REARFNG TILAPIA FOR TUNA BAIT 



15 



111 1959, Maui Fisheries and Marine Products, 

 Ltd., l)uilt a concrete and hollow-tile tank, 10 

 feet X 30 feet X 3 feet deep, at Maalaea Harbor, 

 which was capable of holding about 30 buckets of 

 fish. The fish were acclimatized in this tank 

 by introducing them directly into water with a 

 salinity of approximately 17 Voo and leaving them 

 at tliis salinity for at lea.st 12 lioui-s before intro- 

 ducing them into sea water (35°/oo) in the bait 

 wells of the sampans. Tliis method, developed by 

 the Hawaii Division of Fish and Game in 19.59 

 (unpublished data), was easy to follow and usu- 

 ally resulted in few losses. One gi-eat advantage 

 was that no one needed to monitor the salinitj' 

 and regulate continually the flow of salt and fresh 

 water, as was required for the method employed 

 in 1958. The vrater in the acclimatization tank was 

 aerated by a small compressor-, with a few air- 

 stones distributed over the bottom of the tank. 



UTILIZATION OF BAIT 



The results of fishing operations utilizing tilapia 

 produced at the Paia hatchery along with the nat- 

 urally occurring bait fishes, nehu and iao, are pre- 

 sented in table 16. Tlie amount of bait used was 

 estimated by the fishermen. An observer accom- 

 panied the vessels on most of the trips and re- 



corded the catcli rates with the different types of 

 baits used. 



AVe calculated an average catch of 49 pounds. 

 of skipjack per pound of tilapia used in 1958, as 

 compared with 4S pounds of skipjack per pound 

 of neliu and fJ8 pounds of skipjack per pound of 

 iao. In 1959, the average catch amounted to 53 

 pounds of skipjack per jjound of tilapia. and 64 

 pounds of skipjack per pound of nehu. Iao was 

 used on one trip with a catch of 49 pounds of skip- 

 jack i)er pound of iao. Although most of the 

 catches were made using nehu and tilapia alter- 

 nately, some schools were fished entirely with 

 tilapia with fairly good results. On September 5, 

 1959, the SaiJ-li.sh caught 5,600 pounds of 20-pound 

 skipjack using 90 pounds of tilapia, or 62.2 pounds 

 of skipjack jjer pound of tilapia. 



These results indicated that tilapia could be 

 used to advantage to supplement the supplies of 

 nehu. The fishermen commented on the fact that 

 tilapia were slow swimmers, and necessitated re- 

 ducing the speed of the sampans during the chum- 

 ming and fishing operations. Also, they noted 

 that the tilapia were very hardy and performed 

 well when large wild scliools of skipjack were en- 

 countered, and that they were particularly good 

 bait for large skipjack of 18 to 25 pounds. 



Table 16. — Tilapia as skipjack bait compared with nehu and iao, 1958 and 1959 



' No records. 



