SCOTT and FLITTNER: BEHAVIOR OF BLUEFIN TUNA SCHOOLS 



Table 1. — Terms used by southern California purse-seine 

 tuna fishermen to describe various types of tuna schools 

 and associations (from Scott, 1969). 



School fish 



Associated schools^ 



Surface schools^ 

 Breezer 

 Finner 

 Jumper 

 Boiler, foomer, 



smoker, or meatball 



Subsurface schools^ 



Black spot, dark spot, 

 brown spot, green spot, 

 or black ball 



Shiner 



Night schools^ 

 Fireball, ardura, 



glow spot, white spot, 



or flare 

 Popper 



Fish and mammals^ 

 Porpoise schools 

 Spotters 

 Spinners 



Spotters and spinners 

 Whitebelly 

 Whale schools 



Shark schools 



Inanimate obiect association^ 

 Log school 

 Bait boat 



1 These terms are used for organization of the table and are not used 

 by the fishermen. 



behavior and 12 different combinations of these 

 to the commercial fishermen. Thei-e were dif- 

 ferences in frequency of occurrence, size of the 

 schools, and vulnerability to capture between the 

 schools (Table 2). Differences in the occurrence 

 of the school types in the northern and southern 

 areas of the fishery were also evident (Table 3). 

 In order to eliminate possible bias in analyzing- 

 school size and percentage success, all sets made 



with the assistance of airborne spotters have 

 been separated. The effects of airborne spotters 

 on catch data will be discussed later in this 

 paper. 



Of the 13 school types observed, only 6 were 

 recorded often enough (50 or more times) to 

 warrant attention. 



GEOGRAPHICAL VARIATION 



T. thynnus is taken along the coast of Baja 

 California and southern California from lat 

 23°N to 34°N. Occasionally fish are taken north 

 of this area, especially in warm water years, but 

 they are few, and seiner operations are severely 

 limited by prevailing weather and sea conditions. 

 The g-reatest percentag-e of the bluefin catch is 

 made within 90 miles of shore near shoals, banks, 

 reefs, and islands. 



We have divided the area of the fishery into 

 two major areas: that area north of lat 28°59'N 

 and the area south of and including that same 

 latitude (Figure 1). There is some biolog^ical 

 basis for this division, as Punta Eugenia marks 

 the northernmost extension of the Panamic 

 fauna (Steinbeck and Ricketts, 1941). In ad- 

 dition, oceanographic and meteorological condi- 

 tions also differ considerably. South of Punta 

 Eugenia, an annual visitation of warm tropical 



Table 2. — Catch statistics for 13 different bluefin school types and 4 diff'erent categories 



of combined schooling behavior observed. 

 [All purse-seine sets recording schooling behavior are included.] 



School 

 type 



Average 



catch per 



successful set 



(short tons) 



Breezers 



Boilers 



Jumpers 



Block spots 



Shiners 



Foomers 



Fireballs 



Finners 



Log 



Whales 



Poppers 



White spots 



Meatballs 



Combined sc 

 Breezers 

 Boilers 

 Jumpers 

 Black spots 

 Total 



19.6 



9.1 



5.3 



24.2 



11.6 



20.8 



15.1 



9.0 







15.2 



4.8 



9.7 



20.0 



18.6 

 22.7 

 8.5 

 19.0 

 14.8 



917 



