Because of their widespread popularity as 

 food fish in Africa and east Asia, a wealth of 

 information is available on the culture and bi- 

 ology of the various species of Tilapia (Chimits 

 1955). We shall not attempt a general review of 

 the literature in this brief report. It may 

 suffice to state, however, that the species T. 

 mossambica is a "mouth breeder", or more 

 properly a "mouth brooder " ; i.e., imnnediately 

 after spawning and fertilization have taken place, 

 the female picks up the eggs in her mouth and, 

 following hatching of the eggs in about 60 hours, 

 she continues to carry the young in her nnouth 

 cavity for another 5 to 8 days (Chen 195 3, 

 Chimits 1955). 



The relatively low number of eggs spawned 

 (100 to 1,000 in T. mossambica), the number 

 depending largely on the size of the female (Chen 

 1953), is compensated for by this special care 

 of the young and by a high frequency of spawning, 

 so that the fish actually have a high reproductive 

 potential. These positive factors are partially 

 offset, however, by the susceptibility to preda- 

 tion of the newly released young and by cannibal- 

 istic tendencies in both adult fish and juveniles. 

 The growth of the young fish is quite rapid; they 

 attain a suitable bait-fish size (1-1/2 to 2 inches) 

 for skipjack fishing in abo ut 2 nnonths. The 

 adults reach a maximum size of about 12 inches 

 and 1-1/2 pounds. 



The first sea tests t o evaluate tilapia as 

 skipjack bait were conducted by the Territorial 

 Division of Fish and Game in the summer of 

 1954. On 2 of 5 trials no skipjack schools were 

 encountered; on the remaining 3 trials fish were 

 taken by using nehu to attract the skipjack school 

 to the stern of the boat and then switching to 

 tilapia during the fishing. The conclusions were 

 that although some of the tilapia tended to sound 

 --which is an undesirable trait in a bait fish-- 

 they were adequate in most respects. 



It still remained to be demonstrated, 

 however, that tilapia were equal to nehu in the 

 ability to attract and draw in a tuna school to a 

 fishing position at the stern of the vessel. The 

 principal objectives of the present study were to 

 gain a more thorough evaluation of tilapia as 

 skipjack bait and, by conducting most of the 

 tests on the comnnercial vessels, to introduce 

 the new bait to the sannpan fishermen and obtain 

 their opinions and reactions. 



SEINING TILAPIA 



In March 1955, the Hawaiian Tuna Packers 

 took over the nnanagement of one pond which had 

 been stocked by the Territorial Division of Fish 



and Game, and shortly thereafter they stocked 

 three additional ponds; all are fresh-water ponds 

 located on the Ewa Plantation, Oahu. The ponds 

 vary in size frona 1-1/2 to 4-1/2 acres and in 

 depth from 3 to 13 feet. Since they serve as 

 storage reservoirs for irrigation purposes, they 

 are subject to widely fluctuating water levels. 

 Before the introduction of tilapia some of the 

 ponds were badly choked with filamentous algae. 

 This was cleaned out by the tilapia in less than 

 6 months and since then the ponds have remained 

 clear of vegetation. 



The fish were supplied with a variety of 

 locally available feeds, including a mixture of 

 pineapple stunnp meal and stickwater fronn the 

 fish processing plant, rice bran, stale bread, 

 ground stale bread mixed with fish nrieal, and 

 ground crayfish which had been removed from 

 the ponds. 



In only one pond (pond No. 6) was there 

 successful reproduction during the summer of 

 1956. Another of the ponds (pond No. 9) con- 

 tained a large population of adult fish but there 

 was little or no production of young fish. In two 

 other ponds (ponds No. 3 and No. 5) the tilapia 

 did not establish then-iselves following the initial 

 stocking and apparently disappeared. Pond No. 

 5 has been recently restocked. 



During the period from May to September, 

 1956, the two collaborating organizations (POFI 

 and Hawaiian Tuna Packers) conducted 7 full- 

 day and 2 half-day seining operations to obtain 

 supplies of small bait-size tilapia for testing 

 purposes. In addition to the No. 6 pond at Ewa, 

 some tilapia were obtained from a 3-acre 

 brackish-water pond and from 2 small pools, all 

 on the outskirts of Honolulu. A 40-fathom "nehu" 

 net was used in seining the larger ponds, and a 

 10-fathom net was used in the smaller pools. 

 In making a set with the 40-fathom seine, the 

 net was first stacked on a rubber life raft (turned 

 bottom up) and then pulled fronn the raft as it was 

 towed across the pond (figs. 1 and 2). In the 

 larger ponds, a Japanese-type bait-holding de- 

 vice ("kowari"), somewhat nnodified in structure, 

 was used in sorting the fish according to size 

 and for holding the bait- size fish until the end of 

 each day's seining, when they were transferred 

 to drums of water and treinsported by truck to 

 the fishing docks. The water was aerated during 

 the trip. With this method there was essentially 

 no mortality among the tilapia as the result of 

 handling or while in transit, except among the 

 small fish less than 1 inch in length. 



Table 1 shows the pounds of small (<3"), 

 medium (3 - 8") and large (8 - 12") tilapia 



