GROWTH AND MORTALITY OF PACIFIC RAZOR CLAM 
563 
dens and diggers. The closed season so widely used elsewhere as a protective meas- 
ure, if used alone, simply results in a shift of the time of intense digging and a concentra- 
tion of effort in a shorter period. The total catch is not reduced, but its rapid handling 
leads to greater waste. This has been well illustrated on the Washington beaches. 
The minimum size limit insures a reserve of breeding animals, and protects the 
clam at a time when it is increasing most rapidly in weight and therefore in economic 
value. The wastefulness of unrestricted digging has been emphasized by one of us 
(McMillin, 1927, 1928) in the case of the Washington beaches where, in 1928, the 
young not yet of spawning age constituted 42.5 per cent of the catch. Only the re- 
markable resilience of the clam populations on these beaches resulting from the heavy 
set and rapid growth have saved them from commercial extinction. Even with the 
protection now afforded these younger clams it will require time to rebuild the fishery. 
It was feared when the size limit was first proposed that its enforcement would be 
difficult, but this has not proved to be the case. The small clams, which are largely 
wasted in the canning operations because of the difficulty of cleaning them, are not 
wanted by the canners who have cooperated in enforcing the regulations. The size 
limit results in the practical closure of depleted areas. Beds which will not yield 
enough legal sized clams to repay the digger are carefully avoided. 
(e) Future work . — It is recommended that surveys be made at least biennially of 
those regions where the razor-clam fishery is well developed to furnish material from 
which the age composition of the commercial catch may be found. If new regions are 
opened, these should be sampled at once in order that their subsequent history may 
be followed. Such surveys will show overfishing and permit the intelligent adjust- 
ment of regulations before conditions become acute and necessitate drastic action. 
SUMMARY 
The present paper is a continuation of previous studies of the Pacific razor clam 
undertaken for the Bureau of Fisheries. 
The relationships of the most abundant and only commercially important 
species, Siliqua patula, are considered. 
The variability, mortality, and sexual differences within the species are discussed. 
Data on the growth of clams from 10 localities are presented, together with a dis- 
cussion of methods employed and localities considered. Similarities shown by the 
growth data and the conception of growth to which they lead is given, and a critical 
examination of the graphic representation and terminology follows. The differences 
exhibited by the various localities are discussed. 
Among legal restrictions on the fishery the importance of the size limit is again 
emphasized. 
