and kawakawa (Sivasubramaniam 1973). Trolling, 

 usually limited to 3-5 h in the morning when Auxis 

 schools are at the surface, is effective during periods of 

 monsoon when the water is turbid. The gear was former- 

 ly operated from "orus" (outrigger canoes with sail), but 

 catches were poor because of difficulty in maneuvering 

 the vessel. Nowadays, 3.5-gross ton motorized boats, 

 manned by crews of at least three fishermen, are used 

 and their efficiency have made them popular for fishing 

 the various species of tunas. Trolling contributes over 

 50% of the total Auxis production. 



Pole-and-line fishing boats in Sri Lanka concentrate 

 primeirily on skipjack tuna but also catch significant 

 quantities of other tunas including kawakawa, yellow- 

 fin tuna, and Auxis (Fig. 50). Sivasubramaniam (1965) 

 jxjinted out that Sri Lanka's pole-and-line boats operate 

 gear similar to that used by fishermen of Minicoy, 

 Laccadive, and Maldive Islands. The boats, manned by 

 at least five fishermen, carry live bait in cane baskets 

 that are partially submerged alongside the craft. 

 Wooden spades are used for spraying water. Originally, 

 p)ole-and-line fishing was restricted to waters off the 

 southwest coast of the island, but mechanization of the 

 boats has expanded this type of fishing to the east coast. 

 Like other pole-and-line fisheries operating in the In- 

 dian Ocean, however, the availability of live bait has 

 limited the popularity of this fishing method. 



Although pole-and-line fishing is effective for skip- 



POLE AND LINE 



a n 



TROLL 



n 



r^ 



LONGLINE 



( 



J V////A 



BEACH SEINE 



jack tuna, it is not equally effective for Auxis 

 (Sivasubramaniam 1973). The reason is that Auxis re- 

 spond poorly to chumming probably because the live 

 bait used are usually larger than the most common food 

 items in their stomachs. Furthermore, this type of fish- 

 ing is not effective during periods of southwest mon- 

 soon, because water turbidity makes baiting difficult. 



The best season for pole-and-line fishing is in No- 

 vember-March off the southwest coast and in July-Sep- 

 tember off the east coast. Tuna production depends 

 heavily on the availability of bait during these periods. 



Drift nets are operated around the entire island of Sri 

 Lanka (Sivasubramaniam 1973). A 3.5-gTOss ton boat 

 usually carried 15 pieces of netting whereas as 11-gross 

 ton boat carried 60 pieces. With mesh sizes varying from 

 10.2 to 14.0 cm, the synthetic drift net has proven effec- 

 tive for skipjack and large kawakawa. For Auxis, how- 

 ever, fish <30 cm in length are too small to be enmesh- 

 ed. The catch of Auxis, therefore, amounts to only about 

 18 kg/day for a 3.5-gross ton boat and about 54 kg/day 

 for an 11-gross ton boat. Auxis rochei, being smaller, are 

 very rare in drift net catches. Auxis are usually taken by 

 drift net from about September to March. 



5.12 Boats 



As with gear, a wide variety of fishing boats, ranging 

 from modern high-seas purse seiners and pole-and-line 

 boats to primitive sailing crafts, is used in fishing for 

 Auxis. 



In Japanese waters, the pole-and-line boats that are 

 engaged in theAuxis fishery are small, usually <15 gross 

 tons (Ishida 1972a). These boats are smaller than the 

 usual pole-and-line boats of >30 gross tons which fish in 

 the coastal waters and high seas for surface schools of 

 tunas such as skipjack tuna, yellowfin tuna, and alba- 

 core. Japanese pole-and-line boats that fish in the At- 

 lantic for yellowfin and skipjack tunas and occasionally 

 for Auxis and bigeye tuna vary from 151 to 239 gross 

 tons, whereas the seiners, both single and double boats, 

 range from 50 up to >400 gross tons (Borgstrom 1964; 

 Hayasi 1973, 1974). 



Among the more primitive types of crafts used in 

 Auxis fishing are dugout canoes and catamarans (Silas 

 1967b). In the Maldive Islands, for example, sailing 

 boats called vadu dhony, which are about 6.1 m long 

 and 1.8 m wide, and fish three to four baited trolling 

 lines, are used as trollers (Sivasubramaniam'"). Slightly 

 larger sailing crafts, called the mas dhony, are used in 

 pole-and-line fishing; they vary in length from 10.7 to 

 12.2 m, have a beam of about 3.4 m and a draft of nearly 

 0.8 m. The Maldivian boats are constructed of coconut 

 wood, beautifully streamlined, and keeled for wind- 

 ward sailing. Compartments for carrying live bait have 

 continuous water circulation through holes along the 

 bottom. The fishermen fish at the stem atop a U-shaped 

 removable wooden platform. 



Figure 50.— Percentage composition of tuna species caught by 

 various types of gear from the coastal waters of Sri Lanka (Siva- 

 subramaniam 1%5). 



'"K. Sivasubramaniam. UNDP-Sri Lanka Skipjack Fishery Develop- 

 ment Project. FAO, Colombo, Sri Lanka, pers, commun. August 1975. 



50 



