FISHERIES VESSELS AND GEAR 



The general migratory patterns of commercially sought pelagic 

 species in the North Sea region are well documented by long 

 experience. Individual vessels, however, still face the problem of 

 precise location at a specific time. Although an important question 

 in any fishery, it is more manifest in the case of drifters. For once the 

 net is out, drift net fishing becomes the most passive form of all 

 harvesting techniques. A catch depends solely on the fortuitous 

 encounter with the net by a school. In selecting their grounds, fish- 

 ermen rely heavily on past success, visual sightings, observation of 

 bird activity, and more recently, on fish-finder sonar equipment. 



The drift net can be described as a floating meshed wall. It is 

 maintained in a vertical plane by floats secured to its head line and 

 weights to its bottom line. Small buoys are spaced at intervals along 

 the messenger line to indicate direction of lay and presence to surface 

 observers. British drift nets average 60 yards in length and 10 to 15 

 yards in depth. A single drifter will skoot up to 100 or more nets, 

 each joined to the next, forming a continuous wall of netting 3 miles 

 long. After shooting her nets, the drifter rides moored to the down- 

 wind end until dawn when hauling commences. Mesh size is such 

 that fish swimming into the net get partially through before 

 becoming hopelessly entangled and held by their gills. Because nets 

 are fairly close to the surface and hence visible to schools, all fishing 

 must be done at night. 



The foregoing resume of drift net fishing, of course, outlines the 

 technique at its highest state of development. Drifting, however, is 

 practiced at various stages of refinement throughout the world. Since 

 power is not essential to the operation, many less advanced nations 

 also utilize this harvesting method successfully using sailing craft 

 and even canoes. 



PURSE SEINES 



P*urse seines are the most productive harvesting implements 

 employed by the pelagic fisheries. Unlike the passive drifting 

 technique, purse seining is both active and aggressive with new schools 

 continually being ferreted out. A typical purse seine is 2,000 to 3,000 

 feet long and 100 to 300 feet deep. The net is hung vertically in a 

 circular fashion suspended between a surface float line and a weighted 

 foot line. At intervals along the foot line are fastened seine rings, or 

 eyes, through which a purse line is rove. Once a school has been 

 encircled, the purse line is hauled-in on a power winch thus pursing or 

 closing off the bottom escape route. Net sides are then hauled aboard 

 the vessel, or into seine boats, until only the heavier bunt section 

 remains. This procedure concentrates fish into one portion of the net 

 where they can easily be brailed out. 



Figure 8 



Purse seining as carried out on the United States Atlantic and 

 Gulf coasts is centered around the menhaden fishery. More pounds 

 of menhaden than any other single species are harvested annually by 

 American fishermen. The 1964 crop was about 1.5 billion pounds. 

 Menhaden are an extremely oily fish and except for the roe, which is 

 prepared as a salted, frozen or canned product, are not a table fare. 

 The meat is generally made into fertilizer and the oil used for industrial 

 purposes. Some more highly refined menhaden meal is used in man- 

 ufacturing animal and poultry feeds. 



A menhaden purse seiner does not shoot the net herself. After a 

 school has been sighted, a striker boat is dispatched to follow the fish 

 while the purse boats carrying the net are launched. Using the striker 



boat as a guide, the purse boats quicklv proceed to a point ahead of the 

 school. There they separate, each carrying half of the net, and circle 

 around behind the school. Meanwhile, the striker boat takes up 

 .station to tend the cork line during net retrieval. Encirclement 

 completed, net ends are joined together. Pursing is accomplished by 

 throwing a tom weight overboard to which both ends of purse line 

 have been attached. Purse boat crews then commence hauling in 

 excess net by hand to concentrate fish in the bunt section. The 

 seiner maneuvers alongside and brails fish aboard. Figure 8 shows 

 a menhaden purse seine set with purse boats hauling in net readying 

 catch for brailing. 



Purse seining is the predominant harvesting technique employed 

 by the eastern Pacific tuna, salmon and herring fisheries. Nets in 

 these fisheries are normally set directly from the seiner with the 

 assistance of a small skiff. Nets are stored on large drums or turn- 

 tables located aft to speed shooting time. When a school is sighted, 

 the seiner maneuvers to a favorable position and sets one end of net 

 into the water. The skiff tends this end and keeps it in position. The 

 seiner then proceeds on a circular course to surround the school. After 

 completing the set, net ends are joined and net pursed by a deck winch 

 aboard the seiner. Figure 9 shows a West Coast drum seiner. 



Figure 9 Pf}ofo~U 5 Fizh dnd W>ldl'(e Service 



MADI VALAI 

 A very unusual and interesting net is the madi valai, or vertically- 

 hauled net, used by fishermen off the Madras coast of India. Madi 

 valai nets are worked in conjunction with weed lures designed to 

 congregate fish over a particluar point. The lures, called kambi, are 

 secured to a line having a float at one end and a stone anchor at the 

 other. Water currents acting on the float stream the kambi line out 

 in an inclined plane. Four catamaran type canoes, each handling one 

 of the hauling lines, are paddled into position. Crews lower the madi 

 valai horizontally to the desired depth. Next, they position the net 

 under the kambi line and haul it rapidly to the surface by hand. Both 

 demersal and pelagic species are harvested in this fashion. 



Figure 10 Madi Valai 



37 



