following formula was used to calculate annual indices of apparent 

 abundance, day and night, by zone and by species: 



Index of apparent abundance = 



£N,X, + N 2 X, + N,X, + NJ( 4 

 N, 



where N, , ,_, = number of block area flights in which the species 

 occurred at value X t , , „, 

 X, 2 34 = tonnage range values, 



N, = total number of block area flights in the zone during 

 the year. 



The index value, then, represents the relationship between the 

 amount of fish observed (tonnage range value— x), divided by the 

 amount of search effort (number of block area flights) conducted 

 either during the night or during the day. Day and night indices of 

 apparent abundance for each zone, and the annual average day/ 

 night indices of apparent abundance for all zones, are listed in Table 

 3. The boundaries of the zones were selected to outline important 

 geographical areas where fish were commonly observed. 



The index trends reviewed here are for the major commercial 

 species of northern anchovy. Pacific sardine. Pacific bonito. 

 Pacific mackerel, jack mackerel, and bluefin tuna. Apparent abun- 

 dance trends for yellowtail and Pacific barracuda, species which 

 are primarily targets of the recreational fishery, are given in Table 3 

 but are not reviewed here. During the survey period, sightings of 

 these species were few, and have been much reduced in recent 

 years, with a resultant decrease in indices. 



An analysis of sightings by day or night and of tonnage observed 

 (Squire 1972), indicated that the northern anchovy. Pacific mack- 

 erel, jack mackerel, and Pacific sardine were observed more fre- 

 quently and in greater quantity during the night. Pacific bonito and 

 bluefin tuna were observed in greater quantity in the day. The selec- 

 tion of the index that is most representative of the apparent abun- 

 dance of each species is based on the 1972 study. 



In the following sections, total effort and observations by year 

 are shown in graphic displays of day/night index values and U. S. 

 fishery catch trends during 1963-78 for each species, along with a 

 review of areas of high sighting density during 1962-78. 



Northern Anchovy 



Morro Bay to San Nicolas Island.— 1962-65. Fig. 4; 1966-69. 

 Fig. 5; 1970-73. Fig. 6: and 1974-78. Fig. 7. 



The sighting effort north of Pt. Conception was greatly reduced 

 after the 1962-65 period. Anchovy schools were commonly 

 observed off Morro Bay and Avila. the latter area being a location 

 where schools were commonly observed. The Santa Barbara coast 

 from Gaviota eastward, and into the eastern end of the Santa Bar- 

 bara Channel, had a high level of anchovy sightings, with the major 

 area of sighting located offshore between the cities of Santa Barbara 

 and Ventura. In 1974-78. the center of sighting appeared to be 

 slightly farther offshore between Santa Barbara and Ventura, but in 

 1978. the center of sighting appeared about equidistant between the 

 two cities and much nearer shore than observed in previous years. 



Pt. Hueneme to San Diego.— 1962-65. Fig. 8; 1966-69. Fig. 9: 

 1970-73. Fig. 10: 1974-78. Fig. 11. 



In 1962-65. anchovy sightings were evenly distributed between 

 Pt. Hueneme and Dana Point, in the Catalina Channel, and about 

 Catalina Island. Sightings were less frequent south of Dana Point to 

 San Dieao. From 1966 to 1969. the observations were centered in 



the Catalina Channel and numerous observations were also made 

 off the coast from Long Beach to Newport Beach. 



From 1970 to 1973, the major observation areas were again near 

 the center of the Catalina Channel, with sightings extending 

 northwest from the Channel south of Pt. Dume. 



Sighting occurrences for 1974-78 appeared to "clump" in the 

 Catalina Channel area, extending from southeast of Long Beach to 

 near Pt. Dume. 1978 sightings were more scattered throughout the 

 area, except for high density areas of sightings southeast of Pt. 

 Dume. 



Index Trends. — The northern anchovy night index trend (Figs. 

 12. 13) was somewhat constant during 1963-69, with an average 

 night index level of 3.50. The commercial catch increased sharply 

 in 1969 and 1970, then declined in 1972. A period of warm sea sur- 

 face temperatures which were well above average, occurred from 

 August to December 1972 in the northeastern Pacific (Miller and 

 Laurs 1975), and anomalous warm temperatures may have affected 

 anchovy availability. 



The index rose to 14.99 in 1973. and the commercial catch 

 increased to near 1 17.9 x 10 3 t. Then, in 1974, a decline in index 

 level and catch was evident. In 1975 the index increased to 11.38 

 and the catch increased to a record peak of 146.9 X 10 3 1. The catch 

 decreased slightly in 1976 and 1977. then dropped to a very low 

 level of about 16.3x10' tin 1978. 



The aerial apparent abundance index declined in 1973-78 (see 

 inspection fitted average line, Fig. 12). and this downward trend 

 preceded the decline of the fishery. In 1975, the peak yearof catch, 

 the apparent abundance was not as great as it had been in 1973. 

 However, sufficient fish were available in 1975. at an index level of 

 1 1 .38, to meet the needs of the fishery. The 1978 apparent abun- 

 dance index level of 1.91 was slightly below the index levels 

 observed during the 1963-69 period. The total catch of anchovy in 

 the central stock area, of which the southern California fishery is a 

 part, was greater than the catch totals given in Figure 12, due to 

 substantial quantities of anchovy landed and processed at 

 Ensenada. Baja California, Mexico. 



Night indices observed for the major fishing areas from near 

 Santa Barbara to Dana Point, including the Channel Islands and San 

 Pedro Channel, are shown in Figure 13. Zones G and H. the Cata- 

 lina Channel, and the Catalina/ 14 mile bank area, were the major 

 producing areas, and the highest indices were recorded for these 

 areas. In 1978, a season of much reduced catches, the apparent 

 abundance index increased for the Santa Barbara coastal area (zone 

 C). the only anomalous trend observed. 



Pacific Sardine 



Morro Bay to San Nicolas Island.— 1962-65. Fig. 14: 1966- 

 69. Fig. 15. 



The Pacific sardine fishery in the Monterey Bay area failed in the 

 late 1940s. By the time the aerial monitoring survey program was 

 started, little observation effort was being expended along the cen- 

 tral California coast north of Morro Bay. In 1962-65. some flights 

 were made along the coast from the south, to, and into, Monterey 

 Bay. A few sardine schools were sighted in Monterey Bay but most 

 were sighted along the coast south of Pt. Sur to Cape San Martin. 

 Some schools were sighted from Morro Bay north (Fig. 14). 



The last major catch of sardines off southern California was 

 made near San Nicolas Island (lower right corner. Fig. 14), on 

 opening day of the season. 1 September 1964. Prior to the season 

 opening, aerial spotters estimated a maximum of about 9. 1 x 10 3 1 



