Scomberomorus sierra — Klawe 
449 
Fig. 2. Scomberomorus sierra, 11 mm-long specimen, caught off Punta Foca, Peru. 
easily separable from other tuna and tuna-like 
fishes on the basis of shape, meristic counts, and 
pigmentation patterns. Noteworthy is the ar- 
rangement of head spines illustrated in Figure 
3, which represents the dorsal aspect of the 
head of a specimen 12 mm long from the col- 
lection off Punta Foca, Peru. The serrated 
supraorbital crest shown in that figure is, in 
the family Scombridae, not restricted only to 
young of S. sierra. Such a crest has been re- 
ported for young Sarda chili ensis (Pinkas, 
1961). Perhaps it may be characteristic of some 
other members of the family Scombridae phylo- 
genetically closer to the families of Istiophori- 
dae and Xiphiidae, which are considered to be 
evolved from the scombrids. Young swordfish, 
marlins, and sailfish at a certain stage of their 
development are provided with a serrated supra- 
orbital crest. Such a serrated crest is also present 
in young Gempylidae. Scomberomorus and 
Acanthocybium share with the gempylids a car- 
tilaginous projection surmounting the mandibu- 
lar symphysis (Strasburg, 1964). The appear- 
ance of the specimens of young S. sierra agrees 
with the detailed description given by Hilde- 
brand and Cable (1938) for S. maculatus and 
that of Eckles (1949) for S. sierra. 
Although the number of gill rakers on the 
first gill arch is useful in separating adults of 
the two species of Scomberomorus found in the 
eastern Pacific Ocean, young Scomberomorus 
do not have an entire complement of fully de- 
veloped gill rakers. The full complement is 
present in individuals on young scombroids 
(Thunnus, Euthynnus, Auxis, and Sarda) of 
40-60 mm in total length (Klawe and Shimada, 
1959; Klawe, 1961). Counts were made on the 
material in this report to establish species iden- 
tity and the size at which the full complement 
of gill rakers is attained. Counts of gill rakers 
made on juvenile scombroids are to a certain 
extent subjective because, in the smaller indi- 
viduals, the gill rakers are represented merely 
as small protuberances along the arch. Because 
of this subjectivity it is necessary to be wary 
when comparing counts on young scombroids 
made by different investigators. From the counts 
of the total number of gill rakers (Fig. 4), 
we may assume that the fish in this collection 
belong to one species because the increase in 
the number of gill rakers with the increase in 
size appears to follow a curve which levels off 
at a size between about 30-50 mm. This level- 
ing off occurs at a number of gill rakers charac- 
teristic for S. sierra. 
It is likely that the Peruvian specimen (Fig. 
2) is but a few days old, in view of the rapid 
growth of young sierra noted by Clemens 
(1956) in his experiments. The fact that still 
smaller (9.5 mm) specimens of S. sierra were 
also captured at the same time and in the same 
area suggests that the spawning of S. sierra 
takes place in this region in January. From the 
summary of the records of capture of juvenile 
sierra (Table 1), this species probably spawns 
near the coast over most of its distributional 
limits in the eastern Pacific Ocean. Spawning 
off Mexico takes place in July, August, and 
September, and in lower latitudes perhaps from 
December through April. The conclusions as 
to time of spawning should be considered as 
speculative; the question of the spawning time 
of sierra cannot be resolved until more com- 
plete data on the occurrence of eggs or young 
