Experiments were made witl: sleds under 

 the hag in attempts to clear the mud away 

 from the clams more rapidly. In spite of these 

 modifications, the scraper dredges piled up the 

 sand badly, which choked the forward parts 

 of the bag (Westman, see footnote 2). Be- 

 cause of the deficiencies in these dredges, as 

 well as undesirable results from their oper- 

 ation, experiments were conducted in the mid- 

 1940's by the surf clam industry which led to 

 the development of the more efficient hydraulic 

 jet dredge. 



Hydraulic Dredges 



The hydraulic jet dredge was developed by 

 jetting water directly into the conventional 

 "dry" dredge. The first units built were small 

 but were efl'ective enough to prove their super- 

 iority over simple scraper dredges. One of the 

 main advantages of the hydraulic jet dredge 

 was its tremendous reduction in the number of 

 broken clams and damaged meats taken in the 

 catches. By utilization of the water jets, the 

 area that could be dredged during a tow was 

 more than doubled. This made possible the 

 commercial harvesting of clam populations of 

 far less density than was previously feasible. 

 Furthermore, regions of hard bottom which 

 were previously unsuitable for dredging now 

 became productive. 



Many experiments using difi'erent types and 

 orientation of jets were made. Also, trials 

 using various types and sizes of water pumps, 

 as well as types and sizes of hose, were con- 

 ducted befoi-e the major difficulties were over- 

 come and boats of the commercial fleet were 

 converted to hydraulic jet dredge gear. 



The most popular of the early types of 

 dredges was the "Long Island" hydraulic bar 

 clam dredge (Fig. 3) with three jets (West- 

 man, see footnote 2). Water was pumped to 

 these jets by a gasoline-driven pump located 

 aboard the fishing vessel through a 2V2-inch 

 canvas fire hose. Special hose was later de- 

 veloped by the rubber industry for this spe- 

 cific purpose. This new hose could withstand 

 internal pressures up to 150 psi even with ex- 

 tensive outside wear from the abrasive action 

 of sand, gravel, etc. 



Figure 2. — Types of rakes used for hand collection 

 of surf clams. 



The development of the hydraulic jet dredge 

 did not stop here. Although the basic prin- 

 ciples remained unchanged, the size and effi- 

 ciency of the gear were continually increased 

 during the period 1945-65 (Fig. 4). The dis- 

 covery of large unexploited surf clam beds off 

 the coasts of Maryland and New Jersey (in 

 1949) resulted in a shifting of the center of 

 the industry from the Long Island area to the 

 coasts of New Jersey and Maryland. Because 

 of the increased availability of clams, the in- 

 dustry was able to expand rapidly and to in- 

 crease the size and efficiency of the gear used 

 to fish these beds. Dredge sizes have now 

 reached a maximum size of 84 inches in width 

 (Fig. 5). 



Correspondingly, the size of water pumps 

 has been increased to maintain the proper 

 pressured flow of water required by these 

 larger dredges. The volume of the pumps has 



