FISHERY BULLETIN: VOL. 70, NO. 3 



spotter aircraft in a search for tuna schools in 

 the same area surveyed by a research vessel, 

 found that the aircraft was about two and one 

 half times more efficient than the vessel at lo- 

 cating fish schools. An evaluation of aircraft 

 by the U.S. Navy, for making biological obser- 

 vations, indicated that for whales the frequency 

 of sighting averaged about 20 times greater than 

 that from ships (Levenson, 1968). 



From 1956 to 1964 the California Department 

 of Fish and Game conducted monthly survey 

 flights along the California coast from San Fran- 

 cisco to Mexico. Data were published as flight 

 reports in chart form showing the aircraft's 

 flight track, areas surveyed, notes on species ob- 

 served, and number of schools and their geo- 

 graphical location. Large variations in the num- 

 ber of schools visible over a short-time period 

 appeared to limit the usefulness of the data, and 

 the surveys were discontinued in 1964. The av- 

 erage number of schools sighted per flight was 

 determined by Wood (1964),° and from these 

 data a comparison was made of the relative 

 abundance of northern anchovy, Engraulis mor- 

 dax, schools for the period 1956 through 1963. 

 Limitations on flights to nearshore areas during 

 daylight and low search time in any one area 

 restricted the potential of these surveys for de- 

 termining the apparent abundance of the many 

 pelagic species found off the California coast. 



Fish spotter aircraft range over a large geo- 

 graphical area, and during these flights they may 

 observe concentrations of several species of pe- 

 lagic fish. Many times these fish are not caught 

 for one or more reasons, such as fishing boats not 

 equipped with proper nets, concentrations are 

 small, species is not economically desirable, and 

 fishing boats are not capable of reaching fish 

 within a reasonable length of time. However, 

 the fish spotters are able to identify these con- 

 centrations of fish. 



Species commonly observed by the aerial fish 

 spotters within the survey area were northern 

 anchovy, jack mackerel, Trachurus symmetricus; 

 Pacific bonito, Sarda chiliensis; Pacific mack- 



• Wood, R. 1964. Aerial surveys along the California 

 coastline 1956 to 1963. Document V prepared for the 

 Marine Research Committee meeting, March 6 1964, 

 San Pedro, Calif., 2 p. [Processed.] 



erel, Scomber japonicus; Pacific sardine, Sardi- 

 nops sagax; bluefin tuna, Thunnus thynniis; 

 Pacific barracuda, Sphyraena argentea; white 

 seabass, Cynoscion nobilis; and yellowtail, Seri- 

 ola dor sails . 



The majority of fish spotting effort is directed 

 toward the location and catching of jack mack- 

 erel. Pacific mackerel. Pacific bonito. Pacific sar- 

 dine, and in recent years the northern anchovy. 

 Of these five species the Pacific sardine and Pa- 

 cific mackerel are most economically desirable 

 with jack mackerel, Pacific bonito, and northern 

 anchovy of descending importance. 



To increase knowledge on the apparent abun- 

 dance of pelagic near-surface marine life, the 

 Tiburon Marine Laboratory initiated a pelagic 

 fish monitoring program in cooperation with 

 aerial fish spotter pilots who are active in spot- 

 ting for the southern and central California 

 coastal commercial fishery. These cooperators 

 were individuals with specialized training and 

 experience. When assisting the commercial 

 fleet, fishing success is dependent upon accurate 

 identification of schooling species by the spotters. 

 They have considerable experience in estimating 

 the weight of fish schools, and they are consid- 

 ered to be quite accurate in the estimation of 

 weight. 



There are a number of variables that affect the 

 statistical accuracy of fish spotter data which 

 are difficult to evaluate, such as individual dif- 

 ference in ability of pilots to locate fish, deter- 

 mine species, and estimate school size, and esti- 

 mate total tonnage available in a fishing area. 

 Variation in estimating school size probably has 

 more effect on the data than the other variables. 

 However, since at least five experienced observ- 

 ers were used in the program during each year, 

 it was assumed that reasonable annual averages 

 were obtained. 



This report consists of an analysis of aerial 

 fish spotter data for the period September 1962 

 through December 1969 to determine if, for the 

 species commonly observed, it can be used to: 

 (1) compute an accurate index of apparent 

 abundance and (2) obtain a trend in the appar- 

 ent abundance of pelagic near-surface species 

 and in particular those of underutilized re- 

 sources. 



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