Fishery bulletin of the Fish and Wildlife Service - NOAA

BIOLOGY OF THE ATLANTIC MACKEREL 175
That each series includes truly homologous groups is indicated by several criteria,
independent of the straight-line conformity. In the К series, the modes all tend
toward peakedness. In the S series, they all tend to be broad. In the Т series they
are intermediate in shape. The progress in each series is reasonably consistent and
the course of growth is roughly parallel in the three series; moreover, the slight departure
from parallelism is in the expected direction, the later series having the higher
growth rates consistent with their development in the warmer water to which they
are subjected. Furthermore, the modes are consistently present in the material from
each cruise with only two exceptions, R in cruise III and S in cruise IV. The absence
of S in cruise IV is plainly due to failure on that cruise to visit certain stations in the
southerly end of the spawning area, where previous cruises would lead one to expect
4.0
3.0
(Г 2.0
Ul
Ш
э '-о
z
о
Î.O
2.0
3.0
.6 .в 1.0 |.г 1.4 1.6 1.8
L O Q OF LENGTH
FIQUEI в.—Frequency distribution of lengths of larvae plotted logarithmically.
to mid larvae of sizes appropriate for this series (fig. 13, IV). Absence of К in cruise
III has no such simple explanation, and can be explained only as chance sampling
fluctuation.
Only one other reasonably sensible alternative to the series of homõlogies in figure
7 is possible. According to this alternative, R of cruises I and II would be considered
forerunners of the 9- and 10-mm. larvae of cruise III; S of cruise III considered the
forerunner, of R of cruises V and VI'; the 3- and 4-mm. larvae of cruise IV, the forerunner
of S of cruise V; S of cruises V and VI, the forerunner of R of cruise VII; and
T of cruise VI, the forerunner of S of cruise VIII. But, this would not account for the
presence of such prominent modes as R of cruise IV, S of cruise VII, or T of cruise
VIIÍ; and there are other objections to this alternative set of homõlogies which will
be considered later.