BULLETIN OF THE UNITED STATES FISH COMMISSION. 259 
NOTICE OF THE SMALL SURFACE ORGANISMS TAKEN IN THE TOW- 
NETS, AND OF THE CONTENTS OF MACKEREL STOMACHS , BY RICH- 
ARD RATHBUN. 
The number of lots of towings handed to me for examination was 36. 
Some of these were obtained by means of a large conical net, of rather 
coarse mesh, intended principally for the capture of fish, and in which 
never more then a trifling quantity of the smaller animals was retained; 
the larger number were taken in the ordinary pattern of tow-net, made 
of silk bolting-cloth, and measuring 12 inches across at the mouth and 
about 22 inches deep ; a few were secured with a dip-net. They were 
all taken at the surface between April 25 and May 30, 1887. The po- 
sitions have been described elsewhere by Dr. Bean, and are also given 
below, in connection with the list of species obtained at each locality. 
The best results, as regards the smaller animals, were obtained with 
the 12-inch tow-net, and although the distance actually traversed by 
the net each time that it was used was not determined, yet we have 
been able to form some idea of the relative abundance of life in a given 
area at the surface during the beginning of the mackerel season. The 
usual length of a towing was from one-half hour to one hour, the vessel 
sailing at the rate of 2 or 3 knots an hour. The quantity of material 
from each towing was calculated by liquid measure, the specimens first 
being allowed to settle thoroughly in the bottle containing them. While 
this method did not afford absolute results, by measuring the contents 
of the mackerel stomachs in the same manner a comparison of the two 
was rendered possible. 
The quantity of specimens in each lot of towings was from 1 to 20 
drams. One towing, affording 18 drams, was made in 15 minutes May 
9, beginning at 8.15 p. m. The 25 towings with the 12-inch net resulted 
in a total catch of 115 drams of specimens, or an average of 4J drams 
to a towing. 
The contents of the stomachs of mackerel were preserved on two days 
only, May 10 and May 13. The size of the fish was from 11 to 134 
inches in length. On the first day mentioned the quantity of food 
taken from the stomachs averaged 4 drams to a stomach ; on the second 
day it averaged 5J drams, except in the case of one specimen, which 
afforded 8 drams. The average quantity of food to a stomach, there- 
fore, agreed very closely with the average results of a towing with the 
12-inch net. 
These deductions, however, are based upon too few observations to 
have any special significance. It is well known that the surface organ- 
isms serving as food for mackerel and other pelagic fishes are very un- 
equally distributed, and are constantly changing their position, appear- 
ing and reappearing under the varying conditions of the water and 
atmosphere. While sometimes they are apparently absent over wide 
areas, at others they form dens© clouds, plainly distinguishable by their 
