STUDIES ON TILAPLA. AS SKIPJACK BAIT 



By 



Joseph E. King 



Fishery Research Biologist 



Pacific Oceanic Fishery Investigations 



Honolulu, T. H. 



and 



Peter T. Wilson 

 Hawaiian Tuna Packers, 

 Honolulu, T, H. 



Ltd. 



In the spring of 1956, the Fish and Wildlife 

 Service joined forces with the Hawaiian Tuna 

 Packers, Ltd. , in an informal arrangement for 

 the purpose of seining supplies of young tilapia 

 ( Tilapia nnossambica ) and testing them as skip- 

 jack bait. This report provides a preliminary 

 evaluation of ponds and reservoirs as a nneans 

 of producing bait-size tilapia, it describes 

 briefly the methods used in acclimatizing the 

 fish to sea water, and adds to the available in- 

 formation on the qualities of young tilapia as 

 skipjack bait. 



The skipjack ( Katsuwonus pelamis) is the 

 most important commercial fish species in 

 Hawaii. The annual catch for the 5 years, 

 1951-55, averaged 11,183,000 pounds, with an 

 average annual value to the fishermen of 

 $1,452,000. The fish are caught by pole and 

 line using live bait as chum. The principal bait 

 employed is nehu (Stolephorus purpureus), a 

 small anchovy. The volume of the skipjack catch 

 is largely governed by the bait supply (Tester 

 1951, Brock and Takata 1955). Daring the sum- 

 mer months at the peak of the skipjack season, 

 the demand for bait usually exceeds the amount 

 obtainable, so that an exorbitant amount of time 

 must be spent by the vessel crews searching for 

 bait. 



The nehu is a delicate fish and must be 

 handled with great care; it will survive for not 

 more than a few days, or at most a week, in the 

 bait boxes of the skipjack boats (sampans). Also, 

 its life history and habitat requirements are 

 thought to render the fish unsuitable for cultiva- 

 tion under artificial conditions. It was the con- 

 clusion, therefore, of biologists employed by the 

 Territory, the University of Hawaii, and the 

 U. S. Fish and Wildlife Service that new types 

 of bait, either artificial or natural, were needed 

 if the Hawaiian skipjack fishery were to expand 

 and make better use of the available tuna 

 resource. 



During the years 1952-53, the University of 

 Hawaii, under contract with the Fish and Wild- 

 life Service, undertook an investigation to dis- 

 cover nneans of attracting tuna within reach of a 

 fishing vessel through the use of artificial bait. 

 Both edible materials (nnacaroni, strips of agar 

 and fish flesh, gelatin capsules) and inedible 

 materials (aluminum foil, tin particles, mica 

 flakes) were tested with generally negative or 

 inconclusive results (Tester et al. 1954). 



During this same period, the Territorial 

 Division of Fish and Game was successful in de- 

 veloping improved methods of holding bait fishes 

 with greatly reduced mortality (Brock and 

 Takata 1955), and as early as 1951, the Terri- 

 tory had taken steps to introduce a new species 

 of fish adaptable to pond cultivation and possibly 

 suitable as a bait fish. The problem of bait-fish 

 mortality is receiving further study by the 

 Hawaiian Tuna Packers, Ltd. with the aim of 

 conserving the natural bait supply. 



Tilapia mossambica, a cichlid fish native to 

 EastAfrica, was brought to Hawaii in 1951 from 

 the East Indies, where in a short period of years 

 it had become a popular food fish. The Terri- 

 torial Division of Fish and Game received a 

 shipment of 60 fry from the Singapore Fisheries 

 Comnnission in December 1951 (Brock and 

 Takata 1955). The 15 survivors of this original 

 lot multiplied prodigiously and today the 

 species is well established in private and 

 commercial fish ponds on the major Hawaiian 

 Islands. 



Tilapia were introduced to Hawaii with the 

 expectation from what was known of their food 

 habits that they would be useful in the control of 

 algal growth in water reservoirs. It was hoped 

 also that the young of the species might prove to 

 be satisfactory live bait for use in the skipjack 

 fishery, and that the adults would fill a need for 

 additional food fish. 



