SQUIRE: PELAGIC MARINE FISHES OFF SOUTHERN AND CENTRAL CALIFORNIA 



METHODS AND PROCEDURES 



Five fish spotter pilots were contracted to re- 

 cord observations of pelagic species, giving loca- 

 tion, number of schools, estimated tonnage of 

 each school or groups of schools, counts of large 

 marine animals, and flight track for each survey 

 flight. Two pilots usually covered the Santa 

 Barbara • Channel and Santa Barbara Islands 

 north to Estero Bay and occasionally into Mon- 

 terey Bay. The remaining three spotter pilots 

 normally sui-veyed the area from west of Los 

 Angeles to southwest of San Diego and occasion- 

 ally offshore to San Clemente Island, Cortez 

 Bank, and San Nicholas Island. Flight oper- 

 ations were conducted during daylight hours or 

 on nights during the dark phase of the moon 

 at elevations of 500 to 1,200 ft (152 to 365 m) 

 above the sea surface. 



TECHNIQUES OF OPERATION 



Specific observation of a fish school has three 

 phases: (1) distinguishing a school, (2) identi- 

 fying the species, and (3) estimating weight of 

 the school. The detection of near-surface schools 

 during the day is dependent upon the pilot's 

 ability to distinguish subtle color and light in- 

 tensity differences in the water. Detection of 

 schools at night is possible only during the dark 

 period of the moon and depends on the pilot's 

 ability to discern gradation of light intensity. 

 Bioluminescence of planktonic organisms agi- 

 tated by schooling fish indicates by a dull glow 

 the location and size of the school. Species are 

 identified during the day on the basis of a com- 

 bination of two or more of the following char- 

 acteristics: color of school or individual fish, 

 shape of school, and behavior and size of indi- 

 viduals within the school. At night, species 

 identification is based on shape of the luminous 

 area and behavior of the schooling fish under un- 

 disturbed conditions, or by the behavior of the 

 school after being subjected to a stimulus from 

 an external source such as a flash from the air- 

 craft's landing light. 



At first observations were recorded by the 

 pilots on small portable tape recorders. This 



method was unsatisfactory, and recorders were 

 replaced with three charts covering the coastal 

 waters from the Coronado Islands, Mexico, north 

 to Half Moon Bay, Calif. The charts were com- 

 pleted by the pilots after each flight and were 

 submitted quarterly to the National Marine 

 Fisheries Service. Figure 1 illustrates the type 

 of information recorded by the fish spotter 

 pilot. 



PROCESSING OF OBSERVATION DATA 



Each chart was overlayed with a 10-minute- 

 longitude by 10-minute-latitude grid, numbered 

 according to the California Department of Fish 

 and Game "Block area" statistical system 

 (Clark, 1935). With the gridded chart, the ob- 

 sei-vation and flight track data could be con- 

 veniently tabulated and coded for subsequent 

 computer analysis. California Department of 

 Fish and Game statistical code numbers were 

 assigned to each of the 27 species of marine 

 animals observed. The computer output grouped 

 data by species, year, week, block area, day or 

 night observation, number of schools, tons per 

 school, and tons per block area. The data for 

 block areas were later combined into 11 larger 

 grouped block areas or "zones" lettered A 

 through K (Figures 2 and 3) . These zones were 

 selected to outline important geographical areas 

 where fish were commonly observed. 



The following criteria were used in tabulating 

 the data from the flight charts: 



1. Groups of schools which were indicated on 

 the flight chart as covering more than one block 

 area were listed for each block holding part of 

 the group. For example, if one group of schools 

 (10 schools, 15 tons per school, total 150 tons) 

 overlapped two block areas equally, each area 

 was credited with having 5 schools at 15 tons per 

 school, equalling 75 tons per block area. 



2. If only one school was shown overlapping 

 two block areas, the school was assigned to the 

 block area having the greatest portion of the 

 school. 



3. If a large area of fish was indicated involv- 

 ing more than two block areas and only a total 

 tonnage estimate made, the tonnage was credited 

 to the block areas in proportion to area outlined. 



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