18 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



year for Scalaries. This estimated labor cost is 

 higher than the estimate given for the Paia hatch- 

 ei-y because of the larger scope of the operation. 

 Feed would cost approximately $15,000 annually. 

 Utilities, mostly electricity and water, would cost 

 about $3,000 a year. Another $1,000 would be 

 needed for miscellaneous equipment and for bait- 

 hauling expenses. The annual operating cost 

 would thus be approximately $29,000, with an ad- 

 ditional $13,000 for capital improvements, or a 

 total of $42,000. With the anticipated production 

 of 6,000 buckets of bait, tlie cost per bucket would 

 be $7.00, or $1.00 per pound. Land costs are not 

 included in our estimates since the planned loca- 

 tion of the hatcliery is on State-owned land. 



Brock and Takata (1955) estimated that the 

 break-even value of nehu to the Hawaiian skip- 

 jack fishermen was roughly $4.23 per pound at 

 the peak of the season. Therefore, if the cost of 

 commercially produced bait were higher than 

 $4.23, the fishermen would fare better by catching 

 their own bait; and if the cost of a substitute bait 

 were lower they would be better off to buy their 

 bait. 



ESTIMATED VALUE TO FISHERMEN 

 Fi-om the estimates of bait-production costs 

 given in the previous section,we can estimate the 

 potential value of tilapia to the commercial tuna 

 fisherman. Hawaiian skipjack vessels ordinarily 

 use 20 to 30 buckets of bait per trip when natural 

 bait is in good supply. I^t us assume that a boat 

 purchases 30 buckets of tilapia at a cost of $7.00 

 a bucket and in 1-day's fishing catches 10,000 

 pounds of skipjack (as calculated from our aver- 

 age conversion rate in 1958 and 1959) worth 

 $1,000 to the fishermen. If we deduct $210 for the 

 cost of the bait, $15 for the crew's food, $25 for 

 fuel and ice, for a total of $250, we have $750 re- 

 maining. The crew's share, or 63 percent, equals 

 $472.50 for the day's operation. Based on an 

 average crew per vessel of 10 men, the day's 

 share for each crew member is $47.25. 



We do not visualize that tilapia or any artificial 

 bait substitute will entirely replace the nehu in the 

 Hawaiian skipjack fishery. King and Wilson 

 (1957) have estimated, however, that if the aver- 

 age fishing time for a sampan could be increased 

 from the present 15 days a month to a possible 20 

 days a month through the use of tilapia or other 

 supplemental bait, the total annual skipjack catch 

 for Hawaii might be increased by 3 million to 4 



million pounds. It is probable that the nimiber of 

 fishing days could be increased to well over 25 days 

 a month if the entire bait needs or sufficient sup- 

 plemental bait were supplied by a lai-ge tilapia 

 liatchery. Such an increase in days fished in a 

 month might conceivably increase the total annual 

 skipjack landings for Hawaii by more than 6 mil- 

 lion pounds. 



CONCLUSIONS AND RECOMMENDATIONS 



Location of the Plant 



The site was characterized by strong, gusty 

 winds, above average rainfall for the island of 

 Maui, and a high rate of cloud cover. Although 

 the wind aided in circulating the water, it also 

 brought large quantities of dust and debris into 

 the tanks. We concluded that a sheltered area on 

 the drier and warmer leeward side of the island 

 would have provided a more favorable site. 



Arrangement of the Plant 



The general an-angement was satisfactory but 

 could have been improved in a few respects. 



a. Both brood tanks should have been equipped 

 with drains on their upwind end where the detritus 

 collected. (The drains were installed in 1959.) 



b. Aeration during the hours of darkness would 

 help keep tlie oxygen level fairly high. ( An aera- 

 tion system was in operation in 1959.) 



c. Fry tanks should have been built with a sump 

 or catch basin to facilitate removal of fry. Con- 

 siderable time was expended in seining tlie fish 

 from the tanks, which were difficult to drain. 



d. The plant had a ratio of brood-tank area to 

 fry-tank area of 1 : 3.8. A ratio of 1 : 5 would have 

 permitted less crowded conditions within the fry 

 tanks and probably would have induced faster 

 growth in the young fish. 



Fish Feed 



a. Fish 2 to 3 weeks of age fed well on a mid- 

 dlings-fish meal mixture and Purina starter feed; 

 between 4 weeks and 3 months of age they readily 

 accepted the Purina fry feed and always seemed 

 to be hungry even with three feedings a day. At 

 all ages, they fed on the algae in the tanks. 



b. The particle size of the Purina small finger- 

 ling feed seemed to be too large for the 2- to 3- 

 month-old tilapia. 



c. The adults preferred Purina trout chow (de- 

 veloper), but appeared to remain in satisfactory 

 condition on a millrua-fish meal mixture (4:1 



