Since annual abundance estimates 

 are not available for the years 1963 through 

 1969, a direct comparison with the aerial spotter 

 index cannot be made. The northern anchovy 

 has increased substantially in abundance during 

 the past decade and is classed as an underutilized 

 species (Ahlstrom, 1968) . Since it has been sub- 

 jected only to minor fishery, except in 1969, it is 

 generally agreed that the population level con- 

 tinued to be at high level throughout the years 

 1963-1969. The trend of the night aerial index 

 of apparent abundance shows an overall increase 

 during the years 1963 through 1969. The only 

 significant change in apparent abundance was 

 in 1968 when the index declined sharply; how- 

 ever, in 1969 it again increased to a high level. 



Wide fluctuations in anchovy relative abun- 

 dance were noted by Wood (1964, see footnote 2) 

 during aerial surveys from 1956 to 1963. Future 

 observations will determine if this paralleling of 

 catch and apparent abundance will continue. 

 Since the survey area covers an area common to 

 the anchovy, trends in the annual index should 

 be of use in evaluating catch variations and re- 

 flect the trend of total abundance in this under- 

 utilized resource. 



In summary, for the geographical area nor- 

 mally surveyed by the aerial fish spotter, the 

 author believes these data represent a reasonable 

 index of apparent abundance. Like all other 

 measures presently available, the true relation 

 of the index of apparent abundance to total 

 abundance for each species cannot be deter- 

 mined. However, from all data available con- 

 cerning the Pacific mackerel, a species for which 

 considerable and more reliable data on the adult 

 population are available, the trend of the index 

 follows the downward trend of the total abun- 

 dance estimate. The index shows little effect 

 from fluctuations in economic demand, as shown 

 in data for the Pacific bonito. Trends in the 

 abundance level of the Pacific bonito within the 

 survey area are evident before they are reflected 



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