METHODS 



Vessel Scouting 



Our principal method of scouting follows the practice of the local skipjack fleet. We 

 employ experienced local fishermen, who maintain a constant watch from the bridge of the vessel 

 while cruising at the normal speed of 9 to 10 knots. These nnen locate the schools by the presence 

 of bird flocks, and from the species of birds present and their behavior they can make remarkably 

 accurate guesses about the kind and size of fish that are below them. Fortunately for the skipjack 

 fishermen, approximately 90 percent— of the schools of fish which are to be found by the pres- 

 ence of birds in Hawaiian waters are composed of skipjack, the balance being mostly dolphin 

 (mahimahi), small yellowfin or bigeye tuna (ahi), or little tunny (kawakawa). — 



Apparently the practice of using bird flocks for locating tuna schools is widespread 

 throughout the Pacific region. According to Cleaver and Shimada (1950), the Japanese live bait 

 fishermen rely heavily on birds for locating skipjack schools when they are in the area where 

 schools are to be expected. The Japanese fishermen also expect to find skipjack schools near 

 floating driftwood and debris, or in the vicinity of whales and basking sharks. In addition they 

 sometimes find fish by seeing the wake of the school or fish actually juniping and rolling on the 

 surface. 



In Hawaiian waters the fishermen are almost completely dependent upon the birds for 

 locating tuna. In fact, while they occasionally sight schools not accompanied by birds, on the 

 two principal scouting cruises of the CHARLES H. GILBERT during the spring of 1953, every one 

 of the 253 fish schools sighted was accompanied by birds and was found by nneans of the birds. 

 Undoubtedly this dependence on birds arises partly from their prevalence and partly also from 

 the almost constantly choppy sea conditions with white caps which make it extremely difficult to 

 see the wake of a school or jumping fish at any considerable distance from the vessel. 



Because they rely on the birds, the fishermen adapt their scouting technique to sighting 

 flocks of birds from the deck of the vessel rather than from a crow's nest. Since the Hawaiian 

 sea birds which flock over tuna schools are predominantlydark in color, e.g. wedge-tailed 

 shearwater, sooty and noddy terns— , and the ocean is characteristically a very deep blue, they 

 are best seen above the skyline. Fishermen on the bridge of the vessel, when they think they 

 detect a flock of birds at a maximunn distance, will frequently take the binoculars down to the 

 deck, where they can see more easily. Apparently this method of scouting is quite different from 

 that which prevails in the Annerican tuna fishery off Central America. According to fishermen 

 who have fished there, they depend primarily upon seeing the wake or shadow of the school or 

 jumping fish. They also find fish by fishing near drift logs, under birds, or near porpoise 

 schools. However, the actual fish school is best sighted at a maxinnum distance by observing 

 from as high as possible, and the practice is continually to scan the surface from the masthead. 

 No doubt this technique is more effective because of the prevalence of calm water conditions in 

 that area, and also, we suspect, because of larger and denser schools of tuna. 



Our systenn of scouting is designed to secure as continuous a scanning of the horizon by 

 experienced local fishermen as is practicable. The nnen are assigned 2-hour watches, and each 

 follows the usual fishing practice of making a thorough search of the horizon with the naked eye 



— A value which we cannot precisely substantiate. According to fishermen's estimates on 

 the basis of bird behavior, 75 out of 83, or 90 percent, of the schools sighted during GILBERT 

 cruises 11 and 13 were skipjack. We positively identified 55 schools that we tried to chum, and 

 47, or 85 percent, were either skipjack or a mixture of skipjack with other species. 



2/ 



— Coryphaena hippurua Linnaeus, Neothunnus macropterus (Temminck and Schlegel), 



P arathunnus sibi (Temnainck and Schlegel), and Euthynnus affinis Cantor in the order named. 



— Puffinus pacificus. Sterna fuscata, and Anous stolidus in the order named. 



