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Open Access Publications from the University of California

Fish Bulletin No. 72. Trawling Gear in California


The name trawl is derived from the manner of operating the net rather than from any peculiarity of the net itself. The net is essentially a flattened bag which is towed or trawled over the ocean floor and this manner of fishing has shown itself to be very efficient in taking deep water fishes in large quantity at low operating cost. The capture of demersel fishes by means of hand lines, set or long lines and submerged gill or trammel nets requires more men, working longer hours for a smaller catch than does the dragging of a bag net along the ocean bottom. Another factor contributed to the success of trawling as a method of fishing. The dragging of a deeply submerged net could be continued after the weather became too rough to permit fishing operations by setliners or trammel netters. Trawling vessels averaged larger than set line boats and put to sea in weather that kept smaller craft port bound. Thus in spells of bad weather it frequently happened that no fish was delivered except the trawl-caught fares which benefited from any upward price fluctuation due to bad-weather scarcity of fish. However, trawling was not dependent upon favorable sale price. Quite the contrary, trawling was profitable at low price because of the quantity production at low operating cost. Consequently price to small-boat fishermen usually sagged when trawlers operated in an area. This pinched the small operators and often drove them into some other type of fishing.

Although there are many variations in the construction of trawl nets, there are three basic types determined by the device employed to keep the mouth of the bag open. The simplest method is to attach the net to a rigid horizontal pole or beam. This is the beam trawl.

Another method is to employ two towing lines, each line towed by a separate vessel. The two vessels follow parallel courses but at sufficient distance apart so that the diverging tow lines pull outward and keep the net mouth spread open. This is the two-boat or paranzella type.

The outward pull on the net mouth may be accomplished by a pair of kite-like boards, one at each side of the net, so hung at an angle that the boards tend to diverge or kite outward which keeps the mouth of the net open. This is the otter trawl.

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