The J«pan«B« divide their tuna operations Into two categories: 



Coastal 4/: The set net and the pole and line are used mostly for Inshore 

 operations. Other gear of lesser Importance are the drift net, the circling net, spears, 

 and trolling jigs. Long lines are operated close to the shore during Fe>)ruary and March 

 In the area west of Kyushu. 



Offshore: The skipjack pole and line and the tuna long line are used ex- 

 clusively In the offshore areas. 



2. Tuna Set Het 



Nothing Is known a^oat the construction of the tana set net (maguro dalbo) prior 

 to the 16th Oeatury. Beoorde are avallahle, however, which show that set nets were 'ised 

 during the Keloho Ira (1596-1614) to catch the giant hlack tu as as they migrated northward 

 along the coast In shallow water. 



At first the size of the mesh was made large enough to hold only blsurk tunas, hut 

 mesh size was gradually decreased In order to catch yellowtall. horse mackerel, and other 

 migratory coastal species. Today, set nets for the hlack tuna and for the smaller species 

 are similar, except that those designed specifically for tlack tuna have a wing net construct- 

 ed of rice straw. For smaller species the wing net han smaller mesh and Is made of cotton. 



The tuna set net (Figure 16) Is placed In shallow water, 40 to 8o meters deep, 

 In a position where water currents are advantageous for directing the flsn into the nei. 

 The dl.Denslone and structure of the net viry according to the prpferences of the fishermen 

 and the topography of the ocean hottom. 



The wing or lend net may be from 900 to ."^.eoO meters long and Is, as already noted, 

 made of rice straw rope. The mesh size varies from 90 to 120 centimeters stretched. The 

 main hody of the set net Is generally from 180 to 360 meters long and from 72 to 115 teters 

 wide, and is divided Into two parts. The belly, or playground, is conposed of mesh measuring 

 6 to 12 centimeters stretch»!d. The pocket, which is raised when the fish are removed, is 

 constructed of mesh measuring 4 to 6 centimeters stretched. The mesh Is made of cotton or 

 manila twine. The head ropes are made of wire or manlla rope. Bamboo sticks, 8 to 14 in 

 number depending on the size of the net, are usually used to construct the floats. In 

 Hokkaido, the floats are glass spheres. 



?. Drift Het 



At one time the drift net (raRguro nagashlami) was the most common gear used to catch 

 both the black tuna In the sea regions off Hokkaido and the yellowfin tuna In Sagami Bay, 

 localities where the species come close to the surface of the water. Since the gear is expen- 

 sive, occupies considerable space in a boat, and is difficult to handle In rough and stormy 

 weather (the time during which the best catches of the fish are generally made), its use de- 

 clined when other fishing techniques were developed. In Hokkaido waters the long line pro- 

 vided fishermen with an equally good and much cheaper method of fishing, and in Sagami Bay 

 the circling net replaced the drift net as a means of taking yellowfin tuna. 



A few drift nets (Figure I'') are still operated, to catch the black tuna. It is used 

 chiefly along the southeastern coast of Hokkaiilo where the warm and cold currents meet and 

 the fish tend to concentrate and swim near the surfpce. The fishing grounds are situated 

 from the coast seaward for a distance of about 100 miles. 



In olden times linen was used to make the oesh of the drift net. This proved to be 

 too costly, and Nanking heirp ( Boehmerla tenacisslma ) or, rarely, silk has been used In its 

 place with jiood results. A section of the drift net measures about 38 meters in length. The 

 float line, however, is only about 30 meters in length. Vfhen placed In water the net there- 

 fo-^e occupies a distance of about half its length and hangs loosely in a wavy band. Sinkers 

 are not attached to the bottom, and the fish easily become entangled as they strike against 

 the net. They are not gilled. The twine used to make the mesh of the net Is about 2 milli- 

 meters In diameter, emd the mesh Is about 50 centimeters stretched. From 22 to 25 meshes, 



4/ The areas designated as "coastal" have been arbitrarily fixed by the Tokyo Central Fisher- 

 ies Bxperlmental Station and the Bureau of Fisheries as those waters extending from the 

 coast seaward for a distance of 5<^ miles. 



