by Craig J. Orange and Gordon C. Broadhead 

 of the Inter-American Tropical Tuna Com- 

 mission. 



Three developments have contributed 

 greatly to reducing fishing time of purse 

 seiners - the power-operated block for 

 recovering the tuna seine first introduced 

 in 1955 aboard Anthony M, the all-nylon net 

 which was introduced py Anthony ii at about 

 the same time, and brine -spray circulation 

 first installed on Jo Ann in 1957. 



The power-operated block was used by 

 six seiners in 1958 and at the beginning 

 of this year about half the hh odd large 

 seiners were so equipped. The advantage 

 of handling the net mechanically is the 

 time saved on the many unsuccessful sets 

 and those with small catches. About half 

 of the sets made in 1959 were unsuccessful 

 and they averaged close to 110 minutes to 

 complete. The vessels with power-operated 

 blocks completed unsuccessful sets in 58 

 minutes - about half the average time. 

 They also made about U0 percent more sets 

 each day than did vessels without the 

 powered blocks. However, since these par- 

 ticular vessels did about 10 percent better 

 than the remainder of the fleet in years 

 previous to the installation of this equip- 

 ment, perhaps no more than a 30 percent 

 increase in the number of sets can be at- 

 tributed to it. In 1958, about half the 

 sets of both groups, those with and those 

 without power blocks, were successful. If 

 the power-operated block reduced fishing 

 time by about 30 percent, it probably 

 reduced trips by 15 percent or more because 

 running is not affected. 



It is claimed that the nylon net out- 

 lasts cotton and that the stronger material 

 permits capture and retention of larger 

 schools. Tuna Commission logbook data do 

 not bear this out. In 1958, there was no 

 measurable difference in'the average amount 

 of fish taken in successful sets of nets 

 made of more than half nylon and nets made 

 of less than half nylon. The advantage of 

 nylon nets is that they can be handled more 

 quickly and need less care. 



Development of brine- spray circulation 

 has proved a major time saving device for 

 purse seiners and has been widely adopted. 

 It retains the advantage of the brine im- 

 mersion method of refrigeration without 

 increasing weight. Without it, purse 



seiners could not convert entirely to brine 

 refrigeration. Orange and Broadhead (loc. 

 cit.) show that the all-brine boats can stow 

 15-ton sets in 2 hours compared with 2^ 

 hours for boats using part ice - a saving 

 of 30 minutes. Time saved is proportion- 

 ally greater for larger sets. Sets of 30 

 tons are handled in about U hours and 10 

 minutes on vessels using part ice stowage 

 and 2 hours and 20 minutes on all-brine 

 boats - a saving of lg hours. 



That recent technological advances 

 have greatly aided the purse seine fleet 

 in reducing their fishing time is unques- 

 tionable. Their success during the past 

 two years has been remarkable. It should 

 be born in mind, however, that technolog- 

 ical advances have not been entirely 

 responsible. The unusual oceanic climate 

 during this period has apparently shifted 

 yellow fin and skipjack tuna distrubition 

 and increased their availability in the 

 areas fished by the purse seine fleet, a 

 fact often overlooked by proponents of this 

 gear and bait boat owners considering con- 

 version. Also, bluefin has been more 

 available during the last two years. 

 Certainly the sharp increase in the number 

 of sets-per-day-of-fishing in 1958 was 

 primarily related to high abundance of 

 schools rather than to use of the power- 

 operated block, since only 6 of hk vessels 

 were so equipped. 



One of the large tuna clippers has 

 recently introduced a method that may 

 reduce the time required to catch live 

 bait. The clipper Lois Sievers used a 

 newly designed speed boat on her maiden 

 voyage early this year. It is equipped 

 with power to haul the net. It is reported 

 that the net is set and recovered from 

 the speed boat with less men and in less 

 time than it takes with the usual net 

 skiff. 



Further Possibilities through Knowledge 

 of Oceanography and Biology 



The tuna fleet's reputation of being 

 progressive ensures that fishing methods 

 will continue to improve through the in- 

 genuity of the boat operators. However, 

 it is improbable that improvements, what- 

 ever they may be, will appreciably reduce 

 the considerable time spent scouting for 

 fish or help in catching fish that refuse 

 to bite or schools that are not sui table 



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