62 
BULLETIN OF THE BUREAU OF FISHERIES 
Oyster larvse were taken for the first time in plankton collections on March 28 
in the bayou. These were not numerous and were of the late straight-hinge stage, 
or presumably 2 to 3 days old. This is in substantial agreement with the observa- 
tions on the gonads of the oyster and establishes the initiation of spawning on about 
March 25. 
A quantitative method of measuring the abundance of oyster larvse in plankton 
collections was not employed, for while such a measure might be feasible during a few 
weeks it would be too time consuming over a period of several months. A crude 
method of approximation of abundance was devised which gave values of relative 
significance. After immediate examination to determine if larvse were present the 
17 19 21 23 23 27 
Figure 7.— Charts showing the relative abundance (circles) and approximate size (vertical lines) of oyster 
larvse taken in plankton collections at Deer Islands from May to August, 1929. Size refers to length of 
larval shell in microns. Relative abundance was estimated as follows: 0, none; 1 , very few; 2, few; 3, fair 
number; 4, many; 5, very many; 6, extremely abundant 
samples of plankton were preserved and kept until the end of the summer. Then, 
over a relatively short period, to insure accuracy, the abundance of larvse in each 
sample was estimated by an arbitrary standard. Numbers from 0 to 6 were employed 
to designate from none to extremely abundant and were defined as follows: 1, very 
few; 2, few; 3, fair number; 4, many; 5, very many; and 6, extremely abundant. 
All collections were made in the surface 12 to 15 inches of water and these figures 
refer only to the presence of larvse at this level. However, since larvse were taken in 
nearly every collection after the end of March it improbable that the collections repre- 
sent a reasonable estimate of the abundance of larvse in the water, or the intensity of 
spawning. 
