Threadfins from the Eastern Pacific — Klawe and Alverson 
173 
45 50 55 60 65 70 75 00 85 90 95 
SIZE IN MM 
FIG. 3- Length frequency distribution of two samples 
of P. opercularis captured on the high seas for use 
as tuna bait. 
It would be reasonable to assume that the 
presence of young of small size (for our pur- 
poses less than 40 mm) is an indication of 
recent spawning. We have arbitrarily divided 
the eastern Pacific into three geographical areas, 
north of the Gulf of Tehuantepec, Central 
America, and South America, and plotted the 
occurrence of small fish for each species, by 
month, regardless of the year of collection. 
It appears that P. approximans spawns 
throughout the year in all three areas. Most 
likely the same applies to P. opercularis, al- 
though the evidence is not as strong as that for 
approximans. It should be noted, however, that 
the number of P. opercularis in our collection is 
smaller than that of P. approximans. The fact 
that one of the species definitely and the other 
most likely spawns throughout the year is of no 
surprise, as P. indicus in the region of Bombay, 
India, has a spawning season extending through 
the entire year (Karekar and Bal, I960). 
REFERENCES 
Alverson, F. G., and B. M. Shimada. 1957. A 
study of the eastern Pacific fishery for tuna 
baitfishes, with particular reference to the 
anchoveta ( Cetengraulis mysticetus ) . Inter- 
Amer. Trop. Tuna Comm., Bull. 2(2) : 2 5-61 
(English), 62-79 (Spanish). 
Berdegue, A. Julio. 1956. Peces de importan- 
ce comercial en la costa noroccidental de 
Mexico. Comision para el fomento de la Pis- 
cicultura Rural. 345 pp. 
Bullis, H. R., Jr. 1961. Observations on the 
feeding behaviour of white-tip sharks on 
schooling fishes. Ecology, 42(1): 194-195. 
Godsil, FI. C. 1938. The high seas tuna fishery 
of California. Calif. Div. Fish and Game, Fish 
Bull. 51:41. 
Hildebrand, S. F. 1946. A descriptive catalog 
of the shorefishes of Peru. U. S. Nat. Mus., 
Bull. 189:530. 
Karekar, P. S., and D. V. Bal. I960. A study 
on maturity and spawning of Polydactylur 
indicus (Shaw). Indian Jour. Fish. 7(1): 
147-164. 
Klawe, W. L. 1963. Observations on the 
spawning of four species of tuna ( Neothun - 
nus macropterus, Katsuwonus pelamis, Auxis 
t hazard and Euthynnus Uneatus) in the east- 
ern Pacific Ocean, based on the distribution 
of their larvae and juveniles. Inter-Amer. 
Trop. Tuna Comm., Bull. 6(9) : 447-5 14. 
Shiino, S. M. 1959. Ostpazifische parasitierende 
Copepoden. Report Facul. Fish. Prefect. Univ_ 
Mie 3(2) : 267—333- 
P. approximans 
J 
F 
M 
A 
M 
J 
J 
A 
s 
o 
N 
D 
North of Gulf of Tehuantepec 
X 
X 
X 
X 
— 
X 
X 
X 
X 
X 
X 
X 
Central America 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
South America 
X 
X 
X 
X 
— 
X 
X 
X 
— 
— 
X 
X 
Composite all areas 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
x: 
P. opercularis 
j 
F 
M 
A 
M 
J 
J 
A S O N 
D 
North of Gulf of Tehuantepec 
— 
X 
X 
X 
X 
X 
X 
— — — X 
— 
Central America 
— 
— 
X 
X 
— 
X 
— 
— — — x 
X 
South America 
X 
— 
X 
— 
— 
X 
— 
— — — — 
— 
Composite all areas 
X 
X 
X 
X 
X 
X 
X 
— — “X 
X 
