432
A. SUDA:
line hooking-rate over the period between 1966 and 1968. Here, the longline hooking-rate
is the average number of fish caught per 100 longline hooks. The major concentration
of each species reveals a peculiar pattern as will be described below.
a) Yellowfin (Fig. 1 a and b)
This species generally occurs over the low latitudinal areas north of 10° S. The
distribution also expands southward along the African coast especially during the first
Fig. 1. Distribution of longline hooking-rates of 4 tuna species for 2 quarters of the years 1966 to
1968, expressed as maximum average hooking-rate for each 1 0 square. (Filled circle < 1.0; cross
1.0-3.0; black square> 3.0) a Distribution of longline hooking-rate of yellowfin tuna in the second
quarter ofthe years 1966 -1968
half of the year, and the Australian coast during the second half of the year. Over the
offshore area south of 10° S the occurrence is sporadic.
b) Albacore (Fig. 1 c and d)
Albacore occupies the intermediate latitudinal area between 10° Sand 35 ° Sand
its sphere of occurrence hardly overlaps that of yellowfin.
c) Bigeye (Fig. 1 e and f)
The species occurs in 2 separate areas. The northern concentration is in the waters
of low latitudes as in the case of the yellowfin.
A. SUDA:
line hooking-rate over the period between 1966 and 1968. Here, the longline hooking-rate
is the average number of fish caught per 100 longline hooks. The major concentration
of each species reveals a peculiar pattern as will be described below.
a) Yellowfin (Fig. 1 a and b)
This species generally occurs over the low latitudinal areas north of 10° S. The
distribution also expands southward along the African coast especially during the first
Fig. 1. Distribution of longline hooking-rates of 4 tuna species for 2 quarters of the years 1966 to
1968, expressed as maximum average hooking-rate for each 1 0 square. (Filled circle < 1.0; cross
1.0-3.0; black square> 3.0) a Distribution of longline hooking-rate of yellowfin tuna in the second
quarter ofthe years 1966 -1968
half of the year, and the Australian coast during the second half of the year. Over the
offshore area south of 10° S the occurrence is sporadic.
b) Albacore (Fig. 1 c and d)
Albacore occupies the intermediate latitudinal area between 10° Sand 35 ° Sand
its sphere of occurrence hardly overlaps that of yellowfin.
c) Bigeye (Fig. 1 e and f)
The species occurs in 2 separate areas. The northern concentration is in the waters
of low latitudes as in the case of the yellowfin.