188 DESCRIPTION OF IMPORTANT FISHERIES AND THEIR PRODUCTS 



due to its limited numbers and areas in which it is found. The world's 

 largest clam is found in the South Seas. Tridacna gigas may have a shell 

 weighing 500 pounds and containing 20 pounds of meat. 



The clam, like the oyster, is a bivalve mollusc. Unlike the oyster, the 

 clam does not live out its life on the surface of the ground but spends 

 its life buried in the sand and mud, usually a few inches beneath the 

 surface. To feed, the clam extends to the surface a tubelike appendage, 

 the siphon, which contains two passages, the in-current canal which 

 conveys the food-ladened water to the organism below and the out-cur- 

 rent canal which discharges the water strained of food and containing 

 waste products. When the clam is disturbed, the siphon may be quickly 

 withdrawn from the surface and into the shell for safety. 



Harvesting. For large scale operations power-driven dredges similar to 

 oyster dredges are used. In some cases the clams are pumped aboard 

 the vessel with water as they are picked up by the dredge. 



The aborigines and early settlers harvested clams by the primitive 

 method of '^treading," that is, by wading in the shallow water and feeling 

 for the clams with their bare feet. Where the beds are exposed between 

 tides, the clams may be located by the siphon holes in the sand and the 

 clams dug with a shovel. This is the method used on the Pacific Coast 

 where the long run-out tides may expose large areas of the clam beds. 



On the East Coast, where the beds may not be exposed, other means 

 are used to take the clams. Tongs similar to oyster tongs and having 

 handles 14 to 16 feet long are used by operators on skiffs or bateaus. 

 Also a "basket rake," similar to the tongs but having teeth about 10 

 inches long, is employed. Back of the rake head is a bag formed of wire mesh 

 which will catch and hold the clams as it is dragged along the bottom. 

 Both tongs and rake are operated from a barge or anchored skiff. The 

 basket rake has a handle sometimes 25 feet long with a "T" head. A man 

 standing on a skiff drops the basket rake overboard and by means of 

 the ''T" handle drags the rake towards the skiff and hoists it aboard, 

 dumping the clams which are retained in the basket. 



Processing. For market the clams must be washed free of adhering 

 sand and silt and be graded for size. If market conditions are not favora- 

 ble, the clams may be rebedded in shallow water until conditions improve. 

 Sink floats or live boxes may also be used for a short-time storage. Live 

 boxes may be constructed by using two parallel logs with a slat container 

 resting between them. The water flowing back and forth between the 

 slats serves to cleanse the clams of sand and to wash silt out of the 

 siphons. In some cases shell stock may be given a short-time storage in 

 water treated with chlorine to free the clams from harmful bacteria. 



Clam meats may be canned as whole meats or as minced clams with 



