REARING TILAPIA FOR TUNA BAIT 



By Thomas S. Hida, Fishery Research Biologist, Joseph R. Harada, Fishery Aid, and 

 Joseph E. King, Fishery Research Biologist 



Bureau of Commercial Fisheries 



The jjole-and-line live-bait fishery for skipjack 

 {Katsuioonus felatnis) is tlie most important com- 

 mercial fisliery in tlie Hawaiian Islands. In 195!), 

 the catcli amounted to 12.4 million pounds, wortii 

 $1.5 million to the fishermen. Brock and Takata 

 (1955) and Yamashita (19,'-)8) stated that a criti- 

 cal factor limiting this fishery is tlie sliortage of 

 live bait during the fishing season, which extends 

 generally from May to October and usually 

 reaches its peak in August. Yamashita (1958) 

 has estimated that the Hawaiian live-bait fishery 

 utilizes about 36,000 buckets (•25"2,000 pounds) of 

 bait annually. Much more than tliis amount could 

 be used to advantage in most years, if it were 

 available. 



The principal bait fish is the neliu (Stoleplwnts 

 purpureus) , a small anchovy. The iao {Prane.sus 

 insuJarum) , a silverside, is also used in some quan- 

 tity. The nehu is a delicate fish that, even if 

 handled carefully, will not survive in the bait 

 wells of the sampans (fishing vessels) for more 

 than a few days. It has not been considered fea- 

 sible to attempt to rear tlie nehu artificially. 



As one approach to solving the bait-fish prob- 

 lem, artificial baits of both edible and inedible ma- 

 terials have been tested with generally negative or 

 inconclusive results (Tester et al., 1954). 



In anotiier approach to tiie problem, the staff 

 of the Rureau of Commercial Fisheries Biological 

 Laboratory at Honolulu, Hawaii, in recent years 

 introduced a sardine {Harengvia vittata) from 

 tlie Marquesas Islands (Murphy, 1900) and the 

 tlireadfin shad {Dorosoimi pefenen.se) from the 

 United States. The introductions appear to be 

 successful, but it is too early to predict if these 

 fishes will become abundant enougli to satisfy the 

 needs of the fishery for adtlitional bait supplies. 



Approved for publication, March 29, 1961. Fishery Bulletin 



198. 



A small stock of Tihipla mossambica was 

 biought to Hawaii from Singapore in 1951 by the 

 Hawaii Division of Fish and (iaiue. The species 

 is now well-established in ponds and i-eservoirs on 

 all major islands of the Hawaiian group. The use 

 of tilapia as skipjack bait was fii-st tested by Brock 

 and Takata (1955), who reported that tilapia were 

 used to catch fish from schools that had been first 

 chummed to the stern of tlie boat with nehu. King 

 and Wilson (1957) further demonstrated that 

 small tilapia had many characteristics of a good 

 l)ait fish and judged it to be an adequate skipjack 

 bait. They found tilapia to be a very hardy fish 

 that tolerated a wide range of salinities and sur- 

 vived for indefinite periods in the bait wells of 

 the sampans. It was their opinion, however, that 

 large quantities of bait-size tilajjia could not be 

 produced effectively in reservoirs and natural 

 ponds because of the difficulty of harvesting the 

 young fish and because of the lack of control over 

 cannibalism and predation. 



In December 1957, a contract was signed with 

 Maui Fisheries and Marine Products, Ltd., the 

 Territorial Board of Agriculture and Forestry, 

 and the Bureau of Commercial Fisheries, as prin- 

 cipals, for operation of a hatchery at Paia, Maui, 

 to determine the economic feasibility of producing 

 young tilapia in a system of concrete tanks. I"^ii- 

 der the terms of the contract, Maui Fisheries was 

 to bear the cost of land rental, the major capital 

 improvements, and the water used: tlie Territory 

 was to aid in fencing the area and provide other 

 facilities and services; the Bureau of Commercial 

 Fisheries agreed to provide a biologist to super- 

 vise operation of the plant, to furnish feed for the 

 fish, and to supply miscellaneous equipment such 

 as dipiiets, screens, Hsh-sorting devices, and ciiem- 

 ical supplies. While not parties to the formal 

 contract, Hawaiian Tuna Packers, Ltd., and Ha- 

 waiian Commercial and Sugar Co., Inc., expressed 



