562 
BULLETIN OF THE BUREAU OF FISHERIES 
These studies have furnished what is doubtless the largest body of invertebrate 
growth data as yet available. Since these growth data are uniquely regular it has 
permitted an analysis of certain features of growth not hitherto possible. This 
analysis has substantiated and extended the earlier findings of Minot, making possible 
a valuable mathematical formulation of the course of growth. 
Many problems of growth and its relation to variability and longevity, as yet 
unsolved, may be confidently attacked by this method, and data are already at hand 
or will be obtained incidentally in the surveys hereafter proposed. 
RAZOR-CLAM FISHERY AND ITS REGULATION 
(а) Neither artificial propagation nor culture are feasible. Proper protective 
measures can maintain the present beds, but no extension can be expected. The 
forms suitable for “farming” on the Pacific coast are the oyster and soft-shelled clam 
( Mya ). These may readily be extended to many bays now unproductive. The razor 
clam should and can be protected; it has, however, already spread to all suitable 
locations. 
(б) With the knowledge of the rate of growth, the length of life, and the set at 
different latitudes now available, we may predict the resistance of various beds to 
commercial fishing. In the south the rate of growth is rapid; the life, short; and the 
set, heavy. In the north the rate is low; the life, long; and the set, light. Balancing 
these factors, the Washington beaches are undoubtedly the most resistant- — -a con- 
clusion borne out by the history of the commercial fishery. 
(c) Evidences of overfishing . — The validity of the method of age determination 
developed by the senior author is now well established. By its use the composition of 
the commercial catch may readily be ascertained. A fall in the relative abundance 
of the older age groups (with due allowance for dominant age classes) is the best evi- 
dence of danger from too intense fishing. This method of analysis has been applied 
by one of us (McMillin, 1925, 1927, 1928) to the Washington fishery, with such 
striking evidence of depletion that the State has finally passed protective measures 
including a size limit of 3}i inches and a bag limit of 3 dozen for the unlicensed digger. 
The fishery at Cordova is being followed by the same method and the size limit of 
4% inches set as a result of the first survey (Weymouth, McMillin, and Holmes, 1925) 
is proving an efficient protection. Measured areas, marked with permanent stakes, 
may be dug on successive days, and the same or similar areas examined each year. 
These areas are often avoided by the commercial diggers and are, therefore, not a 
completely satisfactory index of the general conditions of the beds, or contours of 
bottom may so change that successive records are not comparable. Nevertheless this 
method gives valuable supplementary evidence of the trend of the fishery. 
( d ) Methods of protection . — The protective measures available are closed seasons, 
closed areas, bag limits, and size limits. Additional experience in the application of 
these measures have supported the arguments advanced in a previous report (Wey- 
mouth, McMillin, and Holmes, 1925) in favor of the size limit. A bag limit has been 
set on the noncommercial digger for the Washington beaches, but has never been 
advocated for commercial operations. The closing of areas to digging would appear a 
useful method of protection, but experience has not proved it feasible. In the first 
place, the nature of the razor-clam beaches makes them difficult to post and police. 
Accurate description is often impossible because of absence of landmarks and the 
constant changing of the bars. This results in confusion and friction between war- 
