GBOWTH AND AGE AT MATUEITY OF THE PACIFIC RAZOR CLAM 
231 
BEACHES 
No attempts have been made by the Avriters to explore areas that were not being 
exploited at the time the work was carried on in the field. It is impossible to 
find the unit population of any unit area, and in most cases it is difficult to get 
anything but a very rough idea of the size of the clam-producing beds. On 
undepleted beds the same area can be dug over on several consecutive days without 
apparent decrease in the day's catch, a fact which makes an accurate census im- 
possible. Thus indications of depletion can not come from either a census or a 
survey of the beach, but, as we shall later see, show up quickly in the averag'e 
size of clams in the commercial catch and in the average "dig" per man. 
The clam-producing areas of the Washington and Oregon beaches can readily 
be measured. The beach is uniform in width, and the area exposed varies with 
the tide. The Alaska beds, on the other hand, are variable. Those in the vicinity 
of Cordova have been built up by sand brought down by the Copper River. They 
are made up of an intricate series of bars and channels which change their loca- 
tion at irregular intervals. In fact, the whole topography of the clam-producing 
area changes from year to year. Beds that are under several feet of water at the 
lowest tide of one season may be accessible to digging the next, and some high 
bars may be entirely submerged. 
Swickshak beach changes less by shifting of bars and channels. The bottom 
slopes gradually, and the olfshore water is very shallow, giving a wide intertidal 
zone. Since this beach is so flat, the height of tide governs the area exposed ; on 
one spit it was estimated that a change of 1 foot in the tide was accompanied by 
a variation of 40 acres in the area of beach exposed. Owing to this, only rough 
estimates can be made of the areas. 
The condition of the Snug Harbor beds, lying between Chisik Island and Har- 
riet Point on the west side of Cook Inlet, is more like that at Swickshak than at 
Cordova. The tidal range over these beds is greater than elsewhere. Since the 
beach slopes very gradually, it is wide, the tide going out nearly 3 miles in one 
place. It was estimated that about 1% square miles of beach were being dug 
during the summer of 1923. While this bed is not constantly being changed hy 
the shifting of bars and channels, as at Cordova, portions of it are seriously 
menaced at times by deposits of glacial silt, which covers the beds and destroys 
the clams. 
COMMERCIAL CATCH 
As we have mentioned before, overfishing shows up in twO' ways — first, by the 
small size of clams taken, and, second, by the reduced average catch par man. On 
new beds, such as Swickshak in 1923, nearly all th© clams taken were more than 
5 inches in length. The same is true of the early digging at Cordova and for many 
years on the Washington beaches. On the northern beds the large clams appear to 
be very inactive, sometimes remaining with tlie siphon extended until dug. There- 
fore the large clams, on the whole, are more easily found and taken than the small 
ones. It takes as long to dig a small clam as a large one, and the result of taking 
