398 
BULLETIN OF THE BUREAU OF FISHERIES 
and, therefore, the temperatures must be quite representative of those which prevail 
when the pigfish migrates. It is shown by the table that the spring temperatures 
(March and April) are a little lower than the autumn temperatures (October and 
November) when the fish perform their principal migration. It has been pointed out 
elsewhere that the larger and older fish are the first ones to leave the shallow waters 
in the autumn, and that they are also the first ones to return in the spring. Why 
the older fish lead the migrations is not well understood. Possibly they “know” 
the route better, and again they may “understand” better the significance of cooling 
and warming waters. Then, too, in the spring they may be driven on by the “urge” 
to spawn. 
It seems in order to state here in defense of the foregoing statements and the 
use of the terms “know” and “understand” that one is driven to the conclusion by 
numerous observations in support thereof that the older fish of nearly all species 
are much better able to protect and to take care of themselves than the younger 
ones. In other words, intelligence in fishes, as in higher vertebrates, increases con- 
siderably with age. An instance of a seemingly high fish intelligence of adults may 
be seen in overflowed lands. Few large or adult fish become stranded when the 
water recedes, although countless young perish in pools. Yet there is no doubt 
that the large fish follow the flood waters. They seem to know, however, when it 
is time to return to the main body of water. This sense of self-protection appears 
to be possessed alike by both fresh and salt water species. It seems reasonable, 
therefore, to expect the older pigfish, because of their superior intelligence, to lead 
the migrations which no doubt are made in the interest of self-preservation. 
SPAWNING 
Almost nothing appears to have been known prior to the present investigation 
in regard to reproduction in the pigfish, for we find in the literature only the general 
statement that spawning occurs in the spring (May and June). 3 We find nothing 
relative to the place of spawning, the type of eggs produced, and the characters of 
the young — all discussed subsequently in this paper. Concerning the rate of growth 
of the young, also discussed herein, we find only Taylor’s paper (1916, pp. 319-324) 
based partly on length measurements and partly on scale studies. Taylor’s account 
appears quite inadequate to us, especially as he seems to have confused the O class 
with the I class. It is not particularly surprising, however, that such fundamental 
information is missing in regard to the pigfish, as equally as little is known about 
dozens of other common species of even wider distribution and greater economic value. 
During the present investigation, extending over four seasons, recently hatched 
young were taken sparingly as early as March 16 (1927 only), although the eggs did 
not appear in the tow until April 13 (1928). The latest date upon which the eggs 
were observed was June 22 (1927), and they were most numerous each year during 
May. It may be concluded, therefore, that spawning may begin at Beaufort as 
early as the middle of March, that it ends near the latter part of June, and that the 
principal spawning period occurs in May. This conclusion is supported also by 
tables of measurements of young fish and by a growth curve included in this paper. 
(See Tables 3 and 4 and fig. 39.) 
Gravid fish are particularly numerous along the inside shores of Bogue and 
Shackleford Banks during the spawning season, and it is here that the greatest concen- 
j A preliminary account of a part of the present investigation, dealing principally with the embryology of the pigfish is given by 
Towers (1928, pp. 622-624). 
