FORK LENGTH (cm) 



Figure 46. — Length-frequency distribution of Auxis rochei 

 caught by traps at Barbate, Tarifa, and La Linea. by month 

 and year (1961, 1964) ( Rodriguez- Roda 1966). 



Taking a vessel-day as a unit of fishing effort, Ishida 

 (1972a) calculated the monthly landings per day and 

 found that this index fluctuated in a similar fashion as 

 the number of vessels in operation per day (Fig. 47). I- 

 shida also constructed a frequency distribution of the 

 landings per day and found that the primary mode fell 

 at 30 t/day (t = metric tons) (Fig. 48). The annual mean 

 was 52.4 t/day but the seasonal mean, presumably cal- 

 culated from selected data on landings per day for the 

 peak months, reached 56.5 t/day. A plot of landings per 

 day on number of vessels operating ijer day showed that 

 em increase in fishing intensity was usually accompan- 

 ied by a similar increase in catch per day. 



Off the coasts of Sri Lanka, Auxis are distributed in 

 all waters surrounding the island but their densities 

 vary widely (Sivasubramaniam 1973). Using the 

 number of fish caught per standard trolling unit (a ves- 

 sel with a fixed number of lines) per day, Sivasubrama- 

 niam found that A. thazard was most abundant along 

 the southwest coast as catch rates reached 21.7 

 fish/boat-day. Almost equally high were the catch rates 



JAN FEB M4R APR MAY JUNE JULY AUG SEPT OCT NOV DEC 



Figure 47. — Landings of AuxU spp. per day in the fishery off Ashi- 

 zurimisaki, Japan, calculated from data collected from October 

 1964 to June 1967 and combined by months (Ishida 1972a). 



LANDING (METRIC TONS) 



Figure 48. — Frequency distribution of landings per day in the fishery 

 for Auxi» spp. off Ashizurimisaki, Japan (Ishida 1972a). 



along the southern coast which peaked at 21.3 fish/boat- 

 day. Fish appeared to be fewer along the east and west 

 coasts with catch rates of 18.9 and 14.3 fish/boat-day, re- 

 spectively. The lowest catch rate occurred off the north 

 coast with only 4.2 fish/boat-day. For A. rochei, the 

 variation in catch rates followed a similar pattern. Si- 

 vasubramaniam (1973) estimated that usually a fishing 

 vessel will encounter two to three mixed schools per day 

 in waters around Sri Lanka. 



47 



